Muscles of the Arm: Triceps Anatomy Quiz

Questions and Answers

Which head of the triceps brachii originates at the infraglenoid tubercle of the scapula?

Accessory head

Medial head

Long head (correct)

Lateral head

What is the primary action of the triceps brachii in the elbow joint?

Extension of forearm (correct)

Flexion of forearm

Adduction of arm

Internal rotation of shoulder

Which nerve innervates both the triceps brachii and anconeus muscles?

Radial nerve (correct)

Ulnar nerve

Musculocutaneous nerve

Median nerve

Where does the anconeus muscle insert?

Olecranon of ulna Signup and view all the answers

Which structure is the boundary of the canal of the radial nerve?

Lateral head of triceps brachii Signup and view all the answers

What is the main clinical symptom associated with proximal palsy of the radial nerve?

Wrist drop Signup and view all the answers

Which of the following structures is NOT found within the canal of the radial nerve?

Brachial artery Signup and view all the answers

Which of the following could result in an injury to the radial nerve in its canal?

Fracture of the body of the humerus Signup and view all the answers

What is a common name for the condition caused by nerve compression from certain positioning, especially after excessive alcohol consumption?

Saturday night palsy Signup and view all the answers

Which muscle is unaffected by proximal palsy of the radial nerve?

Triceps brachii Signup and view all the answers

Study Notes

Muscles of the Posterior Compartment of the Arm

Triceps Brachii consists of three heads: Long Head, Lateral Head, and Medial Head.
Proximal Attachments:
- Long Head: Infraglenoid tubercle of the scapula.
- Lateral Head: Posterior surface of the humerus, above the radial groove, and ulna.
- Medial Head: Posterior surface of the humerus, below the radial groove.
Innervation:
- Supplied by the radial nerve.
- Branches to the Long and Lateral Heads arise before the radial groove; branches to the Medial Head arise in the radial groove.
Main Actions:
- Long Head: Adduction at the glenohumeral joint.
- All Heads: Extension of the forearm at the elbow joint, making it the primary extensor.

Anconeus

Attachments:
- Originates from the lateral epicondyle of the humerus.
- Inserts at the olecranon of the ulna.
Innervation: Also innervated by the radial nerve.
Action: Assists in extending the elbow joint and stabilizing the elbow.

Canal of the Radial Nerve (Radial Groove)

Location: Found on the posterior aspect of the humerus.
Boundaries:
- Superior: Lateral head of triceps brachii.
- Inferior: Medial head of triceps brachii.
- Posterior: Long head of triceps brachii.
Contents:
- Radial nerve.
- Deep artery of the arm, a branch of the brachial artery.
- Deep veins of the arm, tributaries of the brachial vein.

Clinical Significance of the Radial Nerve Canal

Proximal Palsy of the Radial Nerve:
- Leads to loss of function in posterior forearm muscles, resulting in wrist and digit extension deficits, termed "wrist drop."
- The triceps brachii remains functional in proximal radial nerve palsy.
Possible Causes of Injury:
- Fracture of the body of the humerus.
- Compression from heavy objects or prolonged pressure (e.g., laying on the arm during deep sleep after excessive alcohol consumption), resulting in "Saturday night palsy."

Description

Test your knowledge on the muscles of the posterior compartment of the arm, focusing specifically on the triceps brachii. This quiz covers the origins, attachments, and innervation of the three heads of the triceps. Perfect for students studying anatomy or preparing for medical exams.