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The deltoid muscle is a thick, triangular muscle that forms the rounded contour of the human shoulder. It is responsible for elevating the arm in the scapular plane and is involved in abduction, extension, and rotation of the arm. The deltoid muscle is innervated by the axillary nerve, which is a branch of the brachial plexus. This nerve provides motor and sensory functions to the deltoid muscle, allowing for its movement and sensation. The axillary nerve can be damaged through trauma or injury, affecting the function of the deltoid muscle and resulting in potential paralysis.
| Characteristics | Values |
|---|---|
| Shape | Thick, triangular |
| Muscle fibres | Anterior, lateral, posterior |
| Nerve | Axillary nerve |
| Artery | Thoracoacromial artery, circumflex humeral arteries, profunda brachii artery |
| Function | Abduction of the arm, elevation, extension, internal and external rotation |
| Injury | Trauma, fracture, dislocation, atrophy |
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What You'll Learn
- The axillary nerve innervates the deltoid muscle
- The brachial plexus is the network of innervation to the upper limb
- The axillary nerve can be damaged through trauma to the humerus or shoulder girdle
- The axillary nerve is formed within the axilla area of the upper limb
- Axillary neuropathies lead to deltoid muscle dysfunction
The axillary nerve innervates the deltoid muscle
The axillary nerve is formed within the axilla area of the upper limb and is a direct continuation of the posterior cord from the brachial plexus. It contains fibres from the C5 and C6 nerve roots. The axillary nerve provides motor functions to the deltoid muscle, allowing for the abduction of the arm. This occurs when the arm is already abducted beyond fifteen degrees, with the initial part of abduction produced by the supraspinatus muscle. The deltoid muscle receives a rich vascular supply from various sources, with all arteries supplying it being branches of the axillary artery, except for the deep brachial artery, which is a branch of the brachial artery.
The axillary nerve has anterior and posterior terminal branches that innervate the deltoid muscle. The anterior terminal branch winds around the surgical neck of the humerus and provides motor innervation to the anterior aspect of the deltoid muscle. It terminates with cutaneous branches to the anterior and anterolateral shoulder. The posterior terminal branch provides motor innervation to the posterior aspect of the deltoid muscle and the teres minor. It also innervates the skin over the inferior part of the deltoid as the upper lateral cutaneous nerve of the arm.
The axillary nerve can be damaged through trauma to the proximal humerus or shoulder girdle, often presenting with other brachial plexus injuries. Common mechanisms of injury include fracture of the humeral surgical neck, shoulder dislocation, or iatrogenic injury during shoulder surgery. Damage to the axillary nerve can lead to paralysis of the deltoid muscle, resulting in weakness and permanent numbness at the lateral shoulder region, muscle atrophy, and neuropathic pain. Chronic lesions of the axillary nerve can cause denervation of the deltoid muscle, affecting its function.
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The brachial plexus is the network of innervation to the upper limb
The deltoid muscle is a thick, rounded, triangular muscle located on the uppermost part of the arm and the top of the shoulder. It gets its name from the Greek letter delta, which is shaped like an equilateral triangle. The deltoid muscle is responsible for the abduction of the arm, which is the action of elevating the arm away from the body. This muscle is innervated by the axillary nerve, which is a branch of the brachial plexus.
The brachial plexus is a network of nerves that provides innervation to the upper limb. It originates in the neck and passes between the anterior and middle scalene muscles. It then travels underneath the clavicle and first rib, continuing towards the axilla. The brachial plexus is formed by the ventral rami of C5-T1 nerve roots and provides motor and sensory innervation to the upper limb. This includes stimulation for muscular actions such as flexion, extension, pronation, supination, abduction, adduction, and rotation at the shoulder, arm, forearm, and hand.
The axillary nerve is a direct continuation of the posterior cord of the brachial plexus and contains fibres from the C5 and C6 nerve roots. It provides motor innervation to the deltoid muscle, allowing it to function properly during arm abduction. The axillary nerve has anterior and posterior terminal branches that supply different aspects of the deltoid muscle. The anterior branch provides innervation to the anterior aspect of the deltoid, while the posterior branch innervates the posterior portion.
Injuries to the axillary nerve can occur during shoulder surgery or as a result of trauma to the proximal humerus or shoulder girdle. This can lead to deltoid muscle dysfunction and paralysis. Common mechanisms of injury include fractures of the humeral surgical neck, shoulder dislocation, or iatrogenic injury. Chronic lesions of the axillary nerve can result in permanent muscle atrophy and neuropathic pain.
In summary, the deltoid muscle is innervated by the axillary nerve, which is a branch of the brachial plexus. The brachial plexus is a network of nerves that provides innervation to the upper limb, allowing for various muscular actions and sensory functions. Injuries to the axillary nerve can have significant consequences on the function of the deltoid muscle.
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The axillary nerve can be damaged through trauma to the humerus or shoulder girdle
The axillary nerve is formed within the axilla area of the upper limb. It is a direct continuation of the posterior cord of the brachial plexus, which is a network of nerves that provides innervation to the upper limb. The axillary nerve has several functions, including motor and sensory innervation.
