lecture 7 - Hoof - Dr. Anderson

periople

-Protective layer to prevent desiccation

-Analogous to a cuticle

wall

-Primary weight-bearing structure

-Protection, force dissipation, traction

Keratinized, tubular epidermis

bars

-Extension of wall

-Provides additional weight bearing surface

-Prevents excessive expansion → buttress

heel

Provideshock absorption → Distributes of forces

white line

-Junction between solar and laminar epidermis

-Area where nails are driven in on a shod horse

sole

-Protects bottom of P3

-Bears less weight compared to wall (bottom of hoof is concave)

-Provides traction

frog

-Lies over the digital cushion → Peripheral pump

-Provides traction

coronary band

Hoof wall (coronary epidermis) overlying coronary dermis

coronet

Junction between hoof wall (coronary epidermis) and skin (epidermis)

dermis

Corium = _____

keratinized

Hoof epidermis is _____

coronary dermis

Supplies keratinized coronary epidermis that forms tubule and intertubule horn

laminar dermis

Supplies laminar epidermis

1. coronary dermis

2. laminar dermis

What are the dermal layers?

1. coronary groove (sulcus)

2. coronary epidermis (stratum medium)

3. laminar epidermis (stratum internum)

4. coronary band

What are the epidermal layers?

6-9 mm

How much does a hoof grow per month?

~3 mm

How much does a hoof grow per month in the winter?

1. Keratinized coronary epidermis formed by basal epidermal cells at coronary band**TUBULAR

2. Continuous with keratinized laminar epidermis

3. Desmosomes detach between epidermal and dermal lamina to let coronary and laminar epidermis "ratchet" or move down

Describe hoof wall growth (3)

vertically

Horn tubules orientated _____

curling

Sole growth limited by _____ of tubules at ground

slower

Sole growth is [faster/slower] than wall growth

suspended

The horse does not walk on its third phalanx → P3 is _____ in hoof capsule by the lamina

False (It's not ipsilateral)

T/F - The hoof is a boot

Laminar dermis interdigitates & supplies laminar epidermis

Describe the suspensory apparatus of P3

1. rotating

2. sinking

What happens if the suspensory apparatus fails? (2)

1. Insulin dysregulation

2. Endothelial cell and vascular dysfunction

3. Metabolic syndrome and insulin resistance

4. Pars Pituitary Intermedia Dysfunction (PPID or Cushing's)

5. Endotoxemia

6. Physical demand

Why does the suspensory apparatus of P3 fail? (6)

1. Medial (Vein, Artery, Nerve)

2. Lateral Palmar (Vein, Artery, Nerve)

3. Plantar Digital (Vein, Artery, Nerve)

What are the blood and nerve supplies to the hoof? (3)

palmar/plantar

Vessels enter on _____ aspect of P3

foramen

Arteries pass through _____ in P3

dorsal

Venous drainage primarily along _____ border of P3

true

T/F - The hoof has extensive branching (venous plexuses)

palmar venous plexus

In sole corium, around toe, between sole and digital cushion

dorsal venous plexus

In laminar corium

coronary venous plexus

-At coronet - in coronary and perioplic corium

-Drains into digital veins

-Cuts at coronet bleed

1. palmar venous plexus

2. dorsal venous plexus

3. coronary venous plexus

What makes up the venous plexus?

collateral cartilages

• Attach to P3

• Structural support for heel bulbs

• Shock absorption - dissipates force through their expansion

• Involved in blood pumping action of foot

is no

Muscle normally required to achieve effective venous drainage in periphery. There [is/is no] muscle in the digit

pump

Digital cushion functions as "_____"

diastolic

When horse bears weight digital cushion expands and veins compressed → blood pools in venous plexus and digital cushion. This is the [systolic/diastolic] phase.

systolic

When horse lifts hoof digital cushion contracts and veins open → blood forced out. This is the [systolic/diastolic] phase.

stance

Diastolic - _____ phase

(Venous blood pools)

flight

Systolic - _____ phase (Venous blood forced up leg)

navicular bone (aka distal sesamoidean bone)

-Same function as any other sesamoidean bone

-Acts as pulley

-↓ strain on DDFT as it changes direction to cross coffin joint

-↓ work of DDFT to act on P3 (↑ its mechanical effect)

1. deep digital flexor tendon sheath

2. collateral sesamoidean (suspensory) ligament of the navicular bone

3. navicular bursa

4. impar ligament

What makes up the navicular apparatus?

1. traction

2. shock absorption

3. support of skeletal column

4. protection of inner structures

5. venous return (peripheral pump)

What are the functions of a hoof?

traction

The following is associated with what function of the hoof?

-frog

-shape of hoof (concave)

-wall

shock absorption

The following is associated with what function of the hoof?

-digital cushion

-ability to expand at heels

support of skeletal column

The following is associated with what function of the hoof?

-Weight of horse transmitted via lamina to hoof wall

-Suspends P3

protection of inner structures

The following is associated with what function of the hoof?

-Periople protects from evaporation

-Hoof wall protects lamina

venous return (peripheral pump)

The following is associated with what function of the hoof?

-frog

-digital cushion

-collateral cartilages

1. DIP joint

2. flexor tendon sheath

3. navicular bursa

4. deep digital flexor tendon

What are the synovial structures of the foot?