Maximus Gage
The deltoid muscle is a large, triangular-shaped muscle that covers the top of the shoulder. It is responsible for giving the shoulder its rounded contour and is one of the main abductors of the shoulder, helping to lift the arm to the front, side, and back. The deltoid is a superficial muscle, lying over the glenohumeral joint, and is composed of three distinct parts: the anterior, lateral, and posterior. These parts work together to abduct the arm and assist in flexion and extension movements. The deltoid muscle is also involved in stabilizing the shoulder joint and protecting it from dislocation.
| Characteristics | Values |
|---|---|
| Location | Top of the shoulder |
| Shape | Triangular |
| Appearance | Rounded |
| Function | Allows movement of the arm in different directions |
| Parts | Anterior or clavicular, middle or acromial, posterior or spinal |
| Blood supply | Posterior circumflex humeral artery |
| Innervation | Axillary nerve |
| Conditions | Adhesive capsulitis, axillary nerve palsy, bursitis, rotator cuff tears, shoulder impingement syndrome, shoulder separation, strains and overuse injuries, tendonitis |
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What You'll Learn
The deltoid muscle is located on the uppermost part of the arm and the top of the shoulder
The deltoid muscle is responsible for a wide range of arm and shoulder movements. It helps with arm abduction, flexion, and extension. When the arm is abducted beyond fifteen degrees, the deltoid is the principal abductor. The anterior deltoid flexes and medially rotates the arm, the lateral part abducts the arm, and the posterior part extends and laterally rotates the arm. The deltoid also compensates for lost arm strength due to injury, such as a rotator cuff tear.
The deltoid muscle is innervated by the axillary nerve, which is one of the main branches of the brachial plexus. The deltoid receives its blood supply from the posterior circumflex humeral artery. The muscle fibres converge to form a tendon that inserts into the deltoid tuberosity on the humerus.
The deltoid muscle is superficial, meaning it lies close to the surface of the skin. This makes it easily observable and palpable. The deltoid overlies other muscular structures, such as the rotator cuff muscles, the pectoralis major, and the tendon of pectoralis minor. It also covers bony structures, such as the clavicle, scapula, and humerus.
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It is a thick, triangular muscle
The deltoid muscle is a thick, triangular muscle that forms the rounded contour of the human shoulder. It is also known as the 'common shoulder muscle', particularly in other animals such as the domestic cat. The deltoid muscle is a very powerful muscle and is used in many everyday activities, such as putting on clothes, carrying shopping bags, and washing hair. It is also used in athletic activities such as netball, swimming, and water polo.
The deltoid muscle has a very broad origin and a narrow base, creating its triangular shape. It gets its name from its shape, which resembles the Greek letter delta (Δ). The muscle has a wide origin spanning the clavicle, acromion, and spine of the scapula. It passes inferiorly, surrounding the glenohumeral joint on all sides, and inserts onto the humerus. The deltoid is formed of acromial, clavicular, and scapular spinal parts.
The deltoid muscle has three functionally and anatomically distinct parts, each with its own band of muscle fibres and function. The acromial part, or the middle fibres, abducts the arm. The clavicular part, or anterior fibres, acts as a flexor and internal rotator of the arm. The scapular spinal part, or posterior fibres, extends and externally rotates the arm.
The deltoid muscle is innervated by one of the main branches of the brachial plexus, the axillary nerve (C5, C6). The axillary nerve provides motor innervation to the deltoid and cutaneous sensory innervation over the shoulder. The deltoid receives its blood supply from the posterior circumflex humeral artery.
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The deltoid has three distinct parts
The deltoid muscle, also known as the 'common shoulder muscle', is a large triangular-shaped muscle that covers the front, side and back of the shoulder joint. It is a powerful muscle that is used in many everyday activities and athletic activities. The deltoid muscle is made up of three distinct parts: the anterior or clavicular part (commonly known as the front delt), the intermediate or acromial part (commonly known as the side delt), and the posterior or scapular part (commonly known as the rear delt). Each of these three parts has a different origin and function.
The anterior or clavicular part of the deltoid muscle originates from the superior surface and the anterior border of the lateral third of the clavicle. This part of the deltoid muscle helps to move the arm forward and is used when reaching for an object on a shelf, for example. The anterior deltoid also works with other muscles to internally (medially) rotate the humerus.
