lecture 7- Hoof

Dr. anderson lecture

protective layer to prevent desiccation analogous to a cuticle

periople

primary weight bearing structure protexting, force dissipation, traction keratinized, tubular epidermis

wall

extension of wall

provides additional weight bearing surface

prevents excessive expansion —> buttress

bars

what are the two teal lines

bars

shock absorption —> distributes of forces

heels

where are the heels located on the hoof

towards the back

junction between solar and laminar epidermis

area where nails are driven in on a shod horse

white line

T/F the white line is white

false it actually is really dark

what is this

white line

protects bottom of P3

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

provides traction

sole

what is the black arrow

angle of sole

what is the purple

sole

lies over the digtal cushion —> peripheral pump

provides traction

frog

what is the blue

frog

what is the orange

central sulcus

what is the yellow

collateral sulci

hoof wall (coronary epidermis)

overlying coronary dermis

coronary band

what is the yellow

coronary band

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

coronet

what is the blue

coronet

dermis hoof epidermis is keratinized

corium

supplies keratinized coronary epidermis that forms tubule and intertubule horn

coronary dermis

supplies laminar epidermis

laminar dermis

what is the top arrow

coronary dermis

what is the bottom arrow

laminar dermis

what is known as the sulcus

coronary groove

what is known as the stratum medium

coronary epidermis

what is known as the stratum internum

laminar epidermis

what is the top teal area

coronary groove

what is the middle area

coronary epidermis

what is the bottom area

laminar epidermis

hoof growth rate

6-9 mm per month

when do hooves grow slower

in winter around ~3 mm per month

explain the purple

keratinized coronary epidermis formed by basal epidermal cells at coronary bands **tubular

explain the orange

continuous with keratinized laminar epidermis

how does the laminar epidermis “ratchet” or move down

desmosomes detach between epidermal and dermal lamina to let coronary and laminar epidermis “ratchet” or move down

explain sole growth

horn tubules orientated vertically

growth limited by curling of tubules at ground

• slower than wall ground

what does the suspensroy apparatus of P3

laminar dermis interdigitates and supplies laminar epidermis

what is the white flaky area

laminar epidermis

what is the dark area

coronary epidermis

why does the suspensory apparatus of P3 fail

• Still under investigation

• Insulin dysregulation

• Endothelial cell and vascular dysfunction

• Conditions

• Metabolic syndrome and insulin resistance

• Pars Pituitary Intermedia Dysfunction (PPID or Cushing's)

• Endotoxemia

  • Colic

  • Retained placenta

  • Colitis

• Physical demand

what is the main blood and nerve supply to the hoof

medial/ lateral palmar/ plantar digital

how do vessels enter the hoof

on palmar/plantar aspect of P3

where is palmar venous plexus

in sole corium, around toe between sole and digital cushion

where is dorsal venous plexus

in laminar corium

where is the coronary venous plexus

at coronet- in coronary and perioplic corium

drains into digital veins cuts at coronet bleed

where does the collateral cartilages attach

to P3

what is known as the structural support for heel bulbs

collateral cartilages w

what is the job of collateral cartilages

shock absorption

• dissipates force through their expansion

involved in blood pumping action of foot

explain the hoof as a pump

• Muscle normally required to achieve effective venous drainage in periphery

• No muscle in digit

• Digital cushion functions as “pump”

• When horse bears weight digital cushion expands and veins compressed → blood pools in venous plexus and digital cushion

  • Diastolic phase

• When horse lifts hoof digital cushion contracts and veins

open → blood forced out

• Systolic phase

explain the purpose of the navicular 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)

what is the top pink line

flexor tendon sheath

what is the grey arrow

collateral sesamoidean (suspensory) ligament of the navicular bone

what is the purple line

navicular bursa

what is the blue line

impar ligament

what is the teal arrow

medullary cavity

what is the orange arrow

cortex

what are the hoof functions

• Traction

  • Frog, shape of hoof (concave), wall

• Shock absorption

  • Digital cushion, ability to expand at heels

• Support of skeletal column

  • Weight of horse transmitted via lamina to hoof wall

  • Suspends P3

• Protection of inner structures

  • Periople protects from evaporation

  • Hoof wall protects lamina

• Venous return (peripheral pump)

  • Frog, digital cushion, collateral cartilages