Skin

Question 1

Skin fx

Answer 1

Enviro barrier
Temp reg (insulation, sweat, blood flow reg)
Immunological (via langerhans & dendritic cells)
Mech support
Neurosensory
Metabolic & endocrine
Glandular secretion

Question 2

Epidermis comp

Answer 2

Stratified squamous keratinised epithelium.
No own blood supply, rely on dermis (avascular)
Most of epidermis made of keratinocytes which are divided further

Question 3

Epidermis divisions

Answer 3

Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum

Question 4

Stratum basale

Answer 4

Basal layer
Cuboidal cells act as stem cells to produce new epidermal cells.
New cells continually migrate outwards & become more diff / keratinised
Adhered by hemidesmosomes to BM running between epidermis & dermis

Question 5

Stratum spinosum aka prickle layer

Answer 5

Many layers of polygonal shaped cells which synth cytokeratin - forms tonifibrils that combine to form desmosomes which adhere cells together. Seen well after shrinkage during prep for slide
Varies in thickness
Targetted by some immune diseases

Question 6

Stratum granulosum

Answer 6

Flattened cells containing dense dark keratohyalin & lamelar granules

Question 7

Stratum lucidum

Answer 7

Only at some anatomical sites where skin is v thick of is hairless
Thin translucent layer of compacted cells w/ out nuclear detail

Question 8

Stratum corneum

Answer 8

Variable no of layers of dead keratinised cells continuously replaced
Many diseases resulting in hyperkeratosis

Question 9

Physiology of keratinisation

Answer 9

As keratinocytes mature incr size as they synth intracellular components (tonofibrils, keratihyalin granules, lamelar granules)
Nuclei slowly disintegrate, lamelar granules release lipid-like content into ECspaces. Meanwhile cells become flat dense structures and lose nuclei and cytoplasm eventually to be plates of keratin

Question 10

Epidermal cells

Answer 10

Keratinocytes
Melanocytes
Merkel cells
Langerhans cells

Question 11

Melanocytes

Answer 11

Contain pigmented granules called melanosomes which migrate to cell periphery to be phagocytosed by adjacent keratinocytes

Question 12

Melanocytes found

Answer 12

Often epidermis basal layer
Glands
Hair follicles

Question 13

Merkel sites

Answer 13

Present in basal region
Have vacuolated cyt on dermal side
Can act as mechanoreceptors by assoc with axons

Question 14

Langerhans cells

Answer 14

Potent anitgen presenting cellsmainly found in stratum spinosum
Responsible for canine cutaneous histiocytoma

Question 15

BM anchors

Answer 15

Attach to stratum basale cells via hemidesmosomes and anchoring filaments
Essential for maintaining structural integrity of skin

Question 16

BM unusual features

Answer 16

Sometime dives down into dermis forming projections which help bind epid strongly to dermis aka rete ridges
Common where skin subject to much friction eg footpad

Question 17

Dermis comp

Answer 17

Irregular bundles of coll fibres produce by fibroblasts
Elastic fibres embedded within acellular GS
Blood vessels nerves lymphatics
Fibrocytes and inflamm (dendritic) cells
Can be divided into layers

Question 18

Dermis divisions

Answer 18

Papillary dermis

Reticular dermis

Question 19

Papillary dermis

Answer 19

Adjacent to epid and follows contours of stratum basale (thin layer)
Delicate C bundles

Question 20

Reticular dermis

Answer 20

Deep layer of thicker denser C

Question 21

Subcutus/hypodermis

Answer 21

Anchors dermis to underlying muscle
Cont adipose tissue to act as cushion allow flex and insulation
Less C and more blood vessels than dermis

Question 22

Adnexal structures

Answer 22

Additional structures
All epithelial derivatives separated from dermis by a BM
Eg hair

Question 23

Equine bovine hair

Answer 23

Sigle follicle evenly distributed

Question 24

Pig hair

Answer 24

Single follicle grouped in clusters

Question 25

Dog hair

Answer 25

Compound follicles Single primary hair with smaller secondary underhairs Short coated breed have more primary hairs

Question 26

Cat hair

Answer 26

Single and compound | Single primary follicle with clusters 2-5 compound follicles surrounding

Question 27

Sheep hair

Answer 27

Single and compound Face/legs single follicles Wool areas mostly compound

Question 28

Special hair types

Answer 28

Sinus hairs

Question 29

Sinus hairs

Answer 29

Highly specialised Surrounded bh blood filled sinus Skeletal m attaches to outer sheath - degree of voluntary control. Outer sheath assoc with many nerve bundles

Question 30

Gland types

Answer 30

Sebaceous | Sweat: apocrine & merocrine

Question 31

Sebaceous glands

Answer 31

Antibac Sebum secretion Into hair canal, sometimes direct onto skin (anus) Simple cuboidal epithelium on a BM which diff into classic sebaceous cells w/ a foamy cyt and large & polygonal in shape Cells disintegrate and release content

Question 32

Apocrine sweat glands

Answer 32

Coiled secretory portion & straight duct Evenly distributed Typically cuboidal epi on a BM but can become low columar Possible tonsee myoepi cells between epi cells and BM In horse produce recognisable sweat, others just scent or diff to detect sweat

Question 33

Merocrine sweat glands

Answer 33

In specialised areas eg footpads of dogs, frog if horse Open directly onto skin Simple cuboidal in nature Assoc with myoepi cells

Question 34

Myoepithelial cells

Answer 34

Epi cells with muscle assoc to aid with secretion

Question 35

Footpad adaptations

Answer 35

Thickened stratum corneum for protection Prominent hypodermis with many fat cells for cushioning Abundant merocrine sweat glands

Question 36

Eyelid adaptations

Answer 36

Cont Specialised type of sebaceous gland aka tarsal or meibomian gland. Specialised apocrine sweat glands open into eyelash follicles

Question 37

Meibomian gland

Answer 37

Multilobular Open directly onto palperbral surface at margin of eyelid Best dev in cat Potential tumour source

Question 38

Nose adaptations

Answer 38

In dog and cat comp thick stratified squamous epit with deep grooves in an indiv pattern Cattle similar but lack deep grooves No hair follicles

Question 39

Claws

Answer 39

Modification of the skin Continuous with epidermis Comp much hard keratin to protect distal phalanges

Question 40

Claw anatomy

Answer 40

Hard wall Softer underlying sole V good blood supply to underlying dermis so bleed if nail cut too short

Question 41

Subdivisions of skin

Answer 41

Epidermis Dermis Subcutis(aka hypodermis)