11. 9 skin Flashcards
skin functions
thermoregulation, protection, gives sensory input, excretion, blood reservoic and makes vit D
thermoregulation
Blood can be shunted away capillaries of skin
to reduce heat loss. Hairs can be erected (piloerection) via sympathetic stimulation to trap
insulating air next to skin.
Note that ‘goosebumps’ (piloerection reflex) can occur when cold
or in response to stress/emotion (fxn in human ancestors [vestigial reflex] may have been to
make them appear larger to scare off predators.
Immunity: through skin
specialized cells of the epidermis are components of immune system
Blood reservoir: skin
Vessels in the dermis hold up to 10% of the blood in resting adult
Vit D synthesis: skin
UV radiation activates skin molecule that is a precursor to Vit D
epidermis layers
corneum, lucidum, granulosum, spinosum, basale
top—-> bottom
COME LET’s GET SUN BURNED
Stratum corneum
25-30 dead layers (variable thickness); filled w/ keratin and
surrounded by lipids
i. Lamellar granulues make it water repellent
Stratum lucidum –
only in palms and soles of feet, and finger tips; 3-5 layers, clear/ DEAD
Stratum granulosum
3-5 layer of dying cells; lamellar bodies release hydrophobic lipids HERE
Stratum spinosum
strength and flexibility; 8-10 layers held together by (desmosomes-keratin involving adhesion proteins)
- also have Langerhans cells here
Stratum basale
(germinativum) – deepest layer. contains Merkel cells and stem
cells that divide to produce keratinocytes; attached by basement membrane. Melanocytes are found here.
** rapid division of cells
Keratinocytes:
produce the protein keratin that helps waterproof the skin. As they
are pushed up to top layer of skin they accumulate keratin and die, losing their
organelles along the way. Keratin is most abundant protein in epidermis.
Melanocytes:
transfer skin pigment melanin to keratinocytes
- Langerhans cells:
interact with helper T-cells of immune system
Merkel cells:
attach to sensory neurons and fxn in touch sensation
Dermis
primarily connective tissue; collagen and elastic fibers; contains hair follicles,
glands, nerves, and blood vessels. Tightly connected to the epidermis above via basementmembrane. Highly vascularized.
*has two layers, papillary region and reticular region
Papillary region of dermis
thin vascular network within upward projecting papillae
helps supply nutrients to epidermis + regulate temp. Papillae also contain
Meissner’s corpuscles (sensory touch receptor) and their upward projection is what
creates fingerprint ridges (not to be mixed up w/ tongue papillae that have taste
buds on their surface).
Reticular region of dermis
dense connective tissue, collagen and elastic fibers; packed with oil glands, sweat gland ducts, fat, and hair follicles; provides strength, and elasticity (stretch marks are dermal tears)
dermal chromatophores.
camoflage cells
Hypodermis (subcutaneous)
technically not part of skin (but is part of the integumentary
system); areolar and adipose tissue; fat storage (heat insulator); pressure sensing nerve endings; passage for blood vessels; shock absorber
Sebaceous (oil) glands
– connected to hair follicles; absent in palms and soles. Secretes oil
(sebum) that keeps skin relatively acidic to discourage microbial growth. Acne is caused by these
glands getting plugged.
Sudoriferous (sweat) glands
eccrine or apocrine
eccrine sweat gland
(most of the body)- regulate temperature through perspiration; eliminate urea.
Open directly to skin.
apocrine sweat gland
– armpits, pubic region, and nipples; secretions are more viscous. Open to hair
follicles.
Ceruminous (wax) glands
– found in ear canal; produce wax-like material as barrier to entrance
what stands hair up on arms
smooth muscle
burn degrees
1st (epithelial layer), 2nd (epithelial + part of dermal), 3rd (both skin layers + extends into
subcutaneous)
what skin layer to reptiles molt
corneum
what are the tissues in plants
EM Video Games
- epidermis, meristem, vascular, ground
