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- Covers surfaces
- Lines body cavities
- Forms protective and lubricative sheets around organs
- Epithelial and connective membranes
- Contains cutaneous, mucous, and serous membranes.
- Contain epithelial sheets but is always conbined with an underlying layer of connective tissue.
- Superficial epidermis is composed of a keratinizing stratified squamous epithelium.
- Underlying dermis is mostly dense fibrous connective tissue
- Dry membrane
- Epithelium resting on a loose connective tissue membrane called lamina propria.
- Most mucous contain either stratified squamous or simple columnar.
- Moist membrane, continuously bathed in secretions.
- Adapted for absorption and secretion.
- Layer of simple squamous resting on a thin layer of areolor connective tissue.
- Occurs in pairs: Pariental layer lines a specific portion of the wall of the ventral body cavity. It folds in on itself to form viceral layer, which covers the outside of the organs in that cavity.
- Lines body cavities that are closed to exterior (except for the dorsal body cavities and joint cavities)
- Serous layers are separated by a thin clear fluid called serous fluid which is secreated by both membranes.
- Fluid allows the organs to slide easily across the cavity walls and one another without friction.
- Serosa lining the abdominal cavity and covering its organs is peritoneum.
- In the thorax, serous membranes isolate the lungs and heart from eachother. Surrounding the lungs is the pleura and surrounding the heart is the pericardium.
Connective tissue membranes: Synovial membrane
- Composed of soft aerlor tissue connective tissue and contain no epithelial at all.
- Membranes line fibrous capsules surrounding joints where they provide a smooth surface and secrete a lubricating fluid.
- Lines small sacs of connective tissue called bursae and tube like tendon sheaths.
- Structures cushion organs moving agianst eachother during muscle activity.
- Keeps water and other precious molecules in
- Keeps water and other things out
- Insulates and cushion deeper body organs and prtects entire body from mechanical, Chemical, Bacterial, and thermal damage. As well as Ultraviolet radiation and Desiccation
- Aids in body heat retention and loss: Heat loss: Activates sweat glands and allowing blood to flush into skin cappilay beds. Heat retention: Not allowing blood to flush into skin cappilary beds.
- Aids in excreation od urea and uric acid: contained by persperation
- Synthesized vitamin D:Modified cholesterol molecues in skin converted to vitamin D by sunlight.
- Mechanical damage: Physical Barrier contains keratin which toughens cells and pressure receptors whcih alter the nervous system to possible damage.
- Chemical Damage: Has reletively impermeable keratinized cells than contain pain receptors which alert the nervous system to possible damage.
- Bacterial Damage: Has an unbrken surface and acid mantle. Phagocytes ingest foreign substances and pathogens preventing them from penetrating into deeper body tissue.
- Thermal Damage: Contains heat cold and pain receptors.
- Ultraviolet radiation: Melenin produced by melinocytes offers protection.
- Made up of stratified squamous epithelium that is capable of kertinizing, or becoming hard and tough.
- Avascular: No blood supply of its own.
- Most cells are kertinocytes which produce keratin the fibrous protien that makes the epidermis and tough and protective layer.
- Stratum basale: Deepest, closest to dermis and contains only epidermal cells that recieve adaquete nourishment via diffusion of nutrients from the dermis. These cells are constantly undergoing cell division, then the daghter cells are pushed upward and away from source of nutrients to become apart of layers closer to surface
- Spinosium :
- Granulosum:They become flatter and increasingly full of keratin, then dieing to form clearer stratum lucidium.
- Lucidium: Only occurs where skin is hairless and thick.
- Corneum: Counts for about 3/4 of skin thickness, abundance of keratin in this layer provides a durable overcoat for the body which protects deeper cells from the external enviorment.
- A pigment that ranges from from yellow to brown to balck
- Produced by special cells called melenocytes
- Found in stratum Basale
- When skin is exposed to sunlight whcih stimulate the melenocytes to produce more pigment, tanning occurs. the stratum basale cells eat the pigment as it accumulates.
Homeostatic imbalance: Melenin
- There are positive effects to melenin but over sun exposure damages the skin.
- Causes elactice fiber to clump leading to leathery skin.
- Depresses the immune system
- Can also lead to skin cancer because it cn alter DNA
- Made up of dense connective tissue
- String Stretch envolopethat holds the body together.
