Bio106 Basic A&P Ch. 4 Outline, Skin and Body Membranes PDF

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Skin and Body Membranes Body Membranes  Function of body membranes o Cover body surfaces o Line body cavities o Form protective sheets around organs  Classified according to tissue types

Classification of Body Membranes  Epithelial membranes o Cutaneous membranes o Mucous membranes o Serous membranes  Connective tissue membranes o Synovial membranes

Cutaneous Membrane  Cutaneous membrane = skin o Dry membrane o Outermost protective boundary  Superficial epidermis is composed of keratinized stratified squamous epithelium  Underlying dermis is mostly dense connective tissue

Mucous Membranes  Surface epithelium type depends on site o Stratified squamous epithelium (mouth, esophagus) o Simple columnar epithelium (rest of digestive tract)  Underlying loose connective tissue (lamina propria)  Lines all body cavities that open to the exterior body surface

 Often adapted for absorption or secretion

Serous Membranes  Surface is a layer of simple squamous epithelium  Underlying layer is a thin layer of areolar connective tissue  Lines open body cavities that are closed to the exterior of the body  Serous membranes occur in pairs separated by serous fluid o Visceral layer covers the outside of the organ o Parietal layer lines a portion of the wall of ventral body cavity

Serous Membranes  Specific serous membranes o Peritoneum  Abdominal cavity o Pleura  Around the lungs o Pericardium  Around the heart

Connective Tissue Membrane  Synovial membrane o Connective tissue only o Lines fibrous capsules surrounding joints o Secretes a lubricating fluid

Integumentary System  Skin (cutaneous membrane)  Skin derivatives o Sweat glands o Oil glands o Hair o Nails

Skin Structure  Epidermis—outer layer

o Stratified squamous epithelium o Cornified or keratinized (hardened by keratin) to prevent water loss o Avascular o Most cells are keratinocytes  Dermis o Dense connective tissue

Skin Structure  Subcutaneous tissue (hypodermis) is deep to dermis o Not technically part of the skin o Anchors skin to underlying organs o Composed mostly of adipose tissue

Layers of the Epidermis  Stratum basale (stratum germinativum) o Deepest layer of epidermis o Lies next to dermis o Wavy borderline with the dermis anchors the two together o Cells undergoing mitosis o Daughter cells are pushed upward to become the more superficial layers  Stratum spinosum  Stratum granulosum

Layers of the Epidermis  Stratum lucidum o Formed from dead cells of the deeper strata o Occurs only in thick, hairless skin of the palms of hands and soles of feet  Stratum corneum o Outermost layer of epidermis o Shingle-like dead cells are filled with keratin (protective protein prevents water loss from skin)

Layers of the Epidermis

 Summary of layers from deepest to most superficial o Stratum basale o Stratum spinosum o Stratum granulosum o Stratum lucidum (thick, hairless skin only) o Stratum corneum

Melanin    

Pigment (melanin) produced by melanocytes Melanocytes are mostly in the stratum basale Color is yellow to brown to black Amount of melanin produced depends upon genetics and exposure to sunlight

Dermis  Two layers o Papillary layer (upper dermal region)  Projections called dermal papillae  Some contain capillary loops  Others house pain receptors and touch receptors o Reticular layer (deepest skin layer)  Blood vessels  Sweat and oil glands  Deep pressure receptors

Dermis  Overall dermis structure o Collagen and elastic fibers located throughout the dermis  Collagen fibers give skin its toughness  Elastic fibers give skin elasticity o Blood vessels play a role in body temperature regulation

Normal Skin Color Determinants  Melanin o Yellow, brown, or black pigments

 Carotene o Orange-yellow pigment from some vegetables  Hemoglobin o Red coloring from blood cells in dermal capillaries o Oxygen content determines the extent of red coloring

Alterations in Skin Color  Redness (erythema)—due to embarrassment, inflammation, hypertension, fever, or allergy  Pallor (blanching)—due to emotional stress such as fear, anemia, low blood pressure, impaired blood flow to an area  Jaundice (yellowing)—liver disorder  Bruises—hematomas

