Integumentary System Several different types of cells that serve specific functions

Major Organs and Structures: can be found in the epidermis. These cells are defined in the
❖ skin list below.
❖ hair
❖ nails Keratinocytes (ke-RAT-in-oh-sites)
❖ cutaneous glands -begin in the stratum basale and make up the majority of
Functions: epidermal cells.
❖ protection -Their purpose is to grow and divide.
❖ vitamin D production -As they divide, they push the older cells up toward the
❖ temperature regulation surface.
❖ water retention -The keratinocytes produce and fill themselves with keratin (a
❖ sensation hard, waterproof protein) as they move toward the surface.
❖ nonverbal communication -By the time they reach the stratum corneum, the
keratinocytes are tightly packed, filled with keratin, and have
Anatomy of the Skin, Hair, and Nails died.
− As the body’s largest organ, the skin makes up -This process is called cornification. These cells form a very
approximately 15% of the body’s total weight. durable stratum corneum at the surface.
− It consists of two layers, the epidermis and the
dermis. Melanocytes
− The epidermis is the skin’s most superficial layer, -produce skin pigments called melanin.
composed of stratified squamous epithelial tissue. -These cells stay in the stratum basale, but they have
− Deep to the epidermis is the dermis, which is projections to more superficial layers.
− Composed of loose/areolar connective tissue over -The keratinocytes take in the melanin produced by pinching
dense irregular connective tissue. off bits of the melanocyte extensions that contain melanin-
− The cutaneous glands, the hair follicles, and most of filled vesicles called melanosomes. This is an example of
the skin’s nerve endings can be found in the dermis. endocytosis. Melanocytes may not be evenly distributed
− Deep to the dermis is the hypodermis or across the skin, and denser patches of these cells account for
subcutaneous layer (subcutaneous tissue). freckles and moles.
➢ Although it is technically not part of the skin, this layer
attaches the skin to the rest of the body. Common Misconception
➢ Mainly composed of adipose connective tissue, the The idea that people with dark skin have more melanocytes
hypodermis serves as an insulating layer, a cushioning layer, than people with light skin is a misconception, as both types
and an energy source. of skin contain the same number.
➢ This layer is generally thicker in women than in men
➢ The hypodermis is an ideal site for subcutaneous drug Although the melanocytes function the same, the
injections (which are done with a hypodermic needle) because difference is the amount of melanin they produce. This
it has numerous blood vessels and can absorb the drugs easily. amount is genetically determined.
Epidermis
The epidermis (the superficial layer of the skin) is subdivided ❖ Tactile cells serve as receptors for fine touch only.
into four or five general layers called strata. Although they are found in the stratum basale, they are
The deepest layer is the stratum basale (ba-SAL-eh), which associated with nerve cells in the underlying dermis.
contains a single layer of cuboidal cells. ❖ Dendritic cells are immune system cells found in the
-It is the only stratum of the epidermis with cells that actively stratum spinosum and the stratum granulosum. They alert the
grow and divide to produce new epidermis. body’s immune system to the invasion of pathogens (disease-
-The stratum basale dips into the dermis of the skin to form causing foreign invaders) that could make it through the
the hair follicles. stratum corneum.
Superficial to the stratum basale are the stratum spinosum and
the stratum granulosum. Dermis
The stratum lucidum (loo-SEE-dum) is found only in thick The dermis is sometimes called the “rue skin.”
skin. It is not found in thin skin. Blood vessels, fibers, nerve endings, hair follicles, and
The stratum corneum is the most superficial stratum. cutaneous glands are found in the dermis.
It may have as many as 20 layers of cells. It is composed of ❖ Papillae the superficial edge of the dermis has bumps
tough, waterproof dead cells that eventually flake off called papillae, which are in direct contact with the epidermis.
(exfoliate). The human body sheds thousands of these dead − These papillae, arranged in a random pattern over
stratum corneum cells every day. The exfoliated cells make up most of the body, form individual-specific patterns of
the majority of all the dust you find on your floor and ridges on the palmar and plantar surfaces.
furniture when cleaning. − This unique arrangement creates fingerprints.
Common Misconception − The papillae’s numerous small blood vessels provide
Whether skin is “thick” or “thin” does not have to do nearby stratum basale cells with nutrients they need
With the depth of the skin or the number of cell layers. to grow and divide.
It has to do with the presence of the stratum lucidum, ❖ The stratum basale cells are fed by diffusion.
Which is present only in thick skin. Thick skin is found − Because blood vessels do not extend into the
On the lips, on the palms of the hands, and on the epidermis, the risk of blood loss if the epidermis
Plantar surface of the feet. Thick skin has no hair. becomes injured is reduced.
While thin skin does.
Cells of the Epidermis Fibers
 − The dermis changes from loose/areolar tissue to
dense irregular connective tissue with depth.
− Both of these tissue types are characterized by cells ➢ The direction of the cuticle plates resists the follicle’s cells,
and fibers in a matrix, but they lack a neat dividing so the hair cannot be easily pulled from the follicle.
line between them. ➢ The hair is easy to manage if the plates of the cuticle are
lying smooth on the hair and not sticking out along the length
The cells (fibroblasts) of both tissues produce two types of of the shaft.
protein fibers: collagen and elastin. ➢ Conditioners can be used to ençourage the cuticle to lay
flat.
❖ Collagen fibers give the skin strength. ➢ The hair texture depends on the shaft’s cross-sectional
❖ Elastin fibers provide elasticity, which allows the skin shape.
to come back to shape if stretched. The number of fibers ➢ Straight hair has a round shaft, wavy hair has an oval shaft,
increases with depth in the dermis. and curly hair has a flatter shaft.
➢ Rates of growth within the follicle matter too.
Common Misconception ➢ Straight hair grows evenly within the follicle.
Be careful of the word elastic as it does not mean “the ability ➢ Wavy and curly hair may grow alternately faster on one
to be stretched.” (That is the definition of extensibility, which side of the follicle than on the other.
is covered in the muscular system chapter.) ➢ Hair color depends on the amount and type of melanin
Elasticity is the ability to come back to shape if something produced by the hair follice’s melanocytes.
has first been stretched, like a rubber band. For example, think ➢ Gray to white hair results from a lack of melanin in the
of an elastic waistband on an old pair of sweatpants. This hair’s cortex and from the possible presence of air in the
waistband is no longer elastic if you stretch out the waistband, medulla.
let go, and the pants fall off.
● As with most living things, hair has a life cycle. There is a
Vitamin A and vitamin C are important for healthy skin growing stage, a resting stage, and then a dying stage, when
because they are necessary for collagen production. You can the hair finally falls out. However, not all of the hairs on the
get vitamin A (which is also important in head cycle on the same schedule. Each hair grows about a half
The maintenance of epithelial tissues) by eating green and inch per month, and its growth stage lasts for approximately 3
yellow vegetables, dairy base, making the hair stand years. Each hair then goes into a 1- to. 2-year resting stage,
perpendicular (in an upright position) to the skin’s surface. and then it falls out. If all the hairs on your head were on the
For furry animals, this makes a thicker layer of fur insulation same schedule, you would go bald every 4 to 5 years. Instead,
to help keep the skin warm. roughly 90% of the hairs on your head are somewhere in the
For humans, the visible effect is goose bumps. growing stage at any given time. In fact, it is perfectly normal
to lose about 100 hairs from your scalp every day. You
Hair probably notice this routine hair loss all the time, as your
There are three types of hair on every human body. They are fallen hair accumulates in the tub or sink drain, on the
the following: bathroom floor, and in your brush when you wash, style, and
Lanugo hair, which is very fine and unpigmented (colorless), blow-dry your hair. Eyelashes go through a similar cycle.
forms on a fetus They grow for about 30 days, rest for 105 days, and then fall
During the last 3 months of its development. This hair is out.
usually replaced by birth.
Vellus hair, which is also unpigmented and very fine, Disease Point
replaces lanugo hair around Alopecia, or baldness, is characterized by an excessive
The time of birth. An example of vellus hair is the body hair Loss of hair. This disorder affects both men and women
on most women and And is caused by various factors such as heredity,
Children. Infection, or use of certain medications. Alopecia is
Terminal hair, which is thick, coarse, and heavily pigmented, Diagnosed when you have significantly more than
forms the eyebrows, 100 hairs entering the resting stage at one time.
Eyelashes, and hair on the scalp. At puberty, terminal hair
forms in the axillary and Nails
Pubic regions of both sexes. It also forms on the face and Nails form on the distal end (away from the attachment point)
possibly on the trunk and of the fingers and toes
Limbs of men. The structure of the nail includes the skin-covered nail root
and the visible nail plate.
All types of human hair can be divided into three sections The free edge of the nail and the nail body make up the nail
❖ The bulb is a thickening of the hair at the end of the plate.
hair follicle. The nail body lies over the nail bed.
❖ The root extends from the bulb to the skin’s surface. The nail bed appears pink because of the dermis’s numerous
❖ The shaft is the section of the hair extending out from blood vessels.
the skin’s surface. Laterally, the skin rises to form a nail fold over the nail’s
lateral edge. Here the nail fits into a nail groove.
A cross section of a hair shows three layers: An eponychium (ep-uh-NIK-ee-um), or cuticle, at the
❖ an inner medulla composed of soft keratin, proximal edge of the nail body, is composed of stratum
❖ a middle cortex composed of hard keratin corneum cells extending onto the nail bed.
❖ an outer cuticle that appears as interlocking scaly The nail matrix (the nail’s growth center) at the root of the
plates of dead keratinocytes. nail is composed of active keratinocytes in the stratum basale.
The nail is translucent, although a lunula or lunule (LOON- Vitamin D Production
yule) (white crescent) may be visible under the nail especially Despite the potential dangers of overexposure to the sun’s UV
on the thumbs. This is where the nail matrix is thick enough to rays, minimal exposure to these rays does have a benefit. UV
hide the blood vessels of the dermis deep to it. light encourages skin to produce vitamin D, as it activates a
Composed of stratum corneum cells with hard keratin, nails precursor molecule in the skin. The liver and kidneys then
grow distally throughout life and, unlike hair, do not have a modify this molecule to become active vitamin D. If you live
resting stage. Fingernails grow faster than toenails. Nails in a four-season climate, your exposure to UV light may be
protect the ends of the fingers and toes, aid in grasping small greatly reduced during the winter months. Not only is the sun
