The Forelimb Muscles & Bones Flashcards
What muscle is the clavicle embedded in?
Brachiocephalicus muscle
Glenoid cavity
Distal end of the scapula; articulates with the head of the humerus.
Scapular spine
Ends at the acromion. On the lateral surface of the scapula.
Acromion
A process on the distal end of the scapular spine. Not present in the horse/pig.
Supraspinous fossa
Cranial to the spine. Concavity of the scapula.
Infraspinous fossa
Caudal to the spine. Concavity of the scapula.
Subscapular fossa
Most of the medial surface. Concavity of the scapula.
Supraglenoid tubercle
Process near the cranial aspect of the glenoid cavity.
Infraglenoid tubercle
Process near the caudal aspect of the glenoid cavity.
Greater tubercle
Large process craniolateral to the head (of the humerus). Forms the point of the shoulder.
Lesser tubercle
Process on the medial side of the head (of the humerus).
Intertubercular groove
Exists between the greater and lesser tubercle.
Deltoid tuberosity
Large tuberosity on the lateral side of the humerus.
Humeral condyle
The entire distal extremity of the humerus (includes the trochlea and capitulum).
Extensors of the forearm attach to the lateral epicondyle. Flexor muscles of the forearm attach to the medial epicondyle.
Olecranon fossa
Caudal aspect (of the humerus) that receives the olecranon of the ulna.
Radial fossa
Cranial aspect which receives the head of the radius.
Trochlea
Medial portion of the condyle (larger); articular surface.
Capitulum
Lateral portion of the condyle (smaller); articular surface.
Supratrochlear foramen
The hole between the olecranon fossa and radial fossa, found in the dog.
Supracondylar foramen
Opening in the medial epicondyle of the cat. Median nerve and brachial artery pass through it.
Styloid process of the ulna
Pointed distal end of the ulna. This structure is LATERAL.
Styloid process of the radius
Distal end of the radius. This structure is MEDIAL.
Olecranon
Proximal part of the ulna, forms the “point” of the elbow.
Attachment site for the triceps brachii muscle.
Trochlear notch
Concave articular surface that articulates with the trochlea of the humerus.
Proximal end, half-moon shaped.
Anconeal process
Proximal end of the trochlear notch.
Coronoid process
Distal end of the trochlear notch. Has medial and lateral divisions.
Interosseous space
Space that exists between the ulna and radius.
Where do the extensors and flexor muscles of the forearm attach to the humerus?
Extensors of the forearm attach to the lateral epicondyle.
Flexor muscles of the forearm attach to the medial epicondyle.
What species of animal has a supracondylar foramen?
Cats
Which species of animal has a supratrochlear foramen?
Dogs
Which species of animal has an intermediate tubercle?
Horses
What is the main weight-bearing bone of the forearm?
Radius
What is the difference between pronation and supination? Why are horses and ruminants not capable of either?
Pronation: to rotate outward.
Supination: to rotate inward.
In horses and ruminants, the ulna is fused with the radius, so they can’t supinate or pronate their forearm.
What is the typical carpal pattern of 8 bones (i.e. how many rows and which bones are in each row)? Which species of animal has all 8 bones?
2 rows:
1. Proximal row - radial, intermediate, ulnar, and accessory carpal bones.
2. Distal row - 1st, 2nd, 3rd, 4th carpal bones
Pigs have all 8 bones.
What structures form the different borders of the carpal canal?
Accessory carpal bone (laterally)
Other carpal bones (dorsally)
Flexor retinaculum (palmar)
What two nerves run through the carpal canal?
Ulnar and median nerve.
Which digit(s) are weight-bearing in the pig and the horse?
Pig: digits 3 and 4
Horse: digit 3
What bones are the “splint” and “cannon” bone referring to?
Splint bone: MC II/IV (2/4)
Cannon bone: MC III (3)
What bones are the long pastern, short pastern, and coffin bone referring to?
Long pastern bone: proximal phalanx
Short pastern bone: middle phalanx
Coffin bone: distal phalanx
What bones are the sesamoid and navicular bone referring to?
Sesamoid bone: proximal sesamoid
Navicular bone: distal sesamoids
What joints are the coffin joint, the pastern joint, and the fetlock joint in the horse referring to?
