U3 Summative - Integumentary System Flashcards
Skin Functions
- Makes skin tough (keratin)
- Barrier to penetration/injury
- Contains immune system cells (macrophages/langerhans cells: engulfs bacteria, found in the stratum spinosum)
- Regulates body temp. (maintains homeostasis)
- Houses sensory receptors
- Composed of several tissues
- Retards water loss (stratum corneum)
- Excretes small amounts of waste (sweat)
- Synthesizes chemicals
Skin varies in thickness mostly due to:
variations in the stratum corneum (the uppermost layer)
Epidermis
TOP LAYER - Stratified squamous epithelium, avascular, “cornified” with protein keratin, uses diffusion
Layers of Skin
Epidermis
Dermis
Hypodermis
Stratum Basale (Melanocytes, Merkel Cell/Disc, Cell Production)
Found in the basement membrane of the epidermis! Keratinocytes give rise to most new epidermal cells that are pushed outward during cell division, melanocytes (produce melanin), merkel cells/discs in conjunction with a dermal nerve ending, form a tactile/touch receptor
Stratum Spinosum (Macrophages/Langerhans cells)
Macrophages (called Langerhans cells) are present in this layer and the stratum granulosum, mitosis happens here, several layers of flattened keratinocytes, comprised of filaments making the skin flexible/strong
Statum Granulosum
This layer consists of two to five layers of cells with granules of keratohyalin (living cells); living keratinocytes creating keratin/adding keratin to new cells
Stratum Lucidum
Clear & thin, only seen in thick skin such as the soles of the feet and palms
Stratum Corneum
The stratum corneum is made up of 25-30 layers
of dead, keratinized cells.
A waterproof, protective outer layer.
Dermis
Dermis: composed of fibroconnective tissue, with blood vessels, nerve endings,
sweat glands, hair follicles, and nail roots
Papillary Dermis
Zone of areolar tissue (loose CT) closest to the epidermis, projecting upward as dermal papillae,
blood vessels extend close to the epidermis within the papillae,
the large number of white blood cells within this layer helps prevent infection
Reticular Dermis
Dense irregular connective tissue, stretching of the skin causes tears in this area,
called linea albicantes, or stretch marks
Hypodermis aka subcutaneous layer
Loose CT (adipose tissue), insulates, major BVs present, stores energy, fatty bottom layer
Dermal Vitamin D Synthesis
- UV radiation can penetrate into the dermis where it reaches 7-DEHYDROCHOLESTEROL found in blood/dermis
- UV- rays convert it into CHOLECALCIFEROL
- Kidneys/liver turn it into CALCITRIOL (active Vitamin D)
Cutaneous Absorption
blood receives 1-2% of O2 through the skin, many compounds can be absorbed through the skin!
Thermoregulation
dermail BVs contrict or dilate depending on temp. (sweat allows for evaporative cooling)
Sensory Roles/Cutaneous Sensory Receptors/Corpuscles
Nerve endings, allows for sense and touch signals sent to the brain to be processed
Hair (Pili)
- Made of hard keratin
- Accessory to the skin
- Growth of hair is due to mitosis in the cells in the stratum basale
Lanugo
Covers the fetus before birth
Vellus
Fine, unpigmented hair found all over the body
Terminal hair
long, coarse, and pigemented; found on scalp, face (men), and axillary and pelvic regions after puberty
Vibrissae
Short, “guard” hairs (found in nostrils)
Arector pili muscle
Erects the hair follicles aka “goosebumps”
Structure of nails
- Nail plate/protective, hard-keratin covering
-Nail bed - Lunula (above cuticle)
- Version of stratum corneum
Sudoriferous Glands
the most numerous cutaneous (skin) glands.
Sweat: mostly water; also, salts, ammonia, urea, sugar, uric acid, lactic acid, ascorbic and amino acids.
Eccrine sweat glands
all over the body, produce watery perspiration to cool the body; ducts to skin surface,
functional before and after puberty, sweat not very viscous
Apocrine sweat glands
developed during puberty, odorous, found in the groin, axilla, breast areola
Sebaceous glands
Everywhere minus the palms and soles; produces an oily sebum to moisturize skin and hair
Ceruminous glands
Found in ears, earwax
Breast/mammary sweat glands
Produces milk (for females)
Burns
- First-degree burns
involve only the epidermis - Second-degree burns
involve the epidermis and upper dermis - Third-degree burns destroy the skin and deeper tissue (blackened)
___% of your blood is in your skin?
5%
How skin repairs itself:
Capillaries constrict to lessen bleeding, platlets plug the wound, inflammation, white blood cells clense the wound, fibroblasts build tissue, specialized fibroblasts close/constrict the wound, re-epithelialization
The skin as we age:
- Scaly skin
- Age spots
- Dermis becomes reduced
- Loss of fat
- Wrinkles
- Sagging
- Sebaceous glands secrete less oil
- Melanin production slows
- Hair thins
- Number of hair follicles decrease
- Impaired nail growth
- Sensory receptors decline
- Inability to control body temperature
- Less vitamin D production
Keratinization
involves keratinocytes, process by which cells in the epidermis produce and accumulate to make the skin waterproof and durable (stratum corneum must be strong to prevent injury/penetration)