objects, and are used for scratching. less intense, but you are more likely to cover most of your
skin with clothing to stay warm, therefore reducing your UV
Clinical Point exposure. It is for this reason that vitamin D is added to most
It is important to note that nails can be a good indicator of dairy products. Getting enough vitamin D through proper
health. Respiratory diseases that result in chronic low blood nutrition is important for homeostasis. Vitamin D is important
oxygen levels can cause clubbed fingertips and cyanosis. With for the absorption of calcium from the diet into the blood-
clubbed fingertips, the fingertips widen and the nails become stream. Calcium is needed for bone development and
more convex. In cyanosis (a bluish skin condition), the nail maintenance. You will revisit this topic in the skeletal system
beds may appear blue if there is low blood oxygen circulating chapter.
to the nail bed.
Physiology of the Integumentary System Temperature Regulation
Now find a pen and draw four dots on the posterior surface of Let’s get back to Nick and Kate’s workout. They are outside
your hand to represent the corners of a square inch. running on a cool, sunny morning. If it is very cool out, their
skin may get paler as the APR dermal blood vessels constrict
This 1 square inch of skin you have on your own hand is to preserve heat for the body’s core. As they continue to run,
typically composed of their muscles generate heat and they will notice that their skin
● 20 blood vessels is becoming redder. The dermal blood vessels are now
● 65 hairs and arrector pili muscles dilating and increasing blood flow to the skin, which gives it
● 78 nerve endings for heat more color. The increased blood flow radiates off some of the
● 13 nerve endings for cold excess heat to keep the body’s core from getting too warm. If
● 160 to 165 sensors for pressure this effort is not sufficient to remove the excess
● 100 sebaceous glands Heat, the brain will trigger sweating. In sweating, fluid (not
● 650 sweat glands blood cells) leaks from the dilated blood vessels. Sweat glands
● 19.500.000 cells take in this fluid, process it, and deliver it to the skin’s surface
as sweat to start evaporative cooling. This further reduces
body temperature. The scenario just described is an important
All of these structures work together to accomplish the homeostasis example of negative feedback temperature
functions outlined in the following paragraphs. regulation. The body becomes too warm, so blood vessels
dilate and sweat glands produce sweat to cool the body down
Functions of Skin to a normal temperature. Another example of negative
Your skin has several necessary and important functions. feedback concerning core body temperature
These functions include Occurs in freezing conditions. In this case, you may see the
● Protection skin first redden as blood vessels dilate in the dermis to warm
● Vitamin D production the skin and prevent it from freezing.
● Temperature regulation
● Sensation If, however, this process draws too much heat from the
● Nonverbal communication body's core (heart, lungs, and other organs), the dermal
● Water retention blood vessels will constrict to preserve the heat for the
core and thus preserve life. Frostbite of the skin may
Protection Skin is the body’s first line of defense against the
then occur.
foreign pathogens. Anything that comes in contact with may
be a source of potential pathogens. The dead, cornified
stratum corneum of the skin makes entry for bacteria difficult. Sensation
The skin’s surface is also dry, with an acidic pH, making it an During the run, the nerve endings in the stratum basale
unfriendly place for bacteria to grow. Dendritic cells of the and dermis of the skin constantly send the brain
epidermis stand guard if any pathogens try to make it past the messages. We sense the cool temperature from the cold
stratum corneum. receptors in their dermis. We will feel the sun on their
faces from the heat receptors and feel the presence of
Remember that the skin protects the body in other ways too. their clothing and shoes from the pressure sensors. We
The sun’s ultraviolet (UV) rays can damage the skin cells’ will even detect the ant crawling on his leg as it disturbs
DNA. Some stratum basale cells are actively going through the leg hair, activating the sensors wrapped around his
mitosis every day to make new epidermis. Any damage to the
hair follicles. If we stumble and falls, pain receptors will
DNA of those cells would be carried to future generations of
cells. The stratum basale’s melanocytes react to UV exposure alert her to any skin injury.
by producing more melanin. This melanin is then carried
toward the skin’s surface by the keratinocytes. Melanin Nonverbal Communication
protects underlying cells from the potential damage of UV Aside from the skin's fluctuating temperature or any
light. The skin exposed to the sun will begin to darken. minor injury sustained from a fall while out running, it is
crucial to note that the condition of their skin and their wound's clot. In the meantime, stratum basale cells are
hair sends nonverbal messages to anyone seeing them. actively dividing. They normally divide and push the
We may blush if we are embarrassed by something we older cells toward the surface to form epidermis.
have done, or our face may become pale if we are But if they are not in contact with other stratum basale cells,
frightened. Even the color, texture, silkiness, and other the keratinocytes will divide and push cells laterally toward
qualities of the skin and hair can all be indicative of other stratum basale cells until the edges of stratum basale
overall health. Billion-dollar industries in hair care, skin come in contact with each other again. This is called contact
inhibition. Once these edges are joined, the keratinocytes
care, and cosmetics have been developed to help convey
resume the cornification process described earlier to form new
positive messages to one's self and others to ensure epidermis. The type of healing is determined by who wins the
social acceptance. So it is quite likely that we would race.
want to freshen up their appearance after their run. 4. It all depends on whether the keratinocytes reach contact
inhibition before the fibroblasts can fill the wound with so
Water Retention much collagen that keratinocytes are prevented from meeting.
Taking a bath after the run brings us to the last of the If the stratum basale wins, the wound heals by regeneration
skin's functions: water retention. In this case, let's and normal function results from the new epidermis. If the
assume Kate is going to have a bath. As you know, our fibroblasts win, the wound heals by fibrosis. The scar tissue
body is made up of trillions of cells. You learned in cannot accomplish the same functions as normal epidermis. A
Chapter 2 that a cell will swell through osmosis if placed key factor in who wins the race is how far apart the edges are.
in a hypotonic solution. Yet nothing happens to our
Disease Point
cells when we immerses our body in a tub of bathwater A possible complication of wound healing can be keloid
(a hypotonic solution). As we relaxes in the tub, our formation. A keloid is a raised scar that extends beyond the
body does not swell and her cells do not gain weight. margins of the wound. Keloids are generally hyperpigmented
The skin's epidermis waterproofs the body by keeping or pink in color. A keloid is formed by an overgrowth of scar
water from the environment out and body fluids in. (One tissue. Keloid formation is more common in African
of the major dangers in severe burns is fluid loss when Americans. There are a variety of treatments for keloids, such
the epidermis is completely destroyed.) If we stay in the as corticosteroid injections, surgical excision, laser treatment,
bathwater long enough, we may notice that cryotherapy (freezing the keloid with liquid nitrogen), and
the skin on our fingers and toes becomes wrinkly, like a radiation These treatments may not completely remove the
keloid but can improve the appearance of the keloid by
raisin. Why? Our fingers and toes are the areas of the
flattening it and changing the color.
skin most likely to have abrasions to the epidermis
through everyday activities. The abrasions allow some Burns
water to pass through the epidermis, causing swelling in Burns are a common skin injury. Just think how easy it is to
the underlying tissues. The wrinkling she sees while burn a finger while lighting a candle or how quickly you can
bathing is the swelling of these underlying cells going lose track of time while out in the summer sun without
through osmosis. sunscreen. Burns can be categorized in three degrees by the
skin layers involved.
Injuries to the Skin These categories are described here and shown in
Skin can be damaged by all sorts of injuries, including First-degree burns are the most common burns. Sunburns
cuts, punctures, and burns. These injuries can happen in are often first-degree burns. They involve only the skin’s
epidermis. Symptoms are redness, pain, and
everyday life and are not necessarily from a disease
Swelling. New epidermis will be made by the stratum basale.
process. Let's look at how the physiology of the skin Second-degree burns, sometimes called partial-thickness
works so the skin can repair itself. burns, involve the epidermis and dermis. Symptoms are
redness, pain, swelling, and blisters. New epidermis will be
Regeneration versus Fibrosis made from the stratum basale cells at the burn’s edges and the
Wounds to the skin can heal by regeneration or stratum basale of the hair follicles growing toward each other
fibrosis. until contact inhibition is achieved. Normal epidermis
❖ In regeneration, the wound is healed with the same production then proceeds.
Third-degree burns, sometimes called full-thickness burns,
tissue that was damaged and normal function is returned.
are the most serious burns. They involve the epidermis,
❖ In fibrosis, the wound is healed with scar tissue and dermis, and hypodermis. The symptoms are charring and no
normal function is not returned. pain. There is no pain at the site of a third-degree burn
because all of the nerve endings have been destroyed in the
Consider a cut to the skin that goes into the dermis dermis. However, there is pain in the second- and first-degree
What happens to heal the wound? burns that typically surround the third-degree burn. The size
1. Cutting into the dermis means severing blood vessels, of this type of burn is crucial to healing. Because the dermis
so the wound bleeds and then clots. has been completely destroyed, the third-degree burn site has
2. A scab forms and pulls the edges of the wound closer no hair follicles. Therefore, there is no additional stratum
basale of the hair follicles available to help heal the burn. The
together as it dries. This is called wound contracture.
only stratum basale left is at the burn’s edges. Skin grafting
3. A race begins between the dermis's fibroblasts and the may be necessary if the stratum basale’s edges are too far
stratum basale's keratinocytes. The fibroblasts' collagen apart. The danger with a third-degree burn is infection and
fibers produce granulation tissue to fill in the fluid loss.
 ❖ Skin biopsy
Clinical Point ❖ The removal of a piece of tissue or a sample of cells from a
The treatment options and chance for recovery mav be body so that it can be analyzed in a laboratory
determined by the severity and extent of a burn. You have just ❖ Skin scraping
read about the severity of burns categorized by degree. The ❖ The taking of skin cell scrapings so that the cells can be
extent of a burn can be determined by applying the “rule of viewed under a microscope
nines”: The body is divided into ❖ Wood’s light
