Exam 2: Structure, Function, and Basic Changes of the Skin

Question 1

Where are each of the 3 layers of the epidermis located?

Answer 1

Deepest: stratum basale
Middle: stratum spinosum
Superficial: stratum corneum

Question 2

Where is the stratum basale located?

Answer 2

Bottom layer = 1 cell thick
deepest

Question 3

What is the main function of the stratum basale?

Answer 3

Keratinocyte proliferation
Anchor epidermis to dermis
Attaches to basement membrane via hemidesmosomes

Question 4

Where is the stratum spinosum located?

Answer 4

1 - 2 layers in haired skin
Middle layer

Question 5

What is the main function of the stratum spinosum?

Answer 5

Cell-to-cell mediated attachment
Desmosomes = intercellular attachments
Tonofilaments = intracellular filaments (anchor desmosomes to cell membrane)

Question 6

Where is the stratum corneum located?

Answer 6

Outermost layer

Question 7

What is the function of the stratum corneum?

Answer 7

Thin, squamous, anuclear cells
Form a resistant protective layer/barrier anchored together by intercellular, hydrophobic phospholipid

Question 8

Define: Acanthosis

Answer 8

Hyperplasia of stratum spinosum

Question 9

Define: Hyperkeratosis

Answer 9

Hyperplasia of stratum corneum

Question 10

Where are melanocytes found?

Answer 10

Stratum basale

Question 11

What is the function of melanocytes?

Answer 11

Produce melanin pigment - injects into keratinocytes
Melanin pigment = photoprotection

Question 12

Where are Langerhan cells located?

Answer 12

Stratum basale and stratum spinosum

Question 13

What is the function of Langerhan cells?

Answer 13

Dendritic cells
Trap and process antigen (immune surveillance)

Question 14

What are the components of the dermis?

Answer 14

Acellular components
Cellular components
Sebaceous glands
Apocrine glands
Eccrine glands
Hair and hair follicles

Question 15

What makes up the acellular component of the dermis?

Answer 15

Provides structural support
Fibers: collagen, elastin, reticulin
Ground substance (fluid): water, salts, proteoglycans, glycoproteins

Question 16

What makes up the cellular component of the dermis?

Answer 16

Responsible for producing matrix and tissue response
Fibroblasts, macrophages, T cells, mast cells

Question 17

What is the function of sebaceous glands?
What hormones play a role in this?

Answer 17

Responsive to hormones
Androgens = increase activity
Estrogens, glucocorticoids = atrophy and involution

Question 18

What is the function of apocrine glands?

Answer 18

Thermoregulation (sweat) and surface emulsion
Antimicrobial components = interferon, transferrin, NaCl, complement

Question 19

What is the function of eccrine glands?

Answer 19

Actively secrete product directly onto skin surface

Question 20

What is the function of hair/hair follicles?

Answer 20

Thermoregulation, physical protection, photoprotective

Question 21

What are the 3 stages of the hair follicle growth cycle? What controls these phases?

Answer 21

Anagen = growth
Catagen = transition
Telogen = resting (end stage)
Control via hormones, daylight, temperature, nutrition, growth factors

Question 22

Macule

Answer 22

Primary skin lesion
Flat discoloration < 1 cm in diameter

Question 23

Patch

Answer 23

Primary skin lesion
Macular lesion > 1 cm in diameter

Question 24

Papule

Answer 24

Primary skin lesion
Solid, elevated, firm, circumscribed lesion < 1 cm in diameter

Question 25

What causes a papule? What is it associated with? What is the most common cause?

Answer 25

Caused by infiltration of inflammatory cells
Associated with hair shaft (folliculitis) or not
Most common cause of a papular dermatitis in the dog is bacteria pyoderma

Question 26

Plaque

Answer 26

Primary skin lesion
Elevated, firm lesion with flat top > 1 cm in diameter

Question 27

Pustule

Answer 27

Primary skin lesion
Elevated accumulation of purulent material within epidermis

Question 28

Vesicle

Answer 28

Primary skin lesion
Blister
Elevated fluid filled cavity within or below epidermis (< 1 cm in diameter)

Question 29

Bulla

Answer 29

Primary skin lesion
Blister
Vesicle ( >1 cm in diameter)

Question 30

Cyst

Answer 30

Primary skin lesion
Epithelial lined cavity filled with fluid or semisolid material - located in dermis or subcutis

Question 31

Wheal

Answer 31

Primary skin lesion
Hive, urtica
Raised, solid region of edema, often with irregular borders
Type I Hypersensitivity Rxn

Question 32

Nodule

Answer 32

Primary skin lesion
Raised, firm round lesion > 1 cm in diameter

Question 33

Epidermal Collarette

Answer 33

Primary skin lesion
Flat to minimally raised scale arranged in a circular rim

Question 34

Comedone

Answer 34

Secondary skin lesion
Dilated hair follicle filled with keratin or sebum

Question 35

Callus

Answer 35

Secondary skin lesion
Thick, hard, hairless plaque often located over pressure points (e.g. elbow)

Question 36

Crust

Answer 36

Secondary skin lesion
Scab
Dried exudate in stratum corneum composed of serum, blood, keratin, and degenerate neutrophils

Question 37

Scale

Answer 37

Secondary skin lesion
Loose fragments of keratin on skin surface (hyperkeratosis)

Question 38

Erosion

Answer 38

Secondary skin lesion
Partial loss of epidermis (often secondary to ruptured vesicle)

Question 39

Ulceration

Answer 39

Secondary skin lesion
Full thickness loss of epidermis with exposure of dermis

Question 40

Excoriation

Answer 40

Secondary skin lesion
Linear loss of epidemis
Scratch or abrasion

Question 41

Fissure

Answer 41

Secondary skin lesion
Vertical crack in epidermis to the dermis

Question 42

Lichenification

Answer 42

Rough/thickened epidermis resulting from chronic scratching/irritation