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The infraspinatus muscle is a thick triangular muscle that makes up a significant portion of the infraspinatous fossa's dorsal surface. It is one of the four rotator cuff muscles, and its primary function is to externally rotate the humerus and stabilize the shoulder joint. The suprascapular nerve, a mixed peripheral nerve, innervates the infraspinatus muscle. This nerve is a branch of the superior trunk of the brachial plexus, providing motor innervation and sensory supply to the infraspinatus and supraspinatus muscles.
| Characteristics | Values |
|---|---|
| Nerve that innervates the infraspinatus muscle | Suprascapular nerve |
| Type of nerve | Mixed (sensory and motor) |
| Origin of the nerve | Brachial plexus |
| Brachial plexus origin | Ventral rami of cervical nerves C5-C6 |
| Suprascapular nerve branches | Two branches to the infraspinatus muscle |
| Suprascapular nerve function | Motor innervation and sensory supply for the scapula joints |
| Infraspinatus muscle shape | Thick triangular |
| Infraspinatus muscle location | Occupies the chief part of the infraspinatous fossa on the dorsal surface of the scapula |
| Infraspinatus muscle function | Externally rotates the humerus and stabilizes the shoulder joint |
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What You'll Learn
- The suprascapular nerve is a branch of the superior trunk of the brachial plexus
- The nerve provides motor innervation to the infraspinatus muscle
- The nerve passes through the suprascapular notch and enters the supraspinous fossa
- The infraspinatus muscle is a thick triangular muscle that occupies the dorsal surface of the scapula
- The muscle is one of the four rotator cuff muscles
The suprascapular nerve is a branch of the superior trunk of the brachial plexus
The suprascapular nerve is responsible for providing motor innervation to two muscles: the supraspinatus and infraspinatus muscles. These muscles are part of the rotator cuff muscle group, which consists of four muscles that work together to stabilise and produce movements in the shoulder joint. The infraspinatus muscle, in particular, is a thick triangular muscle that occupies the majority of the dorsal surface of the scapula. It is involved in externally rotating the humerus and stabilising the glenohumeral joint, also known as the shoulder joint.
The suprascapular nerve arises from the upper trunk of the brachial plexus and travels along a specific path. It passes across the posterior triangle of the neck, running parallel to the inferior belly of the omohyoid muscle and deep to the trapezius muscle. It then moves along the superior border of the scapula, passing through the suprascapular notch and entering the supraspinous fossa. In this fossa, the nerve gives off two branches to the supraspinatus muscle.
After supplying the supraspinatus muscle, the suprascapular nerve continues its journey by passing through the spinoglenoid notch at the lateral border of the scapula spine. It then enters the infraspinous fossa, where it provides two terminal branches to the infraspinatus muscle. This nerve is essential for the function and stability of the infraspinatus muscle, which plays a crucial role in the external rotation of the humerus and the overall stability of the shoulder joint.
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The nerve provides motor innervation to the infraspinatus muscle
The nerve that innervates the infraspinatus muscle is the suprascapular nerve. This nerve is a branch of the superior trunk of the brachial plexus, specifically arising from its upper trunk. It is considered a mixed nerve, containing both motor and sensory components. Its main function is to provide motor innervation to the infraspinatus muscle, which is one of the four rotator cuff muscles.
The infraspinatus muscle is a thick triangular muscle that occupies the majority of the dorsal surface of the scapula. It is involved in externally rotating the humerus and stabilising the shoulder joint, also known as the glenohumeral joint. The muscle fibres originate from the medial two-thirds of the infraspinous fossa, with tendinous fibres arising from the ridges on its surface. These fibres converge to form a tendon, which crosses the posterior side of the shoulder and inserts into the greater tubercle of the humerus.
The suprascapular nerve follows a specific path to innervate the infraspinatus muscle. After branching from the brachial plexus, it travels laterally, deep to the trapezius muscle, towards the superior border of the scapula. It then passes through the suprascapular notch and enters the supraspinous fossa, where it gives off branches to the supraspinatus muscle. From there, it curves around the lateral border of the scapula's spine through the spinoglenoid notch to reach the infraspinous fossa.
In the infraspinous fossa, the suprascapular nerve provides two terminal branches to the infraspinatus muscle, thereby ensuring its proper motor innervation. This nerve is crucial for the function of the infraspinatus muscle, and any damage or entrapment of the nerve can lead to weakness or paralysis of the muscle, causing issues with arm abduction and external rotation of the humerus.
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The nerve passes through the suprascapular notch and enters the supraspinous fossa
The nerve in question is the suprascapular nerve, a mixed nerve containing both motor and sensory components. It is a branch of the superior trunk of the brachial plexus, formed from the anterior rami of the fifth and sixth cervical nerves (C5 and C6). The nerve provides motor innervation to the supraspinatus and infraspinatus muscles, which are part of the rotator cuff muscle group.
