Anatomy of the equine thoracic limb Flashcards
What is the fibrous support mechanism?
“Stay apparatus”
- reduces energy expelled to stand and allows efficient movement of the leg
- allows the horse to sleep standing up
Where is the body weight of the horse transferred to?
The deep pectoral and serratus ventralis
What are the nine components of the fibrous support mechanism?
- Tendon of biceps brachii
- Lacertus fibrosus
- Extensor carpi radialis
- Triceps brachii
- SDF and accessory ligament
- DDF and accessory ligament
- Common digital extensor tendon
- Interosseus
- Proximal sesamoiden bones and ligaments(cruciate, oblique and straight ligament)
What is the function of the tendon of the biceps brachii in the stay apparatus?
Prevents shoulder from flexing due to origin engaging on the intermediate tubercle (fixed distance when horse wants it to be)
What is the function of the triceps brachii muscles in the stay apparatus?
They remain flacid during the standing phase
What transfers the tension from the biceps brachii to the extensor carpi radialis?
Lacertus fibrosus
What ligament keeps the carpus from hyperextending?
Palmar carpal ligament
What keeps the fetlock form “sinking” to the ground?
The antagonistic forces of the SDF/DDF and their accessory check ligaments.
What are the components involved in the stabilization of the fetlock, pastern and coffin joints?
Suspensory ligament Proximal sesamoids (and ligaments) SDF DDF Distal sesamoid (navicular bone)
What is another name for the glenohumeral joint?
Shoulder joint
What is the lyman’s term for metacarpal 3?
cannon bone
What is the layman’s term for metacarpals 2 and 4?
Medial and lateral splint bones
What is the layman’s term for the carpus joint?
Knee
What is the layman’s term for the carpometacarpal joint?
Fetlock
What is the layman’s term for the proximal phalanx?
Long pastern
What is the layman’s term for the proximal interphalangeal joint?
Pastern joint
What is the layman’s term for the middle phalanx?
Short pastern
What is the layman’s term for the distal interphalangeal joint?
Coffin joint
What is the layman’s term for the distal phalanx?
Coffin bone
What is the layman’s term for the distal sesamoid bone?
Navicular bone
What ligament stretches out allowing for shock absorption in the suspensory apparatus?
Suspensory ligament
What portion of the suspensory apparatus attaches with the common digital extensor tendon?
Medial and lateral extensor branches of the suspensory ligament
What are the three sesamoidean ligaments?
- Straight
- Oblique
- Cruciate
What counteracts the flexion of the coffin bone?
The extensor branches of the interosseus
What counteracts the hyperextension of the fetlock joint?
Distal sesamoidean ligaments
What is a digitigrade and give examples.
Walks on digits
Ex: dogs and cats
What is an unguligrade and give examples.
Walks on distal phalanx
Ex: horse and cattle
What is a plantigrade and give examples.
Walks on digits, metatarslas, and plantar tarsus
Ex: human, bear, squirrel and skunk
What point of the carpus is fused in canines?
Radius and intermediate carpals are fused
What is fused in equine and bovine that isn’t in the canine.
The radius and ulna. On equine the ulna only runs about 1/2 way down the radius. Bovine the ulna runs the whole distance.
Which metacarpal is weight bearing in equine?
Metacarpal III
What metacarpal is most prominently seen in “popped splints”?
Metacarpal II, bears weight of two carpal bones.
Which metacarpals are weight bearing in bovine?
Metacarpal III & IV
What muscle in the equine gives a smooth and round appearance of the chest?
Subclavius muscle
What muscle forms the ventral border of the jugular groove?
Sternomandibularis muscle
What muscle forms the dorsal border of the jugular groove?
Brachiocephalicus
Where are intramuscular injections given?
Neck
Pectoral muscles
Avoid the tuber ischia
Where will you have access to the heartbeat on the horse?
You go behind the olecranon
Where does majority of the carpal movement come from?
Radiocarpal and midcarpal joint
What joints in the carpus communicate?
Midcarpal and carpometacarpal
Why is the concept of carpal communication important?
If you need to get medication to the carpometacarpal joint, you would inject the medication in the midcarpal joint space, and the medication will travel down to the carpometacarpal.
What is the equivalence of the digital, metacarpal and carpal pads in equine?
Frog (equivalent to the digital pad)
Ergot (equivalent to the metacarpal pad)
Chestnut (equivalent to the carpal pad)
What is the landmark for finding the VAN?
Ligament of the ergot
What are the components of the hoof?
Wall (toe, quarter, and heel)
Sole
Frog
Coronet (coronary band)
What is the landmark for inserting nails into the horseshoe?
The white line-terminal extent of the lamina
What are the germinal tissues of the hoof?
Perioplic corium (cuticle) Coronary corium (crowning the foot) Laminar corium (sensitive and insensitive layer)
What is it called when the laminar corium becomes infected?
Laminitis
The horse’s sole is slightly concave, what keeps the bone column from sinking to the ground?
The lamina (if laminitis occurs, the bone will penetrate to)
If a coranary band lesion occurs, what happens to the hoof?
The hoof will grow back in a irregular fashion
What is sweeny syndrome?
When nerve damage occurs by the scapula, the supraspinatus and infraspinatus atrophies, allowing the spine to protrude.
What is flying scapula?
This occurs when the serratus ventralis ruptures, allowing the scapula to protrude higher than normal. This shifts the weight entirely onto the pectoral muscle
What is occurring during flexoral limb deformity?
The equine limb is constantly flexing. In order to solve this problem, the DDF will be cut, allowing the hoof to return to normal
What is occurring during angular limb deformity?
One side of the knee is growing faster than the other
A splint is placed on the side of faster growth, tied together with wire, stopping the growth of this side so that the other side catches up
What is synovial effusion?
Abnormal accumulation of synovial fluid within a joint, bursa or tendon sheath.
What are the 7 synovial structures on the horse?
Extensor tendon sheath carpus flexor tendon sheath fetlock joint pastern joint coffin joint navicular bursa
What is tendonitis?
Build up of pressure, in the fetlock level, the palmar annular ligament can be cut to relieve impingement, alleviate pain and improve circulation
What is capped elbow?
Effusion of the olecranon bursa
Why is it catastrophic to athletic performance once a synovial structure is infected?
- challenging to treat here
2. Structures are designed for high motion and associated with weight bearing structures
What happens if the SDF fails?
the fetlock will slightly drop
What happens if the SDF and DDF fail?
The fetlock will drop
What happens if the SDF, DDF and suspensory ligament fail?
The fetlock will fall to the floor completely
