Skin Anatomy

layers, tattoos, burns, accessory structures

layers of the skin

epidermis, dermis, hypodermis

epidermis overview

keratinocyte barrier

dermis overview

highly vascular with lots of connective tissue

hypodermis overview

subcutaneous fat

functions of skin

protection, thermoregulation, sensation

epidermis layers (stratum ____)

corneum, lucidium, granulosum, spinosum, basale

stratum corneum description

layers of dead keratinised cells/stratified squamous that aid barrier function

stratum granulosum description

contain keratinocytes and granules that dehydrate/kill cells

stratum lucidum function

extra layer in thick skin to resist shearing forces

stratum spinosum

contains dendritic cells and partially dehydrated keratinocytes connected by desmosomes

stratum basale

layer of basal cells that divide to produce keratinocytes

Cells in epidermis held together by… (2)

desmosomes — neighbouring cells
hemidesmosomes — stratum basale to basement membrane

2 layers of dermis ( + functions)

papillary (nourishment), reticular ( strength)

what are dermal papillae and their function?

extensions of dermis into epidermis that increase contact surface area to aid nutrient supply by blood vessels

2 plexuses (location)

cutaneous (dermis/hypodermis juntion), subpapillary (papillary/reticular junction — loops extend upwards)

why is tattoo ink mistaken for melanoma?

ink in dermis recognised as foreign, captured by immune cells and sent to lymph nodes

1st degree burns (where, looks like, skin function, healing)

epidermis
erythema (red, dry)
barrier still works
3-10 days

2nd degree burns (where, looks like, skin function, healing)

epidermis + dermis
moist, red, blistered (+ waxy white if deeper)
accessory structures may be affected
1-2 weeks normal/1 month deeper

3rd degree burns (where, looks like, skin function, healing)

hypodermis
waxy white to deep red to black, leathery
pain receptors destroyed
weeks + scarring

hair types

terminal (dark, visible) vellus (thin)

what is hair made of?

dead keratinised cells

arrector pili muscles function

contract to pull hairs straight and trap warm air

root hair plexus (what is it and function)

sensory network at base of hair follicles that detect movement of hair shaft

hair shaft vs. hair follicle

follicle = production
shaft = visible

sebum

oily, water repellent secretion of sebaceous glands

holocrine glands

secretory cells that disintegrate to coat the hair shaft

what are eccrine sweat glands (frequency, location, function and type of secretion)

common, increased number on palms and soles of feet, temp regulation and waste, watery secretion onto skin surface

nail body

tightly pressed keratinocytes

nail bed

epidermis nail body sits on

nail root

hidden epidermal fold that produces nail

lunula

impression on nail from layers pushed up by thickened basale (due to underlying blood vessels)

eponychium

thickened layer of living skin at base of nail

hyponychium

thickened layer of living skin at free edge (front) of nail

functions of nails (4)

protection of fingertips/toes
counteractive force prevents distortion of digits and heightens sensation
colour indicates medical condition

how does reduced blood flow cause visble ageing?

less collagen and elastin — looser skin (thinner dermis and epidermis)
slower repair
dendritic cells die
fewer melanocytes
inefficient sweat and sebaceous glands

what accelerates ageing and why?

smoking and vaping by reducing blood circulation

melanocytes (+ location)

cells that produce melanin found in stratum basale

melanin

UV protection pigment

melanosomes

vesicles containing melanin

mole vs. freckle

mole = cluster of melanocytes
freckle = overproduction of melanosomes

basal cell carcinoma (affected cells, danger)

affects basal cells, benign (basal cells shed and metastasis unlikely)

melanoma (affected cells, danger)

affects melanocytes, very dangerous (not shed, metastasis likely — the thicker and the deeper, the more dangerous)

vitamin D deficiency cause

skin pigmentation doesn’t match UV exposure — not enough UV let in to convert precursor molecule to vit D

what are apocrine sweat glands (frequency, location, function and type of secretion)

less common, specific areas (armpits, groin), influenced by hormones, sticky/oily secretion onto base of hair follicle