Functional Anatomy Of The Equine Forelimb

Question 1

Describe the meaning of digitigrade

Answer 1

Locomotion and Weight bearing by digits

Question 2

Describe what is meant by plantigrade

Answer 2

Walk on the soles of the feet

Question 3

Describe what is meant by unguligrade

Answer 3

A animal that walks on hooves- weight bare on ungual process

Eg HORSES

Question 4

What does perissodactyla mean

Answer 4

What bearing on all toes

Question 5

Describe the basic structure of the equine forelimb

Answer 5

Unguligrade, weight bearing distal phalanx of 3rd digit, manus expanded (long metacarpals)

Question 6

Describe the superficial structures of the equine forelimb

Answer 6

Chestnut: vestigial horn pad, 1st metacarpal bone
Ergot- horny lump on skin, palmar aspect of the metacarpal phalangeal joint and is hidden by hairs/ feathers, remnant of metacarpal pad

Question 7

Describe the function, origin and insertion of the biceps branchii muscle

Answer 7

Function-extends shoulder/ flexes elbow
Origin=supraglenoid tubercle (seperated from glenoid cavity)
Insertion=proximal radius

Question 8

Describe the 2 origins of the tendon muscle in the biceps branchii

Answer 8

Intermediate tubercle
2 inter-tubercle grooves
ALL ABOVE ARE PARTS OF THE HUMERUS

Question 9

How is the bicipital bursa different in horses compared to domestic species

Answer 9

Seperate from shoulder joint capsule

Question 10

How is the biceps branchii muscle different in horses

Answer 10

Extends into a fibrous extension called the lacertus fibrosis, which joins extensor carpi radialis and inserts on the proximal MC3. It maintains shoulder and carpus in extension

Question 11

How is the elbow joint different in horses? Describe the clinical significance of this

Answer 11

Radius and ulna fused-no ration, no annular ligament, collateral ligaments present

Bursa present- fluid filled cushion, protection of tendons

Tricipital bursa- between tendon and olecranon process
Subcutaneous bursa- between skin and tendon of insertion of triceps

Clinical significance:

• capped elbow-poor bedding
• deeper swelling-true bursitis

Question 12

Describe how the carpal joint is different in horses from domestic species and how its movement is different
(BONES, SYNOVIAL JOINT AND CARPAL CANAL

Answer 12

Carpal bones- all present except 1st carpal bone, 3rd carpal bone is the largest

Movement:
-most at the antebrachio-carpal joint
-least carpometacarpal joint
COLLECTING JOIONT FLUID SAMPLES

Synovial joint
Support via collateral ligaments, palmar ligaments, palmar fibrocartilagenous plate (origin of the check ligament for the deep digital flexor tendon) and flexor retinaculum

Carpal canal:
Made up of palmar fibrocartilagenous plate, palmar/ flexor reticulum and accessory carpal bone
IN DOGS: ONLY DEEP DIGITAL FLEXOR TENDON PASSES THROUGH THE CARPAL CANAL
IN HORSES: BOTH THE DEEP DIGITAL FLEXOR TENDON AND SUPERFICIAL DIGITAL FLEXOR TENDON PASS THROUGH THE CARPAL CANAL

Question 13

Describe the function of the tendon sheath in horses

Answer 13

Protects tendon in confined spaces and in the dorsal aspect, it surrounds the flexor tendons
There is one sheath for both the Deep digital flexor tendon and the superficial digital flexor tendon (INFLAMMATION=INCREASED PRESSURE)

Question 14

Describe the difference of metacarpal bones in horses compared to domestic species

Answer 14

3rd metacarpal bone=cannon bone, weight bearing
Distal articular surface=Sagittal ridge

2nd and 4th metacarpal bones:
Splint bones, vestigial (non weight bearing), button at distal end (palpable)

Joints between metacarpals- fibrous joints (syndesmosis), mineralise as they age ALSO CALLED SPLINTS

Question 15

Describe how phalanges are different in horses compared to other domestic species

