1
Q
Summary of Functions
A
- protection
- sensory reception
- thermoregulation
- Vitamin D synthesis
- Excretion
2
Q
Epidermis (overview)
A
- outermost layer
- keratinized
- mostly dead epithelial cells
3
Q
Dermis (overview)
A
- CT embedded with hair follicles, nerves, blood vessels, glands, and receptors
4
Q
Hypodermis (overview)
A
- adipose
- other CT
- arteries
5
Q
EPIDERMIS
vascular or avascular?
where does cell division occur?
what does epidermal thickness depend on?
what is melanin and what does it contribute to?
A
- many layers (stratums) of varying age and morphology
- avascular, requiring diffusion to receive nutrients
- deepest layer (basale) where cell division occurs
- outermost layers consisting of dead cells
- epidermal thickness varies depending on weight-bearing and abrasion (#keratin)
- melanocytes found in deepest layer, produce melanin - major contributor to skin color
- DNA damage caused by UV-B triggers melanin production
6
Q
DERMIS
what does it contain?
what are the epidermal derivatives?
A
- deep to epidermis, “true skin”
- contains small blood vessels to maintain metabolic rate, and temp regulation
- contains nerves, sensory receptors, smooth muscle around hair follicles, and macrophages
- epidermal derivatives include:
- HAIR
- NAILS
- SUDORIFEROUS GLANDS
- SEBACIOUS GLANDS
- CERUMINOUS GLANDS
7
Q
HAIR
what does it grow from?
what is the muscle surrounding the follicles?
A
- grows from a follicle (where the cell division is happening)
FLAT: curly; ROUND: straight; OVAL: wavy
- follicles surrounded by a muscle called arrector pili
—–> sympathetic innervation; contraction triggers sebum secretion and piloerection (goosebumps)
8
Q
NAILS
where does it grow from?
what is it made of?
what is it supplied by?
A
- grow from root under lunula (1mm/6-10 days)
- both hair and nail mostly keratin
- roots supplied by BV and nerves
9
Q
SUDORIFEROUS GLANDS
(Merocrine)
A
- contain vesicles that secrete odorless water with few electrolytes (sweat proper)
- largest concentration in palms and soles, but found everywhere
- continuous excretion, though increased by sympathetic stimulation
- thermoregulation (max loss ranges from 1-3 L/hour)
10
Q
SUDORIFEROUS GLANDS
(Apocrine)
A
- through exocytosis secrete sweat along with fatty acids, hormones, and other proteins into hair follicles
- largest concentration around genitalia and axillae
- odor produced by bacteria feeding on secretions
- become active after puberty; periodic excretion; ACh sensitive-triggered by emotions of fear, anxiety, stress, sexual arousal, and pain
11
Q
SABACEOUS GLANDS
what does sebum do?
what are the glands stimulated by?
what is the composition of sebum affected by?
A
- produce an oily substance called sebum
- antimicrobial, moisturizing, and inhibits water loss
- stimulated by sex hormones
- decrease #s with age
- composition of sebum afected by the types of fatty acids in the diet
12
Q
CERUMINOUS GLANDS
what is cerumen?
what does cerebum do?
what is composition affected by?
A
- a modified sudoriferous gland that produces cerumen
- cerumen is a mix of apocrine secretion, sebum, and dead epithelial cells
- antimicrobial, lubricating, and cleansing
- composition affected by diet, irritants, and genetics
13
Q
HYPODERMIS
A
- also called the subcutaneous layer as it is below the skin (dermis)
- mostly adipose, though other CT fibers extend through both the dermis and hypodermis
14
Q
FUNCTIONS OF THE SKIN
Protection
A
- keratin helps waterproof the skin
- sebum is acidic and bacteriostatic (controls bacteria and growth)
- melanin helps protect underlying tissue from UV light
- mechanical barrier to many external forces (1st line of defense)
15
Q
FUNCTIONS OF THE SKIN
sensory reception
A
- contains neurologic receptors for hot, cold, touch, pressure, vibration, pain, and light
- motion of hair shaft is interpretable by the brain
16
Q
FUNCTIONS OF THE SKIN
thermoregulation
A
- blood vessels and sweat glands help regulate internal temp (via hypothalamic and midbrain control)
- to cool the body: dermal capillaries dilate and sweat glands are activated
- to preserve heat: dermal capillaries constrict and arrector pili contract to close sweat glands
- long term cold exposure eventually leads to surface capillary dilation to warm skin
17
Q
Fever Response
A
- an increase in the set point temp of the body by the hypothalamus in response to pyrogens such as cytokines released by macrophages during phagocytosis of bacterial or viral particles.
- initially, the higher set of point makes the person feel cold as it works to increase temp
- as pyrogens are cleared set point is lowered causing the hot sensation (fever break)
18
Q
Vitamin D Synthesis
A
- a cholesterol compound found in the skin is converted to Vitamin D3 upon UV exposure
- very little UV light is required to achieve adequate conversion
- D3 is activated by kidney or macrophages resulting in:
- facilitated Ca and P absorption from the gut OR
- immune modulation
19
Q
Excretion
A
- is a waste removal
- quantitatively the skin plays a minimal role in comparison to the other excretory routes of the body
- qualitative changes to WHAT is secreted through the skin occur in response to consumption, exposure, metabolism and detoxification abilities, and excretion potential of the other routes
- this qualitative change in discharge leads to a change in the terrain of the skin
