Tissue Transes
Tissue Transes
Tissue Transes
Types of Cell Junctions: The three basic types of cell-to-cell junctions are tight junctions, gap
junctions, and anchoring junctions.
Cells of Epithelial Tissue: Simple epithelial tissue is organized as a single layer of cells and stratified
epithelial tissue is formed by several layers of cells.
Tissue Membranes: The two broad categories of tissue membranes in the body are (1) connective
tissue membranes, which include synovial membranes, and (2) epithelial membranes, which include
mucous membranes, serous membranes, and the cutaneous membrane, in other words, the skin
Goblet Cell: (a) In the lining of the small intestine, columnar epithelium cells are interspersed with Modes of Glandular Secretion: (a) In merocrine secretion, the cell remains intact. (b) In apocrine
goblet cells. (b) The arrows in this micrograph point to the mucous-secreting goblet cells. secretion, the apical portion of the cell is released, as well. (c) In holocrine secretion, the cell is
destroyed as it releases its product and the cell itself becomes part of the secretion.
Reticular Tissue: This is a loose connective tissue made up of a network of reticular fibers that
provides a supportive framework for soft organs. LM × 1600.
Dense Connective Tissue (a) Dense regular connective tissue consists of collagenous fibers packed
into parallel bundles (b) Dense irregular connective tissue consists of collagenous fibers interwoven
into a mesh-like network. From top, LM × 1000, LM × 200.
Sebaceous Glands: These glands secrete oils that lubricate and protect the skin. They are holocrine
glands and they are destroyed after releasing their contents. New glandular cells form to replace
the cells that are lost. LM × 400.
Connective Tissue Proper Fibroblasts produce this fibrous tissue. Connective tissue proper includes Types of Cartilage: Cartilage is a connective tissue consisting of collagenous fibers embedded in a
the fixed cells fibrocytes, adipocytes, and mesenchymal cells. LM × 400. firm matrix of chondroitin sulfates. (a) Hyaline cartilage provides support with some flexibility. The
example is from dog tissue. (b) Fibrocartilage provides some compressibility and can absorb
pressure. (c) Elastic cartilage provides firm but elastic support. From top, LM × 300, LM × 1200, LM
×1016.
Adipose Tissue: This is a loose connective tissue that consists of fat cells with little extracellular
matrix. It stores fat for energy and provides insulation. LM × 800.
Blood: A Fluid Connective Tissue Blood is a fluid connective tissue containing erythrocytes and
various types of leukocytes that circulate in a liquid extracellular matrix. LM × 1600.
Tissue Healing: During wound repair, collagen fibers are laid down randomly by fibroblasts that
move into repair the area.
Muscle
Tissue: (a) Skeletal muscle cells have prominent striation and nuclei on their periphery. (b) Smooth
muscle cells have a single nucleus and no visible striations. (c) Cardiac muscle cells appear striated
and have a single nucleus.
The Neuron: The cell body of a neuron, also called the soma, contains the nucleus and
mitochondria. The dendrites transfer the nerve impulse to the soma. The axon carries the action
potential away to another excitable cell. LM × 1600.
Development of Cancer: Note the change in cell size, nucleus size, and organization in the tissue.
Nervous Tissue: Nervous tissue is made up of neurons and neuroglia. The cells of nervous tissue are
specialized to transmit and receive impulses. LM × 872.
INTEGUMENTARY SYSTEM Merkel Cell - functions as a receptor and is
- made up of skin and its accessory structures, w/c responsible for stimulating sensory nerves that
provides the body with overall protection. the brain perceives as touch.
the largest organ system in the body Melanocyte – cell that produces the pigment
melanin.
skin is 16% of body weight; 1.5 – 2m 2
Melanin – gives hair and skin it’s color, and
protects internal organs
helps protect the living cells from ultraviolet
(UV) radiation damage.