- Dermis varies in thinkness
- Upper dermal region
- Uneven with finger like projections from its superior surface called dermal papillae which indent the dermis above.
- Contain cappilary loops which furnish nutrients to the epidermis.
- Some house pain receptors and touch receptors called Meissners Corpuscle
- On pals of hands and soles of feet the papilea arearranged in patterns on epidermal surface that increase friction and enhance gripping ability.
- Deepest skin layer
- Contains blood vessels, sweat and oil glands and deep pressure receptors called Pacinian corpuscles
- Many phagocytes are found here and prevent bacteria that have managed to get throught epidermis get any farther into body.
- Collogen and elastic fibers are found here
- Collogen fibers are responsible for the toughness of the dermis, they also attract and bind water thus keeping the skin hydrated.
- Elastic fibers give skin its elasticity when young
- both these kinds offiber decrease with age and hypodermis loses fat
- This layer is supplied with blood vessels that maintain body temperature.
- When body temp is high the cappilaries of the dermis become swollen with heated bood and the skin become reddened and warm allowing body heat to radiate from surface.
- When body temperature is cool blood bypasses the dermis cappilaries temporarily, allowing internal body temp to stay high.
- Any restriction of normal blood supply to skin results in cell death, and if sever and prolonged enouggh skin ulcers.
- Decubitus ulcers occur when the weight of the body out pressure on the skin.
- It restricts blood supply skin becomes pale, skin reddens when pressure is relieved but if not corrected the cells begin to die leading to craking and breaking of the skin.
- Adipose tissue
- Anchors skin to underlying organs
- Shock absorber and insulates deeper tissue from extreme tempeture changes
- Three pigment contribute to skin color:
- The amount and kind of melenin in the epidermis
- The amount of cartene deposited in the stratum corneum and subcutaneous tissue
- The amount of oxygen bound to hemigoblin (pigment in red blood cells) in the dermal blood vessels
Homeostatic imbalance: Skin Color
Cutaneous glands, hairs, hair follicles and nails.
- Cutaneous glands are all exocrine glands that release the secreation to the skin surface via ducts.
- Two groups: Sebaceous glands and sweat glands.
- As these glands are formed by the cells of the stratum basale, they push into the deeper skin regions and ultimately reside almost entirely in te dermis.
Sebaceous oil glands
- Found all over the skin except on the palms of the hands and soles of the feet
- Ducts empty into hair follicle but some open directly to skin surface
- Product is sebum, a mixture of oily substances and fragmmented cells
- Sebum is a lubricant that keeps the skin soft and miost and prevents the hair from becoming brittle.
- Contain chemical that kills bacteria so its important in preventing the bacteria present on the skin surface from invading the deeper skin regionss.
- The glands become very active when male sex hormones are produced in increased amounts during adolesence. Thus, the skin tends to become oilier during this period of life.
Homeostatic imbalance: Sebaceous oil glands
- Also called sudoriferous glands and are widely distributed in the skin.
- Two types: Eccrine and apocrine
- The eccrine are far more numerous and are found all over the body they produce sweat a clear secretion that is primarly water plus some salt, vitamin C, traces of metabolic wastes and lactic acid.
- Sweat is acid, a characteristic that inhibits the growth of bacteria which are always present on the skin surface.
- Sweat reaches the skin surface via a duct that opens externally as a funnel shaped pore.
- The apocrine sweat glands are largely confined to the axillary and genital areas of the body.
- Larger than eccrine, there ducts empty into hair follicles.
- Their secretion contain fatty acids and protiens, as well as the substances present in eccrine secretion.
- Begin to fuction during puberty.
- Hair produced by hair follicle is a flexable epithelial structure.
- That part of the hair enclosed in the follicle is called the root.
- Part projecting from the surface of the scalp or skin is called shaft.
- A hair is formed by the division of the well nourished stratum basale epithelial cells in the growth zone or hair bulb matrix at the inferior end of the follicle.
- Dead material and alsmost entirely protien
- Each hair consists of a core call medulla surrounded by bulky cortex layer
- The cortex is enclosed by an outermost cuticle formed by a single layer of cells that help to keep the hairs apart and from matting.
