SKIN AND BODY MEMBRANES

2 Major groups of body membranes:

1. Epithelial membranes
 Cutaneous membranes(skin)
Epidermis- composed of stratified squamous epithelium
Dermis- composed of dense fibrous connective tissue
 Mucous membranes- composed of epithelium called lamina propria
- lines all body cavities that open to the exterior
such
as hallow organs of respiratory, digestive, urinary and
reproductive tracts.
- composed either stratified squamous epithelium
(as in the mouth and esophagus) or simple
columnar epithelium (as in the rest of the digestive
tract)
 Serous membranes- composed of simple squamous epithelium resting on
the areolar connective tissue.
- line body cavities that are closed to the exterior
(except for the dorsal body cavity and joint cavities)
- pairs of serous membranes:
parietal layer
visceral layer
serous layers are separated by serous fluid
-Peritoneum- The serosa lining the
abdominal cavity and covering its organs
- Pleurae- The membranes surrounding
the lungs
- Pericardia- The membranes surrounding
the heart.
2. Connective tissue membranes
 Synovial membranes- composed of loose areolar connective tissue and
contain no epithelial cells at all.
- Bursae- small sacs of connective tissue
- Tendon sheaths

INTEGUMENTARY SYSTEM
- It insulates and cushions the deeper body organs
and protects the entire body from mechanical
 damage (bumps and cuts), chemical damage (such
as from acids and bases), thermal damage (heat
and cold), ultraviolet (UV) radiation (in sunlight),
and microbes
2 parts of skin that has been controlled by nervous system:
1. Capillary network
2. Sweat glands
- Skin acts as a mini-excretory system
- The skin also produces acidic secretions, called the
acid mantle, that protect against bacterial invasion

Structure of the Skin

Blister- interstitial fluid that accumulate in the cavity between the layers of epidermis
and dermis due on burning or friction which separate them.
 Epidermis- Most cells of the epidermis are keratinocytes (keratin cells),
which produce keratin, the fibrous protein that makes the epidermis a
tough protective layer in a process called keratinization.
- Epidermal dendritic cells- important sentries that
alert and activate immune system cells to a threat
such as bacterial or viral invasion.
- Merkel cells- they are associated with sensory nerve
endings and serve as touch receptors called Merkel
disc

5 layers of epidermis from the inside and then out:

1. Stratum Basale (Germinativum)- closest to the dermis
- Stem cells in this layer are constantly dividing, and
millions of new cells are produced daily.
- Melanocytes-a special spider-shaped cells that
produces melanin.
2. Stratum Spinosum- cells are keratinized here. Largest part in
the epidermis.
3. Stratum Granulosum- cells are keratinized here and as they
leaves they died forming the other upper layer
4. Stratum Lucidum- they are not present in all skin regions. They
only occur where the skin is hairless and thick (i.e., palms and
soles)
5. Stratum Corneum- cornified or horny cells- The shinglelike dead
cell remnants, completely filled with keratin
  Dermis- The “hide.” It is a strong, stretchy envelope that helps to bind
the body together. Contains abundantly with blood vessels and nerve
supply

Dermis contains:
1. Collagen- responsible for the toughness of the dermis; they also attract
and bind water and thus help to keep the skin hydrated.
2. Elastic fibers- give the skin its elasticity when we are young.

2 Connective tissue layers in Dermis:

1. Papillary layer- composed of areolar connective tissue

- The superficial dermal region. It is uneven and has
peglike projections from its superior surface, called
dermal papillae. Dermal papillae contain the ff.:
- Capillary loops- furnish nutrients to the epidermis.
- Pain and touch receptors
- Responsible for gripping
- Finger prints
2. Reticular layer- composed of dense irregular connective tissue
- Deepest skin layer
- Contains blood vessels, sweat and oil glands and
deep pressure receptors called lamellar corpuscles.
- Cutaneous sensory receptors, which are actually
part of the nervous system, are also located in the
skin. Which is responsible for touch, pressure,
temperature and pain receptors.
- Phagocytes are found here that act to prevent
microbes that have managed to get through the
epidermis from penetrating any deeper into the
body.
-
 Hypodermis (Subcutaneous tissue)- composed of adipose (fat) tissue
- Not considered as part of the skin
- Serves as a shock absorber and temperature
insulation.
- Responsible for the curves in women’s anatomy