11 areas, each of which represents approximately 9% of the ❖ The use of a black light to view pigment changes in the
body’s surface area—with the exception of the genital area, skin
which is 1% of the body’s surface area.
Integumentary System Disorders
Effects of Aging on the Integumentary System Skin disorders may or may not have anything to do with
Skin changes with age. The epidermis becomes dry due to the aging. There are many types of skin disorders, and in the
loss of some of the sebaceous and sweat glands in the dermis. following paragraphs you will learn about two: skin cancers
Also, reductions in estrogen and testosterone slow the and skin infections.
production of sebum from the existing sebaceous glands.
Skin Cancer
Some melanocytes in the epidermis are also lost, while others Skin cancer is the most common type of cancer. Although
begin to overproduce melanin. The result is uneven tanning cancer has many causes, skin cancer is usually associated with
and age spots. Age spots are flat, brown spots produced by sun exposure and it is more common in older, light-skinned
melanocytes, sometimes called liver spots.” They have people. The amount of exposure is cumulative with age.
nothing to do with the liver, but they are colored like the liver. Light-skinned people have less melanin present to protect
They typically occur on sun-exposed skin surfaces. Over time, them from the sun’s UV rays. The follow ing list explains the
the dermis thins and the number of collagen and elastic fibers three forms of skin cancer and will help you see how they
is reduced. This, together with gravity, causes the skin to sag differ.
and wrinkle. Blood vessels become more fragile and respond
less quickly to temperature regulation. Combined with the ❖ Basal cell carcinoma is the most common form of skin
decrease in dermis sweat glands and the reduction in cancer. It starts in stratum basale cells and first appears as a
hypodermis adipose tissue, all of this makes temperature small, shiny bump on the face, hands, ears, and neck. As it
regulation much more difficult.The thinning of the progresses, it develops a central depression and a pearly edge.
hypodermis also reduces the cushioning layer between the It rarely metastasizes.
skin and underlying tissues. Bumps resulting in bruises
become more frequent and apparent. In older persons, the skin ❖ Squamous cell carcinoma starts from keratinocytes in the
over bony prominences may become necrotic (the tissue dies) stratum spinosum. First appearing as a red, scaly patch that
if the individuals remain in the same position for too long. develops a central crust, it commonly forms on the face,
This can cause pressure ulcers or bedsores. hands, ears, and neck. If detected early, it can be surgically
Nails are also affected by aging. The nail plate and nail matrix removed. Unlike basal cell carcinoma, this form of skin
thin with age. The thinning of the nail matrix is visible with cancer can metastasize.
the loss of the lunule. Nail fractures become
More common as the nail body thins. Toenails may thicken ❖ Malignant melanoma is the rarest but deadliest form of
and yellow due to fungal infections, which the body is less skin cancer.
prepared to fight.
It metastasizes easily and can occur anywhere on the body. It
Hair, too, is affected by aging. Terminal hairs on the ears, starts with melanocytes, usually in a pre-existing mole.
nose, and chin become coarser. The loss of hair follicle Malignant melanoma may be seen as a dark spot under a nail
melanocytes causes hair to go gray. Because hair does not or as a mole that is asymmetrical and has uneven color and
replace itself as rapidly in later years, the hair on the scalp scalloped borders.
becomes thinner. It also becomes drier, as the hair follicle has
a reduced number of sebaceous glands. Clinical Point
A change in the number, size, or shape of moles or other
Disease Point highly pigmented areas of the
Onychomycosis (tine unguium) is a fungal infection of the Skin can be evaluated through the ABCDEs of skin cancer:
nails. Onychomycosis can develop causes nails to thicken and ❖ Asymmetry. One half does not match the other half.
become discolored. While anyone onychomycosis, this ❖ Border irregularity. The edges are ragged or blurred.
condition often affects older people due to reduced blood flow ❖ Color. More than one color is present, and the color is
and slower-growing nails. uneven.
Onychomycosis is usually treated by oral antifungal drugs, ❖ Diameter. The growth of a mole is in excess of 6
medicated nail polish, or an antifungal nail cream. These millimeters.
medications can be used in combination with each other to ❖ Evolving. The mole looks different from other moles or is
relieve the symptoms of the infection. Even if onychomycosis changing in size, shape, and color
Is successfully treated, it is common for a repeat infection to
occur Clinical Point
A biopsy is often used to diagnose skin cancers. This common
Diagnostic Tests for Integumentary System Disorders diagnostic procedure involves excising or removing an area of
Common Diagnostic Tests Used for Skin Disorders skin that the health care provider may suspect is cancerous or
Diagnostic Test
that may appear suspicious. The excised skin is viewed under HSV-1 causes viral herpes infections seen on the lips or
a microscope to determine whether cancer is present. mouth
HSV-2 causes viral herpes infection on the genitals. Both
Clinical Point HSV-1 and HSV-2 are extremely contagious and can be
In the 1930s, Dr. Fredrick Mohs developed what is now spread through direct contact of the infected area, even when
known as Mohs micrographic surgery for the treatment of skin there is no active infection present. There is no cure for HSV,
cancer. Treatment of skin cancer involves excising the but antiviral therapy can help slow the duration and the
cancerous tissue. With Mohs micrographic surgery, the frequency of the outbreaks.
surgeon removes thin layers
Of tissue and looks at them under a microscope. Each layer is ❖ Herpes varicella-zoster virus, another type of herpes
examined for cancerous cells. When the surgeon obtains a infection, causes chicken pox in children and shingles in
layer that is free of cancerous cells, the excision is complete. adults:
The advantages of Mohs micrographic surgery are ● Chicken pox is a common childhood disorder characterized
preservation of healthy tissue and precise removal of all by red, itchy, fluid-filled vesicles or pox that appear on the
cancerous tissue, even malignant cells that cannot be seen skin. The rash is also accompanied by fever, headache, and
with the naked eye. malaise. Chicken pox is contagious and can be contracted
through direct or indirect contact. The chicken pox vaccine
Skin Infections helps prevent or lessen the severity of the illness. It is
Unlike skin cancers, skin infections can stem from an recommended that children receive this vaccine at 1 year of
assortment of bacterial, viral, and fungal infections. In the age. There is no cure for chicken pox; most treatments are
following paragraphs, we discuss one or more representatives geared toward making the patient comfortable.
of each type of skin infection.
Bacterial Skin Infections ● Shingles occurs in adults and is similar in appearance to
Several common bacterial infections are described in the chicken pox. It is characterized by, small, painful vesicles that
following list: usually follow a path along an area of skin supplied by a
❖ Impetigo is an infectious skin disease caused by the spinal nerve.
bacterium Staphylococcus or Streptococcus. Impetigo appears ● Shingles usually occurs in older individuals or in
as a cluster of vesicles, which are fluid-filled blisters that burst patientswho are immunocompromised. With shingles, the
and crust over. Pain and itching may be associated with the herpes virus has remained dormant in the patient’s body from
vesicles, and scratching them will cause them to spread to the time that the person first contracted it. \
other areas of the skin. Risk factors involved in contracting ● Shingles occurs in adults who have had chicken pox in the
impetigo include a possible break in the skin, moist past. When a patient presents with shingles, the herpes virus
environment of the skin, poor hygiene, and the existence of has been reactivated. Although there is no treatment for
the Staphylocoecus bacterium in the nose. Impetigo is usually shingles, pain medications are often used to treat the severe
treated with either oral or topical antibiotics or a combination pain associated with the disease and antiviral medications can
of both. be helpful in speeding up the recovery process.
❖ Cellulitis is an infection of the skin’s dermis or
hypodermis and is frequently caused by Streptococcus or Fungal Skin Infections
Staphylococcus bacteria. Cellulitis commonly occurs on the Common fungal infection of the skin:
face and lower legs, characterized by redness and swelling of
an area of the skin that increases in size rapidly. The infected Tinea infections are caused by a fungus. Contact with an
area has a tight, glossy appearance and is tender or painful. infected person, damp surfaces such as shower floors or pool
Cellulitis is also accompanied by other signs of infection, such decks, or even pets can transmit the fungus.
as fever, chills, and muscle aches. Cellulitis can be serious and Examples of tinea fungal infections include ringworm,
even deadly. It is treated with antibiotics. Viral Skin athlete’s foot, and jock itch.
Infections
Ringworm is a circular rash that clears from the center,
These infections, including several types of herpes viral Giving it a ringlike appearance. It is a fungal infection and has
infections, are described in the following list: nothing to do with worms.
❖ Warts are growths caused by an infection of the skin Athlete’s foot causes burning, itching, and cracking of the
produced by the human papillomavirus (HPV). skin between the toes.
Types of warts include common warts (found most often on Jock itch causes an itchy, burning rash in the groin region.
the fingers), plantar warts (found on the soles of the feet), Tine infections are treated with fungicides.
genital warts (which are sexually transmitted, and flat warts
(found on frequently shaved surfaces). Parasitic Skin Infections
Warts that appear in children often go away as the immune Following is a description of a parasitic skin infection:
system develops to fight them, but they may also be removed Scabies is a parasitic infection of the skin caused by an
by freezing. infestation of mites. Scabies causes small red bumps on the
skin that itch severely. The rash and itching result from the
❖ Herpes simplex virus (HSV) has two forms: HSV-1 and burrowing of the mite into the skin and the deposit and
HSV-2. This virus is characterized by small, painful blisters hatching of eggs, which causes an allergic reaction. Scabies is
that appear on the skin and on the mucous membranes of the very contagious and can spread from direct or indirect contact.
mouth or genitals. Although these blisters eventually subside, A topical ointment can be applied to the skin to kill the mites.
the virus remains dormant in the body for life.
Other Common Skin Disorders
In addition to understanding the skin disorders you have ability of the immune system to assist in healing, can make
already reviewed in this chapter, you should be familiar with recovery very difficult. Treatment of decubitus ulcers includes
some of the other common skin disorders that you will likely reduction of pressure to the site of the ulcer, wound care,
encounter as a health care provider. These skin disorders management of any pain or infection associated with the
include psoriasis, dermatitis, decubitus ulcers, hives, and ulcer, and sometimes surgery.
scleroderma.