The suprascapular nerve arises from the brachial plexus and runs laterally, deep to the trapezius muscle, towards the superior border of the scapula. At this point, the nerve passes through the suprascapular notch, which is located inferior to the superior transverse scapular ligament. From there, it enters the supraspinous fossa, where it gives off two branches to the supraspinatus muscle.
The supraspinatus muscle helps in the abduction of the arm, specifically in the 0°-15° range. It also works together with the infraspinatus muscle as a functional unit to abduct and laterally rotate the arm. The supraspinatus and infraspinatus muscles are closely related anatomically, separated only by the spine of the scapula.
After passing through the supraspinous fossa, the suprascapular nerve continues its course by passing beneath the supraspinatus muscle. It then curves around the lateral border of the spine of the scapula through the spinoglenoid notch to enter the infraspinous fossa. In this region, the nerve provides two terminal branches to the infraspinatus muscle.
The infraspinatus muscle is a thick triangular muscle that occupies a significant portion of the dorsal surface of the scapula, particularly the infraspinous fossa. It arises from the infraspinous fossa of the scapula and connects to the proximal humerus. The infraspinatus muscle fibres converge to form a tendon, which crosses the posterior side of the shoulder joint and inserts into the greater tubercle of the humerus.
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The infraspinatus muscle is a thick triangular muscle that occupies the dorsal surface of the scapula
The infraspinatus muscle plays a crucial role in shoulder joint stability and arm movement. It works in conjunction with the teres minor muscle to rotate the head of the humerus outward and assist in carrying the arm backward. The infraspinatus muscle fibres course towards the shoulder joint, running almost parallel to the teres minor and major muscles. As the infraspinatus muscle approaches the shoulder joint, it can be separated from the neck of the scapula by the infraspinatus bursa, which may communicate with the shoulder joint cavity.
The infraspinatus muscle is innervated by the suprascapular nerve, which arises from the upper trunk of the brachial plexus, specifically from the ventral rami of cervical nerves C5 and C6. The suprascapular nerve provides motor innervation to the infraspinatus muscle, allowing it to contract and perform its functions. It enters the infraspinatous fossa, where it provides two terminal branches to the infraspinatus muscle.
The suprascapular nerve is a mixed nerve, containing both motor and sensory components. In addition to providing motor innervation to the infraspinatus muscle, it also supplies sensation to the acromioclavicular and glenohumeral joints. The suprascapular nerve follows a specific path, passing deep to the trapezius muscle and through the suprascapular notch to enter the supraspinous fossa. It then continues through the spinoglenoid notch and terminates within the infraspinatus muscle.
Damage to the suprascapular nerve can result in suprascapular paralysis, causing back pain, abduction problems, and external rotation issues of the humerus. It can also lead to wasting away of the infraspinatus muscle and shoulder pain. This condition is known as suprascapular nerve entrapment syndrome, which occurs when the nerve becomes entrapped and compressed within the suprascapular canal.
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The muscle is one of the four rotator cuff muscles
The infraspinatus muscle is one of the four rotator cuff muscles, along with the subscapularis, teres minor, and supraspinatus muscles. It is a thick triangular muscle that occupies the majority of the dorsal surface of the scapula. The infraspinatus muscle is innervated by the suprascapular nerve, which is a branch of the superior trunk of the brachial plexus. This nerve provides motor innervation to the infraspinatus muscle, allowing it to externally rotate the humerus and stabilize the shoulder joint.
The suprascapular nerve arises from the upper trunk of the brachial plexus, which is formed by the union of the ventral rami of the fifth and sixth cervical nerves (C5-C6). After branching from the brachial plexus, the nerve passes across the posterior triangle of the neck, running parallel to the inferior belly of the omohyoid muscle and deep to the trapezius muscle. It then continues along the superior border of the scapula, passing through the suprascapular notch and entering the supraspinous fossa.
In the supraspinous fossa, the suprascapular nerve gives off two branches to the supraspinatus muscle. The nerve then passes through the spinoglenoid notch at the lateral border of the scapula spine and enters the infraspinous fossa. Here, it provides two terminal branches to the infraspinatus muscle. The infraspinatus muscle fibers course towards the shoulder joint, almost parallel to the teres minor and major muscles.
The infraspinatus muscle is involved in the external rotation of the humerus, also known as the lateral rotation of the arm. It works together with the teres minor muscle to rotate the head of the humerus outward and assist in carrying the arm backward. The infraspinatus muscle also helps to stabilize the glenohumeral, or shoulder, joint. This function is crucial for maintaining a wide range of arm motion while keeping the head of the humerus centralized within the glenoid cavity.
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Frequently asked questions
The suprascapular nerve innervates the infraspinatus muscle.
The suprascapular nerve is a mixed nerve that branches from the upper trunk of the brachial plexus. It provides motor supply to the infraspinatus muscle.
The infraspinatus muscle is a thick triangular muscle that occupies the majority of the dorsal surface of the scapula. It is one of the four rotator cuff muscles and its main function is to externally rotate the humerus and stabilize the shoulder joint.
