Muscles of the Upper Arm (glenohumeral and elbow joints)

Summary

This script offers an in-depth look at the muscles involved in shoulder and elbow movements. It explains the deltoid's role in shoulder abduction, flexion, and extension, the supraspinatus's contribution to abduction, and the pectoralis major's function in flexion and adduction. The rotator cuff muscles—supraspinatus, infraspinatus, teres minor, and subscapularis—are highlighted for their roles in supporting the humerus and enabling rotation. The script also covers the biceps brachii, brachialis, brachioradialis for elbow flexion, and the triceps brachii and anconeus for extension, providing a comprehensive guide to arm anatomy and function.

Takeaways

• 💪 The deltoid muscle is crucial for shoulder movements, with its anterior fibers causing flexion and posterior fibers causing extension.
• 🤔 The supraspinatus muscle, located above the spine of the scapula, is involved in abduction of the shoulder and is part of the rotator cuff, supporting the humerus.
• 🏋️‍♂️ The pectoralis major muscle, originating from the body and inserting on the humerus, is responsible for shoulder flexion and adduction.
• 🤸‍♂️ The coracobrachialis muscle, located on the underside of the arm, contributes to shoulder adduction and flexion.
• 🏃‍♂️ The latissimus dorsi, being a large muscle on the back, causes shoulder extension and adduction.
• 🤲 The rotator cuff consists of four muscles: supraspinatus, infraspinatus, teres minor, and subscapularis, which collectively support the humerus and assist in rotation.
• 🤔 The supraspinatus, despite being part of the rotator cuff, primarily abducts the shoulder and supports the humerus in the joint.
• 👉 The infraspinatus and teres minor, located below the spine of the scapula, are responsible for lateral rotation of the shoulder.
• 🤛 The teres major and subscapularis muscles perform medial rotation of the shoulder, with the teres major crossing over to the opposite side.
• 💪 The biceps brachii, brachialis, and brachioradialis muscles are key flexors of the elbow, while the triceps brachii and anconeus are the primary extensors.

Q & A

What is the primary function of the deltoid muscle?

The primary function of the deltoid muscle is to abduct the shoulder. However, its anterior fibers cause shoulder flexion, and its posterior fibers cause shoulder extension.

What muscle has an insertion point on the superior aspect of the head of the humerus and what is its function?

The supraspinatus muscle has an insertion point on the superior aspect of the head of the humerus, and it causes abduction of the shoulder.

Why is the pectoralis major included on the arm model even though it is visible on a torso model?

The pectoralis major is included on the arm model because its insertion point is on the humerus, making it a humerus mover.

What movement does the pectoralis major cause at the shoulder joint?

The pectoralis major causes flexion at the shoulder by pulling the humerus forward and adduction by bringing the arm closer to the body's midline.

Which muscle is mentioned that adducts and flexes at the shoulder, and where is it located?

The coracobrachialis muscle adducts and flexes at the shoulder, and it is located on the underside of the arm.

What is the primary function of the latissimus dorsi in relation to the shoulder joint?

The latissimus dorsi causes extension of the shoulder and adduction by pulling the humerus closer to the body's midline.

What are the four muscles that make up the rotator cuff?

The four muscles that make up the rotator cuff are the supraspinatus, infraspinatus, teres minor, and subscapularis.

Why is the supraspinatus considered part of the rotator cuff even though it does not perform rotation?

The supraspinatus is part of the rotator cuff because it supports the humerus and assists other muscles in rotation by helping to keep the humerus in the joint.

Which muscles are responsible for lateral rotation of the shoulder?

The infraspinatus and teres minor muscles are responsible for lateral rotation of the shoulder.

Which muscles perform medial rotation of the shoulder?

The subscapularis and teres major muscles perform medial rotation of the shoulder.

What muscles are primarily responsible for flexion at the elbow joint?

The biceps brachii, brachialis, and brachioradialis are the muscles that primarily cause flexion at the elbow joint.

Which muscles cause extension at the elbow joint and what other movement is mentioned in the script?

The triceps brachii and anconeus cause extension at the elbow joint. The script also mentions the anconeus crossing the elbow in the back.