Muscle That Adducts The Shoulder

9.9C: Muscles of the Shoulder

Final updated
Save equally PDF

Folio ID: 7568

Muscles of the shoulder include those that attach to the bones of the shoulder to motility and stabilize the articulation.

Learning Objectives

Outline the movements of the muscles of the shoulder

Key Points

The shoulder exhibits a wide range of movement, which makes it susceptible to dislocation and injury.
The trapezius muscles rotate the scapulae upward.
The rhomboid major and the rhomboid small press the scapula against the thoracic wall, retracting the scapula towards the spine.
The deltoid is a complex musculus that forms the rounded edge of the shoulder and participates in many articulations of the shoulder articulation.
The rotator cuff are the muscles that stabilize movement of the shoulder.
The pectoralis modest and pectoralis major are large muscles of the chest that participate in many movements, including flexion of the humerus.

Fundamental Terms

pectoralis major: A large, fan-shaped muscle of the chest.
rotator cuff: A ready of 4 smaller muscles in the shoulder responsible for rotating the humerus (upper arm bone).
trapezius: A large vertebrate skeletal muscle divided into an ascending, descending, and transverse portion, attaching the neck and central spine to the outer extremity of the scapula. It functions in scapular acme, adduction, and low.
deltoid: The deltoid muscle, a triangular muscle on the human shoulder.

The shoulder or glenohumeral joint is a ball and socket joint formed betwixt the humerus and scapula. Due to the shallowness of the socket and relatively loose connections, the shoulder joint allows for a wide range of motion; nonetheless, this wide range makes the articulation unstable and thus more than prone to dislocation and injury than other joints.

Two other joints make upwards the shoulder; the acromioclavicular articulation of the clavicle and scapula, which allows the arm to exist raised in a higher place the head, and the sternoclavicular articulation of the clavicle and sternum, which plays an of import role in facilitating movement of the upper arm and connecting it to the rest of the skeleton.

Muscles that human action on the shoulder can be classified as extrinsic, intrinsic, pectoral, or upper arm. Upper arm muscles will exist discussed in a after section since they primarily promote forearm movement.

Extrinsic Shoulder Muscles

Extrinsic muscles of the shoulder originate from the trunk and attach to the bones of the shoulder. They tin can be farther subdivided into superficial and deep layers.

Superficial

This diagram illustrates the lumbar triangle in relation to the deltoideus, infraspinatus, teres major, lattissimus dorsi, and lumbodorsal fascia.

Location of the trapezius muscle: Highlighted in orange, the trapezius is a large, broad muscle of the dorsum that acts on the shoulder.

As suggested by the name, superficial muscles lie on the surface. There are 2 superficial extrinsic muscles.

Trapezius: The trapezius is the well-nigh superficial muscle of the back and forms a broad flat triangle.
- Attachments: The trapezius originates from the skull and spine of the upper back and cervix. It attaches to the clavicle and scapula.
- Actions: The superior region supports the arm and elevates and rotates the scapula, the intermediate region retracts the scapula, and the inferior region rotates and depresses the scapula.
Latissimus Dorsi: The latissimus dorsi originates from the lower back and covers a wide surface area.
- Attachments: The latissimus dorsi originates from the lower spine and ribs and the upper pelvis and fascia of the deep torso muscles. The muscle converges into a tendon attaching to the humerus.
- Actions: Extends, adducts, and medially rotates the upper arm.

Deep

Three deep muscles lie below the superficial muscles of the shoulder.

Levator Scapulae: A minor, strap-similar muscle that joins the neck to the scapula.
- Attachments: Originates from the side of the spine in the neck and attaches to the scapula.
- Deportment: Elevates the scapula.
Rhomboid Major: Sits inferiorly to the levator scapulae.
- Attachments: Originates from the spine in the upper back and attaches to the scapula in an inferior position to the levator scapulae attachment.
- Actions: Retracts and rotates the scapula.
Rhomboid Minor: Sits betwixt the levator scapulae and rhomboid major, with which it is paired in activeness and part. It retracts and rotates the scapula.