❖ Psoriasis This is a common skin disease characterized by Hives This skin condition, also known as urticaria, is a skin
the overgrowth of skin cells and improper keratinization of the reaction that can be caused by insect bites or by contact with
epidermis and nails. Psoriasis is a hereditary autoimmune substances that cause an allergic reaction, such as certain
disorder that runs in families. The immune system is triggered foods or drugs. Symptoms of hives include raised areas of the
to cause an inflammatory response in the epidermis and skin, redness, and itching. Hives usually resolves without any
dermis, accompanied by overproduction of keratinocytes. treatment, but in some cases antihistamines and
Psoriasis causes red, irritated skin that appears thick and flaky. corticosteroids may
Scales (silvery white patches) can also be seen on the skin. Be recommended to reduce itching and swelling.
The nails may appear to have white spots, pitting, ridges, and
scaling as well. A variety of treatments can be used to help A Scleroderma
with the symptoms associated with psoriasis, such as topical This disease involves the accumulation of excess connective
creams and immunosuppressive drugs. tissue in the skin and various organs. It is characterized by
increased collagen production in
Antibiotics can also be used to treat any secondary skin These connective tissues. The excess collagen works to
infections that might occur. harden the skin and organs, decreasing their elasticity and
therefore decreasing their ability to function. Scleroderma can
❖ Dermatitis characterized by inflammation of the skin and be caused by exposure to certain chemicals or can be
may also show symptoms of redness, swelling, oozing, associated with auto-immune diseases such as lupus and
crusting, scaling, pimples or vesicles, and itching. There are polymyositis. Signs and symptoms of scleroderma can include
various types of dermatitis, but the two most common types skin discoloration, skin thickening and hardening, hair loss,
are contact dermatitis and atopic dermatitis (eczema): ulcers on fingertips and toes, and tight skin on the face.
Additional symptoms can occur if the disease is systemic,
Contact dermatitis is inflammation of the skin caused by affecting internal organs as well as the skin. Although there is
direct contact with a substance that can be categorized as currently no treatment for the disease, certain medications -
either à skin irritant or one that causes an allergic reaction. such as nonsteroidal anti-inflammatory drugs (NSAIDs),
These substances can vary greatly. The contact causes the skin corticosteroids, or immunosuppressants -are used to treat its
to become inflamed, red, and itchy; these symptoms are signs and symptoms.
localized to a specific area. The most important factor in
treating contact dermatitis is to have the patient avoid contact SKIN
with the substance that causes the reaction. • largest organ in our body
• Also known as the cutaneous membrane
Atopic dermatitis, also known as atopic eczema, is an • Has two main components:
allergic reaction that causes an infection. Atopic dermatitis or * Epidermis
eczema can show the same symptoms as contact dermatitis * Dermis
and can also cause the skin to have a leathery appearance and
be discolored. COMPONENTS OF THE SKIN
Atopic dermatitis is most common in children and Epidermis (epi-on top, dermis-skin)
Is typically outgrown by the teenage years. Treatment for • Keratinized stratified epithelium
atopic dermatitis includes avoiding anything that makes the Dermis
symptoms worse. This could include detergents, soaps, and • Loose connective tissue and dense irregular tissue
lotions or even various foods. Over-the-counter (OTC) Hypodermis (hypo-below)
antihistamines can help with the itching. If the disease is • Also known as "superficial fascia" or "subcutaneous tissue"
severe enough, the health care provider may prescribe • Anchors skin to the muscle
corticosteroids to help with inflammation, antibiotics to help • Loose connective tissue
with infection, and allergy shots to minimize the reaction to • Where medicines are administered via
the allergen. FUNCTIONS OF THE SKIN
Protection
❖ Decubitus Ulcers Another common skin disorder is The skin protects the body from mechanical trauma,
decubitus ulcers, also known as pressure ulcers or bedsores. pathogens, and environmental damage.
They are areas of necrotic or ulcerated tissue caused by the Excretion
pressure of a bony prominence in the body and another The skin excretes waste and impurities via sweat.
surface. Although these ulcers are usually seen in people with Vitamin D Synthesis
limited mobility, other risk factors such as age, poor or The skin synthesizes vitamin D when exposed to ultraviolet
inadequate nutrition, and existing diseases also play a role. radiation
Each body system is affected by aging, which causes a Thermoregulation
thinning of the hypodermis and decreased blood flow. This, The skin maintains a stable internal body temperature through
combined with limited mobility, can cause compressed tissues negative feedback loops.
to die off or become necrotic. Once the skin has been Sensation
damaged, further effects of aging, such as a decrease in the
The skin has sensory receptors that detect internal and • Sensory receptors that detect light touch, shapes, and
external environmental change such as heat, cold, and/or pain. textures
Keratinocytes (cytes-cells) • Also found in the fingertips, lips, and base of hair
• Make up 95% of cells in the epidermis Melanocytes (melan-black)
• Strengthens epidermis, makes it resistant to mechanical Found in the Stratum Basale
trauma • Produces melanin, a protein that gives pigment to skin
• Joined by desmosomes
• Arranged into "strata (layers)" Thick vs Thin Skin
Thick Skin
The Epidermis • Consists of all five layers of the epidermis with a thick
LAYERS OF EPIDERMIS Stratum Corneum
• Stratum Corneum • Equivalent to the size of a paper towel
• Stratum Lucidum • Lacks hair follicles
• Stratum Granulosum • Contains sweat glands
• Stratum Spinosum • Found in palms of hands and soles of feet
• Stratum Basale • Subject to lots of mechanical stress

