integumentary system Flashcards
(19 cards)
what is the skin?
- organ: different tissues working together
- largest organ in the human body
- 7% of total body weight
what are the functions of the skin?
- protection against mechanical damage
- prevent water loss
- vitamin d production
- sensory reception
- temperature regulation
- excretion of salts/waste
what is the epidermis?
- keratinized stratified squamous epithelium
- 4 cell types
- avascular
- regenerates every 35-45 days
- 4 or 5 cell layers (thin vs. thick)
what are the 4 types of cells in the epidermis?
- keratinocytes: produce keratin, most abundant
- melanocytes: produce melanin to shield from UV
- merkel cell: sensation
- dendritic cell: immune cell
what are the layers of the epidermis? (superficial to deep)
- stratum coreneum
- stratum lucidum
- stratum granulosum
- stratum basle
- dermis
what is the dermis?
- underlies epidermis
- strong, flexible connective tissue
- highly vascularized
- innervated (sensation)
- 2 cell layers: papillary (20%), reticular (80%)
describe the layers of the dermis
- papillary layer: superficial, about 20%. areolar connective tissue, provides nutrients to epidermis, dermal papillae increase surface area for transport of material into epidermis
- reticular layer: deep, about 80%. mostly dense irregular tissue. network of collagen and elastic fibers provide stretch, strength
what is the hypodermis (subcutaneous)?
- supports skin (epidermis and dermis)
- areolar and adipose loose connective tissue (mostly adipose)
- stores fat
- provides insulation
- anchors skin to muscles
- allows movement of skin over muscle and bones
what are fingerprints?
dermal papillae push up and elevate the overlying epidermis (create epidermal ridges). patterns are unique
what is hair?
- flexible strands made of keratin
- pigement comes from melanocytes
- functions: sensation (light touch), protection, insulation
what are nails?
- modified stratum corneum
- protects the fingers
- parts: free edge (white), nail body, nail root (embedded in skin)
describe the structure of a hair follicle
- basic: shaft (exposed), root (embedded)
- hair follicle: bulb (innervation), papilla (blood supply)
- arrector pili muscle: contraction of this muscle raises (erects) hair, causes goosebumps
what are sweat glands?
- sweat glands can be eccrine (a form of merocrine gland) or apocrine
- eccrine sweat glands: secreted onto skin surface. allows evaporating cooling
- development: invaginate from skin surface
- product: 99% water, 1% salts/wastes
- acidic; antibacterial properties
- apocrine sweat glands discharge into hair follicles, not body surface
- development: outgrowths from hair follicles
- product: complex molecules, odorous, found in armpits/genitals
what is a modified sweat gland?
- ceruminous: line external ear canal, produce earwax
- mammary: secrete milk
what is a sebaceous gland?
- multicellular exocrine glands
- open into hair follicles
- secrete sebum (oil): holocrine secretion-cells accumulate sebum and burst to release product
- moisturizes hair and skin
- blocked hair follicle = acne
what is melanin?
- melanin acts as a natural sunblock, determines skin tone
- number of melanocytes does not vary among individuals; activity level of melanocytes does
what is the correlation between skin color and UV?
- some exposure to sunlight is essential: uv rays cause epidermis to produce vitamin d, needed for absorbing calcium (light skin in the north facilitates this)
- excessive exposure is dangerous: reduces folate levels needed for embryonic development, promotes skin cancer
- skin color affects amount of uv absorbed: darker skin in tropical (high sun) environment reduces uv absorption, protects folic acid levels
what is skin cancer?
most common form of cancer
- basal cell carcinoma originates in the stratum basale. metastasis is rare
- melanoma is potentially life-threatening, because cancerous melanocytes grow rapidly and spread through the lymphatic system
what are the ABC’s of skin cancer?
- a: asymmetry
- b: border
- c: color
- d: diameter
- e: elevation
