Maximus Gage
The shoulder adductors refer to the muscles that move the shoulder towards the body's midline. These muscles include the pectoralis major, latissimus dorsi, and teres major. The deltoid muscle also plays a role in shoulder adduction, specifically in arm abduction. The rotator cuff muscles, which include the supraspinatus, infraspinatus, teres minor, and subscapularis, are important for stabilizing the shoulder joint and enabling a wide range of arm movements. The scapular retractors, such as the rhomboids and middle trapezius, are involved in scapular retraction, pulling the shoulder blades together. These muscles work together to provide strength, stability, and a wide range of motion to the shoulder complex.
| Characteristics | Values |
|---|---|
| Shoulder adductors | Pectoralis major, latissimus dorsi, and teres major |
| Function | Moving the shoulder towards the body's midline |
| Role | Shoulder complex strengthening and glenohumeral joint stability |
| Innervation | Lower subscapular nerve |
| Shoulder internal rotators | Subscapularis, pectoralis major, latissimus dorsi, teres major, and anterior deltoid |
| Shoulder external rotators | Infraspinatus and teres minor |
| Shoulder abductors | Deltoid, supraspinatus |
| Shoulder adduction range of motion | 150º |
| Shoulder flexion and extension positions | Seated, supine, modified supine |
| Shoulder adduction muscles | Originate from scapula and/or clavicle, attach to humerus |
| Rotator cuff muscles | Supraspinatus, infraspinatus, subscapularis, teres minor |
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What You'll Learn
- The pectoralis major, latissimus dorsi, and teres major are the shoulder adductors
- The deltoid muscle is involved in arm flexion, internal rotation, abduction, extension, and lateral rotation
- The latissimus dorsi is a large muscle in the posterior shoulder area
- The rotator cuff muscles are supraspinatus, infraspinatus, subscapularis, and teres minor
- The scapular retractors are the rhomboids and the middle trapezius
The pectoralis major, latissimus dorsi, and teres major are the shoulder adductors
The pectoralis major is a large muscle located on the anterior surface of the chest wall, contributing to the characteristic shape of the shoulder. It has two heads, the sternocostal and clavicular, and works alongside the deltoid muscle in the upper arm to accomplish shoulder flexion and extension.
The latissimus dorsi is the largest muscle in the upper body, originating from the lumbar vertebra and pelvis. It is the prime mover of shoulder extension and adduction, and it may also contribute to internal rotation (medial rotation) of the shoulder.
The teres major is located inferior to the teres minor muscle, a rotator cuff muscle, and originates on the inferior angle of the scapula (shoulder blade). It performs the same joint actions as the latissimus dorsi, including shoulder extension, adduction, and internal rotation.
These three muscles work closely with the scapular downward rotators to produce adduction of the shoulder as a whole. They are also involved in other shoulder movements, such as abduction and external and internal rotation, which are important for activities like tennis and reaching into back pockets.
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The deltoid muscle is involved in arm flexion, internal rotation, abduction, extension, and lateral rotation
The deltoid muscle is one of the muscles of the shoulder. It is a skeletal muscle, which means it is a voluntary muscle that moves when you choose to move it. The deltoid muscle is involved in arm flexion, internal rotation, abduction, extension, and lateral rotation.
Deltoid muscles help you move your arms in different directions and protect and stabilize your shoulder joint. They crown your shoulder, covering the front, side, and back of the joint. The deltoid looks like an upside-down triangle, and tendons connect each of its three sides to bones. The base of the deltoids connects to the upper part of your scapula (shoulder blade) and the side of your clavicle (collarbone). The point of the deltoids attaches to the side of your humerus (the arm bone between your shoulder and elbow).
The deltoid muscle has three functionally and anatomically distinct parts: the acromial, clavicular, and scapular spinal parts. The acromial part, or the middle fibres, is the largest and strongest part of the muscle. It abducts the arm, while the clavicular and scapular spinal parts play a significant role in stabilization, ensuring a steady plane of abduction. The clavicular part (anterior fibres) can act as a flexor and internal rotator of the arm, while the scapular spinal part (posterior fibres) can extend and externally rotate the arm.
The deltoid muscle is the principal abductor of the arm at the glenohumeral joint. However, it can only do so when the arm is already abducted beyond fifteen degrees. The initial part of abduction is produced by the supraspinatus muscle. The deltoid also assists in external (or lateral) rotation of the humerus. This is important because strengthening the posterior fibres of the deltoid muscle can help to offset the tendency of the shoulder to become internally rotated due to poor posture.
