forms the external body covering and protects deeper tissues from injury. Synthesize vitamin D and houses cutaneous (pain, pressure) receptors and sweat/oil glands.
Layers of the integumentary system
Epidemis and dermis
superficial region; epithelial cells; nonvascularized; 4 cell types and 4 or 5 layers
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.
fibrous protein that helps give the epidermis its protective properties.
epithelial cells that synthesize the pigment melanin. Found in the stratum basale.
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.
covers the palms, fingertips, and soles of the feet
What kind of skin covers the rest of the body
(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.
What granules help to form keratin in the upper layers
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
Middle region, vascularized, bulk of the integumentary system; fibrous connective tissue.
strong flexible connective tissue. Cells include: fibroblasts, macrophages, mast cells and white blood cells. Supplied with nerve fibers, lood vessels, and lymphatic vessels.
What are the 2 layers of the dermis?
Papillary and Reticular
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.
single most abundant protein in the body
fat storage, oils having unsaturated bonds (c=c; carbon-carbon double bonds) found in the hypodermis layer.
What are the 3 pigments that contribute to skin color?
Melanin, carotene and hemoglobin
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.
What are the appendages of the skin?
sweat glands, oil glands, hairs and hair follicles, nails
Sweat (Sudoriferous) glands
Eccrine and Apocrine sweat glands
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.