Stratum Corneum Thin Skin

• Most superficial layer of the epidermis • Consists of only four layers of the epidermis, lacking the
• Several layers of dead, flattened keratinocytes Stratum Lucidum
• Sheds dead keratinocytes • Equivalent to the size of a sheet of printing paper
• Has hair follicles
Stratum Lucidum • Subject to less mechanical stress
• Deep to the Stratum When exposed to extra pressure, both thick and thin skin will
Corneum develop extra layers of the Stratum Corneum. This will result
• Found in thick skin in a callus
• Clear layer of dead keratinocytes

Stratum Granulosum The Dermis

• Middle layer of the epidermis • Houses blood supply
• Named for prominent granules • Anchors epidermis in place
• 3-5 rows of cells • Two layers:
• Excretes a lipid-based substance * Papillary Layer
* Reticular Layer
Stratum Spinosum (spino-prickly)
• Deep to the Stratum Basale
• Thickest stratum of the epidermis Papillary Layer
• Named due to its spiky appearing cells • Most superficial layer of the dermis
• Cells are metabolically active • Consists of loose connective tissue
• Undergo mitosis • Collagen fibers anchor dermis and epidermis together
• Help to synthesize vitamin D • Dermal Papillae:
* Found on the surface of the papillary layer
Stratum Basale (basal-bottom) * Houses tiny blood vessels called capillaries
• The deepest layer of the epidermis * Houses sensory receptors called Tactile (Meissner)
• Consists of a single layer of stem cells corpuscles
• Richest supply of blood
• Most metabolically active Reticular Layer
• Undergo mitosis • Deepest and thickest layer of the dermis
• Also known as "Stratum Germinativum (germinating)" • Consists of dense irregular connective tissue
• Helps to synthesize vitamin D • Collagen fibers that strengthen the dermis
• Elastic fibers that allow skin to revert after stretching
Keratinocyte Life Cycle • Proteoglycans that hydrate the skin
• Begins in the Stratum Spinosum • Blood vessels and accessory structures (hair, sweat glands,
• Sheds in the Stratum Corneum sebaceous glands)
• Can shed from environmental and physical stress • Sensory receptors, such as Pacinian (lamellated) corpuscles
• Shed cells are replaced by mitosis that respond to changes in pressure and vibration
• Cells primarily divide at night
Skin Markings
OTHER CELLS OF THE EPIDERMIS Interactions between the dermis and epidermis are shown on
Dendritic (Langerhans) Cells the skin as small lines called "skin markings".
• Found in the Stratum Spinosum Thick collagen fibers arrange the dermal papillae into dermal
• Phagocytes of the immune system ridges.
• Protects the skin and underlying tissue from pathogens The epidermis will blend in with the dermal papillae that lies
Merkel Cells underneath, creating epidermal ridges. Epidermal ridges
• Oval cells found in the Stratum Basale function to increases gripping ability of hands and feet.
Tiny sweat pores open along the ridges to form a thin film • Hair Matrix - Structure at the base of hair bulb that
called a fingerprint. produces new hairs via mitosis.
Gaps found in between bundles of collagen will indent to • Hair Follicle - Unfolding surrounding the hair root.
form cleavage lines, also known as tension lines. • Epithelial Root Sheath - Has two parts:
As the reticular layer tightly fixes to deeper structures of the * Outer component: Anchors hair follicle to the dermis.
skin, this creates a deep crease called a flexure line. * Inner component: Anchors tightly to the root.
• Dermal Root Sheath - Supports the hair follicle and
Skin Pigmentation separates it from the dermis.
Melanin ranges in colors of orange-red to black. Melanin is • Arrector Pili Muscles - Tiny bands of smooth muscle that
produced by melanocytes in the stratum basale It is composed causes hairs to stand up when they contract, this is known as
of two "tyrosine" amino acids that are joined by the enzyme piloerection. Piloerection occurs when we are cold or
"tyrosinase". More melanin is synthesized when exposed to frightened. giving the skin what we know as "goosebumps".
UV radiation (tanning).
Structures of the Hair
Melanin functions to: One strand of hair has 3 regions:
• Protect keratinocytes from mutating due to UV exposure. Inner Medulla
• Prevent the skin from synthesizing too much Vitamin D in • Found in thick hairs only
response to radiation. • Contains soft keratin
Middle Cortex
• Highly structured with several layers
Melanin can be unevenly distributed throughout the skin: • Contains hard keratin
• Moles are produced when a high amount of melanocytes are Outer Cuticle
proliferated in one spot. • Most superficial layer
• Freckles are are produced when pigment is concentrated in • Single layer of hard keratinocytes that overlap
one spot from a high amount of melanin production.
• Albinism is when melanocytes fail to produce the tyrosinase Hair Growth
enzyme. This lack of skin pigmentation can increase the risk Hair growth averages about 1-1.5 cm per month, but can vary
of DNA damage of keratinocytes. amongst individuals.
Hair growth occurs through a two-stage cycle:
Other Pigments That Affect Skin Color 1. Growth Stage
There are two other pigments that contribute to skin color, a. Mitosis occurs in the matrix of the root
carotene and hemoglobin. b. As cells divide, cells above are pushed upward from blood
Carotene: supply
• Gives yellow-orange pigment c. Cells keratinize and die
• Lipid-soluble molecule 2. Resting Stage
• Usually ingested in diet from yellow and orange foods a. Cells in matrix stop dividing and begin to die
• Accumulates in stratum corneum b. The follicle shortens
Hemoglobin: c. Hair is pushed upward and remains dormant for a few
• Gives skin a pinkish hue months
• Protein found in red blood cells that binds and transports
oxygen Age, environment, diet, and genetics can all impact the rate at
• Turns a bright-orange red color when oxidized which hair grows.
When hair begins to fall out faster than it grows (which leads
Accessory Structures to thinning), this is a condition called Alopecia.
Hair or pili, are filamentous structures that project from the
skin's (thin skin) surface. Hair in different areas of the body Hair Pigment & Texture
all carry out different protective functions, for example:
• Eyelashes & eyebrows keep foreign objects out of the eyes Lanugo is a type of thin hair that has no pigment. It grows on
• Nose hairs prevents the inhalation of insects and harmful the skin of a fetus, and usually falls out by the time the baby is
particles born. It is then replaced by either terminal hair, or vellus hair.
• Hair on the head protects the body from UV radiation and Vellus hair is thinner than terminal hair, and is
mechanical nonpigmented. It is found around various places of the body.
trauma Terminal hair is thick, coarse, and pigmented. It is found on
Sensory neurons help the hair to detect environmental the scalp and around the eyes (eyelashes,eyebrows).
changes.
The pigment of hair is determined by melanin. Melanocytes in
Structures of the Hair the hair matrix interact with keratinocytes. As we age,
They are many structures that make up the hair, with the root melanocytes produce less melanin, and the hairs that are
and shaft being the main two: growing begin to lose pigment, causing white or grey hairs.
• Shaft - Part of the hair that projects from the surface of the
skin. Nails
• Root - Part of the hair that is embedded in the dermis of the Nails are hard structures located at the end of our digits that
skin. contain hard keratin. Nails function to protect our underlying
• Hair Papilla - Indentation at the base of the hair bulb that tissue and enable
contains blood vessels. gripping and manipulation. There are many structures of the
• Hair Bulb - Structure at the deep end of the hair follicle. nail that Structure of a Nail
help it to carry out its functions: Sudoriferous glands excrete their product by
merocrine(eorgans) secretion, which is a type of exocytosis.
•Nail plate - Part of the nail that rests on top of the epidermal Sebaceous glands secrete their product using holocrine
nail bed secretion, in which the secretory cell accumulates its product
•Nail bed - Deep to the nail plate, nourishes and protects the until rupture occurs.
nail.
•Nail body - Visible part of the nail. Pathology of the Skin
•Nail root - Lies under the skin. The most common type of skin pathology is a wound, a
•Nail matrix - Part of the nail with living, dividing cells. wound is any disruption of the skin's integrity. They may
Supplies oxygen to the nail, sight of nail growth. disrupt the epidermis, dermis, or deeper. There are different
•Proximal nail fold - Covers the edge of the root. kinds of wounds:
•Eponychium - Also known as the "cuticle", found at the base • Lacerations (cuts)
of the nail, protects matrix from infection. • Burns
•Nail folds - Overlapping of skin that borders the nail laterally • Skin cancers
and medially. Wound treatment can vary amongst severity. For instance, a
•Hyponychium - Skin that lies under the free edge of the nail. laceration may be treated with sutures (stitches), where as a
•Lunula - Crescent shaped area where keratin accumulates. burn may be treated with surgical repair.

Nail Growth Burns

Nail growth occurs in the matrix. On average, fingernails A burn is a skin wound caused by heat, extreme cold,
grow about 0.5 mm a week. Toenails on the other hand grow chemicals, and/or radiation. There are three classifications of
more slowly. burn wounds, all based on the extent of tissue damage.
One of the most common conditions of the nail is an "ingrown • First-degree burns: The most minor, also called
nail. Ingrown nails usually occur in the toenail. This is a "superficial burns" because only the epidermis is damaged.
condition in which the nail grows into the tissue medial or Symptoms are erythema (redness) and minor pain. Usually
lateral to the nail. Symptoms include pain, inflammation, require no treatment, no blisters or permanent damage.
softening of the nail, and sometimes infection. An ingrown •Second-degree burns: Also called "partial thickness burns".
nail can be treated by the removal of the nail or by Damage is caused to the epidermis and either some or all of
administering chemicals to the matrix of the nail, to kill off the dermis. Symptoms are pain, blistering, scarring. Usually
the cells. require medical treatment.