Intrinsic

This diagram illustrates the deltoideus in relation to the lumbar triangle, infraspinatus, teres major, lattissimus dorsi, and lumbodorsal fascia.

Location of the deltoid muscles: Highlighted in orange, the deltoids cover the rounding of the shoulder joint.

Intrinsic muscles originate from the scapula or clavicle and attach to the humerus. There are half dozen intrinsic muscles, four of which form the rotator gage.

Deltoid: The deltoid muscle is a triangular musculus which covers the shoulder. The action of the muscle is circuitous, with the components acting in opposing and separate ways during the course of a contraction.
- Attachments: The deltoid musculus originates from the scapula and clavicle and attaches to the lateral surface of the humerus.
- Deportment: The anterior region assists the pectoralis major during transverse flexion of the shoulder and acts weakly in strict transverse flexion. The lateral region assists in shoulder flexion when the shoulder is rotating, although it also assists the transverse abduction of the shoulder. The posterior region is the hyperextensor of the shoulder, contributing to transverse
  extension.
Teres Major: The teres major is a thick flattened musculus connecting the lower scapula with the humerus.
- Attachments: Originates from the posterior of the scapula and attaches to the humerus.
- Deportment: Adducts the shoulder and assists in rotation of the arm.

Rotator Cuff

The rotator cuff is a group of four muscles that pull the brawl of the humerus into the shallow socket of the scapula, calculation required stability. The rotator cuff complex is composed of the supraspinatus, infraspinatus, subscapularis, and teres minor all of which originate from the scapula and connect to the humerus. The supraspinatus is involved in abduction of the arm in association with the deltoid, while the other muscles facilitate rotation of the arm.

This image displays the rotator cuff muscles, including the supraspinatus, infraspinatus, subscapularis, and teres minor.

Muscles of the rotator gage: Muscles of the rotator cuff and presented with the triceps brachii.

Pectoral

Pectoral muscles lie in the chest and exert force through the shoulder to move the upper arm. 3 pectoral muscles interact with the shoulder.

Pectoralis Major: The pectoralis major is a large, fan-shaped muscle covering the chest. It is comprised of clavicular and sternocostal regions.
- Attachments: The clavicular region originates from the clavicle and the sternocostal region originates from the sternum and the fascia of the oblique muscles of the abdomen. Both attach to the humerus.
- Actions: Adducts and rotates the upper arm.
Pectoralis Minor: The pectoralis small-scale musculus is smaller and lies beneath the pectoralis major.
- Attachments: The pectoralis pocket-size originates from the third to fifth ribs and attaches to the scapula.
- Actions: Supports and depresses the scapula.
Serratus Anterior: The serratus inductive is located in the lateral wall of the breast.
- Attachments: The muscle is formed of several strips originating from the second to 8 ribs, each of which attaches to the scapula.
- Actions: Supports the scapula allowing for pinnacle of the upper arm.

KEY MOVEMENTS

Extension (upper limb backwards behind dorsum): Produced by the posterior deltoid, latissimus dorsi, and teres major.
Flexion (upper limb frontwards past breast): Produced past the biceps brachii (both heads), pectoralis major, anterior deltoid, and corocobrachialis.
Abduction (upper limb away from trunk, spreading arms broad): Produced by the supraspinatus and deltoid. Past xc degrees, the scapula needs to be rotated past the trapezius and serratus anterior to achieve abduction.
Adduction (upper limb towards body, bringing artillery down to side): Produced by contraction of pectoralis major, latissimus dorsi, and teres major.
Medial Rotation (rotation of arm inwards to cover abdomen): Produced by wrinkle of subscapularis, pectoralis major, latissimus dorsi, teres major, and anterior deltoid.
Lateral Rotation (rotation of arm outwards abroad from the abdomen): Produced by contraction of the infraspinatus and teres minor.