- The cuticle is the most heavily keratinized region it provides strenghth and helps keep the inner hair layers tightly compacted.
- Hair pigment is made by melenocytes in the hair bulb and varying amounts of melenin.
- Oval hair shaft: smooth, silky, and curly
- Flat hair shaft: curly or kinky
- Round hair shaft: straight, coarse.
- Hair follicles are compounded structures. the inner epidermal sheath is composed of epithelial tissue and forms the hair.
- The outer dermal sheath is actually dermal connective tissue this layer supplies blood vesslels to the epidermal portion and reinforces it.
- Small bands of smooth muscle cells or arrector pili connect each side of the hair folicle to the dermal.
- A scale like modification of the epidermis that corresponds to the hoof or claw of other animals
- Each nail has a free edge, a body (nail), and a root the borders are over lapped by skin folds called nail folds (cuticle)
- The stratum basale of the epidermis extends beneath the nail as the nail bed
- Its thinkended proximal area is called the nails matrix its is resposible for nail growth.
- As the cells are produced by the matrix they become heavily kertinized and die
- Clear, look pink because of rich blood suply in dermis
- Exception is region over the thinkedned nail matrix that appears as a white cresent caled the lunula.
Homeostatic Imbalances of the skin
- Athletes foot: peeling condition, itchy and red, fungus infection
- Boils are carbuncles: bacterial infection, inflamation of the hair folicles and sebaceous glands
- Cold sores: small fluid filled blisters that itch and sting, activated by emotions fever or sun
- Contact dermatitis: itching redness and swelling of the skin progressing to blistering exposure to chemicals
- Impetigo: pink, water filled raised lesions that develop a yellow crust and eventually rupture
- Psoriasis: chronic condition, reddened epidermal lesions covered with dryscaled attacks triggered by trauma infection hormonal changes and stress
- Tissue damage and cell death caused by intense heat, electricity, uv raditation, or certain chemicals. Body loses supply of fluids containing protien and electrolytes as these seep from the burned surfaces
- Dehydration and Electrolyte imbalance can occur
- Rules of nines: Divideds body into 11 areas accounting for 9 percent of the total body surface area
- Infection becomes the most important threat and is the leading cause of death in burn victims
- Critical if:
- Over 25 percent of the body has second degree burns. Over 10 percent of the body has third degree burns, there are third degree burns onface, hands, or feet.
- Facial burns are dengerous because of burnt respiratory passageways that can swell and cause suffication.
- Joint injuries are troublesome because the scar tissue that eventually forms can limit mobility.
- Burnes are classified according to severity:
- First degree: only the epidermis is damaged
- Second degree: Epidermis and upper region of dermis are damaged
- Third degree: Destroy entire thinkness of skin, never endings are destroyed so it is painless, skin regeneration is not possible.
- ◦Most skin tumors are benign and dont spread to other body parts, some are cancerous and tend to ivade other body areas.
- Skin cancer is most common form of cancer
- Most important risk factor is over exposure to sun.
Basal cell Carcinoma
- Least malignant type and most commen
- Cells of the stratum basale are altered so that they cannot form keratin, and no longer honor the boundry between epidermis and dermis
- They proliferate invading the dermis and subcutaneous tissue
- Cancer lesions occur most often in sun exposed areas of face and appear shiny dome shaped nodules that develop a central ulcer with a pearly beaded edge
- Slow growing
Squamous cell Carcinoma
- Arises from the cells of the stratum spinosium
- Leasion appear scaly, reddended papule that gradulally forms a shallowulcer with a firm raised border
- Apparsmost often on the sclap, ears, dorsum of the hands, and lower lip◦Grows rapidly and metastasizes to adjacent lymph nodes if not removed
- Sun induced
- A cancer of melenosytes◦Accounts for about 5 percent of skin cancers
- Incidence is increasing rapidly and is often deadly
- Can begin wherever pigment is but some can come from pigmented moles
- Usually appears as a spreading brown to black patch that metasies rapidly to surrounding lymph and blood vessels.
- Asymmetry: The two sides of the pigmented spot or mole do not match
- Border irregularty: the borders of the lesion are not smooth but exhibit identations
- Color: The pigmented spot contains are of different colors
- Diameter: the spot is larger than 6mm in diameter