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forms the external body covering and protects deeper tissues from injury. Synthesize vitamin D and houses cutaneous (pain, pressure) receptors and sweat/oil glands.
What are the cells of the epidermis
keratinocytes, melanocytes, epidermal dendritic cells, and tactile cells
produce fibrous protein keratin; arise in stratum basale; these cells undergo continuous mitosis
Composition and function of Keratinocytes
Which cells are tightly connected to one another by desmosomes. Arise in the stratum basale and undergo constant mitosis for epidermal growth. They are dead by the time they reach the surface of the skin.
Epidermal dendritic (Langerhans) cells
macrophages that help activate the immune system; first line of defense against pathogens
Tactile (Merkel) cells
touch receptors that expand into the epidermis. Associated with sensory nerve endings.
What are the 5 layers of the epidermis ?
(1) stratum corneum (2) structum lucideum (3) Stratum granulosum (4) stratum spinosum (5) Stratum Basale
(horny layer) 20 to30 cell layers thick that accounts for up to ¾ of the epidermal thickness. Keratin and thickened plasma membranes of cells protect the skin against abrasion and penetration and glycolipids b/w its cells waterproofs this layer. Barrier against biological, chemical, and physical assaults.
thin translucent band, consists of rows of clear, flat, dead kertinocytes. Visible only in thick skin.
consists of 3-5 layers in which the cells flatten. Keratinization begins. Cells flatten, nuclei and organelles begin to disintegrate and begin to accumulate 2 types of granules: keratohyaline granules and the lamellated granules.
granules that contain water resitant glycolipid that is spews into the extracellular space and is a major factor in slowing water loss across the epidermis.
Which stratum is several cell layers thick; Contain intermediate filaments mainly pre-keratin filaments that attaches to the desosomes. Abundant melanin granules and dendritic cells.
deepest epidermal layer, contain single row of stem cells, youngest keratinocytes, 10-25% of cells are the melanocytes. Also called, germinativum: cells that undergo rapid division
strong flexible connective tissue. Cells include: fibroblasts, macrophages, mast cells and white blood cells. Supplied with nerve fibers, lood vessels, and lymphatic vessels.
What layer forms the thin superficial, areolar connective tissue in which collagen and elastic fibers form woven mat with small blood vessels.
superior surface of papillary layer contain capillary loops, non encapuslated free nerve endings (pain receptors) and ecapsulated touch receptors (meissner's corpuscles)
makes up 80%of the thickness of dermis. Dense fibrous connective tissue, elastic fibers provide stretch-recoil properties.
deepest region; anchors to muscles; subcutaneous deep into skin in various regions. Shock absorber and insulator
network of blood vessels that nourishes the hypodermis it also contains collagen fibers that forms cleavage of tension lines.
fat storage, oils having unsaturated bonds (c=c; carbon-carbon double bonds) found in the hypodermis layer.
produced in melanocytes; migrates to keratinocytes where it forms "pigment shields" for nuclei (protects DNA from UV light damage); concentrated amounts found in freckles and pigmented moles
yellow to orange, mostly in the palms and soles; Vitamin A precursor (necessary for normal vision); acquired from diet
oxygen carrying pigment of red blood cells. Produce pink or red color skin when concentrated in surface capillaries.
Eccrine sweat glands
(merocrine exocytosis secretion) abundant on palms, soles, and forehead; 99% water, NaCl, vitamin C, antibodies, and metabolic wastes; ducts connect to pores; body temperature regulation by cooling as the water of sweat evaporation
Apocrine sweat glands
(merocrine exocytosis glands) approx. 2000 of the; largely confined to axillary and anogenital areas. produce during puberty. Larger than eccrine glands and lie deeper in the dermis. Ducts connect to hair follicles.
Modified apocrine glands in external ear canal; secrete cerumen (wax); mammary glands
Sebaceous (oil) glands
develop from hair follicles; become active at puberty; create sebum (oily substance)
oily holocrine secretion (secretion by cell rupture) softens and lubricates the hair and skin, prevents hair from becoming brittle and slows water loss from the skin; has bactericidal action
guarding the scalp against physical trauma; helps prevent heat loss; protects from sunlight (UV rays)
consists of dead keratinized cells; contains hard keratin; more durable than soft keratin of skin
extends from the epidermal surfaced into dermis; two-layered wall: outer connective tissue root sheath, inner epithelial root sheath
coarse, long hair of eyebrows, scalp, axillary, and pubic regions (and face and neck of males)
Structure of a nail
scale-like modifications of the epidermis on fingers and toes. Hard keratin composition
Functions of the integumentary system
1) protection 2) body temperature regulation 3) cutaneous sensations 4)metabolic function 5) blood reservoir 6) excretion
What are the 3 types of barriers used for Protection
(1) chemical, (2) physical/mechanical, and (3) biological.
which barrier has low pH secretion (acids) and defensins (antimicrobial proteins) retard bacterial activity.
keratin and glycolipids block most water and water-soluable substances; limit penetration of skin by lipid-soluble substances (poison ivy)
macrophage and macrophage-like cells; dendritic (taking up the bacteria and activate immune system) cells of the epidermis
temperature, touch, and pain; exteroceptors-- respond to stimuli arising outside the body
nutrients reach the surface of the skin by diffusion; synthesis of Vitamin D precursor (UV light converts precursor to Vitamin D); what function of the integumentary system is this?
What integumentary system function holds up to 5% of body's blood volume (not in epidermis)
what integumenatary system function has nitrogenous wastes and salt in sweat (ammonia urea, uric acid)
most skin tumors (undifferentiated cells) are benign; primary risk factor is overexposure to UV radiation.
Basal Cell Carcinoma
least malignant, most common; stratum basale cells (undifferentiated) proliferate and slowly invade dermis and hypodermis. Cured by surgical removal.
Squamous Cell Carcinoma
second most commom; involves keratinocytes of stratum spinosum; most common on scalp, ears, lower lip, and hands; grow rapidly and metasize. Treated by radiation therapy and surgically removed.
Most dangerous; involves melanocytes; highly metastatic and resistant to chemotherapy; treated by wide surgical excision accompanied by immunotherapy
heat, electricity, radiation, certain chemicals; causes tissue damage, denatured cell protein and cell death
Immediate threat of burns
dehydration and electrolyte imbalance leading to renal shutdown and circulatory shock.
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