Glands • Third-degree burns: Most damaging, also known as "full

The skin has two main types of glands, sudoriferous glands thickness burns". Damages the epidermis, dermis, and
that produce sweat, and sebaceous glands which produce hypodermis. Muscle and bone may also be damaged.
sebum (oil). Both are located in the dermis of the skin. Symptoms are severe scarring, lost of hair follicles, and
Sudoriferous (sweat) glands have four types: dehydration due to fluid loss. Swelling and infection may also
• Eccrine sweat glands: Released through sweat pores. occur. Treatment mar result in clin raftino
Produces sweat that contains antimicrobial compounds to
prevent the growth of pathogens. Also functions in Skin Cancer
thermoregulation. Cancer is a very common skin disease. It is caused due to
• Apocrine sweat glands: Sweat released into hair pores. mutations in the DNA that cause cells to lose control over
Only in certain parts of the body such as armpits, areolas, and their cell cycle. This can lead to tumors, which is a cluster of
the anal area. Sweat metabolized by bacteria which produces undifferentiated cells.
an odor.
• Ceruminous Glands: Secretes a thick fluid called cerumen Tumor cells can metastasize, or travel to other parts of the
(earwax) into hair follicles. Cerumen lines the ears and body, alter the structure of a tissue and prevent the tissue from
functions to lubricate the eardrum. Traps particles before they functioning properly. There are three common types of skin
reach the eardrum. cancers:
• Mammary Glands: Produces a sweat called milk. Milk
contains, proteins, lipids, sugars, and immune cells to nourish • Basal Cell Carcinoma: The most common type of skin
a newborn cancer, a cancer of keratinocytes in the stratum basale.
Usually found in skin that is frequently exposed to UV
Glands radiation. Forms a nodule with a central crater that develops
The skin has two main types of glands, sudoriferous glands into an ulcer. Can be completely treated by surgical removal.
that produce sweat, and sebaceous glands which produce
sebum (oil). Both are located in the dermis of the skin. • Squamous Cell Carcinoma: Second most common. A
Sebaceous glands are branched glands with clusters of small cancer of keratinocytes in the stratum spinosum. Most
ducts surrounded by secretory cells called named acini cells. commonly found on the head and neck. Forms scaly patches
These ducts empty a waxy oily liquid called sebum (oil) into that ulcerates or bleed. Can be surgically removed.
either a hair follicle or through a small pore. They function to
coat the skin and hair with moisture. • Malignant Melanoma: Most severe, cancer of melanocytes.
In sebaceous secretions, an acini cell will accumulate products More likely to metastasize due to the arms of cancerous cells.
such as dead cells and different types of lipids until it Arms of melanocytes allow cancerous cells to extend down to
ruptures. However, some bacteria can thrive in sebum, the blood vessels of the dermis and access cardiovascular &
causing something that we know as a "pimple" or a "bump". lymphatic system. Treatment can include surgical removal,
chemotherapy, and radiation therapy.
 3. Diabetes: a metabolic disorder
characterized by high blood sugar levels due to insufficient
Malignant Melanoma mole can be detected early on and is insulin production or resistance to insulin.
distinguishable from other skin cancers using the "ABCDE" 4. Adrenal insufficiency: a condition where
rule: the adrenal glands do not produce enough cortisol, leading to
• Asymmetrical shape: Both sides of the mole are uneven. fatigue, weight loss, and low blood pressure.
• Border irregularity: Mole has jagged edges or blurriness. 5. Polycystic ovary syndrome (PCOS): a
• Color: Mole is blue-black, or different colors. hormonal disorder in women, causing enlarged ovaries,
• Diameter: Mole is larger than 6mm or the size of a pencil irregular periods, and fertility issues.
eraser.
• Evolving: Mole is continuously changing in shape and size. Regional Terms

HAIR DISEASES There are many visible landmarks on the surface of the body.
Once you know their proper anatomical names, you can be
1. Alopecia areata: an autoimmune disease specific in referring to different regions of the body.
causing hair loss in patches.
2. Dandruff: a common scalp condition Anterior Body Landmarks
characterized by flaking and itching.
3. Tinea capitis: a fungal infection of the Look at Figure 1.5a to find the following body regions. Once
scalp causing hair loss and scaling. you have identified all the anterior body landmarks, cover the
4. Trichotillomania: a psychological disorder labels that describe what the structures are, and again go
where individuals compulsively pull out their hair. through the list, pointing out these areas on your own body.
5. Telogen effluvium: a condition where hair
prematurely enters the resting phase, leading to hair thinning Abdominal (ab-dom’i-nal): anterior body trunk inferior to ribs
and shedding. Acromial (ah-kro’me-ub): point of shoulder
Antecubital (an”te-ku’bi-tal): anterior surface of elbow
SKIN DISEASES Axillary (ak’si-lar’e): armpit
Brachial (bra’ke-al): arm
1. Acne: a skin condition characterized by Buccal (buk’al): cheek area
clogged pores, pimples, and inflammation. Carpal (kar’pal): wrist
2. Eczema: a chronic inflammatory skin Cervical (ser’vi-kal): neck region
condition causing itchy, red, and dry patches. Coxal (kox’al). hip
3. Psoriasis: an autoimmune disease causing Crural (kroo’ral): leg
rapid skin cell growth, resulting in thick, red, and scaly Digital (dif’1-tal): fingers, toes
patches. Femoral (fem’or-al): thigh
4. Rosacea: a chronic condition causing facial Fibular (fib’u-lar): lateral part of leg
redness, flushing, and small visible blood vessels. Inguinal (in ‘gwi-nal: area where thigh meets body trunk;
5. Athlete’s foot: a fungal infection causing groin
itching, peeling, and cracking of the skin on the feet. Nasal (na’ zul): nose area
Oral (o’ral): mouth
NAIL DISEASES Orbital (or’bi-tal): eye area
Patellar (pah-tel’er): anterior knee
1. Onychomycosis: a fungal infection of the Pelvic (pel’vik): area overlying the pelvis ante-riorly
nail causing discoloration, thickening, and crumbling. Pubic (pu’bik): genital region
2. Paronychia: an infection of the skin around Sternal (ster’nul): breastbone area
the nail, causing redness, swelling, and pain. Tarsal (tar’sal): ankle region
3. Ingrown toenail: a condition where the Thoracic (tho-ras’ik): chest umbilical (um-bil’i-kal): navel
edge of the nail grows into the surrounding skin, leading to
pain and inflammation. Posterior Body Landmarks
4. Beau’s lines: horizontal depressions or
grooves in the nails due to temporary disruption of nail Identify the following body regions in Figure 1.5b, and then
growth. locate them on yourself without referring to this book.
5. Nail psoriasis: a condition where psoriasis
affects the nails, causing pitting, discoloration, and separation Calcaneal (kal-ka’neul): heel of foot
from the nail bed. Cephalic (she-fa’lik): head
Deltoid (del’toyd: curve of shoulder formed by large deltoid
muscle
GLANDS DISEASES Femoral (fem’or-al): thigh
Gluteal (gloo’te-al): buttock
1. Hypothyroidism: a condition where the
thyroid gland does not produce enough thyroid hormone,
leading to fatigue, weight gain, and depression.
2. Hyperthyroidism: a condition where the Lumbar (lum’bar): area of back between ribs and hips
thyroid gland produces excessive thyroid hormone, causing Occipital (ok-sip’i-tal): posterior surface of head
weight loss, rapid heartbeat, and anxiety. Olecranal (ol-eh-cra’nel) posterior surface of elbow
Popliteal (pop-lit’e-al): posterior knee area
Sacral (sa “krul): area between hips A body in the standard anatomical position looks like this:
Scapular (skap’u-lar): shoulder blade region The body is upright; the legs are close together; the feet
Sural (soo’ral): the posterior surface of lower leg, the calf are flat on the floor; the arms are close to the sides; and
Vertebral (ver’tê-bral): area of spine the head, toes, and palms of the hands are facing forward.
The plantar region, or the sole of the foot, actually on the
inferior body surface, is illustrated along with the posterior Anatomical Terms of Direction
body landmarks in Figure 1.5b. Once the standard anatomical position has been considered,
anatomical terms of direction are used to describe the
DIRECTIONAL TERMS following: the location of a particular structure in the body,
Directional terms used by medical personnel and anatomists the location of a structure relative to another structure, or the
allow them to explain exactly where one body structure is in location of something within a structure.
relation to an-other.
Anatomical Regions
ORIENTARION AND DIRECTIONAL TERMS The two major regions of the body are the axial region (head,
neck, and trunk) and the appendicular region (arms and
Superior (cranial or cephalad) legs). These regions are further subdivided.
Toward the head end or upper part of a structure or the body.
Above The abdominal region can be divided in either of two ways:
into four quadrants or into nine regions similar to a tic-tac-toe
Inferior (caudal) grid.
Away from the head end or toward the lower part of a
structure or the body; below The four quadrants are the;

Anterior (ventral) − Right upper quadrant

Toward or at the front of the body; in front of
− Left upper quadrant
Posterior (dorsal)
Toward or at the backside of the body; behind − Right lower quadrant

Medial − Left lower quadrant

Toward or at the midline of the body; on the inner side of
ANATOMICAL TERMS OF DIRECTION
Lateral
Away from the midline of the body; on the outer side of Anterior or ventral – Front or belly side

Intermediate Posterior or dorsal – Back side

Between a more medial and a more lateral structure
Superior -Closer to the top of the head (used for head, neck,
Proximal and trunk)
Close to the origin of the body part or the point of attachment
of a limb to the body trunk Inferior – Farther from the top of the head (used for head,
neck, and trunk)
Distal
Farther from the origin of a body part or the point of Medial – Toward the midline of the body
attachment of a limb to the body trunk
Lateral – Away from the midline of the body
Superficial (external)
Toward or at the body surface Bilateral – Relating to or affecting two sides

Deep (internal) Proximal – Closer to the connection to the body

Away from the body surface;
More internal Distal – Farther from the connection to the body

Anatomy is the study of body structures, including structures Superficial – Closer to the surface (used for layered
of all sizes, from microscopic red blood cells to the heart, structures)
which is the size of a fist.
Deep – Farther from the surface (used for layered structures)
Physiology is the study of exactly how all of these structures
function. Right – On the body’s right side (not the viewer’s right side)

Pathology is study of what causes disease and disease’s Left – On the body’s left side (not the viewer’s left side)
specific effects on biological tissues and fluids.