The axillary nerve is responsible for innervating the deltoid muscle, which is the muscle that allows for the abduction of the arm. It also innervates the teres minor muscle, which is part of the rotator cuff muscles that stabilise the glenohumeral joint.
The axillary nerve is susceptible to injury due to its anatomical location in the quadrangular space on the posterior scapula. It can be damaged through trauma to the proximal humerus or shoulder girdle. Common mechanisms of injury include a fracture of the humeral surgical neck, shoulder dislocation, or iatrogenic injury during shoulder surgery.
During a shoulder dislocation, the axillary nerve can be stretched over the humeral head, causing elongation of the nerve and increased tension, which can result in avulsion from the posterior cord of the brachial plexus. This type of injury can also occur during a forced abduction movement of the shoulder joint or from compressive forces.
Injury to the axillary nerve can result in weakness or loss of movement in the deltoid and teres minor muscles, affecting the patient's ability to abduct the affected limb. Sensory functions may also be impacted, leading to a loss of sensation over the inferior deltoid and chronic lesions can cause permanent numbness, muscle atrophy, and neuropathic pain.
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The axillary nerve is formed within the axilla area of the upper limb
The deltoid muscle is a thick, rounded, triangular muscle located on the uppermost part of the arm and the top of the shoulder, named after the Greek letter delta, which is shaped like an equilateral triangle. It is formed of acromial, clavicular, and scapular spinal parts. The acromial part, also known as the middle or central part, is the largest and strongest. The deltoid muscle is responsible for the abduction of the arm, which is the action of moving the arm away from the body. It also contributes to lateral rotation and extension of the posterior fibres, as well as medial rotation and flexion of the anterior fibres.
The deltoid muscle is innervated by the axillary nerve, which is formed within the axilla area of the upper limb. The axillary nerve is a direct continuation of the posterior cord from the brachial plexus and contains fibres from the C5 and C6 nerve roots. The brachial plexus is a network of nerves that originate in the neck and travel towards the axilla, where the terminal branches provide motor and sensory innervation to the upper limb.
The axillary nerve has anterior and posterior terminal branches that innervate the deltoid muscle. The anterior terminal branch provides motor innervation to the anterior aspect of the deltoid muscle and the posterior terminal branch innervates the posterior aspect. The axillary nerve also provides sensory innervation to the upper lateral cutaneous nerve of the arm, which can result in a loss of sensation over the inferior deltoid if damaged.
Injuries to the axillary nerve can occur during shoulder surgery, shoulder dislocation, or fracture of the surgical neck of the humerus. This can lead to deltoid muscle dysfunction, paralysis, or atrophy, resulting in a loss of function and a flattened shoulder curvature. Chronic lesions of the axillary nerve can cause permanent numbness, muscle atrophy, and neuropathic pain.
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Axillary neuropathies lead to deltoid muscle dysfunction
The deltoid muscle is a thick, triangular shoulder muscle that is innervated by the axillary nerve, which is a branch of the brachial plexus. The axillary nerve provides motor innervation to the deltoid muscle, allowing for the abduction of the arm. The deltoid muscle has three functionally and anatomically distinct parts: the acromial, clavicular, and scapular spinal parts.
Axillary neuropathies can lead to deltoid muscle dysfunction. This can be caused by various factors such as trauma, muscle hypertrophy, or space-occupying lesions. Athletes who perform overhead activities are particularly susceptible to axillary nerve injuries. The nerve can also be damaged during shoulder surgery or as a result of a fracture of the humeral surgical neck or shoulder dislocation.
Symptoms of axillary nerve dysfunction include pain, loss of movement, and a lack of sensation in the shoulder area. Patients may also experience weakness in the deltoid muscle, rendering them unable to abduct the affected limb beyond 15 degrees. Chronic axillary nerve lesions can result in permanent numbness, muscle atrophy, and neuropathic pain.
Accurate diagnosis and management of axillary nerve injuries are crucial to prevent long-term disability and maintain the quality of life. Physical examination, nerve tests such as electromyography (EMG), and imaging tests like MRI may be necessary for diagnosis. Treatment options include conservative management, physical therapy, and in some cases, surgical intervention.
In summary, axillary neuropathies can lead to deltoid muscle dysfunction by causing pain, weakness, and loss of sensation in the shoulder area. Proper diagnosis and treatment are essential to prevent permanent damage and maintain the overall quality of life.
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Frequently asked questions
The axillary nerve innervates the deltoid muscle.
The axillary nerve is formed within the axilla area of the upper limb and is a direct continuation of the posterior cord from the brachial plexus.
The deltoid muscle is responsible for elevating the arm in the scapular plane. It is also the prime mover of arm abduction along the frontal plane.
Damage to the axillary nerve can lead to paralysis of the deltoid muscle and permanent numbness at the lateral shoulder region.