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The latissimus dorsi is a large muscle in the posterior shoulder area
The latissimus dorsi is a large, broad, and flat muscle in the posterior shoulder area. It occupies the majority of the lower posterior thorax and is considered an extrinsic muscle of the back. The latissimus dorsi is responsible for several functions, including extension, adduction, transverse extension (horizontal abduction), flexion from an extended position, and internal rotation of the shoulder joint.
The muscle's primary function is related to the upper extremity, but it is also considered a respiratory accessory muscle. It assists in depressing the arm, along with the teres major and pectoralis major muscles. This group of muscles plays a crucial role in shoulder complex strengthening and glenohumeral joint stability, especially for athletes involved in throwing activities. The latissimus dorsi is also active during deep inspiration and forceful respiratory functions such as coughing and sneezing.
The latissimus dorsi has attachments to the lower six vertebral spinous processes and connects to the lumbar and sacral spinous processes (T6 to S5 levels) through the thoracolumbar fascia. It also attaches to the posterior iliac crest, the lower ribs, and the inferior angle of the scapula. The muscle fibres are oriented in different directions, with superior-most fibres being almost horizontal and inferior fibres being more vertical on the thorax.
Injuries to the latissimus dorsi are rare but can occur in baseball pitchers. Tightness in this muscle has been linked to chronic shoulder and back pain. Assessment of the latissimus dorsi is crucial for patients with upper extremity pathology and low back pain. Proper function and coordination with the teres major and pectoralis major muscles are essential for smooth and fluid movements of the upper extremity.
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The rotator cuff muscles are supraspinatus, infraspinatus, subscapularis, and teres minor
The rotator cuff muscles are a group of four muscles that originate from the scapula and attach to the humeral head. These muscles are supraspinatus, infraspinatus, subscapularis, and teres minor. The rotator cuff muscles collectively act to 'pull' the humeral head into the glenoid fossa, providing the glenohumeral joint with additional stability.
The supraspinatus muscle is the only muscle of the rotator cuff that is not a rotator of the humerus. It is the muscle most commonly affected by rotator cuff tendonitis, which refers to inflammation of the tendons of the rotator cuff. The supraspinatus initiates the abduction of the arm and performs the first 0-15 degrees of abduction, assisting the deltoid muscle for 15-90 degrees.
The infraspinatus is a powerful lateral rotator of the humerus and assists in both abduction and adduction. It reaches from the bottom of the scapula and connects to the humerus behind the supraspinatus.
The subscapularis is a powerful internal rotator which also supports the arm during abduction and adduction. It allows you to hold your arm outstretched, away from your body, by attaching to the middle of the scapula and stretching to the lower part of the humeral head.
The teres minor's function consists primarily of external rotation and adduction of the arm. It also helps to turn and rotate the arm by attaching to the outside edge of the scapula and attaching to the humerus beneath the infraspinatus.
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The scapular retractors are the rhomboids and the middle trapezius
The scapular retractors are part of a group of muscles known as the scapular muscles or the intrinsic muscles of the scapula. These muscles attach directly to the surface of the scapula bone, which is a sturdy, flat, triangular bone that provides attachment to several groups of muscles. The scapula is an important bone in the function of the shoulder joint, allowing for multiple types of motion, including protraction, retraction, elevation, depression, upward rotation, and downward rotation.
The scapular retractors work together with other muscles to produce movement in the shoulder. For example, the rhomboids work together with the levator scapulae and trapezius muscles to accomplish scapular elevation. Similarly, the middle trapezius works with the serratus anterior muscle to produce upward rotation of the scapula.
The scapular retractors are important for maintaining shoulder health and stability. Exercises involving scapular retraction, such as those using resistance bands, can help improve posture and strengthen the middle and upper back muscles. These exercises are beneficial for individuals experiencing shoulder or back pain as they can help improve function in the upper extremity area.
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Frequently asked questions
The muscles that adduct the shoulder are the pectoralis major, latissimus dorsi, and teres major.
Adduction moves the upper limb toward the midline in the coronal plane.
The pectoralis major covers the anterior thoracic cage and has three heads: clavicular, sternocostal, and abdominal. It enables adduction and internal rotation of the arm.
The latissimus dorsi pulls the inferior angle of the scapula in various directions, producing movements on the shoulder joint. It also assists in respiration.