Skin Color
 Amount of Melanin- tanning of the skin. It is produced by melanocytes
when exposing to sunlight. As the melanocytes produce melanin, it
 accumulates in their cytoplasm in membrane-bound granules called
melanosomes. These granules then move to the ends of the melanocytes’
spidery arms, where they are taken up by nearby keratinocytes. Inside the
keratinocytes, the melanin forms a pigment umbrella over the superficial,
or “sunny,” side of their nuclei and shields their genetic material (DNA)
from the damaging effects of UV radiation in sunlight
 The amount of Carotene deposited in stratum corneum and subcutaneous
tissue
 The amount of oxygen-rich hemoglobin (pigment in red blood cells) in the
dermal blood vessels
 Emotions also influence skin color
• Redness, or erythema. Reddened skin may indicate
embarrassment (blushing), fever, hypertension, inflammation, or
allergy.
• Pallor, or blanching. Under certain types of emotional stress (fear,
anger, and others), some people become pale. Pale skin may also
signify anemia, low blood pressure, or impaired blood flow into the
area.
• Jaundice or a yellow cast. An abnormal yellow skin tone usually
signifies a liver disorder in which excess bile pigments accumulate
in the blood, circulate throughout the body, and become deposited
in body tissues.
• Bruises. The black-and-blue marks of bruising reveal sites where
blood has escaped from the circulation and has clotted in the tissue
spaces. Such clotted blood masses are called hematomas. An
unusual tendency to bruise may signify a deficiency of vitamin C in
the diet or hemophilia (bleeder’s disease).

Appendages of the Skin

 Cutaneous Glands- they are exocrine glands that release their secretions to the
skin surface via ducts. They are formed in the stratum basale.

Sebaceous glands (Oil Glands)- they are found all over the skin, except on
the palms of the hands and the soles of the feet. Their ducts usually empty
into a hair follicle, but some open directly onto the skin surface.
- Sebum- the product of sebaceous glands. It is a
mixture of oily substances and fragmented cells.
Sebum is a lubricant. Sebum also contains
chemicals that kill bacteria, so it is important in
preventing bacterial infection of the skin. The
sebaceous glands become very active when
androgens (male sex hormones) are produced in
 increased amounts (in both sexes) during
adolescence. Thus, the skin tends to become oilier
during this period of life.
- Seborrhea- known as “cradle cap” in infants, is
caused by overactivity of the sebaceous gland
Sweat glands (Sudoriferous Glands)- The eccrine sweat glands are an
important and highly efficient part of the body’s heat-regulating
equipment. They are supplied with nerve endings that cause them to
secrete sweat when the external temperature or body temperature is too
high

 Eccrine Glands- they produce sweat

Sweat composed of:
- Water plus salts
- Vitamin C
- Traces of metabolic waste (ammonia, urea, uric
acid)
- Lactic acid

Sweat is acidic (4 to 6 pH level)

 Apocrine Glands- confined to the axillary (armpit) and genital areas
of the body. They are larger than the eccrine glands. It starts to
function during puberty under the influence of androgens. They are
activated by nerve fibers during pain and stress and during sexual
arousal.
Aprocrine glands contains:
- Fatty acids
- Proteins
- All substances present in the eccrine glands.

 Hair- Hormones account for the development of hairy regions—the scalp and, in
the adult, the pubic and axillary areas

Parts of hair:
Root- the part of the hair enclosed in the hair follicle
Shaft- a part projecting from the surface of the scalp or skin
Medulla- central core of hair
Cortex layer- encloses the medulla, composed of several layers of flattened
cells
Cuticle- encloses the cortex layer, composed of single layer of cells that
overlap one another like shingles on a roof. It is the heavily keratinized
region; it provides strength and helps keep the inner hair layers tightly
compacted.
 - Split ends- a phenomenon wherein the inner hair
regions frizz out.
Sizes of hair:
When the hair shaft is oval, hair is smooth, silky, and wavy.
When the shaft is flat and ribbonlike, the hair is curly or kinky.
If it is perfectly round, the hair is straight and tends to be coarse

 Hair follicle
Inner epithelial root sheath- composed of epithelial tissue and forms the
hair.
Outer fibrous sheath- composed of dermal connective tissue. It supplies
blood vessels to the epidermal portions and reinforces it.

Hair papilla- a nipplelike that provides the blood supply to the matrix in
the hair bulb.
Hair bulb- the deepest part of the follicle
Arrector pili- small bands of smooth muscle cells that connect each side of
the hair to the dermal tissue. When these muscles contract (as when we
are cold or frightened), the hair is pulled upright, dimpling the skin
surface with “goose bumps.”

