Anatomy Ch 6 Muscles

Muscles of the shoulder can be divided into groups based on their distribution and functional relationships. This means that muscles that have similar functions or work together to perform a specific movement are grouped together. This classification helps in understanding the coordination and interaction between different muscles in the shoulder region. It allows for a better understanding of muscle function and helps in diagnosing and treating shoulder-related injuries or conditions.

The correct answer is levator scapulae, rhomboideus minor, rhombideus major, and trapezius. These four muscles are part of the posterior group of the pectoral girdle. The levator scapulae muscle helps elevate the scapula, the rhomboideus minor and major muscles retract and stabilize the scapula, and the trapezius muscle helps with scapular movement and shoulder elevation.

The movement of opposition refers to the action of bringing the thumb and little finger together, which occurs at the carpometacarpal joint of the hand. This movement is not associated with the scapula, as the scapula is not directly involved in the movement of opposition. The scapula is primarily involved in movements such as protraction (forward movement), elevation (upward movement), and depression (downward movement).

Elevation is the action that moves the scapula towards the head. This movement involves lifting the scapula upward, towards the upper part of the body. It is commonly observed when performing exercises such as shoulder shrugs or when raising the arms overhead. Elevation helps in various movements of the shoulder and upper limb, such as reaching for objects above the head or lifting heavy weights.

The shoulder joint is considered the most flexible joint in the body. This is because it is a ball-and-socket joint, allowing for a wide range of motion in multiple directions. The shoulder joint allows for movements such as flexion, extension, abduction, adduction, rotation, and circumduction. It has a greater range of motion compared to other joints like the wrist, elbow, and hip joints, making it the most flexible joint in the body.

The serratus anterior muscle is responsible for scapular protraction and rotation. When this muscle contracts, it pulls the scapula forward and causes it to rotate outward. This movement is important for reaching forward and pushing movements, as well as stabilizing the scapula during overhead movements. Scapular retraction involves pulling the scapula back towards the spine, scapular elevation involves lifting the scapula upwards, and abduction of the humerus refers to moving the upper arm away from the body.

The pectoral girdle is the skeletal structure that connects the upper limbs to the axial skeleton. It consists of the clavicle and scapula. The clavicle, also known as the collarbone, is a long bone that runs horizontally across the upper part of the chest. The scapula, or shoulder blade, is a flat triangular bone located on the upper back. Together, the clavicle and scapula provide support and stability to the shoulder joint, allowing for a wide range of motion in the upper limbs.

The teres major muscle is not part of the rotator cuff. The rotator cuff is composed of four muscles: the supraspinatus, infraspinatus, teres minor, and subscapularis. These muscles work together to stabilize and rotate the shoulder joint. While the teres major muscle is located near the rotator cuff, it is not directly involved in its function. The teres major muscle is responsible for adducting and extending the arm, rather than providing stability to the shoulder joint like the rotator cuff muscles.

The supraspinatus muscle is responsible for stabilizing the glenohumeral joint and preventing downward dislocation of the humerus when carrying weight. This muscle is one of the rotator cuff muscles located in the shoulder. It runs from the supraspinous fossa of the scapula to the greater tubercle of the humerus. Its main function is to initiate abduction of the arm and assist in maintaining the head of the humerus within the glenoid cavity. By contracting and providing stability to the joint, the supraspinatus muscle helps to prevent the humerus from dislocating downward during activities that involve carrying weight.

The rhomboideus minor muscle originates on the spinous process of the vertebrae.

The tendons of the rotator cuff muscles combine at the humeral head. The humeral head is the rounded part of the upper arm bone (humerus) that fits into the shoulder socket. This is where the tendons of the rotator cuff muscles, including the supraspinatus, infraspinatus, teres minor, and subscapularis, come together to form a cuff-like structure around the humeral head. This arrangement provides stability and helps to control the movement of the shoulder joint. The other options, coranoid process, radial tuberosity, and scapula, are not the correct locations where the tendons of the rotator cuff muscles combine.

The subscapularis muscle is located on the anterior side of the shoulder joint and is responsible for internal rotation of the arm. When the arm is raised, the subscapularis muscle contracts to stabilize the humeral head and prevent it from sliding upward out of the joint. This muscle plays a crucial role in maintaining the stability and proper functioning of the shoulder joint during arm movements.

The anterior flexor muscles are not muscles of the shoulder. The shoulder is primarily composed of the rotator cuff muscles, which help stabilize and move the shoulder joint. Additionally, the muscles that stabilize and cross the glenohumeral joint and the muscles that act on the pectoral girdle are also considered shoulder muscles. However, the anterior flexor muscles are not directly involved in shoulder movements and are therefore not considered shoulder muscles.

The rotator cuff is a group of muscles and tendons that play a crucial role in stabilizing and reinforcing the glenohumeral joint. The glenohumeral joint is the main joint of the shoulder, where the head of the humerus (upper arm bone) connects with the glenoid cavity of the scapula (shoulder blade). The rotator cuff muscles and tendons surround this joint, providing support and allowing for a wide range of motion in the shoulder.

The pectoral girdle serves as an attachment site for muscles that move the arm. This means that the muscles responsible for moving the arm, such as the deltoid and pectoralis major, attach to the pectoral girdle. These muscles then contract and pull on the pectoral girdle, causing movement in the arm. The pectoral girdle does not provide the only connection between the arm and the axial skeleton, as there are other structures such as ligaments and tendons involved. It also does not directly connect the humerus and the scapula, as there are other bones and joints involved in this connection.