19.💗MUSCLES OF UPPER ARM – GROUPS, ATTACHMENT, ACTION, NERVE SUPPLY.💗

What are the components and functions of the biceps brachii muscle?

- *Components*: Two-headed muscle (long head and short head).
- *Function*: Primarily involved in supination of the forearm, flexion of the arm at the elbow and shoulder.

Where does the biceps brachii muscle originate and insert? What is its nerve supply?

- *Origin*: Long head from the supraglenoid tubercle of the scapula; short head from the coracoid process of the scapula.
- *Insertion*: Both heads insert distally into the radial tuberosity and fascia of the forearm via the bicipital aponeurosis.
- *Nerve Supply*: Musculocutaneous nerve; involved in the biceps tendon reflex testing spinal cord segment C6.

Describe the coracobrachialis muscle, including its attachments, actions, and nerve supply.

- *Attachments*: Originates from the coracoid process of the scapula and attaches to the medial side of the humeral shaft at the level of the deltoid tubercle.
- *Actions*: Flexion of the arm at the shoulder, with a weak adduction function.
- *Nerve Supply*: Musculocutaneous nerve; lies deep to the biceps brachii muscle.

Explain the structure and function of the brachialis muscle.

- *Structure*: Found distally compared to other arm muscles, forming the floor of the cubital fossa.
- *Attachments*: Originates from the medial and lateral surfaces of the humeral shaft, inserting into the ulnar tuberosity distal to the elbow joint.
- *Function*: Primarily responsible for flexion at the elbow joint.
- *Nerve Supply*: Musculocutaneous nerve, with contributions from the radial nerve.

What are the components of the triceps brachii muscle? Describe its attachments, actions, and nerve supply.

- *Components*: Comprises three heads: long head, lateral head, and medial head.
- *Attachments*:
- Long head: Originates from the infraglenoid tubercle of the scapula.
- Lateral head: Arises from the humerus above the radial groove.
- Medial head: Originates from the humerus below the radial groove. All heads converge distally and insert onto the olecranon of the ulna.
- *Actions*: Extension of the arm at the elbow joint.
- *Nerve Supply*: Radial nerve (in most cases, can also be innervated by the axillary nerve). Testing involves tapping on the triceps tendon to assess C7 function.

These questions and answers should help reinforce your understanding of the muscles of the shoulder girdle and arm for your exam preparation.