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Pema Lama
integumentary system
| Term | Definition |
|---|---|
| Two primary layers of skin | epidermis and dermis; joined by dermo epidermal junction |
| Thin skin | covers most of body surface (1 to 3 mm thick); has hair and smooth surface |
| Thick skin | soles and palms (4 to 5 mm thick); ridged surface with no hair |
| Keratinocytes | constitute over 90% of cells present; principal struc-tural element of the outer skin; sometimes called corneocytes after they are fully keratinized |
| Melanocytes | pigment-producing cells (5% of the total); contribute to skin color; filter ultraviolet light |
| Epidermal dendritic cells | branched antigen-presenting cells (APCs); they play a role in immune response; also called Langerhans cells |
| Tactile epithelial cells (Merkel cells) | attach to sensory nerve endings to form “light touch” receptors |
| Stratum basale (base layer) | single layer of columnar cells; only these cells undergo mitosis and then migrate through the other layers until they are shed; stratum germinativum (growth layer) is another name for stratum basale (or stratum spinosum and stratum basale together) |
| Stratum spinosum (spiny layer) | cells arranged in 8 to 10 layers with desmosomes that pull cells into spiny shapes; cells rich in RNA |
| Stratum granulosum (granular layer) | cells arranged in two to four layers and filled with keratohyalin granules; contain high levels of lysosomal enzymes; helps form a leakproof barrier |
| Stratum lucidum (clear layer) | cells filled with keratin precursor called eleidin; absent in thin skin |
| Stratum corneum (horny layer) | most superficial layer; dead cells filled with keratin (barrier area) |
| Dermoepidermal junction (DEJ) | 1)A basement membrane, with unique fibrous elements, and a polysaccharide gel serve to “glue” the epidermis to the dermis below 2. The junction serves as a partial barrier to the passage of some cells and large molecules |
| Dermis | 1)Sometimes called “true skin”—much thicker than the epidermis and lies beneath it 2) Gives strength to the skin 3. Serves as a reservoir storage area for water and electrolytes 4. Contains various structures |
| Layers of dermis: Papillary layer | composed of dermal papillae that project into the epidermis; contains fine collagenous and elastic fibers; contains the dermoepidermal junction; forms a unique pattern that gives individual fingerprints |
| Layers of dermis: Reticular layer | contains dense, interlacing white collagenous fibers and elastic fibers to make the skin tough yet stretchable; when processed from animal skin, produces leather |
| Hypodermis | A) also called the subcutaneous layer or superficial fascia B. forms connection between skin proper and other structures C. Mostly loose fibrous and adipose connective tissue, along with nerves, blood/lymphatic vessels |
| Melanin | Basic determinant is quantity, type, distribution of melanin |
| Types of melanin | a) Eumelanin—group of dark brown (almost black) melanin b) Pheomelanin—group of reddish and orange melanin |
| Melanin formed from tyrosine by melanocytes | a) Melanocytes release melanin in packets called melanosomes b) Melanosomes are ingested by surrounding keratinocytes and form a UV-protective cap over the nucleus |
| Albinism | congenital absence of melanin |
| Beta-carotene | (group of yellowish pigments from food) can also contribute to skin color |
| Lipofuscin | —accumulates in cells that have ceased mitosis in aging skin, producing brown-yellow age spots |
| Hemoglobin | color changes also occur as a result of changes in blood flow a) Redder skin color when blood flow to skin increases b) Cyanosis—bluish color caused by darkening of hemoglobin when it loses oxygen and gains carbon dioxide c. Bruising |
| lanugo | Fine and soft hair coat existing before birth |
| terminal hair | Coarse pubic and axillary hair that develops at puberty |
| Papilla of hair | cluster of capillaries under germinal matrix |
| Root of hair | part of hair embedded in follicle in dermis |
| Shaft of hair | visible part of the hair |
| Medulla of hair | inner core of hair |
| cortex of hair | outer portion of hair |
| androgenic alopecia | Male pattern baldness results from combination of genetic tendency and male sex hormones |
| Nails | 1. Consist of epidermal cells converted to hard keratin 2. Nail body—visible part of each nail 3. Root—part of nail in groove hidden by fold of skin, the cuticle 4. Lunula—moon-shaped white area nearest root |
| Nail bed | layer of epithelium under nail body; contains abundant blood vessels a) Appears pink under translucent nails b) Nails may have pigmented streaks c) Separation of a nail from the nail bed is called onycholysis |
| Nail Growth | nails grow by mitosis of cells in stratum basale beneath the lunula; average growth about 0.5 mm per week, or slightly over 1 inch per year |
| types of sweat glands: Eccrine glands | 1) Most numerous sweat glands 2) Simple, coiled, tubular glands 3) Function throughout life 4) Secrete perspiration or sweat; eliminate wastes and help maintain a constant core temperature |
| types of sweat glands: Apocrine glands | 1) Located deep in subcutaneous layer 2) Limited distribution—axilla, areola of breast, and around anus. 3) Large 4) Simple, branched, tubular glands 5) Begin to function at puberty 6) Secretion shows cyclic changes in female with menstrual cycle |
| Sebaceous glands | a. Secrete sebum b. Lipid components have antifungal activity c. Simple, branched glands d. Found in dermis except in palms and soles e. Secretion increases in adolescence; may lead to formation of pimples and blackheads |
| Ceruminous glands | a) Modified apocrine sweat glands b) Empty contents into external ear canal alone or with sebaceous glands c) Function of cerumen to protect area from dehydration; excess secretion can cause blockage of ear canal and loss of hearing |
Created by:
Pemalama