Introduction

Question 1

Layers of the epidermis

Answer 1

“Canadians Like Good Sushi Boxes”

Stratum corneum 
lucidum 
granulosum 
spinosum 
basale

Question 2

epidermis characteristics

Answer 2

■ avascular: receives its nutrition from the dermal capillaries

■ derived from keratinocytes with the youngest presenting at the stratum basale

■ cells progress from stratum basale to stratum corneum in about 4 wk
◆ stratum basale (germinativum): mitotic figures that give rise to keratinocytes
◆ stratum spinosum (prickle cells): junctions in this layer (tonofilaments) give the epidermis its strength
◆ stratum granulosum: flat cells containing basophilic g anules which characterize skin
◆ stratum lucidum: transparent layers of packed dead cells
◆ stratum corneum: flat scales of the water-resistant protein keratin

Question 3

Cells of the epidermis

Answer 3

◆ keratinocytes: located in all layers of the epidermis, except the stratum corneum; connected to each other by desmosomes
◆ melanocytes: located in the stratum basale; keratinocyte to melanocyte ratio in the basal layer is 10:1; melanocyte number is equal among races; produce melanosomes containing melanin, which are transferred to keratinocytes
◆ Langerhans cells: dendritic cells which are important for immune surveillance ◆ Merkel cells: located in the basal layer; involved in touch sensation

Question 4

dermis regions

Answer 4

■ papillary: contains numerous capillaries that supply nutrients to the dermis and epidermis

■ reticular: provides a strong structure for skin; consists of collagen bundles woven together along with elastic fibres, fibroblasts, and macrophages

Question 5

cells of the dermis

Answer 5

◆ fibroblasts: produce collagen, elastin, and ground substance

◆ mast cells: release histamines which mediate type I ypersensitivity

Question 6

subcutaneous tissue (hypodermis) components

Answer 6

consists primarily of adipose cells, larger calibre vessels, nerves, and fascia

Question 7

what are epidermal appendages

Answer 7

epidermal in origin, can extend into the dermis; includes hair, nails, and cutaneous glands

Question 8

what is a pilosebaceous unit

Answer 8

hair + hair follicle + sebaceous gland + arrector pili muscle

Question 9

sebaceuos gland

Answer 9

part of pilosebaceous unit, produces sebum which is secreted into the hair follicle via the sebaceous duct, where it covers the skin surface (protective function)

■ sebum has some antifungal properties

■ these glands cover entire skin surface and are absent only in non-hair bearing areas (e.g. palms, soles, lips

Question 10

apocrine sweat gland

Answer 10

apocrine duct empties into hair follicle above sebaceous gland
■ found in axillae and perineum
■ likely a vestigial structure functions in other species to produce scent (e.g pheromones)

Question 11

eccrine sweat gland

Answer 11

not part of pilosebaceous unit

■ found over entire skin surface except lips, nail beds, and glans penis

■ important in temperature regulation via secretion of sweat to cool skin surface

Question 12

skin functions

Answer 12

protection

thermal regulation

sensation

metabolic function (vitamin D synthesis, energy storage as TGs)