Question

Infraspinatus

Origin: Infraspinous fossa of scapula
Insertion:Greater tubercle of the humerus
Action:Laterally rotate the shoulder (glenohumeral joint)
Adduct the shoulder(glenohumeral joint)
Stabilize the head of humerus in glenoid cavity
Nerve: Suprascapular C(4),5,6

Answer 1

The Infraspinatus muscle originates from the infraspinous fossa of the scapula, inserts into the greater tubercle of the humerus, and plays a key role in laterally rotating the shoulder (glenohumeral joint), adducting the shoulder (glenohumeral joint), and stabilizing the head of the humerus in the glenoid cavity. Innervated by the suprascapular nerve (C₄, ₅, ₆), the Infraspinatus is integral to the functionality and stability of the shoulder joint.

Step-by-step explanation:

The Infraspinatus is a muscle located on the posterior aspect of the scapula, originating from the infraspinous fossa and inserting into the greater tubercle of the humerus. Its primary action involves laterally rotating the shoulder joint, contributing to the range of motion in the arm. Additionally, the Infraspinatus plays a role in adducting the shoulder, moving the arm toward the body's midline. These actions are essential for various daily activities that require shoulder movement and control.

A notable function of the Infraspinatus is its role in stabilizing the head of the humerus within the glenoid cavity of the scapula. This stabilization is crucial for maintaining the integrity and proper alignment of the shoulder joint during movement. The innervation of the Infraspinatus by the suprascapular nerve (C₄, ₅, ₆) ensures proper signaling for these coordinated movements and stabilizing actions, contributing to the overall functionality and health of the shoulder joint.

In summary, the Infraspinatus muscle's origin, insertion, actions, and nerve innervation collectively define its role in shoulder movement and stability. Its contributions to lateral rotation, adduction, and humeral head stabilization highlight the complexity and precision of the musculoskeletal system, emphasizing the importance of this muscle in facilitating functional shoulder mobility and maintaining joint stability.

Answer 2

Main Answer:

The infraspinatus muscle originates from the infraspinous fossa of the scapula, inserts onto the greater tubercle of the humerus, and is innervated by the suprascapular nerve (C4, 5, 6). Its actions include lateral shoulder rotation, shoulder adduction, and stabilization of the humeral head in the glenoid cavity.

Step-by-step explanation:

The infraspinatus muscle plays a crucial role in shoulder function and stability. Originating from the infraspinous fossa of the scapula, it attaches to the greater tubercle of the humerus, forming part of the rotator cuff. The suprascapular nerve, derived from spinal nerves C4, 5, and 6, provides innervation to this muscle, ensuring its proper functioning.

The primary action of the infraspinatus is the lateral rotation of the shoulder at the glenohumeral joint. This movement is vital for various arm motions, such as reaching for objects and throwing. Additionally, the muscle contributes to shoulder adduction, bringing the arm closer to the body. This dual functionality highlights the infraspinatus's importance in executing diverse upper limb activities.

Moreover, the infraspinatus aids in stabilizing the head of the humerus within the glenoid cavity during shoulder movements. This stabilization is crucial for maintaining joint integrity and preventing dislocations or injuries during dynamic activities. The coordinated actions of the infraspinatus contribute to the overall stability and functionality of the shoulder complex.

In summary, the infraspinatus muscle's origin, insertion, actions, and innervation collectively define its role in shoulder movement and stability. Understanding these aspects is essential for clinicians, anatomists, and individuals involved in rehabilitative or sports-related activities.