skin

Question 1

functions of the skin

Answer 1

• protective + waterproof
• regulates body temp
• sensory receptorz

Question 2

epidermis

Answer 2

stratified squamous keratinized, ectoderm
- Specialized skin appendages: sweat + sebaceous glands, hair follicles
- Specialized cell types (melanocytes, merkel cells, langerhans cells)

• Mostly keratinocytes

Question 3

dermis

Answer 3

dense irregular CT, mesoderm
- vascularized
- nerves
- receptors for temp, pain, touch (meissner’s corpuscles) in dermal ridges/papillae
- deep pressure (pacinian corpuscles)
- arrector pili

Question 4

Meisner’s corpuscules

Answer 4

fine touch and pressure, in dermis

Question 5

Pacinian corpuscules

Answer 5

deep pressure, dermis

Question 6

Arrector pili

Answer 6

smooth muscles that attach at base of hair follicle
- anchor to dermis surrounding hair follicle
- goosebumps

Question 7

Hypodermis

Answer 7

Beneath dermis, loose CT and adipose tissue
- connects skin to tissues + organs

Question 8

Stratum basale

Answer 8

Innermost part of epidermis
- cuboidal-low columnar stem cells
- some desmosomes cell:cell
- many hemidesmosomes cell:basement
- attach epidermis to dermis
- maintain stem cell phenotype
- stem cells detach from basement membr and move up strata, begin to differentiate
- melanocytes + merkel cells

Question 9

Stratum spinosum

Answer 9

differentiation to epithelial keratinocytes
- prod many keratin intermediate filaments (tonofilaments)
- many desmosomes cell:cell ends of keratinocyte/processes spines
- Langerhans cells

Question 10

melanocytes

Answer 10

prod pigment, migrate into epidermis stratum basale
- derived from embryonic/fetal nervous system

Question 11

merkel cells

Answer 11

mechano/touch receptors migrate into epidermis stratum basale

Question 12

Langerhans cells

Answer 12

HSC-derived APCs, migrate into epidermis stratum spinosum

Question 13

melanosome

Answer 13

melanocyte vesicles containing UV-absorbing melanin
- melanin prod by mod of tyrosine
- sent apically into stratum spinosum, phagocytosed by keratinocytes

Question 14

stratum granulosum

Answer 14

cells fully diff, squamous
- Prod lipid-rich vesicles, exocytosed to generate waterproof barrier b/w granulosum and lucidum
- prod kerothyalin

Question 15

keratohyalin

Answer 15

glycoprotein complex
- forms cytoplasmic granules (not membr-bound) in cells of s. granulosum
- cross-link tonofilaments

Question 16

stratum lucidum, eleidin

Answer 16

Above waterproof barrier, fully diff cells
- prod eleidin, glycoprotein that aligns cross-linked tonofilaments parallel
- start to die and enucleate

Question 17

stratum corneum

Answer 17

enucleated squamous cells, completely dead
- filled w/ protective cross-linked + bundled keratin filaments (squames)
- desmosomes deteriorate, squames slough off

Question 18

hair follicles

Answer 18

invagination of epidermis, pushing down into dermis
- follicle terminates at epidermal hair root, indented by dermal papilla
- papilla: supply bv and nerves to hair root area

Question 19

hair follicle - hair

Answer 19

cuticle, cortex, medulla (outside in)

Question 20

hair follicle - internal root sheath

Answer 20

differentiating s. granulosum-like cells
- very orderly arranged cells
- cells move inward and die to prod. hair shaft
- henle’s layer, huxley’s layer, cuticle (outside in)

Question 21

hair follicle - external root sheath

Answer 21

modified stratum basale and spinosum

Question 22

sebaceous glands

Answer 22

outpouching of hair follicle epidermis (above hair bulb)
- ducts branch a lil and empty into hair canal
- alveolar secretory portion, prod lipid-rich sebum (pale H&E)
- secretion by necrosis - all contents released
- duct obstruction -> bacterial infection -> acne formation

Question 23

eccrine sweat glands

Answer 23

coiled tubular glands, invaginations of epidermis
- mostly clear cells: secrete watery serous secretions, req secretion of Cl- via CFTR
- Interspersed dark cells: secrete sum glycoprotein- + proteoglycan-containing mucous
- contractile cells (epithelial, ectoderm) expel secretory products
- secretory portion deep, duct portion stratified cuboidal