ANATOMICAL REGIONS

Standard anatomical position Axial – Head, neck, and trunk

Abdominal – Belly Supine – Anterior surface facing up
Axillary – Armpit Prone – Anterior surface facing down
Cephalic or cranial – Head
Cervical – Neck
Facial – Face
Inguinal – Groin ANATOMICAL CAVITIES
Pelvic – Lower end of the trunk Most of the body’s organs are located in cavities, which are
Thoracic – Chest pocket like spaces of various sizes.
Umbilical – Navel
THREE GENERAL CAVITIES
Appendicular – Arms and legs
Brachial – Arm  the dorsal cavity
Carpal – Wrist  the thoracic cavity
Cubital – Elbow  the abdominopelvic cavity—that can be further
Femoral – Thigh subdivided.
Palmar – Palms of the hands
Patellar – Knee − There is no wall dividing the cranial and vertebral
Plantar – Soles of the feet cavities.
Tarsal – Ankle
− There is also no wall separating the pleural and
NINE REGIONS OF THE ABDOMEN pericardial cavities or the abdominal from the pelvic
− Right hypochondriac region cavity.

− Epigastric region − The diaphragm, however, serves as a wall separating

the thoracic cavity from the abdominopelvic cavity.
− Left hypochondriac region
− The space between the pleural cavities that contains
− Right lumbar region the heart, esophagus, trachea, thymus, and major
vessels is called the mediastinum (MEE-dee-ass-TIE-
− Umbilical region num). Again, see Figure 1.8 for the locations of these
cavities in the body.
− Left lumbar region
− The cavities are in relation to the organs they house,
− Right inguinal region it is important to note that these cavities are lined
with membranes.
− Hypogastric region
− The cranial and vertebral cavities are lined by the
− Left inguinal region. meninges (meh-NIN-jeez)-three layers of membrane
surrounding the brain and spinal cord. You will learn
more about the meninges in the nervous system
chapter.
Anatomical Planes
In order to view the location of structures from different − The thoracic and abdominopelvic cavities contain
angles, the body may be cut along anatomical planes fluid-filled serous membranes. (SEER-us), which
line the cavities and surround the organs.
Anatomical Positions
Anatomical terms may also be used to describe body position,
such as standard anatomical position.
Anatomical Cavities
Prone and supine are terms that may be used to describe the
position of either the entire body or individual parts Cavity – Associated Organs – Lining Membrane

Anatomical Planes Dorsal:

Sagittal (SAJ-ih-tal) − Cranial cavity – Brain – Meninges

Separates right from left. If the plane is exactly down the
midline of the body, it is midsagittal. − Vertebral cavity – Spinal cord – Meninges

Transverse or horizontal Thoracic:

Separates top from bottom; commonly called a cross section
− Pleural cavities – Lungs – Pleurae
Frontal or coronal
Separates anterior from posterior (front from back) − Pericardial cavity – Heart – Pericardium

Anatomical Positions Abdominopelvic:

 − Abdominal cavity – Digestive organs, spleen – visceral portion of the peritoneum covers several, but
Peritoneum not all, of the organs in the abdominal cavity.

− Pelvic cavity – Urinary bladder, rectum, reproductive − The kidneys and most of the pancreas are
organs – Peritoneum retroperitoneal, meaning they are between the
parietal peritoneum and the posterior abdominal wall.

− The membrane starts at the posterior abdominal wall,

SEROUS MEMBRANES extends out and surrounds the section of small
intestine (this part of the membrane is the visceral
− Serous membranes are double-layered membranes peritoneum), and then returns parallel to itself to the
that contain fluid between the two layers. posterior wall before extending out again to surround
the next organ.
− A good analogy for a serous membrane is a very soft
water balloon. Body Planes and Sections

− You slowly push your fist into the balloon so that it When the section is made through the body wall or through an
does not break. organ, it is made along an imaginary line called a plane.

− Part of the water balloon will be in direct contact Since the body is three-dimensional, we can refer to three
with your fist, and part of the balloon will not. types of planes or sections that lie at right angles to one
another
− Water exists between the two layers. Your fist
represents the individual organ, while the layers of A sagittal (saj’i-tal) section is a cut made along the
the water balloon represent the layers of the serous lengthwise, or longitudinal, plane of he body, dividing the
membrane. body into right and left parts. If the cut is made down the
median plane of the body and the right and left parts are equal
− A serous membrane called the pleura surrounds each in size, it is called a midsagittal, or median, section.
of the lungs in the thoracic cavity just as the water
balloon surrounds your fist. A frontal section is a cut made along a lengthwise plane that
divides the body (or an or-gan) into anterior and posterior
− The part of the pleural membrane in direct contact parts. It is also called a coronal (ko-ro’nal) section.
with the lung is called the visceral pleura (VISS-er-al
PLUR-ah) A transverse section is a cut made along a horizontal plane,
dividing the body or organ into superior and inferior parts. It
− The part of the pleural membrane not in direct is also called a cross section.
contact with the lung is the parietal pleura (pah-RYE-
eh-tal PLUR-ah). Body Cavities

− Pleural fluid fills the space between the two layers. Dorsal Body Cavity

− The heart is surrounded by a similar serous The dorsal body cavity has two subdivisions, which are
membrane called the pericardium. continuous with each other.

− The cranial cavity is the space inside the bony skull.

The pericardium has two layers: The brain is well protected because it occupies the
cranial cavity.
− The visceral pericardium (in contact with the heart)
and − The spinal cavity extends from the cranial cavity
nearly to the end of the vertebral column. The spinal
− The parietal pericardium (not in contact with the cord, which is a continuation of the brain, is
heart). protected by the vertebrae, which surround the spinal
cavity.
− Pericardial fluid fills the space between these two
layers. Ventral Body Cavity

− The abdominopelvic cavity contains another serous The ventral body cavity is much larger than the dorsal cavity.
membrane called the peritoneum. It contains all the structures within the chest and abdomen,
that is, the visceral organs.
− This double-layered serous membrane has many
abdominal organs pushed into it from the posterior DIGESTIVE SYSTEM
wall of the abdominopelvic cavity.
The food you eat takes an incredible journey through your
− The parietal portion of the peritoneum lines the body, from top (your mouth) to bottom (your anus).
anterior wall of the abdominopelvic cavity, while the
Along the way the beneficial parts of your food are absorbed, After you start eating, you chew your food into pieces that are
giving you energy and nutrients. Here’s a step-by-step account More easily digested.
of the digestive system’s workings. Your saliva mixes with the food to begin to break it down into
a form your body can absorb and use.
What is the digestive system? When you swallow, your tongue passes the food into your
Your digestive system is a network of organs that help you throat and into your esophagus.
digest and absorb nutrition from your food.
It includes your gastrointestinal (GI) tract and your biliary Esophagus
svstem. Located in our throat near vour trachea (windpipe) the
Gl tract is a series of hollow organs that are all connected to esophagus receives food from your mouth when you swallow
each other, leading from your mouth to your anus. The epiglottis is a small flan that folds over vour windpipe as
Biliary system is a network of three organs that deliver bile you swallow to prevent you from choking (when food goes
and enzymes through to your Gl tract your bile ducts into your windpipe)
A series of muscular contractions within the esophagus called
Gastrointestinal (GI) tract peristalsis delivers food to your stomach.
The organs that make up your GI tract, in the order that they But first a ring-like muscle at the bottom of vour esophagus
are connected, include your; called the lower esophageal sphincter has to relax to let the
Mouth food in.
Esophagus The sphincter then contracts and prevents the contents of the
Stomach stomach from flowing back into the esophagus. When it
Small doesn’t and these contents flow hack into the esophagus, you
Intestine may experience acid reflux or heartburn)
Large intestine
Anus. Stomach
The stomach is a hollow organ, or “container,” that holds food
Biliary system while it is being mixed with stomach enzymes.
Biliary system includes your ; These enzymes continue the process of breaking down food
Liver into a usable form.
Gallbladder Cells in the lining of your stomach secrete a strong acid and
Pancreas powerful enzvmes that are responsible for the breakdown
Bile ducts process.
When the contents of the stomach are processed enough,
What does the digestive system do? they’re released into the small intestine
Your digestive system is uniquely constructed to do its job of
turning your food into the nutrients and energy you need to Small intestine
survive. And when it’s done with that, it handily packages Made up of three segments
your solid waste, or stool, for disposal when you have a bowel Duodenum
movement. Jejunum
Ileum
Why is digestion important? The small intestine is a 22-foot long muscular tube that breaks
Digestion is important because your body needs nutrients down food using enzymes released by the pancreas and bile
from the food you eat and the liquids you drink in order to from the liver.
stay healthy and function properly. Peristalsis also works in this organ, moving food through and
Nutrients include carbohydrates, proteins, fats, vitamins, mixing it with digestive juices from the pancreas and liver
minerals and water. The duodenum is the first segment of the small intestine. It’s
Your digestive system breaks down and absorbs nutrients largely responsible for the continuous breaking-down process.
from the food and liquids you consume to use for important The jejunum and ileum lower in the intestine are mainly
things like energy, growth and repairing cells responsible for the absorption of nutrients into the
bloodstream
ANATOMY Contents of the small intestine start out semi-solid and end in
What organs make up the digestive system? a liquid form after passing through the organ.
The main organs that make up your digestive system are the Water, bile, enzymes and mucus contribute to the change in
organs known as your gastrointestinal tract. consistency.
They are: your mouth, esophagus, stomach, small intestine, Once the nutrients have been absorbed and the leftover-food
large intestine and anus. residue liquid has passed through the small intestine, it then
Assisting your Gl organs along the way are your pancreas, moves on to the large intestine (colon)
gallbladder and liver.
Pancreas
The pancreas secretes digestive enzymes into the duodenum
Here’s how these organs work together in your digestive that break down protein, fats and carbohydrates.
system. The pancreas also makes insulin, passing it directly into the
Mouth bloodstream.
The mouth is the beginning of the digestive tract. Insulin is the chief hormone in vour bod for metabolizing
In fact, digestion starts before you even take a bite. sugar
Your salivary glands get active as you see and smell that pasta
dish or warm bread. Liver
The liver has many functions but its main job within the The pelvic floor muscle creates an angle between the rectum
digestive system is to process the nutrients absorbed from the And the anus that stops stool from coming out when it’s not
small intestine. supposed to.
Bile from the liver secreted into the small intestine also plavs The internal sphincter is always tight, except when stool
an important role in digesting fat and some vitamins. enters the rectum.
The liver is your body’s chemical “factory.” This keeps us continent (prevents us from pooping
It takes the raw materials absorbed by the intestines and involuntarily) when we are asleep or otherwise unaware of the
makes all the various chemicals your body needs to function. presence of stool
The liver also detoxifies potentially harmful chemicals. When we get an urge to go to the bathroom, we rely on our
It breaks down and secretes many drugs that can be toxic to external sphincter to hold the stool until reaching a toilet,
your body. where it then relaxes to release the contents.

