Question

Shoulder and arm Muscles and movements #1

Shoulder and arms muscles and movements #1
Please list the action demonstrated, two synergist and one antagonist. The first letter of each muscles has been provided

Answer 1

Shoulder Joint

The shoulder is a complex ball-and-socket joint comprising the head of the humerus, the clavicle (collarbone), and the scapula.

The muscles in the shoulder help in a wide range of movement and also protect and maintain the main shoulder joint, known as the glenohumeral joint.

The shoulder has about nine muscles that attach to the scapula, humerus, and clavicle. These muscles form the outer shape of the shoulder and underarm. The muscles in the shoulder aid in a wide range of movement and help protect and maintain the main shoulder joint, known as the glenohumeral joint.

The largest of these shoulder muscles is the deltoid. This large triangular muscle covers the glenohumeral joint and gives the shoulder its rounded-off shape. It stretches across the top of the shoulder from the clavicle in the front to the scapula in the back. It then stretches downward to near the center of the humerus bone.

One important function of the deltoid is preventing joint dislocation when a person carries heavy objects.

The muscles that aid in shoulder movement include:

• Infraspinatus: This rotator cuff muscle helps with the raising and lowering of the upper arm.
• Triceps brachii: This large muscle in the back of the upper arm helps straighten the arm.
• Pectoralis major: This large fan-shaped muscle stretches from the armpit up to the collarbone and down across the lower chest region. It connects to the sternum (breastbone).
• Pectoralis minor: The smaller of the pectoralis muscles, this muscle fans out from the upper ribs up to the shoulder area.
• Teres major: This muscle helps rotate the upper arm.
• Biceps brachii: Commonly known as the bicep muscle, this muscle rests on top of the humerus bone. It rotates the forearm and also flexes the elbow.
• Latissimus dorsi: This flat rectangular muscle of the back helps the arms rotate as well as move away and closer to the body.
• Subscapularis: This is a large triangular muscle near the humerus and collarbone. It helps rotate the humerus.
• Supraspinatus: This small muscle is located at the top of the shoulder and helps raise the arm away from the body.

Four muscles—the supraspinatus, infraspinatus, teres minor, and subscapularis—make up the rotator cuff. It stabilizes the shoulder and holds the head of the humerus into the glenoid cavity to maintain the principal shoulder joint.

movement:

1. flexion: movement of the shoulder in a forward motion

2. extension: the movement of the arm directly behind the body.

3. adduction to lower the arm toward the body.

4. abduction to lift the arm away from the body.

synergist and antagonist of shoulder muscle

A synergist can be a fixator that stabilizes the muscle’s origin. A muscle with the opposite action of the prime mover is called an antagonist.

synergist:   Only three of the nine muscles act as prime movers for arm movements – pectoralis major, latissimus dorsi and the deltoid muscles. The other six are used as synergists or fixators.

antagonist: Pectoralis major and latissimus dorsi act as antagonists.

ARM

Arm is composed of your upper arm and forearm. Upper arm extends from shoulder to elbow. forearm runs from elbow to wrist.

Upper arm muscles

upper arm contains two compartments, known as the anterior compartment and the posterior compartment. There are four muscles in the upper arm split into an anterior and posterior compartment.

1. Anterior Compartment

Three muscles are located in the anterior compartment of the upper arm.

· Biceps Brachii: The biceps brachii is a two-headed muscle.The majority of the muscle mass is located anteriorly to the humerus, it has no attachment to the bone itself. Both heads of it originate from the scapula and attach via the bicipital aponeurosis to the fascia of the forearm.

· Coracobrachialis: The coracobrachialis lies within the two heads of the biceps brachii.It originates from the scapula and attaches to the humerus.

· Brachialis: The brachialis muscle lies within the distal region of the biceps brachii.It originates from the humerus and attaches to the ulna.

1. posterior compartment

The posterior compartment of the upper arm contains only one muscle.

· Triceps Brachii: The triceps brachii is a three-headed muscle.The long head of it originates from the scapula, the lateral head from the proximal region of the humerus, and the medial head from the distal region of the humerus. All three converge into one tendon which attaches to the ulna.

Forearm

The forearm is split into anterior and posterior compartments.

Anterior

The anterior compartment of the forearm is split into superficial, intermediate, and deep regions.

· Pronator Teres: A rectangular muscle located in the superficial region of the anterior compartment. The pronator teres has two origins, one on the proximal end of the humerus and one of the distal end of the ulna. It attaches to the mid region of the radius..

· Pronator Quadratus: A square shaped muscle located adjacent to the wrist in the deep region of the anterior compartment.It originates from the ulna and attaches to the radius.

posterior

The posterior compartment of the forearm is split into superficial and deep regions.

· Anconeus: The anconeus is located in the superficial region of the forearm posterior compartment and is blended with the triceps brachii. It originates from the humerus and attaches to the ulna.

· Brachioradialis: The brachioradialis is located in the superficial region of the forearm posterior compartment. It originates from the humerus and attaches to the distal end of the radius..

· Supinator: The supinator is located in the deep region of the forearm posterior compartment. The supinator has two heads: one originating from the humerus, the other from the ulna. Together they attach to the radius

movement

1. Flexion. This movement brings two body parts closer together, such as forearm and upper arm.

2. Extension. This movement increases the space between two body parts. example:straightening your elbow.

3. Abduction. This refers to moving a body part away from the center of body, such as lifting arm out and away from your body.

4. Adduction. This refers to moving a body part toward the center of body, such as bringing arm back in so it rests along your torso.

synergist and antagonist of arm muscle

biceps brachii has two synergist muscle: brachioradialis muscle and brachialis.

antagonist to the biceps brachii is triceps brachii muscle.