Integument and Barriers to Infection

Question 1

dermal-epidermal junction

Answer 1

surface of palms/soles has epidermal ridges with intervening furrows
each ridge follows the outline of an underlying dermal ridge/papilla – hemidesmosomes create tight junction

Question 2

Layers of Epidermis

Answer 2

Stratum: Corneum 
lucidum (not in thin skin) 
granulosum
spinosum 
basale

Question 3

stratum basale

Answer 3

mitotically active layer
replaces skin every 15-30 days
single layer of cuboidal, low columnar cells bound to keratinocytes apically

Question 4

stratum spinosum

Answer 4

polyhedral keratinocytes

produces cytokeratin which aggregates to tonofilaments

Question 5

malpghian layer

Answer 5

consists of the stratum basale and the stratum spinosum

Question 6

stratum granulosum

Answer 6

contain granules

1) keratohyalin granules: basophilic, non-membrane bound granules (cystine and histadine rich protein, assembles keratin into bundles)
2) lamellar granules: lipid rich, barrier to foreign material and water loss

Question 7

stratum lucidum

Answer 7

translucent band of cells with no organelles or nuclei

densely packed keratin filaments

Question 8

stratum corneum

Answer 8

multiple layers of cells with mature keratin (Squames == fully keratinized)
continuously shed
thick skin: 15-40 layers
thin skin: 10-20 layers

Question 9

melanocytes

Answer 9

originate from neural crest - first cells to arrive in epidermis
located in stratum basale - contacts about 36 keratinocytes, imparting melanin to the differentiating cells in granules

Question 10

langerhans cells

Answer 10

originate from bone marrow - found in stratum of malpighi (mostly the stratum spinosum) - peripheral dendritic cells == APCs

Question 11

Merkel cells

Answer 11

derived from neural crest - nonencapsulated tactile mechanoreceptors - associated with basal lamina (stratum basale), cytoplasm contains granules, small nerve plate is connected to myelinated axon

light touch, more numerous in thick skin

Question 12

keratinocytes

Answer 12

makes keratin and lamellar granules
form squames in stratum corneum
houses melanin, pigment protein

Question 13

melanin

Answer 13

pigment protein that protects nuclei from UV radiation

Question 14

melanin production

Answer 14

tyrosinase converts tyrosine into DOPA in the presence of UV light
DOPA is polymerized to melanin

Question 15

dermal layers

Answer 15

papillary layer: superficial, loose (areolar) CT - meissner corpuscles and dermal papilla
sub-papillary plexus, capillary branches provide nutrient source
reticular layer: deep, dense irregular CT (type I collagen) - with elastic fibers, more fibers and fewer cells

Question 16

hypodermis

Answer 16

subq tissue

vascular, fat resides here

Question 17

free nerve endings

Answer 17

simple, numerous afferent fibers
dermal-epidermal junction
temperature, touch, itch, pain

Question 18

Meissner Corpuscle

Answer 18

encapsulated
dermal papillae of fingertips, palms, soles
light touch, low frequency

Question 19

Pacinian Corpuscle

Answer 19

CT capsule surrounds 15-50 think, concentric layers
reticular dermis or hypodermis
coarse touch, vibration, pressure

Question 20

merocrine/eccrine gland

Answer 20

exocytosis of apical end cells

Question 21

holocrine glands

Answer 21

disinigration of cell with contents becoming secretion

cell secretes its w[hol]e body

Question 22

apocrine gland

Answer 22

membrane enclosed vesicles

Question 23

suderiferous glands

Answer 23

eccrine (merocrine)
acinus- simple cuboidal surrounded by myoepithelial cells
duct - stratified cuboidal epithelium

Question 24

myoepithelial cells

Answer 24

surround an acinus and express its content by squeezing it

Question 25

eccrine sweat glands

Answer 25

found extensively throughout skin
produce sweat used for thermoregulation
components: water, salt, ammonia, uric acid and mucinogen granules

Question 26

apocrine glands

Answer 26

restricted to axilla, circumanal region, areolar
merocrine secretion - milky sweat secretion
responds to hormones and adrenergic (fight of flight) signals

Question 27

sebaceous glands

Answer 27

face, scalp, fair follicles
produce lipid mixture, sebum via holocrine secretion
simple branched acinar
single duct
waxy mix of TAGs and cholesterol - lubricates and waterproofs skin

Question 28

hair shaft

Answer 28

medulla - core
cortex - middle layer
cuticle - outer layer

Question 29

vellus vs terminal hair

Answer 29

vellus = baby hair 
terminal = AK chest carpet

Question 30

nails

Answer 30

highly keratinized cells on bed of epidermis
nail root - primal region of plate
nail plate remains attached to nail bed and pushed forward by continous growth
lanula: crescent shaped white area near nail matrix