Coffin joint: distal interphalangeal joint
Pastern joint: proximal interphalangeal joint
Fetlock joint: metacarpophalangeal joint
Where are the metacarpophalangeal, the proximal, and the distal interphalangeal joints located?
Metacarpophalangeal: located between the metacarpal bones and the proximal phalanges.
Proximal interphalangeal joint: located between the metacarpophalangeal and distal interphalangeal joint.
Distal interphalangeal joint: furthest from carpal bones.
What ligament is responsible for keeping claws retracted in cats?
Dorsal ligaments.
What ligaments prevent abnormal separation of the two digits in cattle?
Proximal/distal interdigital ligaments.
What is the difference between extrinsic and intrinsic muscles?
Intrinsic muscles: Muscles having both attachments on the limb.
Extrinsic muscles: Muscles that attach the forelimb to some other part of the body (head, neck, or trunk).
What superficial muscle originates on the spine of the scapula and inserts on the dorsal neck/thorax?
Trapezius
What superficial muscle originates on the spine of the scapula and extends to the atlas? Is it proximal or distal to the trapezius?
Omotransversarius. It is distal to the trapezius.
What long flat superficial muscle extends from the head/neck to the arm? What are the 2 divisions of this muscle (as demarcated by the clavicular insertion)?
Brachiocephalicus.
Two divisions:
Cleidobrachialis
Cleidocephalicus
What extrinsic muscle of the shoulder originates on the dorsal border of the scapula and inserts on the dorsal neck/thorax/skull?
Rhomboideus
What extrinsic muscle of the shoulder supports the weight of the trunk?
Serratus ventralis
What two muscles make up the “brisket” in beef cattle?
Superficial pectoral
Deep pectoral
Is the teres major on the caudal or cranial aspect of the limb?
Caudal aspect. Arises from the caudal angle of the scapula.
Is the subscapularis on the lateral or medial aspect of the limb?
Medial aspect.
What are the 4 heads of the triceps brachii? What is its action on the elbow?
*Extends the elbow, flexes the shoulder.
1. Long head (originates on the caudal edge of scapula)
2. Lateral head (originates on the humerus)
3. Medial head (originates on the humerus)
4. Accessory head (originates on the humerus)
Is the biceps brachii on the cranial or caudal aspect of the humerus? What is its action on the elbow?
Cranial aspect of the humerus. *Flexes the elbow, extends the shoulder.
Where do the extensor muscles of the carpus and digit originate?
Lateral epicondyle of the humerus.
What is the most medial of the dorsolateral muscles of the forearm?
Extensor carpi radialis.
Where does the common digital extensor insert?
From the humerus to the distal phalanges.
Where does the lateral digital extensor insert?
From the proximal radius to the middle phalanges.
Where do the flexor muscles of the carpus and digit originate? Are they caudal or craniolateral?
Originate from the medial epicondyle of the humerus. They are caudal.
Which of the caudal antebrachial muscles are innervated by the median nerve and is the most medial of the group?
Flexor carpi radialis
What are the structures of the stay apparatus of the equine forelimb? Know how they function to stabilize the limb.
Lacertus fibrosus - tendinous band connecting the tendon of the biceps brachii muscle to the tendon of the extensor carpi radialis muscle.
Collateral ligaments - are placed behind the axis of the joint. Stabilize a joint as it flexes and extends through its range of motion.
Tendon of the extensor carpi radialis muscle - inserts on the proximal metacarpus; when pulled by the lacertus fibrosus, it maintains the carpus in extension.
Palmar carpal ligament - runs palmar to the joint, prevents carpal hyperextension.
Suspensory ligament - joins the common extensor tendon, thereby transferring the tension from the extensor tendon to the suspensory ligament
Sesamoidean ligaments - counteract the pull of the suspensory ligament and stabilize the fetlock joint, prevents fetlock from sinking.
Proximal check ligament - transfers tension from the superficial digital flexor to the radius
Distal check ligament - transfers tension in the deep digital flexor tendon to the metacarpal bone.
In summary, equine stay apparatus:
> Locks the limb so the horse can stand while
exerting minimal effort.
> Prevents flexion of the shoulder, elbow, and
carpus.
> Prevents overextension of the carpus and
pastern.
> Prevents collapse of the fetlock.
