1
Q
skin derived from…
A
ectoderm
2
Q
layers of skin
A
hypodermis, dermis, epidermis
3
Q
hypodermis
A
- connective tissue
- fat and fibrous tissue
4
Q
dermis
A
- papillary layer, loose connective tissue
- below is dense reticular layer
- sweat glands, blood vessels, and hair follicles originate in dermis
- merkel discs, deep pressure and texture sensation
- Pacinian corpuscles, deep pressure and vibration
- Meissner’s corpuscles, light touch
- free nerve endings for pain
5
Q
epidermis layers deepest to outermost
A
stratum…
basale, spinosum, granulosum, lucidum, corneum
superficial to deep Come Let’s Get Sun Burned
6
Q
basale
A
stem cells, keratinocytes, Langerhans cells
7
Q
granulosum
A
keratinocytes die and lose their nuclei
8
Q
lucidum
A
- only present in thick hairless skin (palms and soles)
- nearly transparent
9
Q
corneum
A
- several dozen layers of flattened keratinocytes
- prevents pathogen invasion, loss of salt and fluid
- openings for glands
10
Q
calluses
A
XS keratin
11
Q
fingernails and hair…
A
formed from keratin
12
Q
melanocytes…
A
- derived from neural crest cells and found in stratum basale
- produce melanin, transferred to keratin
- UV radiation protection
13
Q
Langerhans cells
A
- macrophages
- capable of presenting antigens to T-cells in order to activate immune system
14
Q
sweating
A
- hypothalamus determines set point for body temp
- autonomic NS
- postganglionic sympathetic neurons use Ach and innervated sweat glands and promote secretion of water with certain ions onto skin
- evap absorbs heat from skin
- arteriolar vasodilation
15
Q
arrector pili…
A
- contract in the cold causing piloerection
- trap layer of heated air to skin
- arterioles constrict
16
Q
shivering…
A
- skeletal muscles contract rapidly in response to cold
- requires sizeable amount of ATP
- thermal energy produced as a result
17
Q
white fat…
A
just below skin helps in heating
18
Q
brown fat…
A
less efficient in ETC, more heat energy is released as fuel is burned
MCAT Biology
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