Forelimb Musculoskeletal System

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Questions and Answers

What percentage of the animal's weight is transferred to the thoracic limbs when standing?

60%

What is the primary function of the forelimb in the canine?

Support

Which muscles are responsible for transferring the weight of the head, neck, and trunk to the forelimb?

Serratus ventralis and pectoral

What is the term for the extrinsic muscles that attach the forelimb to the trunk?

Synsarcosis Signup and view all the answers

What happens when the limb is weight-bearing?

The limb stays fixed to the ground and the head, neck, and trunk move Signup and view all the answers

What is the example of the deep pectoral muscle's action in the lecture?

Dog digging vs. walking Signup and view all the answers

What type of joint is the glenohumeral joint?

Ball and socket joint Signup and view all the answers

Which muscle is responsible for flexing the glenohumeral joint?

Deltoideus Signup and view all the answers

Which of the following muscles helps to prevent medial rotation of the glenohumeral joint?

Subscapularis Signup and view all the answers

What is the name of the bursa located between the Infraspinatus muscle and the scapula?

Subtendinous bursa of Infraspinatus Signup and view all the answers

Which radiographic view is best for visualizing the scapular spine and the supraglenoid tubercle?

Lateral view Signup and view all the answers

What is the role of the Teres minor muscle in the glenohumeral joint?

Stabilizes the joint Signup and view all the answers

Which joint provides the greatest range of motion in the carpus?

Antebrachiocarpal joint Signup and view all the answers

What is the function of the palmar carpal ligament?

To oppose hyperextension of the carpal joint Signup and view all the answers

Which of the following bones forms the lateral border of the carpal canal?

Accessory carpal bone Signup and view all the answers

What is the role of the carpal canal?

To make a tunnel for and protect the tendons of the digital flexor muscles Signup and view all the answers

How many joints make up the carpus?

3 Signup and view all the answers

What is the movement of the distal phalanges when the claws are retracted?

They slide next to the middle phalanges Signup and view all the answers

What is the origin of the extensors of the carpus and digits?

Lateral epicondyle of the humerus Signup and view all the answers

What is the function of the flexor manica?

Supports the metacarpophalangeal joint Signup and view all the answers

What is the insertion point of the bifurcated tendon?

Proximal sesamoid bones Signup and view all the answers

What is the role of the common digital extensor?

Extends the digits Signup and view all the answers

What is the function of the flexor carpi radialis?

Flexes the carpus Signup and view all the answers

What is the purpose of the flexor manica 'sleeve'?

To allow tendons to cross Signup and view all the answers

What is the purpose of the palmar annular ligament in the digits?

Holds down the flexor manica and DDF tendon Signup and view all the answers

Which ligament is responsible for attaching the middle phalanx to the distal phalanx in the digits?

Dorsal ligament Signup and view all the answers

In cats, what is the function of the dorsal (elastic) ligaments in the digits?

Passively maintains the extended rest position of the distal interphalangeal joint Signup and view all the answers

What is the name of the muscle responsible for protracting the claw in cats?

Deep digital flexor Signup and view all the answers

What is the name of the pad located on the wrist in the manus?

Carpal pad Signup and view all the answers

What is the name of the view that shows the palmar surface of the manus bones?

Palmar view Signup and view all the answers

What type of joint is the elbow joint classified as?

Hinge joint Signup and view all the answers

Which muscle has a long head that acts on both the shoulder and elbow joints?

Triceps brachii Signup and view all the answers

Which process fits into the olecranon fossa during extension of the elbow joint?

Anconeal process Signup and view all the answers

What is the function of the triceps mm. in the forelimb?

Extending the elbow joint Signup and view all the answers

Which of the following bones articulates only with the head of the radius?

Capitulum Signup and view all the answers

What type of ligaments are present in the elbow joint?

Strong collateral ligaments Signup and view all the answers

What is the function of the biceps brachii muscle?

Flexes the shoulder and elbow joints Signup and view all the answers

What type of muscles are the brachialis and biceps brachii?

Synergistic Signup and view all the answers

What type of joint is the glenohumeral joint classified as?

Ball and socket joint Signup and view all the answers

What is the function of the pronator teres and pronator quadratus muscles?

Pronate the forearm Signup and view all the answers

Which muscle helps to prevent medial rotation of the glenohumeral joint?

Infraspinatus Signup and view all the answers

What is the relationship between the triceps brachii and biceps brachii muscles?

They are antagonistic Signup and view all the answers

What is the primary movement allowed by the joints of the canine manus?

Flexion and extension Signup and view all the answers

What is unique about the ligaments in the glenohumeral joint?

There are no collateral ligaments Signup and view all the answers

What is the purpose of the transverse humeral retinaculum?

