Integumentary System
Forms boundry between body and extenernal environment. Consists of skin, hair, nails, glands
Functions of Integumentary System
Protection, Sensation, Temp Regulation, Vit D production, Excretion, Immunity
Skin Tissue Layers
Epidermis, Dermis, (Not part of skin but under it - Subcutaneous tissue (hypodermis))
Epidermis - Basic
most superficial layer of the skin, consists of epithelial tissue
resists abrasion on skin's surface and reduces H2O loss
Dermis - Basic
Layer of connective tissue. responsible for most of structural strength of skin
Subcutaneous Tissue (hypodermis)
layer of loose connective tissue - not part of skin or integumentary system, but connects skin to underlying muscle or bone
Epidermis Structure
Avascular (no blood vessles), nourished by diffusion from capilalries of papillary layer of dermis, composed of cells arranged into strata (layers) and separated from dermis by basement membrane
Epidermal Cell Types
Karatinocytes, Melanocytes, Langerhans Cells, Merkel Cells
Karatinocytes
most cells of epidermis - produce protein (keratin) that makes cells more durable. gives epidermis ability to resist abrasions and water loss
Melanocytes
contribute to skin color - melanin produced is then transferred to keratinocytes, same # of melanocytes in all people
Langerhans Cells
part of immune system
Merkel Cells
detect light touch and superficial pressure
Desquamate
cells of the deeper layers undergo mitosis, as they move toward the surface, older cells slough off
Keratinization
as cells move outward through the layers, they fill with karatin, die, and serve as a layer that resists abrasion and forms permeability layer
5 Epidermal Strata
Stratum Basale (germinitvum), Stratum Spinosum, Stratum Granulosum, Stratum Lucidum, Stratum Corneum
Stratum Basale
deepest portion of epidermis, single layer. High mitotic activity and cells become karatinized - divides aprox every 19 days and takes aprox 40-56 days for cell to reach epidermal surface & slough off
Stratum Spinosum
8-10 layers of cells - Limited cell division. As cells push to surface, they flatten;Desmosomes break apart and new ones form. Lamellar bodies (lipid-filled membrane-bound organelles) and additional keratin fibers form
Stratum Granulosum
2-5 layers of cells - containes keratohyalin (non-membrane bound protein granules). in most superficial layers, nucleus and other organelles degenerate and cell dies
Stratum Lucidum
thin, clear zone. Consits of several layers of dead cells w/ indistinct boundaries that appear somewhat transparent. Found only in palms and soles
Stratum Corneum
25 or more layers of cells - most superficial layer of skin consisting of cornified cells (dead cells, w/hard protein envelope/filled w/keratin). Desmosomes break apart and cells are shed from surface of skin
Epidermal Layers & Keratinization
Cells are produced at botom of epidermis (S. Basal), keratin fibers and lamellar bodies accum. (S. Spinosum), keratohyalin granulues accum., hard protein env. form, lamellar bodies release lipid, cells die (S. Granulosum), cells dead & conatin dispersed keratohyalin (S. Lucidum), dead cells have hard env., contain keratin & surrounded by lipids (S. Corneum)
Comparison of Skin Chart
Thick Skin
all 5 epithelial strata and S. Corneum has many layers of cells. Found in areas subject to pressure or frinction - ex. palms of hands, fingertips, soles of feet. Gives fingerprints/footprints du to papillae in parallel rows
Thin Skin
Covers rest of body and is more flexible than thick. Each strata contain fewer layers of cells. Hair grows here
Callus
Increase in number of layers in stratum corneum to produce thickened area where in skin subjected to friction or pressure.
Corn
When a callus occurs over a bony prominence. Base is at surface but apex is deep in epidermis and can be painful
3 Factors for Skin color
Pigments in skin, Blood circulationg through skin, Thickness of S. Corneum
2 Pigments in Skin Color
Melanin and Carotene
Melanin
provides for protection against UV light. Group of chemicals derived from amino acid tyrosine which is converted to molecules colored brown to black, may be yellowish or reddish. Determined by genetic factors, exposure to light, hormones.
Melanocytes
irregularly shaped cells w/ many long processes that extend between karatinocytes of S. Basal & S. Spinosa
Albinism
deficiency or absence of pigment. Production determined by genetics, hormones, exposure to light
Blood in Skin for Skin Color
blood flowing through skin imparts a reddish hue during blushing, anger, inflamation; decrease in blood flow (shock) can make skin appear pale or by cyanosis - decrease in blood oxygen imparts bluish color
Cyanosis
blue color caused by decrease in blood oxygen content
Carotene
yellow pigment found in vegetables (carrots,corn). Humans injest as source of Vit A. Lipid-soluble and excess accumulates in stratum corneum, in adipose cells of dermis, and in Subcutaneous tissue causing skin to develop yellowish tint.
How melanin works for Skin Color
Melanosomes proced by golgi apparatus of melanocyte. Melanosome moves into melanocyte cell process and the epitherlial cells phagocytize end of it and melanosome moves into epitherlial cells