Structure Of The Skin - Appendages Flashcards
What are the three skin appendages
Hair, nails, glands
What are the three main skin glands
•Sebaceous
•Apocrine
•Eccrine
Where are sebaceous glands found in the body
Widely distributed:
largest glands in face and chest
=> most common areas of acne!!
Where are sebaceous glands in the skin and where do their secretions leave the skin
Wrapped around the hair follicle (pilosebaceous unit)
Holocrine secretion opening into pilary canal
Are sebaceous glands always active
No, they are hormone sensitive & so are quiescent pre-puberty. This explains the relationship between puberty & acne
What liquid do sebaceous glands secrete & what is this composed of
Sebum
- a mixture of lipids
- e.g. squalene, wax esters, TG and FFA
What is the role of sebaceous glands
Control moisture loss & protect against fungal infection
Where are eccrine sweat glands located in the skin and where do they open into
Located in the dermis
Secrete onto skin surface
Where are eccrine sweat glands most prominent
palms, soles, forehead and axillae
How are eccrine sweat glands regulated
Sympathetic cholinergic nerve supply –
mental, thermal and gustatory stimulation
What is the function of eccrine glands
cooling by evaporation
moisten palms / soles to aid grip
Describe the secretions produced by the eccrine sweat glands
Sweat
- Hypotonic fluid
- Mainly water (~98%)
- Some electrolytes e.g. NaCl, but most electrolytes reabsorbed
Where are apocrine sweat glands located in the skin
The dermis
They develop as part of the pilosebaceous unit
Where are apocrine sweat glands most prominent
Axillae, groin, eyelids, ears, mammary and perineal regions
How are apocrine sweat glands regulated
Androgen dependent
Describe the fluid secreted by apocrine glands & explain its odour
Produce an oily fluid which produces an odour after hitting the skin and being decomposed by bacteria
Name the phases of hair follicle growth & state what happens in them
Anagen = growing
Catagen = involuting
Telogen = resting
Exogen = shedding
Where in the body does skin not have hair follicles
(& so no pilosebaceous units & so no sebaceous/ apocrine glands)
Hands, soles of the feet & lips
How is hair follicle growth regulated
It is influenced by hormonal levels e.g. thyroxine, androgens
Is hair loss permanent in alopcia areata (autoimmune hair loss) Why or why not?
No - autoimmune reaction doesn’t permanently damage the follicle
What are pilosebaceous units composed of
Hair follicle
Hair shaft
Arrector pili muscle
Sebaceous glands
What is the role of arrector pili muscles
When it contracts it causes the hair to stand erect, and a “goosebump” forms on the skin
This serves as a thermoregulator to help maintain body temp in cold conditions
What are the three segments of a hair follicle
- Infundibulum - between the sebaceous gland duct & the epidermal surface
- Isthmus - between the insertion of the arrector pili muscle & the sebaceous gland duct
- Hair bulb - contains the hair matrix & hair papilla, is the deepest part of the hair follicle
What determines/ produces hair pigmentation
Melanocytes, that are located just above the dermal papilla