To hold the biceps brachii and brachialis muscles in place Signup and view all the answers

Which muscle is responsible for extending the glenohumeral joint?

Supraspinatus Signup and view all the answers

What is the name of the bursa located between the Infraspinatus muscle and the scapula?

Subtendinous bursa of Infraspinatus Signup and view all the answers

Which radiographic view is best for visualizing the scapular spine and the supraglenoid tubercle?

Lateral view Signup and view all the answers

What is the origin of the flexors of the carpus and digits?

Medial epicondyle of the humerus Signup and view all the answers

What is the function of the Flexor manica 'sleeve'?

To allow the tendons to cross Signup and view all the answers

What is the role of the Extensor carpi radialis?

To extend the carpus Signup and view all the answers

What is the insertion point of the bifurcated tendon?

Proximal sesamoid bones Signup and view all the answers

What is the function of the Flexor carpi radialis?

To flex the carpus Signup and view all the answers

What is the role of the Palmar carpal ligament?

To support the metacarpophalangeal joint Signup and view all the answers

What is the function of the palmar annular ligament in the digits?

Holds down flexor manica and DDF tendon Signup and view all the answers

In the digits, which ligament is responsible for attaching the middle phalanx to the distal phalanx?

Dorsal ligament Signup and view all the answers

What is the function of the dorsal (elastic) ligaments in the digits of cats?

Passively maintains the extended rest position of the distal interphalangeal joint Signup and view all the answers

What is the name of the muscle responsible for protracting the claw in cats?

Deep digital flexor Signup and view all the answers

What is the name of the pad located on the wrist in the manus?

Carpal pad Signup and view all the answers

What type of view shows the palmar surface of the manus bones?

Palmar view Signup and view all the answers

What is the primary function of the serratus ventralis muscle in the canine thoracic limb?

To transfer the weight of the head, neck, and trunk to the forelimb Signup and view all the answers

What is the result of the extrinsic muscles of the thoracic limb contracting without weight-bearing on the limb?

The head, neck, and trunk move relative to the limb Signup and view all the answers

What is the role of the trapezius muscle in the canine thoracic limb?

To rotate the scapula Signup and view all the answers

What is the direction of movement of the head, neck, and trunk when the thoracic limb is weight-bearing?

Relative to the limb Signup and view all the answers

What is the function of the deep pectoral muscle in the canine thoracic limb?

To propel the trunk forward Signup and view all the answers

What is the term for the muscles that attach the thoracic limb to the trunk in the canine?

Extrinsic muscles Signup and view all the answers

What is the primary function of the glenohumeral joint?

To flex and extend the limb Signup and view all the answers

Which muscles are responsible for stabilizing the glenohumeral joint?

Supraspinatus, Infraspinatus, and Subscapularis Signup and view all the answers

What is the purpose of the subtendinous bursa of the Infraspinatus muscle?

To reduce friction between the Infraspinatus muscle and the scapula Signup and view all the answers

What is the name of the ligament that connects the scapula to the humerus?

There is no ligament connecting the scapula to the humerus Signup and view all the answers

What is the role of the Deltoideus muscle in the glenohumeral joint?

It only flexes the joint and does not assist in weight bearing Signup and view all the answers

What is the name of the radiographic view that shows the scapular spine and the supraglenoid tubercle?

Lateral view Signup and view all the answers

What is the main function of the muscles acting on the elbow joint?

Flexion and extension Signup and view all the answers

What type of joint is the elbow joint?

Hinge joint Signup and view all the answers

Which muscle has a long head that acts on both the shoulder and elbow joints?

Triceps brachii Signup and view all the answers

What is the name of the process that fits into the olecranon fossa during extension of the elbow joint?

Anconeal process Signup and view all the answers

What is the function of the tensor fasciae antebrachii muscle in the elbow joint?

Not pictured in the diagram Signup and view all the answers

Which bone articulates only with the head of the radius in the elbow joint?

Capitulum Signup and view all the answers

What is the primary function of the biceps brachii muscle?

To flex the shoulder and elbow joints Signup and view all the answers

What is the relationship between muscles that cross the same side of a joint?

They are synergistic Signup and view all the answers

What is the function of the pronator teres and pronator quadratus muscles?

To pronate the antebrachium Signup and view all the answers

What is the function of the transverse humeral retinaculum?

To prevent the biceps brachii tendon from displacing Signup and view all the answers

What is the primary movement allowed by the joints of the canine manus?

Flexion and extension Signup and view all the answers

What is the relationship between the triceps brachii and biceps brachii muscles?

They work against each other, with the triceps extending the elbow and the biceps flexing it Signup and view all the answers

How many joints make up the carpus in felines?

