Skin Physiology Flashcards
Identify skin layers
- stratum corneum
- stratum granulosum
- stratum spinosum
- basal cell layer
- DEJ (BMZ)
- Papillary dermis
which 3 pigments contribute to skin color?
- Melanin: dark color
- Carotene: most obvious in palms and soles of feet
- hemoglobin: pinkish hue of skin
what synthesizes Melanin?
It is synthesized by Melanosomes (organelle)
what are the 2 types of Melanosomes?
1-Eumelanosomes: synthesize from Tyrosine eumelanin, a dark pigment (africans)
2-Pheomelanosomes: that make from tyrosine and cysteine Phemelanin (orange pigment) (Whites europeans)
Genes implicated in skin tones?
-OCA2
MC1R
SLC24A5
What is Melanin?
a high molecular weigh polymer
Melanocytes are derived from?
Neural crest
-Melanocytes inject melanosomes into keratinocytes
how is regulated skin pigmentation?
Stimulus=> a-melanocortin stimulating hormone (MSH)=>Melanocortin-1 receptor (MC1R)=> Tyrosinase=>Eumelanin/ Pheomelanin production
What is a transporter gene mutation?
OCA2 P-protein Tyrosine
Albinism and blue eyes
SLC24A5 (threonine)
Light
SLC24A5 (Alanine)
Dark
Endogenous pigmentation protects?
- from Solar radiation
- absorbing free radicals
- tanning reactions
facultative pigmentation?
tanning in light skinned people
premature aging of skin
Natural tanning process occurs in response to?
UVR
natural tanning process characterized by?
- increased number of melanocytes
- increased dendricity of melanocytes
- increased size and number of melanosomes
- increased proliferation of keratinocytes
Why is there skin pigmentation?
1- Prevention of photolysis
2-photosyntesis
Vit D3/ Folic acid
UVA
penetrates deeper
OCA2 mutation?
oculocutaneous albinism
identify appendages of the skin?
Glands (sweat, sebaceous), hair, nails
identify types of sweat glands?
- Eccrine sweat glands: palms and soles of feet
- Apocrine: axillary and anogenital areas
- Ceruminous: ext. ear canal
- Mammary glands: secretion of milk
types of nervous or reflex sweating?
- cortical (emotional) eccrine sweating
- hypothalamic (thermoragulator)
- Medullary (gustatory)
- spinal cord transection
- intrasympathetic
- Axon reflex
identify innervation of sweat glands?
anatomically sympathetic
functionally: parasympathetic
Nerves are Sympathetic cholinergics
sweating after direct heat is a ?
non-nervous sweating
- does not involve sudomotor nerves
- it is unaffected by acclimatization
- no seasonal variation in response
how is the regulation of chemical content of sweat?
CFTR controls amount of water associated with Cl transport
how is heat produced?
it is produced in the core (Liver)
Where are located the core sensors?
-primarily in Hypothalamus and spinal cord
Hypothalamic neurons are located in?
-preoptic and anterior region
what are hypothalamic centers
centers set to respond to very small changes in temperature. Finely controlled
when do hypothalamic centers mature?
Late in development: problem for premature infants!
What are the mechanisms for removal of body heat?
infrared radiation
evaporation
convection
conduction
What are the mechanism for conservation of body heat?
- increased heat production
- vasoconstriction
- protective clothing
Effect of alcohol in body heat?
dilation of peripheral blood vessels
Hypothermia
In warm conditions how heat is regulated?
- heat lost by radiation
- more blood flow through dilated capillaries
- shunt vessel constricted diverting blood to capillaries
in cold conditions?
- less blood flow in capillaries
- shunt vessel dilated to divert blood from capillaries
- cyanosis
receptors in cold conditions?
-active vasoconstriction
alpha-adrenergic= smooth muscle to contract
in warm conditions?
active vasodilation
beta-adrenergic decrease smooth muscle activity (dilates)
M3 (NO)-AchR= decrease SmM (All sympathetic)
What are the failures in temperature control
- fever
- drugs acting on hypothalamus
- abnormal sweating
- Malignant hyperthermia= increase Ca release, stiffness
- erythroderma
- menopausal flushing
- age
What is trans-epidermal water loss (TEWL)?
water lost though skin in normal circumstances
-barrier to water loss: stratum corneum
How lipophilic materials penetrates the skin barrier?
Easily
eg. Strogens are highly lipophilic
how is the sensory function of the skin?
- tactile sensation =>rapidly adaptating receptor
- thermal sensations=> adaptating
- pain sensation (non-adaptating!)
- itch sensation (nociceptors)
identify neuro-inflammatory functioning of the skin
- Axon reflex
- Neuropeptides
- bradykinin
- Mast cells
identify receptors of fine touch and fine discrimination?
- Meissener’s corpuscle
- Merkel cells
identify receptor of crude appreciation of signal, that sense vibration and are general not specific?
- Pacinian corpuscle
- Ruffini endings
What is Triple response of Lewis?
-cutaneous response from stroking the skin= Wheal
-release of Histamine (skin)
-red spot= capillary dilatation
-Flare= redness due to arteriolar dilatation mediated by axon reflex
Wheal
What cells are involved in this immediate hypersensitivity response?
Mast cells and basophils effector cells involved
The release of Histamine triggers response of?
CGRP= arterial vasodilation in the area
Epidermis develops from?
Ectoderm
Dermis and Hypodermis from?
Mesoderm
In adolescent skin become oilier and acne appear due to
Sex steroids
Skin shows effect of environmental assaults around?
30 y/o
Skin in the old?
- skin thinner
- dry and itchy
- intolerance to cold due to fat layer decreases
- decrease elasticity
- decrease numbers of Melanocytes and more risk of Cancer
