Histology of the Skin Tutorial Flashcards
name 7 basic tissue groups found in the skin
epithelia hair glands nervous tissue muscle fibres connective tissue nails
name 3 types of epithelia that exist in the skin
stratified squamous - lines epidermis
simple squamous - endothelium lining blood vessels
glandular epithelium - sweat and sebaceous glands
what are eccrine sweat glands?
found all over body except lips and genitals
regulate heat and salt loss through sweat
what are apocrine sweat glands?
found only in axillae, nipples and genitals
only develop at puberty and open into hair follicles
what are sebaceous glands?
masses in the dermis, derived from the epidermis, that secrete sebum into hair follicle to coat hair and skin
not present in palms or soles
what muscle fibres exist in the skin and what do they do?
arrector pili muscles (smooth muscle)
attached to hair follicle and pull hair perpendicular to skin
what connective tissue exists in the skin?
collagen and elastin fibres present in the dermis
what 3 types of nervous tissue is are present in the skin?
meissners corpuscles = tactile sensation (in dermis)
Pacinian corpuscles = deep pressure (in dermis)
free nerve endings = for pain (in epidermis basal layer)
what are the components of hair?
follicle = invagination of epidermis
medulla = contains soft keratin
cortex = hard keratin
bulb = bulge at base containing papilla and hair matrix - vascular channels and keratin producing cells
melanocytes sit above papilla giving hair colour
what are nails?
plates of cells filled with hard keratin
what are the components of a nail?
nail plate - sits on nail bed
matrix - cells divide and produce keratin
cuticle - extension of skin fold covering nail root
hyponychium - secures free nail edge
what causes bullous pemphigoid?
problem with dermo-epidermal junction meaning the epidermis and dermis cant stick together and fluid builds up in between
histological appearance of psoriasis?
dense nuclei at keratin layer as there is no granular layer and the cells don’t have enough time to differentiate
what are the 4 layers of the epidermis, from bottom to top?
basal layer > prickle layer > granular layer > keratin layer
thick keratin layer with gaps?
palm of hand or sole of foot
holes are for sweat glands
what are the signs and symptoms of toxic epidermal necrosis (skin failure)?
widespread rash with blisters and sheets of skin falling off following antibiotic treatment
what causes toxic epidermal necrosis?
usually drug induced
death of keratinocytes results in detachment at dermo-epidermal junction causing skin to detach in large necrotic sheets
what are the possible consequences of toxic epidermal necrosis?
loss of thermoregulation
increased infection risk
failure of homeostatic function - high/electrolyte loss = hypotension = renal failure
cardiovascular instability
list 7 requirements for healthy skin
water/hydration nutrition good vascular supply functioning immune system hygiene limited sun damage vitamin D
what are the 3 stages of healing?
inflammation
proliferation
tissue remodelling
what happens in the inflammation stage?
platelets form clot and release inflammatory mediators
leukocytes phagocytose bacteria in wound sites
inflammation decreases as keratinocyte proliferation and new tissue formation become predominant
what is involved in the proliferation and tissue remodelling stage?
cells divide to re-epithelialize the wound surface
granulation tissue formation
fibroblasts lay down matrix and contract wound
endothelial cells develop into new vessels
thus, new tissue is formed
what is involved in the tissue remodelling stage?
new tissue is converted into mature scar tissue over months
fibroblasts lay down collagen to improve tensile strength of scar and restore normal dermal matrix
what is the difference between primary and secondary intention healing?
primary intention = acute wound (e.g surgical wound)is closed by bringing the edges together
secondary = acute wound is left to heal on its own
what are the risks with primary and secondary intention healing?
primary = haematoma, infection, bad suturing secondary = infection, longer healing time
what is a first degree burn?
epidermis only
what is a second degree burn?
epidermis and dermis
what is a third degree burn?
extends beyond dermis
what is the definition of a chronic wound?
a wound that does not heal within 3 months
often exhibit a surface slough (yellow/green mixture of dead cells, polymorphs and bacteria)
E.g - diabetic foot ulcer
what must be considered with a chronic wound?
infection blood supply nutrition venous return trauma/pressure systemic diseas (diabetes, anaemia etc)
what is a bed sore?
erosion and ulceration of skin due to prolonged pressure over a bony area causing a lack of blood flow to the area as well as friction from bedding/clothing or bodily fluids
what are the stages in the development of a bed sore?
- reddening of skin
- swollen, painful blisters, upper layers of skin begin to die
- sore breaks through skin and extends into deeper layers, creating deep ulcers prone to infection
- sore extends past the skin and into fat, muscle and bone
black dead tissue may appear