3 Signup and view all the answers

What is the role of the palmar carpal ligament in the carpal joint?

To oppose hyperextension of the carpal joint Signup and view all the answers

What is the function of the carpal canal?

To protect the tendons of the superficial digital flexor and deep digital flexor muscles Signup and view all the answers

What happens to the distal phalanges when the claws are retracted in felines?

They slide next to the middle phalanges Signup and view all the answers

Which bone forms the lateral border of the carpal canal in felines?

Accessory carpal bone Signup and view all the answers

Which joint provides the greatest range of motion in the carpus of felines?

Antebrachiocarpal joint Signup and view all the answers

Study Notes

Forelimb

The forelimb has a weight-bearing function, with 60% of the animal's weight transferred to the thoracic limbs when standing
The front limb is for support, while the hindlimb is for propulsion
The weight of the head, neck, and trunk transfers to the forelimb
The forelimb is attached to the trunk via extrinsic muscles (synsarcosis)

Shoulder Joint

Ball and socket joint
No collateral ligaments, so muscle stabilization is needed
Range of movements: primary - extension/flexion; also allows some abduction/adduction, lateral and medial rotation
Head of humerus
Joint capsule (cut open)
Radiographs: shoulder joint

Muscles of Scapula and Shoulder

Deltoideus
Subtendinous bursa of Infraspinatus m
Muscles working together to assist in weight bearing of the glenohumeral (shoulder) joint:
- Supraspinatus m. - extends and prevents medial rotation
- Deltoideus - flexes
- Infraspinatus m. - helps extension and prevents medial rotation
- Teres minor m. - only stabilizes (flexes and prevents rotation)
- Subscapularis m. - extends and prevents rotation
- Teres major m. - only stabilizes (flexes and prevents rotation)
- Coracobrachialis m. - extends

Elbow Joint

Hinge joint
One synovial cavity
Strong collateral ligaments
Very stable joint, congruent
Allows flexion and extension only
Anconeal process fits into the olecranon fossa during extension
C=capitulum articulates only with head of radius
T=trochlea articulates with both radius and ulna

Caudal (Cd.) mm. of Brachium: Elbow Extension

Triceps brachii m.:
- Long head - acts on shoulder and elbow
- Lateral head - elbow only
- Medial head - elbow only (not visible)
- Accessory head - elbow only (not visible)
Tensor fasciae antebrachii m. (not pictured)
Anconeus (red arrows) m.

Extrinsic Muscles of the Thoracic Limb (TL)

Originate on the head, neck, and/or trunk
Insert on the Limb
Movement occurs in both directions:
- If no body weight is placed on limb, the limb will move towards head/neck/trunk
- If limb is weight-bearing, then head/neck/trunk will move relative to the limb (which will stay fixed to the ground)
Pictured: brachiocephalicus m (2, 2’); omotransversarius m. (3); trapezius m. (5, 5’); latissimus dorsi m. (7); deep pectoral m. (9)

Practice Photos

Scapula
Humerus
Radius
Ulna
Sternum
Deep pectoral m.
Serratus ventralis m.
Trapezius m.
Rhomboideus m.### Elbow Flexors
Biceps brachii muscle acts on shoulder and elbow joints.
Brachialis muscle flexes the elbow joint.
Biceps brachii and brachialis muscles work together to flex the elbow joint.

Transverse Humeral Retinaculum

A structure that facilitates the movement of Biceps brachii and brachialis muscles.

Muscle Concepts

Synergistic muscles: muscles that work together, crossing the same side of a joint (e.g., brachialis and biceps brachii).
Antagonistic muscles: muscles that work against each other, crossing opposite sides of a joint (e.g., triceps brachii and biceps brachii).

Forearm and Hand

Pronation vs supination of antebrachium (forearm): more developed in cats.
Muscles involved in pronation and supination: pronator teres, pronator quadratus, and supinator.

Canine Manus (Forepaw)

Joints of the canine manus allow flexion and extension, caused by two main muscle groups antagonistic to each other.
Radiographs of the canine manus: dorsopalmar and lateral views (FIG. 16.10).

Carpus Joint Complex

Consists of three joints: antebrachiocarpal, middle carpal, and carpometacarpal joints.
Antebrachiocarpal joint provides the greatest range of motions and has a separate synovial cavity.
Middle carpal and carpometacarpal joints have less motion, with their synovial cavities communicating.

Carpal Joints

Clinical relevance: antebrachiocarpal joint is used for arthrocentesis, with possible pathology in distal radius.
Carpal canal: a tunnel that protects tendons of superficial digital flexor and deep digital flexor muscles, bounded by the palmar carpal ligament, accessory carpal bone, and flexor retinaculum.

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