Skin Appendages  Cutaneous glands are all exocrine glands o Sebaceous glands o Sweat glands  Hair  Hair follicles  Nails

Appendages of the Skin  Oil (sebaceous) glands o Produce oil (sebum)  Lubricant for skin  Prevents brittle hair  Kills bacteria o Most have ducts that empty into hair follicles; others open directly onto skin surface o Glands are activated at puberty

Appendages of the Skin  Sweat (sudoriferous) glands o Produce sweat o Widely distributed in skin

Appendages of the Skin  Two types of sudoriferous glands o Eccrine  Open via duct to pore on skin surface  Produce sweat (clear) o Apocrine  Ducts empty into hair follicles  Begin to function at puberty  Release sweat that also contains fatty acids and proteins (milky/yellowish color)

Sweat and Its Function  Composition o Mostly water o Salts and vitamin C o Some metabolic waste o Fatty acids and proteins (apocrine only)  Function o Helps dissipate excess heat o Excretes waste products o Acidic nature inhibits bacteria growth  Odor is from associated bacteria

Appendages of the Skin  Hair o o o o

Produced by hair follicle Consists of hard keratinized epithelial cells Melanocytes provide pigment for hair color Hair grows in the matrix of the hair bulb in stratum basale

Appendages of the Skin  Hair anatomy o Central medulla o Cortex surrounds medulla o Cuticle on outside of cortex

 Most heavily keratinized

Appendages of the Skin  Associated hair structures o Hair follicle  Dermal and epidermal sheath surround hair root o Arrector pili muscle  Smooth muscle  Pulls hairs upright when cold or frightened o Sebaceous gland o Sudoriferous gland

Appendages of the Skin  Nails o Scale-like modifications of the epidermis  Heavily keratinized o Stratum basale extends beneath the nail bed  Responsible for growth o Lack of pigment makes them colorless

Appendages of the Skin  Nail structures o Free edge o Body is the visible attached portion o Root of nail embedded in skin o Cuticle is the proximal nail fold that projects onto the nail body

Skin Homeostatic Imbalances  Burns o Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals o Associated dangers  Dehydration  Electrolyte imbalance  Circulatory shock

Rule of Nines  Way to determine the extent of burns  Body is divided into 11 areas for quick estimation  Each area represents about 9 percent of total body surface area

Severity of Burns  First-degree burns o Only epidermis is damaged o Skin is red and swollen  Second-degree burns o Epidermis and upper dermis are damaged o Skin is red with blisters  Third-degree burns o Destroys entire skin layer; burned area is painless o Burn is gray-white or black

Critical Burns  Burns are considered critical if o Over 25 percent of body has second-degree burns o Over 10 percent of the body has third-degree burns o There are third-degree burns of the face, hands, or feet

Skin Homeostatic Imbalances  Infections o Athlete’s foot (tinea pedis)  Caused by fungal infection o Boils and carbuncles  Caused by bacterial infection o Cold sores  Caused by virus

Skin Homeostatic Imbalances  Infections and allergies o Contact dermatitis  Exposures cause allergic reaction o Impetigo

 Caused by bacterial infection o Psoriasis  Cause is unknown  Triggered by trauma, infection, stress

Skin Cancer  Cancer—abnormal cell mass  Classified two ways o Benign  Does not spread (encapsulated) o Malignant  Metastasized (moves) to other parts of the body  Skin cancer is the most common type of cancer

Skin Cancer Types  Basal cell carcinoma o Least malignant o Most common type o Arises from stratum basale

Skin Cancer Types  Squamous cell carcinoma o Metastasizes to lymph nodes if not removed o Early removal allows a good chance of cure o Believed to be sun-induced o Arises from stratum spinosum

Skin Cancer Types  Malignant melanoma o Most deadly of skin cancers o Cancer of melanocytes o Metastasizes rapidly to lymph and blood vessels o Detection uses ABCD rule

ABCD Rule  A = Asymmetry o Two sides of pigmented mole do not match

 B = Border irregularity o Borders of mole are not smooth  C = Color o Different colors in pigmented area  D = Diameter o Spot is larger then 6 mm in diameter

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