 Nails - scalelike modification of the epidermis

Parts of the Nail:

Free edge
Body
Root
Nail folds- it is a fold of skin that overlaps towards the boarder of the nail
Cuticle- the edge of the thick proximal nail fold.
Nail bed-
Nail matrix- responsible for nail growth
Lunule- a region over the thickened nail matrix that appears as a white
crescent
when the supply of oxygen in the blood is low, the nail beds take on a
cyanotic (blue) cast.

Homeostatic Imbalance of Skin

- Due on pathogens such as bacteria, viruses or fungi
Allergies- caused by abnormally strong immune responses
Infections and Allergies:
Athlete’s Foot- due on the fungus TINEA PEDIS
Boils and carbuncles- caused by the bacterium STAPHYLOCOCCUS AUREUS
Cold sores (fever blisters)- caused by HUMAN HERPESVIRUS 1 infection
Contact Dermatitis- caused by exposure to chemicals such as POISON IVY
Impetigo- caused by STAPHYLOCOCCUS or STREPTOCOCCUS infections
Psoriasis- it is an autoimmune disorder triggered by trauma, infection, hormonal
changes or stress.

BURNS- A tissue damage and cell death caused by intense heat, electricity, UV
radiation (sunburn), or certain chemicals (such as acids), which denature proteins and
cause cell death in the affected areas
2 Life threatening than occur during burns:
1. Dehydration and electrolyte imbalance
2. Infections
Rule of nines:

4 classifications of burns:
1. First-degree Burns- destroy superficial epidermis is damaged. Can heal in 2-3
days. No blister
2. Second-degree Burns- destroy epidermis and superficial dermis. Has blister.
Regeneration can occur. No permanent scars
3. Third-degree Burns- destroy both the epidermis and dermis and even extend into
subcutaneous tissue. Full thickness burns. burned area appears blanched (gray-
white) or blackened. Has blisters. Regeneration is not possible and Skin Grafting
must be done to cover the underlying exposed tissues.
4. Fourth-degree Burns- from epidermis until deeper tissues such as bone, muscle,
or tendons. Also, a full-thickness burns. These burns appear dry and leathery,
and they require surgery and grafting to cover exposed tissue. In severe cases,
amputation may be required to save the patient’s life.

In general, burns are considered critical if any

of the following conditions exists:
1. Over 30 percent of the body has second-degree burns.
2. Over 10 percent of the body has third- or fourth-degree burns.
 3. There are third- or fourth-degree burns of the face, hands, feet, or genitals.
4. Burns affect the airway.
5. Circumferential (around the body or limb) burns have occurred

Skin Cancer- due on UV radiation and tanning beds

Warts- caused by HUMAN PAPILLOMA VIRUS. This is benign
Basal Cell Carcinoma- least malignant and most common skin cancer. . Cells of
the stratum basale, altered so that they cannot form keratin, no longer honor the
boundary between epidermis and dermis. They proliferate, invading the dermis
and subcutaneous tissue. Metastasis seldom occurs.
Squamous Cell Carcinoma- arises from the cell of stratum spinosum. Grows
rapidly and metastasize to adjacent lymph nodes.
Malignant Melanoma- a cancer of melanocytes. Id developed from the pigmented
moles. It arises from accumulated DNA damage in a skin cell and usually appears
as a spreading brown to black patch that metastasizes rapidly to surrounding
lymph and blood vessels. The usual therapy for malignant melanoma is wide
surgical excision along with immunotherapy, a treatment that involves the
patient’s immune system. Large lesions may also require radiation or
chemotherapy after surgical removal
ABCDE rule for recognizing melanoma:
(A) Asymmetry. Any two sides of the pigmented spot or mole do not match.
(B) Border irregularity. The borders of the lesion are not smooth but exhibit
indentations.
(C) Color. The pigmented spot contains areas of different colors (black, brown, tan, and
sometimes blue or red).
(D) Diameter. The lesion is larger than 6 millimeters (mm) in diameter (the size of a
pencil eraser).
(E) Evolution. One or more of these characteristics (ABCD) is evolving, or changing.

Lanugo- downy- type of hair

Vernix caseosa- This white, cheesy-looking substance, produced by the sebaceous
glands, protects the baby’s skin while it is floating in its water-filled sac inside the
mother
Milia- can be found in baby’s nose and forehead.
Male pattern baldness