The Integument 1

Question 1

what does the integument include

Answer 1

1. skin
2. hair and variety of skin associated glands
3. claws, hoofs, and horns

Question 2

what are the functions of the integument

Answer 2

1. protective- wear and tear
2. barrier- microbial penetration
3. thermoregulation
4. sensory perception
5. storage organ
6. synthesis of vit D
7. glandular (sebum and sweat secretions)
8. photo-protection/sensitization
9. immuno-surveillance
10. capture of prey

Question 3

what is the structure of skin

Answer 3

contains

1. epidermis
2. dermis
3. hypodermis
4. often contains hair follicles, and skin associated glands (adnexa)

Question 4

name the layers

Answer 4

epidermis

basement membrane

dermis or corium (dense irregular connective tissue layer)

subcutis or hypodermis (adipose tissue and loose CT)

Question 5

what is the function of the epidermis

Answer 5

outer layer, protection

Question 6

what does the epidermis contain

Answer 6

keratinocytes, melanocytes, Langerhans cells, merkel cells

Question 7

what is the function of the basement membrane

Answer 7

below epidermis and connects epidermis to dermis

Question 8

what is the function of the dermis

Answer 8

support + nourishment to the epidermis and skin appendages

Question 9

what does the dermis contain

Answer 9

blood vessels

sensory nerves

motor nerves

immune cells

Question 10

what are the skin appendages

Answer 10

hair follicles, oil + sweat glands, claws

Question 11

what is the function of sebaceous glands and where are they found in dogs

Answer 11

secrete oily substance –> sebum

near paws, back of neck, rump, chin, tail area

Question 12

what is the subcutis or hypodermis layer

Answer 12

innermost layer

subcutaneous fat + muscles

Question 13

what is the embryological development of the skin

Answer 13

primitive epidermis is of ectodermal origin

dermis is of mesodermal origin

basal cells undergo proliferation, migration and differentiation resulting in cell death

stratified keratinized squamous epithelium –> forms a physical and permeability barrier

melanocytes from neural crest origin migrate to the dermal-epidermal border –> responsible for pigmentation

Question 14

what are the strata layers in the epidermis

Answer 14

1. stratum corneum (dead keratinocytes)
2. stratum lucidum
3. stratum granulosum (lamellar granules)
4. stratum spinosum (keratinocyte, langerhans cell, melanocytes)
5. stratum basale (merkel cell)
6. dermis

Question 15

what is the sequence of events from the dermis to the stratum corneum

Answer 15

1. cells continuously divide at the basal layer
2. cells become keratinized as they move away from the basal layer
3. cells are dead and are continuously lost from the skin surface

Question 16

what occurs at the stratum basale or basal layer

Answer 16

basal cells –> single layer of mitotically active diving stem cells move outward

tonofilaments appear in the cytoplasm (precursor of keratin)

Question 17

what occurs at the stratum spinosum layer

Answer 17

several layers thick

layers of polyhedral cells with spiny projections

cells become progressively flattened

lamellar bodies appear –> ogranells containing lipid

Question 18

what occurs at the stratum granulosum layer

Answer 18

cells become flattened

organelles start to break down

keratohyalin granules appear –> contain pro-filaggrin a precurso of filaggrin (causes tonofilaments to aggregate and form tonofibrils)

Question 19

what occurs at the stratum lucidum layer

Answer 19

flattened cells lack nucleus or organelles –> cytoplasm now contains keratin aggregates

Question 20

what occurs at the stratum corneum layer

Answer 20

layers of highly keratinzed dead cells

keratin filaments polymerize to form strong disulphide bonds (filaggrin is involved)

thickened cell envelope forms –> composed of involucrin, loricrin, and other proteins

lipids, discharged by lamellar granules fill intercellular spaces and contribute to skin barrier

special cell junctions rivet the squames together –> absent in outermost layer –> shedding

Question 21

how is the skin barrier regenerated

Answer 21

by continuous process of keratinization –> proliferation, migration, differentation, cell death and loss

Question 22

what does the control of desquamation at the surface depend on

Answer 22

balance between stratum corneum protease inhibitor and proteases (enzymatic degeneration of desomsomes –> junctional complexes which anchor the cells to the surface

skin pH

Question 23

what are the histological features of thick hairless skin

Answer 23

1. epidermis thick
2. stratum corneum is particularly thickened (12-20 layers) –> subject to constant abrasive forces
3. dermal-epidermal border interdigitates –> anchors epidermis to dermis
4. no hair follicles
5. sweat glands (eccrine) are often present in the dermis

Question 24

what type of skin is this

Answer 24

thick hairless skin

Question 25

what are the histological features of thin hairy skin

Answer 25

1. epidermis is very thin –> different strata can still be recognized at thigh magnification
2. hair follicles + sebaceous and sweat glands all in the dermis

Question 26

which type of skin is this

Answer 26

thin hair skin

Question 27

what cells does the dermis consist of

Answer 27

fibroblasts, mast cells, plasma cells, macrophages, adipocytes, melanocytes, lymphocytes, neutrophils

Question 28

what fibres does the dermis contain

Answer 28

different types and proportions –> collagen, reticular and elastic fibres

Question 29

what is the ground substance in the dermis

Answer 29

dense fluid (proteoglycans and glycoprotein)

Question 30

what is the function of the fibroblasts in the dermis

Answer 30

produce/maintain the extracellular matrix

Question 31

what is the blood supply to the skin

Answer 31

located in the dermis

nourished by diffusion

arterio-venous anastomosis –> important for thermoregulation

Question 32

why is the skin sensitive

Answer 32

melssner’s corpuscle (touch)

free sensory nerve endings (pain, heat, cold)

pacinian corpuscle (pressure)