The upper arm and elbow joint Flashcards
What are the lateral and medial distal projections of the humerus called? Which is more prominent?
The lateral and medial epicondyles. The medial epicondyle is the more prominent of the two
What are the two cartilage covered surfaces at the lower end of the humerus called? What do these surfaces look like? What do they articulate with?
On the lateral side there is the capitulum, a rounded surface which articulates with the head of the radius.
On the medial side there is the trochlea which is larger and pulley shaped. It articulates with the ulna
What are the two projections of the ulnar which articulate with the trochlea called?
The olecranon projects around the posterior aspect of the trochlea
The coranoid process projects in front of the trochlea
Describe the various excavations of the humerus. Why are these excavations necessary?
The humerus is excavated about the capitulum and trochlea to form two fossae- the radial and coronoid fossae. Posteriorly, the humerus is excavated distally to form the olecranon fossa. With flexion of the elbow, the coronoid process abuts onto the humerus and is accepted into the coronoid fossa in extreme flexion. Similarly, with full extension, the olecranon fits into the olecranon fossa. On the lateral side, the head of the radius fits into the radial fossa in flexion. In extension, however, the head of the radius does not reach as far back as the olecranon and there is therefor no radial fossa on the posterior aspect of the humerus
Describe the compartments of the upper arm
On either side of the humerus there is a condensation of connective tissue between which gives the impression of two septa which stretch from the margins of the humerus to the sleeve of deep fascia surrounding the arm. They are called the medial and lateral intermuscular septa. The upper arm can therefore be thought of as having two compartments, the anterior compartment- which contains the flexor musculature, and the posterior compartment, which contains the extensor musculature.
What three muscles make up the flexor musculature of the upper arm?
Coracobrachialis
Biceps brachii
Brachialis
What is the origin of coracobrachialis?
Coracoid process
What is the insertion of coracobrachialis?
Half way down the shaft of the humerus
What is the action of coracobrachialis?
It is a weak adductor of the shoulder joint. Powerful adduction has been taken over by the pec major and lat dorsi
Describe the origin of biceps
The biceps arises by two heads
The long head arises from the supraglenoid tubercle of the scapula, just above the apex of the glenoid cavity. It passes over the upper end of the humerus inside the capsule of the shoulder joint. It leaves the interior of the joint by passing along the intertubercular groove underneath the transverse ligament
The short head arises from the coracoid process
The heads unite in the upper arm and give rise to the biceps muscle
Describe the insertion of the biceps
The muscle inserts into both forearm bones. Its main insertion is into the radial tuberosity by means of a strong tendon. From the medial border of this tendon, a thin aponeurosis spreads into the deep fascia and blends with the periosteum on the ulna.
What is the action of the biceps?
Flexion of the elbow joint
Supination of the forearm
What is the origin of the brachialis?
Distal half of the shaft of the humerus and intermuscular septa
What is the insertion of the brachialis?
The coronoid process of the ulnar
What is the action of the brachialis?
Flexion of the elbow joint