The intermediate or acromial part of the deltoid muscle arises from the lateral margin and superior surface of the acromion of the scapula. This part of the deltoid muscle performs basic shoulder abduction, particularly when the shoulder is internally rotated. It also performs shoulder transverse abduction when the shoulder is externally rotated.
The posterior or scapular part of the deltoid muscle originates from the lateral third of the spine of the scapula, on the crest. This part of the deltoid muscle assists in the extension of the arm and external (or lateral) rotation of the humerus. Strengthening the posterior fibres of the deltoid muscle can help to offset the tendency of the shoulder to become internally rotated due to poor posture.
While the deltoid muscle is made up of three distinct parts, studies have shown that there are seven neuromuscular segments to the muscle. Three of these lie in the anatomical anterior head of the deltoid, one in the anatomical middle head, and three in the anatomical posterior head of the deltoid.
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It is responsible for arm abduction
The deltoid muscle is a large, triangular-shaped muscle that covers the top of the shoulder. It gets its name from its shape, which resembles the Greek letter delta (Δ). The deltoid muscle is responsible for arm abduction, which is the movement of raising your arm out to the side of your body. This function is mainly performed by the intermediate or acromial part of the deltoid muscle.
The deltoid muscle is made up of three distinct sets of muscle fibres: the anterior or clavicular part (commonly known as the front delt), the posterior or scapular part (commonly known as the rear delt), and the intermediate or acromial part (commonly known as the side delt). These fibres work together to allow for a wide range of movements. The anterior and posterior fibres guide the arm through the abduction motion, while the intermediate fibres are in the most efficient position to perform the abduction function.
The deltoid muscle is a powerful muscle that is used in many everyday activities, such as putting on clothes, carrying shopping bags, or washing hair. It is also used in athletic activities such as netball, swimming, and water polo. The muscle is responsible for elevating the arm in the scapular plane, and its contraction elevates the humeral head. This contraction also helps to stabilise the shoulder joint and prevent dislocations.
The deltoid muscle can be tested by abducting the arm from a resting position at the side of the body. If the deltoid muscle is functioning properly, a contraction of the muscle should be felt near the acromion of the scapula when the arm is beyond 15 degrees of abduction. This test is important for determining muscular or nervous injury, as fatigue or injury to the deltoid muscle can result in a decline in abduction ability.
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The deltoid is a very powerful muscle
The deltoid muscle is a very powerful muscle that forms the rounded contour of the human shoulder. It is a large, thick, triangular muscle that sits between the acromion and the deltoid tuberosity of the humerus. The deltoid muscle is involved in many everyday activities and athletic movements. It helps with arm abduction, flexion, and extension, allowing you to lift your arm to the front, side, and back. This muscle is essential for activities such as putting on clothes, carrying shopping bags, and washing hair. It is also used in sports such as netball, swimming, and water polo.
The deltoid muscle has three distinct parts, each with its own function: the anterior or clavicular part, the posterior or scapular part, and the intermediate or acromial part. The anterior deltoid flexes and medially rotates the arm, allowing movements such as reaching forward or throwing a ball underhand. The lateral or acromial part abducts the arm, moving it away from the body, as in reaching out to the side. The posterior or scapular part extends and laterally rotates the arm, enabling movements like reaching backward or winding up to throw a ball.
The deltoid muscle is a prime mover of arm abduction when all its fibres contract simultaneously. However, the arm must be medially rotated for the deltoid to have its maximum effect. Additionally, the deltoid works in conjunction with the rotator cuff muscles to perform abduction and can compensate for the loss of strength in the rotator cuff. The deltoid also plays a crucial role in stabilising the shoulder joint, preventing subluxation or dislocation of the head of the humerus.
The deltoid muscle is superficial, lying close to the surface of the skin, which makes it easily observable and palpable. It is supplied by the thoracoacromial artery, the circumflex humeral arteries, and the profunda brachii artery. The deltoid receives its nerve supply from the axillary nerve, which can be injured in cases of shoulder fracture or dislocation, leading to potential weakness or atrophy of the deltoid muscle.
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Frequently asked questions
The deltoid muscle is a large, triangular-shaped muscle that covers the top of the shoulder. It is responsible for forming the shoulder's rounded contour.
The deltoid muscle is anatomically divided into three parts: the anterior, or clavicular; lateral, or acromial; and posterior, or spinal.
The deltoid muscle is one of the main abductors of the shoulder, helping to lift the arm when reaching for objects or brushing hair. It also helps to prevent dislocation of the glenohumeral joint when carrying heavy weights.
