Lecture 8: Integument

Question 1

Integument serves many functions

Answer 1

protection
excretion of salt, water and organic wastes
temperature regulation
production of melanin and keratin
synthesis of Vit D3
storage of lipids
sensory reception of touch, pressure, pain and temperature

Question 2

Epidermal layers include

Answer 2

stratum basale 
stratum spinosum
stratum granulosum
stratum lucidum
stratum corneum

Question 3

Stratum basale

Answer 3

single layer of cuboidal or columnar keratinocytes on basal lamina

• large, ovoid nucleus
• function: stem cells (migrate up to form other layers) and anchors

Question 4

stratum spinosum

Answer 4

• prickle cell layer
• cells within deeper layers are still alive
• have tonofilaments (processes) that connect to tonofilaments of adjacent cells by desmosomes

Question 5

Stratum granulosum

Answer 5

• formed by cells migrating to the surface
• squamous, dead cells
• accumulate keratohyalin granules- basophilic keratin precursor

Question 6

Stratum lucidum

Answer 6

• only found in areas where skin is thick or hairless (food pad, muzzle)
• thin eosinophilic line between granulosum and corneum
• cells are dead

Question 7

stratum corneum

Answer 7

• outermost layer composed of many layers of keratinized dead cells
• cells lose nucleus and organelles, making keratin prominent
• thickness varies by body region and by species

Question 8

Cells of the epidermis include

Answer 8

keratinocytes
melanocytes(non ker)
merkel cells (non ker)
langerhans cells (non ker)

Question 9

Keratinocytes

Answer 9

-85-95% of epidermal cells
-produced by constant mitosis in stratum basale
-daughter cells migrate to the surface to die- form keratin
(dandruff, dander)

Question 10

Melanocytes

Answer 10

within stratum basale

exhibit brown granules within the cytoplasm

Question 11

Merkel cells

Answer 11

• within stratum basale
• mechanoreceptors
• mostly found in thicker skin–> hands, feet, foot pads
• hard to tell apart from melanocytes

Question 12

Langerhans cells

Answer 12

• within stratum spinosum
• part of the immune system
• APCs- participate in allergic response

Question 13

The dermis

Answer 13

dense irregular CT

• transversed by nerves and vasculature–> blood and lymph
• superficial dermis= protrude into epidermis
• deeper dermis- thicker or more dense CT

Question 14

Hypodermis

Answer 14

• technically not part of integument (skin)
• large fat depots in healthy animals
• BVs within as they head towards the dermis
• Adipose tissue

Question 15

Epidermal derivatives

Answer 15

hair follicles and hair
sweat glands
sebaceous glands 
nails
mammary glands
hoof

Question 16

Hair

Answer 16

-flexible and keratinized
Function
-insulation, camo, display (aggression, sex recognition)
-follicle is an invagination of the epidermis
-hair formed within the follicle
-follicle varies in appearance depending on phase of growth

Question 17

Anagen vs Catagen vs Telogen

Answer 17

Anagen - nourishment via the papilla , cell division
catagen (transition)- cell division and growth ceases, follicle shrinks
Telogen (resting) - hair not anchored and falls out, new hair grows in papilla

Question 18

Structure of the Follicle

Answer 18

• internal root sheath
• thin, eosinophilic, adjacent to hair
  - cuticle
  - huxley’s layer
  - henle’s layer
• external root sheath (ERS)
• stratified outer sheath
• dermal papilla- looks like bulb, it is the region of CT under the hair matrix

Question 19

Vibrissae

Answer 19

Specialized for tactile sense
typical structures of a hair follicle
also contain ring sinus- blood sinus surrounded by CT capsule
-sensory nerves sometimes seen

Question 20

Mammary gland

Answer 20

• compound tubuloalveolar gland
• groups of secretory units form lobules
  - separated by CT
• lobule activity
  - not all active at the same tiime

Question 21

Appearance of active vs inactive mammary gland follicle cells

Answer 21

inactive
-low cuboidal 
-no evidence of lipid production
active
-high (tall) cuboidal/columnar 
-lipid droplets occur at apex

Question 22

Equine foot bones

Answer 22

cannon
proximal sesamoid
long pastern
short pastern
navicular
coffin

Question 23

Hoof

Answer 23

high specialized derivative of epidermis

-epidermis markedly keratinized and forms outer surface of the hoof

Question 24

Hoof wall layers

Answer 24

epidermis- stratum tectorium and stratum medium
stratum lamellum
(laminar corium= dermis)
coffin

Question 25

Layers of the stratum lamellatum

Answer 25

stratum medium
-primary lamellae
-secondary lamellae- lateral feather
stratum (laminar) corium
-Dense CT (dermis)
-forms primary and secondary dermal lamina that interdigitate with the lamellae of stratum medium

Question 26

What is the difference between sheep of ruminants and horses

Answer 26

main difference is NO secondary laminae

Question 27

Laminitis

Answer 27

• cause of lameness and disability
• inflammation of laminae that attach hoof wall to coffin bone
• laminar region supports hoof wall
• when falls can result in hoof wall separating from the coffin bone and rotation or sinking (through the sole) of the bone can occur