Papillary Layer – fingerprints form where the
cells of the stratum basale meet the papillae of
the underlying dermal layer.
o Fingerprint - unique to each individual and are used for
forensic analyses because the patterns do not change with
the growth and aging processes.
Layers of Skin The skin is composed of two main layers: the epidermis, made of closely packed
epithelial cells, and the dermis, made of dense, irregular connective tissue that houses blood
vessels, hair follicles, sweat glands, and other structures. Beneath the dermis lies the hypodermis,
which is composed mainly of loose connective and fatty tissues.
EPIDERMIS
- composed of keratinized, stratified squamous
epithelium.
- does not have any blood vessels within it (avascular)
Keratinocyte – cell that manufactures and Layers of the Epidermis: The epidermis of thick skin has five layers: stratum basale, stratum
spinosum, stratum granulosum, stratum lucidum, and stratum corneum.
stores the protein keratin. Stratum Spinosum
- cell in all the layers of the skin EXCEPT the
- spiny in appearance due to the protruding cell
stratum basale.
Keratin – intracellular fibrous protein that gives
processes that join the cells via a structure called
hair, nails, and skin their hardness and water- a desmosome.
resistant properties. - composed of eight to 10 layers of
keratinocytes, formed as a result of cell division
in the stratum basal.
- the keratinocytes in the stratum spinosum
begin the synthesis of keratin and release a
water-repelling glycolipid that helps prevent
water loss from the body, making the skin
relatively waterproof.
Thin Skin versus Thick Skin: These slides show cross-sections of the epidermis and dermis of (a) thin Langerhans Cell - type of dendritic cell,
and (b) thick skin. Note the significant difference in the thickness of the epithelial layer of the thick interspersed among the keratinocytes of this
skin. From top, LM × 40, LM × 40.
layer.
Thin Skin
- macrophage by engulfing bacteria, foreign
- skin that has four layers of cells.
particles, and damaged cells that occur in
- most of the skin can be classified as a thin skin this layer.
Stratum Basale Desmosome - the “spiny” nature of this
- also called as stratum germinativum. layer is an artifact of the staining process.
- deepest epidermal layer and attaches the - structure w/c interlocks with each other
epidermis to the basal lamina, below which lie and strengthen the bond between the cell.
the layers of the dermis.
- single layer of cells primarily made of basal
cells.
Dermal Papilla – finger-like projection, or fold
found in the superficial portion of the dermis.
- increase the strength of the connection
between the epidermis and dermis; the greater
the folding, the stronger the connections made.
Basal Cell – cuboidal-shaped stem cell that is a
precursor of the keratinocytes of the epidermis. Cells of the Epidermis: The cells in the different layers of the epidermis originate from basal cells
located in the stratum basale, yet the cells of each layer are distinctively different. EM × 2700.
Stratum Granulosom
- grainy appearance due to further changes to
the keratinocytes as they are pushed from the
stratum spinosum.
cells become flatter
cell membranes thicken
generate large amount of protein keratin
(fibrous)
Keratohyalin – which accumulates as
lamellar granules within the cells.
- make up the bulk of the keratinocyte mass
in the stratum granulosum and give the layer
its grainy appearance.
Stratum Lucidum
- smooth, seemingly translucent layer of the
epidermis located just above the stratum
granulosum and below the stratum corneum.
only found in the thick skin of the palms,
soles and digits
keratinocytes are dead and flattened
Eleidin – clear protein, derived from
Layers of the Dermis: This stained slide shows the two components of the dermis—the papillary
keratohyalin w/c packs the cells densely. layer and the reticular layer. Both are made of connective tissue with fibers of collagen extending
Stratum Corneum from one to the other, making the border between the two somewhat indistinct. The dermal
papillae extending into the epidermis belong to the papillary layer, whereas the dense collagen
- most superficial layer of the epidermis and is fiber bundles below belong to the reticular layer. LM × 10.
