Structure of the skin (superficial to deep)
- Epidermis
- stratum basale
- stratum spinosum
- stratum granulosum
- stratum lucidum
- stratum corneum
- Dermis
- Hypodermis
Epidermis
- Function- protection of skin & underlying tissues, prevents H2O loss
- Structure- stratified squamous
Cells of the epidermis
- Keratinocytes- “horn like,” 90% of epithelium, produce keratin (fibrous protein)
- Melanocytes- 8% epithelium, produce melanin, transfer melanin to keratinocytes
- Cells form a “veil” over nucleus
- protect DNA from UV rays
- Langerhan’s cells- dendritic cells, originate in red bone marrow (long bones), initiate immune response
- Meeker cells- least abundant, found in deepest layer of epidermis, touch & pressure
- Nervous system
Stratum basale
- base
- furthest from surface
- single layer
- tissue regeneration
Stratum spinosum
- thorn like
- 8-10 layers
- when cells are fixed gives spiny thorn-like appearance
- help connect joining cells
Stratum granulosum
- little grains
- 3-5 layers
- cells look flat
- cells are dying/deteriorating
- apoptosis
Stratum lucidum
- clear
- 3-5 layers
- only found in the skin
- fingertips, palms, bottom of feet
Stratum corneum
- horn like
-25-30 layers
-continuously shed - loose 40 lbs of skin in lifetime
-layer thickens = callous
Dermis
- Function- lots of collagen & elastic fibers, bind to H2O to skin - hydrated, helps body stay together, nutrition for skin & sensory perception (feel touch)
- Structure- blood vessels, nerves, glands, hair follicles, dense irregular CT
- Papillary layer- causes epidermis to raise (fingertips), areolar CT, receptors for touch, pain, & pressure
Hypodermis
Function- fat storage, alternative energy source, insulation, never endings to detect pressure
Structure- areolar & adipose CT, attach itself to surrounding organs/tissues, large blood vessels to supply skin with blood
Skin color
- Melanin
- produced by melanocytes
- all humans have the same number of melanocytes (skin color depends on amount of melanin produced)
1. Albinism- no melanin in hair, skin, eyes
2. Freckles- local accumulation of melanin
- Carotene
- vitamin A is a precursor to helping with vision
- Hemoglobin
- pink to red pigment
- Carrie’s oxygen in blood cells
- color depends on amount of hemoglobin + H2O in blood
Accessory structures of the skin
-hair, nails, glands
Hair
-protects scalp, decrease heat loss, sense touch, no hair on palms, bottom of feet, produced from epidermal cells & blood cells in dermis
1. Structure
- hair follicle
- root
- shaft
- hair root plexus
2. Pigment
3. Longevity- eyelashes = 3-4 months, scalp hair = 3-4 years
4. Sebaceous glands- oily secretions (one or more per follicle), washing hair everyday takes away natural oils
5. Arrector pili- smooth muscle attached to follicle, contracts = goosebumps
Nails
- Nail root- buried beneath skin
- Nail bed- site of attachment
- Cuticle- cover base of nail
- Lunula- white crescent at base
- Pigment- pink
Sweat glands
- all regions of the skin
- most on fingertips
1. Structure- coiled tubular glands opening up to body surface- apocrine glands: pubic + auxiliary regions, produce true sweat (fatty substances & protiens)
- eccrine glands- most common, skin surface, lower body temp when too warm
- ceruminous glands- “wax,” ears, produce ear wax
Sebaceous glands
- hair follicle
- lubricate hair & skin
- “water proofing” the skin
1. Acne- inflammation of sebaceous glands
Mammary glands
- modified sweat glands
- located in breast
- produce milk at childbirth
