L36: foot and claw

what is the equine hoof?

horny enclosure of the distal phalanx (epidermal hoof)

what is the equine foot?

equine hoof and everything inside

what re the three layers of the equine hoof?

1. epidermis

2. dermis

3. subcutaneous tissue

what is the epidermis of the hoof also known as?

horn

what is the dermis of the hoof also known as?

corium

which layer of the hoof is insensitive and non-innervated?

epidermis

which layer of the hoof is soft, sensitive, and innervated?

dermis

which layer of the hoof has digital and coronary cushions?

subcutaneous tissue

what are the topographical regions of the hoof wall?

1. toe

2. quarters

3. heels

4. bars

what is the most dorsal region of the hoof wall?

toe

what is the most palmar part of the hoof wall?

heels

which of the quarters in the hoof wall has a thicker wall?

lateral (outer) has thickest wall

what do the bars offer to the hoof wall?

stability for the heels

what seperates the bars from the frog?

paracuneal grroves

describe the thickness of the hoof wall?

wall thickest at toes and thins progressively towards the heel

how do we see the bars of the hoof wall?

must lift hoof off the ground as it is on the sole surface

what is the sole?

space between the wall and the frog

describe the nature of the sole in the equine foot

concave

what is the angles of the sole?

parts between the bars and quarters

what is “corns”

trauma at the angles of the sole in the equine foot

what does the image show?

corns

what region of the hoof is the black box?

hoof

what region of the hoof is the pink box?

quarters

what region of the hoof is the red box?

toe

what structure is the yellow box?

hoof wall

what structure is the gray box?

white line

what structure is the blue box?

sole

what structure is the orange box?

collateral sulcus

what structure is the brown box?

frog

what structure is the green box?

bars

what structure is the light blue box?

central sulcus

what structure is the purple box?

heel bulbs

what is the function of the frog?

1. weight bearing of body

2. schock absorption

what is the role of the frog when the foot hits the ground?

yields pressure forces and dissipates most of the impact

what is the central groove/sulci of the frog?

the space between the bases on the side of the frog

what does the frog stay correspond to?

an internal spine formed by the reflection of the central groove

what are the components of the frog?

1. apex

2. base

3. crura

4. central groove/sulci

what is the intratoric fossa?

groove that divides the heel bulbs of the equine foot into lateral and medial parts

what is the digital cushion in the equine foot?

extensive fibrous fatty tissue above the crura of the frog and below the DDFT that helps the frog with shock absorption

what is the red arrow pointing at?

digital cushion of the equine foot

what bacteria causes thrush in the equine foot?

fusobacterium necrophorum

what is thrush in the equine foot?

degenerative condition of the central sulci and/or collateral sulci of the frog caused by bacteria or fungi

what are the characteristics of thrush in the equine foot?

black, necrotic, foul-smelling material

what surrounding tissues can be infected by thrush if it spreads from the frog?

digital cushion and skin at the heel bulbs

what is occurring in the image?

thrush

hoof capsule

skin derivative that entirely encloses the third phalanx

what is the hoof capsule a product of?

the dermis

what does the dermis of the hoof capsule continue with?

the common dermis of the skin at the coronet

what does the hoof capsule NOT have?

blood vessels or nerves

MCQ: what structure is the most important for shock absorption in the equine foot?

the frog

what is the coronet in the equine foot?

the junction between the skin and the hoof

what are the three layers of the epidermis in the equine hoof wall?

1. stratum externum

2. startum medium

3. startum internum

which area of the epidermis in the hoof wall is predisposed to fissures leading to cracks in the foot potentially?

boundary between the startum internum and startum medium

what connects the distal phalanx to the hoof wall?

dermis

what is the outer layer of the epidermis?

startum externum

what is the inner layer of the epidermis?

startum internum

what are the parts of the stratum externum?

1. periople

2. stratum tectorium

what is the function of the periople horn?

acts as a fluid reservoir to keep the underlying coronary horn moist

where does the periople of the stratum externum extend to?

onto the heel bulbs and blends with frog dermis

which structure is the proximal part of the stratum externum?

periople (closer to coronary band)

what is the stratum tectorium?

the rest of the covering of the hoof wall that is impervious to water

what does parallel proximo-distal lines of the stratium tectorium mean?

shows the growth of the horny tubules

what does horizontal smooth ridges of the stratium tectorium mean?

evidence of nutritional issues or laminitis

where does the stratum medium begin?

distal to the coronary groove

what does hte stratum medium possess?

openings for the papillae of the underlying dermis

describe the structure of the stratum medium

horny tissue with tubular structure formed by tubules and intertubular horn

what layer makes up the majority of the hoof wall?

stratum medium

what produces the stratum medium?

coronary dermis

what else can the stratum internum be referred to as?

1. epidermal laminae

2. insensitive laminae

what does the stratum internum fuses to?

stratum medium and connects hoof wall to dermis

what does the inner surface of the stratum internum have?

keratinized primary laminae and non-keratinized secondary laminae

what else does the stratum internum form?

laminae of the bar

what does the secondary laminae of the stratum internum interlock with?

dermal lamina

which layer of the epidermis no longer has tubules?

stratum internum

what is the function of the dermis?

1. attaches hoof wall to internal foot structures

2. produces various parts of the hoof wall via their papillae

what part of the dermis does not produce the tubules of the hoof wall?

laminar dermis

what is another name for the dermal laminae?

sensitive laminae

what does the papillae of the sole and frog do?

arranges the rest of the hoof capsule in tubules

what are the 5 areas of the dermis from most external to internal?

1. perioplic dermis

2. coronary dermis

3. laminar dermis

4. frog dermis

5. sole dermis

what do all parts of the dermis produce and connect to?

epidermis

what layer of the epidermis does the perioplic dermis produce?

stratum externum

what layer of the epidermis does the coronary dermis produce?

stratum medium

what does the laminar dermis produce?

produces insensitive laminae that will connect to sensitive laminae

what is important to understand about the structure of the laminar dermis layer?

no tubules present

what layer of the epidermis does the laminar dermis produce?

stratum internum

what portion of the dermis produces most of the hoof wall?

coronary dermis

how are the papillae arranged within the coronary dermis?

papillae fit into holes in strata medium and internum of the coronary groove

what happens if there is trauma that affects the coronary dermis of the equine foot?

causes horn defects that will descend within the wall and reach the ground in about 8 months

how will the corresponding part of the hoof capsule in relation to the dermal papillae be arranged?

epidermal part will be arranged as tubules

what else can you call the primary laminae of the larminar dermis layer?

dermal laminae

what does the laminae of the laminar dermis layer interdigitate with?

the laminae of the walls and bars (epidermal laminae)

what does weight of the horse bare down on?

wall of hoof

when horse is bearing down weight, what connection in the hoof needs to be strong?

connection between the wall, dermis (connective tissue) , and P3

the following image is a section of the horse hoof. what is the white layer showing?

epidermal lamina

the following image is a section of the horse hoof. what is the pink layer showing?

dermal layer

what is the sole dermis in contact with?

direct contact with the sole surface of the distal phalanx

what makes up the frog dermis?

densely covered with plump papillae (shorter than sole)

what is the white line in the equine foot?

the thin soft pale horn between the hoof wall and sole

what forms the white line that binds hoof wall to the sole?

distal aspect of sensitive lamina reaching ground surface via terminal papaillae

what is the clinical importance of the white line?

a point of weakness due to it being a mixture between the har laminar and soft tubular horn