the layer exposed to the outside environment. Papillary Layer – made of loose, areolar
- this dry, dead layer helps prevent the connective tissue, which means the collagen and
penetration of microbes and the dehydration of elastin fibers of this layer form a loose mesh.
underlying tissues, and provides a mechanical - contains phagocytes, defensive cells that help
protection against abrasion for the more fight bacteria or other infections that have
delicate, underlying layers. breached the skin.
increased keratinization (cornification) - also contains lymphatic capillaries, nerve fibers,
usually, 15-30 layers of cell and touch receptors called the Meissner
cells are shed periodically during a period of corpuscles.
about 4 weeks Reticular Layer - composed of dense, irregular
Microdermabrasion – cosmetic procedure connective tissue.
that helps remove some of the dry, upper - well vascularized and has a rich sensory and
layer and keep the skin looking fresh & sympathetic nerve supply. The reticular layer
healthy. appears
THICK SKIN reticulated (net-like) due to a tight meshwork of
- found only on the palms of the hands and the soles fibers.
of the feet. Elastin Fibers - provide some elasticity to the
Stratum Lucidum – fifth layer, located skin, enabling movement.
between the stratum corneum and the Collagen Fibers
stratum granulosum. Collagen Injections and Retin A – helps
restore skin turgor
DERMIS HYPODERMIS
- considered the “core” of the integumentary - also known as subcutaneous layer or superficial
system. fascia.
- contains blood and lymph vessels, nerves, and - layer directly below the dermis and serves to
other structures, such as hair follicles and sweat connect the skin to the underlying fascia (fibrous
glands. tissue) of the bones and muscles.
- made of two layers of connective tissue that mode of fat storage and provides insulation
compose an interconnected mesh of elastin and and cushioning for the integument
collagenous fibers, produced by fibroblasts
Derma = skin PIGMENTATION
Epi = upon or over - color of skin is influenced by a number of pigments,
Hypodermis = below (hypo) including melanin, carotene, and hemoglobin.
Hair: Hair follicles originate in the epidermis and have many different parts.
Melanosome – a cellular vesicle where
melanin is transferred into the keratinocytes.
Accessory Structures of the Skin
o dark-skinned individuals produce more
melanin than those with pale skin. Hair Follicle - where strands of hair originate in
o too much melanin can interfere with the an epidermal penetration of the
production of vitamin D, an important nutrient dermis.
involved in calcium absorption. Hair Shaft - part of the hair not anchored to
o 10 days for peak melanin synth the follicle, and much of this is
exposed at the skin’s surface.
SENSORY FUNCTION
- epidermis, dermis, and the hypodermis contain
specialized sensory nerve structures that detect
touch, surface temperature, and pain. Rickets - painful condition in children where the
- receptors are more concentrated on the tips of bones are misshapen due to a lack of calcium,
the fingers, which are most sensitive to touch causing bowleggedness.
Meissner Corpuscle (tactile corpuscle) absence of sun exposure can lead to a lack
- light touch of vitamin D in the body
Pacinian Corpuscle (lamellated corpuscle)
- vibration
Merkel Cells - in the stratum basale, touch
receptors
Rickets: painful condition in children due to lack of calcium and exposure to the sun.
Light Micrograph of a Meissner Corpuscle: In this micrograph of a skin cross-section, you can see a
Meissner corpuscle (arrow), a type of touch receptor located in a dermal papilla adjacent to the
basement membrane and stratum basale of the overlying epidermis. LM × 100.
secreted a day
Decrease temp -> arterioles constrict
(minimize heat loss) -> ends of digits and tip of
nose -> reduce circulation -> whitish hue ->
frostbite
Thermoregulation: During strenuous physical activities, such as skiing (a) or running (c), the dermal
blood vessels dilate and sweat secretion increases (b). These mechanisms prevent the body from
overheating. In contrast, the dermal blood vessels constrict to minimize heat loss in response to low
temperatures