Functional Anatomy Of The Equine Forelimb Flashcards
Describe the meaning of digitigrade
Locomotion and Weight bearing by digits
Describe what is meant by plantigrade
Walk on the soles of the feet
Describe what is meant by unguligrade
A animal that walks on hooves- weight bare on ungual process
Eg HORSES
What does perissodactyla mean
What bearing on all toes
Describe the basic structure of the equine forelimb
Unguligrade, weight bearing distal phalanx of 3rd digit, manus expanded (long metacarpals)
Describe the superficial structures of the equine forelimb
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
Describe the function, origin and insertion of the biceps branchii muscle
Function-extends shoulder/ flexes elbow
Origin=supraglenoid tubercle (seperated from glenoid cavity)
Insertion=proximal radius
Describe the 2 origins of the tendon muscle in the biceps branchii
Intermediate tubercle
2 inter-tubercle grooves
ALL ABOVE ARE PARTS OF THE HUMERUS
How is the bicipital bursa different in horses compared to domestic species
Seperate from shoulder joint capsule
How is the biceps branchii muscle different in horses
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
How is the elbow joint different in horses? Describe the clinical significance of this
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
Describe how the carpal joint is different in horses from domestic species and how its movement is different
(BONES, SYNOVIAL JOINT AND CARPAL CANAL
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
Describe the function of the tendon sheath in horses
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)
Describe the difference of metacarpal bones in horses compared to domestic species
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
Describe how phalanges are different in horses compared to other domestic species
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’’)
Describe how the distal phalanx (p3) is different in horses compared to domestic species
‘’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)
Describe the development of the manus bone in horses
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
Describe how the proximal SESAMOID bones are different in horses to domesticated species and what is their function
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!!!!!!!!
Describe the structure of navicular bones in horses and its clinical significance
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
Describe how the metacarpo-phalangeal joint is different in horses compared to domestic species
‘’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
Describe the motion of the fetlock joint
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)
Describe the origin and branches of the suspensory ligaments.
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
Describe the function of suspensory ligaments
- 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
Describe the support of the carpal joints
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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