Answer 15

Proximal phalanx (P1) : ‘’log pastern’’ bone, raised v on the palmar surface ATTACHMENT OF OBLIQUE DISTAL SESAMOIDEAN LIGAMENT

Middle phalange (p2): ‘’short pastern’’ bone 
Bony contours: attachment of collateral ligaments (‘’RINGBONE’’)

Question 16

Describe how the distal phalanx (p3) is different in horses compared to domestic species

Answer 16

‘’pedal/coffin bone’’:

• complex shape
• extensor process= attachment of common digital extensor tendon
• palmar processes=support lateral cartilages
• solar surface=attachment of Deep digital flexor tendon

DORSAL SURFACE:

• striations (hoof attachment and blood vessels)
• vascular channel (nutrient foramen)

Question 17

Describe the development of the manus bone in horses

Answer 17

In metacarpal 3- 2 centres of ossification at the body and distal epiphysis
In metacarpal 2 and 4- 2 centres of ossification at the proximal epiphysis and body
At the proximal phalanx, there is 2 centres of ossification at the proximal epiphysis and body
At the middle phalanx, there is 2 centres of ossification at the proximal epiphysis and the body
At the distal phalanx, there is only one centre of ossification at the body

Question 18

Describe how the proximal SESAMOID bones are different in horses to domesticated species and what is their function

Answer 18

They are triangular shaped, at the distal end of metacarpal 3 at either side of the Sagittal ridge. They are embedded in the suspensory ligament (interosseous ligament)
FUNCTION= TO PROTECT THE SUPERFICIAL DIGITAL FLEXOR TENDON AND THE DEEP DIGITAL FLEXOR TENDON

NO DORSAL SESAMOID!!!!!!!!

Question 19

Describe the structure of navicular bones in horses and its clinical significance

Answer 19

Navicular bone is also called the distal SESAMOID

2 flat articular surfaces
Covered in hyaline cartilage
Cancellous centre
Vascular channels
Located at the palmer aspect of distal interphalangeal joint
On the dorsal surface, it articulates with the middle phalanx and the distal phalanx
On the palmar surface, it guides the deep digital flexor tendon over the sitar interphalangeal joint
UNDER A LARGE AMOUNT OF PRESSURE

Clinical considerations:
NAVICULAR DISEASE SYNDROME:
-erodes with age
-bone dissolves (visible on radiographs)
-poor correlation between clinical signs and radiographic findings

Question 20

Describe how the metacarpo-phalangeal joint is different in horses compared to domestic species

Answer 20

‘’Fetlock’’
Metacarpal 3 and proximal phalanx
Synovial joint
Extensive joint capsule- large dorsal pouch (protects extensor tendons)
Large palmar pouch (incorparates proximal SESAMOIDs)

NO DORSAL SESAMOID

Question 21

Describe the motion of the fetlock joint

Answer 21

Neutral position= extension
Limited to flexion and extension: Sagittal ridge distal to metacarpal 3, Sagittal groove proximal to proximal phalanx, collateral ligaments between the metacarpals and the proximal phalanx

Has the tendency to collapse into hyperextension (suspensory ligament and sesamoidean ligaments)

Question 22

Describe the origin and branches of the suspensory ligaments.

Answer 22

ENTIRELY LIGAMENTOUS
Origin= proximal palmar metacarpal 3 and fills area between split bones

Branches=

• abaxial aspect proximal sesamoids
• passes to dorsal aspect
• fuses with common digital extensor tendon

Question 23

Describe the function of suspensory ligaments

Answer 23

• prevent collapse of metacarpal joint during weight bearing
• return metacarpal joint from hyperextension to normal extended position
• relies on the stability of proximal SESAMOID bones

Question 24

Describe the support of the carpal joints

Answer 24

Inter-sesamoidean ligament:

• reinforced fibrocartilage
• proximal scrutum
• passage of deep digital flexor tendon and superficial deep flexor tendon over tendon

Collateral sesamoidean ligaments:
Proximal sesamoids- metacarpal and proximal phalanx Nmmm=
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