Colon CONDITIONS AND DISORDERS

The colon is responsible for processing waste so that What are some common conditions that affect the
emptying your bowels is easy and convenient. digestive system?
It’s a 6-toot long muscular tube that connects the small There are temporary conditions and long-term, or chronic,
intestine to the rectum diseases and disorders that affect the digestive svstem.
The colon is made up of the cecum, the ascending (right) It’s common to have conditions such as constipation, diarrhea
colon, the transverse (across) colon. The descending (left) or heartburn from time to time.
colon, and the sigmoid colon, which connects to the rectum If you are experiencing digestive issues like these frequently,
Stool, or waste left over from the digestive process, is passed be cure to contact vour healthcare professional.
through the colon by means of peristalsis, first in a liquid state It could be a sign of a more serious disorder that needs
and ultimately in a solid form. medical attention and treatment
Stool passes through the colon water is removed
Stool is stored in the sigmoid (S-shaped) colon until a “mass Short-term or temporary conditions that affect the digestive
movement” empties it into the rectum twice a dav system include:
It normally takes about 36 hours for stool to get through the
colon. Heartburn:
The stool itself is mostly food debris and bacteria. Although it has “heart” in its name, heartburn is actually a
These “good” bacteria perform several useful functions, such digestive issue.
as synthesizing various vitamins, processing waste products Heartburn is an uncomfortable burning feeling in your chest
and food particles and protecting against harmful bacteria. that can move up your neck and throat.
When the descending colon becomes full of stool, or feces, it It happens when acidic digestive juices from your stomach go
empties its contents into the rectum to begin the process of back up your esophagus
elimination (a bowel movement)
Diarrhea:
Gallbladder Diarrhea is when vou have loose or watery poop.
The gallbladder stores and concentrates bile from the liver, Diarrhea can be caused by manv things including bacteria, but
and then releases it into the duodenum in the small intestine to sometimes the cause is unknown
help absorb and digest fats.

Rectum Hemorrhoids:
The rectum is a straight, 8-inch chamber that connects the Hemorrhoids are swollen, enlarged veins that form inside and
colon to the anus. outside of your anus and rectum.
The rectum’s job is to receive stool from the colon, let you They can be painful, uncomfortable and cause rectal bleeding.
know that there is stool to be evacuated (pooped out) and to
hold the stool until evacuation happens. Constipation:
Constipation generally happens when you go poop (have a
When anything (gas or stool) comes into the rectum, sensors bowel movement) less frequently than you normally do.
send a message to the brain When you’re constipated, our poop is often dry and hard and
The brain then decides if the rectal contents can be released or it’s difficult and painful for your poop to pass
not.
If they can, the sphincters relax and the rectum contracts, Stomach flu (gastroenteritis):
disposing its contents. The stomach flu is an infection of the stomach and upper part
If the contents cannot be disposed, the sphincter contracts and of the small intestine usually caused bv a virus
the rectum accommodates so that the sensation temporarily It usually last less than a week
goes away Millions of people get the stomach flu every year.

Anus Ulcers:
The anus is the last part of the digestive tract. An ulcer is a sore that develops on the lining of the esophagus,
It is a 2-inch long canal consisting of the pelvic floor muscles stomach or small intestine.
and the two anal sphincters (internal and external). The most common causes of ulcers are infection with a
The lining of the upper anus is able to detect rectal contents. bacteria called Helicobacter pylori (H. pylori) and long-term
It lets you know whether the contents are liquid, gas or solid. use of anti-inflammatory drugs such as ibuprofen.
The anus is surrounded bv sphincter muscles that are
important in allowing control of stool. Gallstones:
Gallstones are small pieces of solid material formed from Regular bowel movements.
digestive fluid that form in your gallbladder, a small organ Be sure to incorporate both soluble and insoluble fiber into
under your liver your diet.

Common digestive system diseases (gastrointestinal Eat a balanced diet:

diseases) and disorders include: Be sure to eat several servings of fruit and vegetables every
GERD (chronic acid reflux): day.
GERD is a gastroesophageal reflux disease, or chronic acid Choose whole grains over processed grains and try to avoid
reflux processed foods in general.
Is a condition in which acid-containing contents in vour Choose poultry and fish more often than red meat and limit all
stomach frequently leak back up into your esophagus. deli (processed) meats
Limit the amount of sugar you consume
Irritable bowel syndrome (IBS):
IBS is a condition in which your colon muscle contracts more Eat foods with probiotics or take probiotic supplements:
or less often than normal Probiotics are good bacteria that help fight off the bad bacteria
People with IBS experience excessive gas, abdominal pain in your gut.
and cramps They also make healthy substances that nourish your gut.
It can be especially helpful to consume probiotics after you
Lactose intolerance: have taken an antibiotic because antibiotics often kill both bad
People with lactose intolerance are unable to digest lactose, and good bacteria in your gut.
the sugar primarily found in milk and dairy products.
Eat mindfully and chew your food:
Diverticulosis and diverticulitis: Eating slowly gives your body time to digest your food
Diverticulosis and diverticulitis are two conditions that occur properly.
in your large intestine (also called your colon). It also allows your body to send you cues that it is full.
Both share the common feature of diverticula, which are It is important to chew your food thoroughly because it helps
pockets or bulges that form in the wall of your colon to ensure your body has enough saliva (spit) for digestion.
Chewing your food full also makes it easier for vour digestive
Crohn’s disease: system to absorb the nutrients in the food
Crohn’s disease is a lifelong form of inflammatory bowel
disease (IBD). Exercise:
The condition irritates the digestive tract. Physical activity and gravity help move food through vour
digestive system.
Celiac disease: Taking a walk, for example, after you eat a meal can help
Celiac disease is an autoimmune disorder that can damage your body digest the food more easily
your small intestine.
The damage happens when a person with celiac disease Manage your stress:
consumes gluten, a protein found in wheat, barley and rye Stress is associated with digestive issues such as
Cancer: Constipation, diarrhea and IBS.
Cancers that affect tissues and organs in the digestive system
are called gastrointestinal (GI) cancers. Avoid alcohol and smoking:
There are multiple kinds of (GI) cancers Alcohol can increase the amount of acid in your stomach and
The most common digestive system cancers include: can cause heartburn, acid reflux and stomach ulcers.
Esophageal cancer Smoking almost doubles your risk of having acid reflux.
Gastric (stomach) cancer Research has shown that people who have digestive issues
Colon cancer that quit smoking have improved symptoms.
Rectal (colorectal) cancer
Pancreatic cancer
Liver cancer

How can I keep my digestive system healthy?

If you have a medical condition, always ask your healthcare
provider what you should do and eat to stay healthy and
manage your condition.

In general, the following are ways to keep your digestive

system healthy:

Drink water often:

Water helps the food you eat flow more easily through your
digestive system.
Low amounts of water in your body (dehydration) is a
common cause of constipation

Include fiber in your diet:

Fiber is beneficial to digestion and helps your body have