Dermatology

Question 1

Most likely diagnosis

1. Acute onset
2. Progressively worse

Answer 1

1. Scabies

2. Allergies

Question 2

Composition of the skin:

1. Epidermis
2. Dermis
3. Hypodermis

Answer 2

1. Keratinocytes 85% Non-keratinocytes 15%
2. Collagen and elastin fibers, ground substance, adnexal structures
3. Panniculus or subcutis Adipose tissue,
   blood vessels, nerves

Question 3

Layers of the skin

Answer 3

Horny cell layer (Stratum corneum)
Clear cell layer (Stratum lucidum; footpad and nasal planum only) Granular cell layer (Stratum granulosum)
Spinous/prickle cell layer (Stratum spinosum)
Basal cell layer (Stratum basale)

Question 4

How this is the dermis (cat/dog)

Answer 4

In haired skin, it is 0.1-0.5 mm thick (footpad and nasal planum up to 1.5 mm)

Question 5

How long does keratinocyte cell turnover take in a healthy dog

Answer 5

This process takes 22 days in normal dogs (>< 9 days in seborrheic dogs = increased epidermal turnover)

Question 6

Corneodesmosomes

Answer 6

Definition

Question 7

Intracellular laminar lipids

Answer 7

Ceramides are the largest group and the most important class of stratum corneum lipids
 5 ceramides identified in dogs (>< 11 in people)
 Other components : cholesterol, free fatty acids, cholesterol
sulfate/esters
 Barrier function of the skin cannot be disrupted unless ceramides are removed
 Control of percutaneous absorption of irritants and allergens
 Regulation of transepidermal water loss (TEWL)

Question 8

Hair follicle part

Answer 8

Infundibulum
Isthmus
Bulb

Question 9

Hair composition in dogs & cats

Answer 9

The dog and cat both have compound hair follicles
 A cluster consists of 2-5 large primary (guard) hairs surrounded by
groups of smaller secondary hairs (wool or down hairs, undercoat)
 Largest central primary hair is flanked by several smaller lateral primary hairs
 Each primary hair has an arrector pili muscle and emerges independently through an individual hole
 The secondary hairs emerge through a common hole