Dermis and adnexal structures

Question 1

dermis:

Answer 1

• tough and elastic
• contains blood vessels, nerves and cutaneous appendages
• 2 zones
• –papillary dermis (immediately beneath the epidermis)
• –reticular dermis (deeper)

Question 2

-composition of the dermis

Answer 2

• –collagen fibers
• –elastic fibers
• –ground substance

Question 3

synthesis of collagen

Answer 3

• procollagen synthesized intracellularly within fibroblasts
• 3 protein chains arranged in an a-helix structure
• striations with 68 nm intervals
• Gly-X-Y structure
• secreted and assembled into collagen fibrils extracellularly using cofactors including vit C

Question 4

different types of collagen relevant to the skin

Answer 4

• I: most prevalent, component of bone
• III: fetal dermis (resistant to scarring)
• IV: present in the basement membrane zone and around vessels
• VII: anchoring fibrils (epidermis to dermis)

Question 5

components and function of the ground substance of the dermis

Answer 5

• gelatinous material between the collagen, elastic and adnexal structures in the dermis
• 2 glycosaminoglycans (hyaluronic acid and dermatan sulphate) that absorb >100000x their weight in water and + fibronectin -> act like sponges
• facilitates nourishment to the epidermis (water-based environment for diffusion)

Question 6

Collagen defects (acquired)

Answer 6

scurvy

• –insufficient Vit C -> decreased mature collagen
• –Without vitamin C, the collagen fibers will not attain their final desired strength. As a result, minor wounds will fail to heal, hair will grow abnormally, and the blood vessels will be quite fragile due to inadequate support from the surrounding collagen. Teeth will fall out

Question 7

Collagen defects (congenital)

Answer 7

EDS

• –abnormally formed collagen
• –skin hyperextensibility, joint hypermobility, tissue fragility, poor wound healing

Question 8

Elastin defects (acquired)

Answer 8

solar elastosis

—sunlight exposure -> degeneration of the elastic fibers -> become dystrophic -> clump and aggregate

Question 9

Elastin defects (congenital)

Answer 9

pseudoxanthoma elasticum (PXE)

• –mutation in gene encoding for part of the MDR complex
• –enlarged, tangled and calcified
• –“plucked chicken” appearance of the flexural areas of the body

Question 10

pathophysiology and clinical manifestations associated with disorders of the vascular supply

Answer 10

involved in wound healing, control of homeostasis (blood towards or away from the skin) and modulation of inflammation/leukocyte traffickings

• verruca: require increased blood supply -> appear brownish
• leukocytoclastic vasculitis
• –insult -> formation of immune complexes in the walls of the vessels (type III) -> inflammation
• –NEs degranulate -> extravasion of RBCs to the dermis -> fibrinoid deposition + infiltrating NEs and NE debris = leukocytoclasia
• –clinically = “palpable purpura” (nonblanchable)

Question 11

skin nervous composition

Answer 11

• –pacinian corpuscle (look like an onion) – pressure and vibration (genitals)
• –Meissner’s corpuscle (pine-cone) – fine touch and tactile discrimination (fingertips)
• –Free nerve ending (pain and itch) (pruritis -> free nerve endings -> afferent nerves to the spinal cord by slow conducting, unmyelinated C fibers) -> cerebral cortex

Question 12

pathophysiology and clinical manifestations associated with disorders of the innervation of the skin

Answer 12

• function: inform and protect
• congenital: insensitivity to pain
• –nly coexisting with anhidrosis
• –huge numbers of injuries to skin including corneal erosions
• –NTRK1 gene which encodes for nerve GF receptor

Question 13

hair follicles

Answer 13

• –anagen (growth), telogen (rest) and catagen (involution)
• –(upper to lower) infundibulum, isthmus, and metrical area
• Bulges of the PEG by induction
• –lower = arrector pili
• –middle = sebaceous gland
• –upper = apocrine gland

Question 14

abnormality in the hair follicles

Answer 14

• androgenic alopecia
• –hairs become miniaturized, finer and lie higher in the dermis
• –men tx with finasteride and both tx with minoxidil (promote anagen phase)

Question 15

Eccrine glands

Answer 15

• –sweat glands -> coiled deep in dermis, straight in dermis, spiraled in epidermis
• –thermoregulation (evaporation)
• –forehead, upper cutaneous lip and palms/soles
• –although sweating is mediated by the symp ANS, it is triggered via Ach secretion
• –hence, why you sweat under stress, but also why drugs that inc Ach levels inc sweating

Question 16

Apocrine glands

Answer 16

• –upper bulge of PEG
• –axillary and anogenital area -> stim at puberty
• –Moll’s glands on the eyelids, cerumen glands, lactation glands
• –coiled deep in the dermis (lumen much larger than eccrine) and straight duct to hair follicle
• –decapitation of apical portion (odorless) -> contact with nl bacterial flora -> orod
• chromohidrosis (face, axilla and breast)
• –yellow, green, blue or black secretions

Question 17

Apoeccrine glands

Answer 17

• –hybrid sweat glands in the axilla
• –respond to cholinergic stimuli
• –secrete 10x as much sweat as eccrine glands

Question 18

Sebaceous glands:

Answer 18

oil-secreting glands on scalp, face, neck, upper chest and upper back

• –sex hormones -> acne happens after puberty
• –holocrine glands
• –isotretinoin (accutain) -> decrease sebum production

Question 19

abnormality in the sebaceous glands

Answer 19

• acne
• –multifactorial plugging of the ostia by hyperkeratotic debris of the pilosebaceous unit
• –p. acnes multiplies and converts sebum to pro-inflam fatty acids