Logan Steele
The deltoid muscle is a thick, triangular shoulder muscle that covers the top of the shoulder. It is a key shoulder stabiliser, allowing for arm movement in different directions. The muscle is divided into three parts: the anterior or clavicular part (front delt), the posterior or scapular part (rear delt), and the intermediate or acromial part (side delt). The deltoid muscle is a common site for intramuscular injections, including vaccinations.
| Characteristics | Values |
|---|---|
| Location | Top of the shoulder |
| Shape | Triangular |
| Muscle fibres | Anterior, lateral, and posterior |
| Proximal attachment | U-shaped |
| Distal attachment | Deltoid tuberosity of the humerus |
| Blood supply | Thoracoacromial branch of the axillary artery |
| Innervation | Axillary nerve |
| Function | Abduction, flexion, and stabilisation of the shoulder |
| Common injuries | Rotator cuff tears, Adhesive capsulitis, Axillary nerve palsy |
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What You'll Learn
The deltoid muscle is a large triangular-shaped muscle
The deltoid muscle is divided into three distinct portions: the anterior or clavicular, the middle or acromial, and the posterior or spinal. These three parts originate from the scapular spine, superior acromial surface, and lateral third of the clavicle, respectively. The anterior and posterior portions are unipennate, while the lateral region is multipennate. The deltoid's fibres are pennate muscle, and it receives blood from the thoracoacromial branch of the axillary artery.
The deltoid muscle is a powerful muscle used in many daily activities and athletic pursuits. It assists in forward elevation and helps to raise the arm to the front, side, and back. The deltoid also compensates for lost arm strength due to injuries such as rotator cuff tears. However, it is susceptible to conditions such as adhesive capsulitis, axillary nerve palsy, bursitis, and tendonitis, which can cause pain and affect shoulder function.
The deltoid is a common site for intramuscular injections, including vaccinations. It is important to administer these injections into the lower half of the deltoid to avoid injury to the axillary nerve, which supplies sensation to the deltoid muscle. Overall, the deltoid muscle plays a crucial role in shoulder stability and motion, allowing for a wide range of movements and activities.
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It covers the top of the shoulder
The deltoid muscle is a thick, triangular shoulder muscle that covers the top of the shoulder. It gets its name from its shape, which resembles the inverted Greek letter delta (Δ). This muscle forms the shoulder's rounded contour, with its fibres converging to form a short tendon that inserts into the deltoid tuberosity of the humerus. The deltoid is a key shoulder stabilizer, helping to raise and move the arm in different directions. It also protects and stabilizes the shoulder joint.
The deltoid is divided into three distinct parts based on origin: the anterior or clavicular part (front delt), the posterior or scapular part (rear delt), and the intermediate or acromial part (side delt). These parts correspond to two or three discernible areas of insertion. The anterior and posterior portions are unipennate, while the lateral region is multipennate. 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 muscle has a very broad origin, spanning the clavicle, acromion, and spine of the scapula. It has a narrow base, which contributes to its triangular shape. The deltoid passes inferiorly, surrounding the glenohumeral joint on all sides, and inserts onto the humerus. The muscle receives its vascular supply from various sources, including branches of the axillary artery and the posterior humeral circumflex artery.
The deltoid muscle is innervated by the axillary nerve, which arises from the brachial plexus. It receives minor contributions from the posterior humeral circumflex and profunda brachii arteries. The axillary nerve is vulnerable to injury during shoulder dislocation or fracture, which can lead to paralysis of the deltoid muscle. The deltoid is a common site for intramuscular injections and vaccinations.
The deltoid muscle is a powerful muscle used in many daily activities and athletic endeavours. It is susceptible to various pathologies, including tears, fatty atrophy, and enthesopathy. Deltoid pain can occur in individuals who perform repetitive overhead activities or experience shoulder trauma and chronic wear and tear.
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It helps raise the arm and move it in different directions
The deltoid muscle, often shortened as "delt", is a large triangular-shaped muscle that covers the top of the shoulder. It is called the deltoid because its shape resembles the inverted Greek letter delta. The muscle is composed of three distinct sets of muscle fibres, or parts: the anterior or clavicular part (front deltoid), the posterior or scapular part (rear deltoid), and the intermediate or acromial part (side deltoid).
The deltoid muscle helps raise the arm and move it in different directions. The anterior deltoid helps move your arm forward, for example, when you reach for an object on a shelf. The lateral deltoid helps move your arm out to the side, as well as up and down, for example, when you do jumping jacks. The posterior deltoid helps with extension and external rotation of the arm. For example, when performing extension and external rotation, a therapist will place one hand on the patient's forearm and push the shoulder anteriorly from the posterior, thereby lengthening the muscle.
The deltoid muscle is a key shoulder stabilizer. It prevents inferior glenohumeral joint displacement while the arm is completely adducted and bearing a heavy load, such as during deadlift exercises. The deltoid also compensates for weak shoulder abduction due to rotator cuff tears. When the three parts of the deltoid contract simultaneously, the muscle assists in abducting the arm past 15 degrees. The deltoid cannot initiate abduction because it contracts parallel to the humeral axis. However, the clavicular and scapular spinal fibres of the muscle guide the arm through the abduction motion.
The deltoid muscle is commonly used in everyday activities and athletic activities. For example, it is used when putting clothes on a line, carrying shopping bags, washing hair, playing netball, swimming, and playing water polo.
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The deltoid is a key shoulder stabiliser
The deltoid muscle is a large, triangular-shaped muscle that covers the top of the shoulder. It is comprised of three distinct sections: the anterior or clavicular, the middle or acromial, and the posterior or spinal. The deltoid muscle is a key shoulder stabiliser, working alongside other shoulder muscles, such as the rotator cuff muscles, to help perform a variety of movements.
The deltoid muscle is responsible for arm abduction, which is the action of raising your arm out to the side of your body. It also compensates for lost arm strength in the event of an injury, such as a rotator cuff tear. The anterior deltoid, for example, helps move your arm forward and is used when reaching for an object on a shelf. The muscle also plays a role in flexion (moving your arm forward, towards an overhead position) and extension (moving your arm backward, behind your body).
The deltoid is a powerful muscle and is used in many everyday activities, such as putting clothes on a line, carrying shopping bags, or washing hair. It is also used in athletic activities such as netball, swimming, and water polo. The deltoid is a common site for intramuscular injections, including vaccinations.
The deltoid muscle is susceptible to various conditions and injuries, including adhesive capsulitis (frozen shoulder), axillary nerve palsy, bursitis, and deltoid fibrosis. These conditions can cause shoulder pain, muscle spasms, stiffness, and irritation. Deltoid pathologies can lead to functional disfunction of the shoulder complex. Tears in the deltoid muscle are often associated with rotator cuff tears and may further compromise shoulder function.
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It is made up of three distinct parts
The deltoid muscle is a large, thick, triangular shoulder muscle. It gets its name from its shape, which resembles the inverted Greek letter delta (Δ). It covers the top of the shoulder and helps us lift our arms to the front, side, and back. It is a key shoulder stabilizer and is used in many everyday activities and athletic activities.
The deltoid is made up of three distinct parts, each with a different origin: the clavicular (anterior) part, the acromial (middle) part, and the scapular spinal (posterior) part. The clavicular part originates from the superior surface and the anterior border of the lateral third of the clavicle. The acromial part arises from the lateral margin and superior surface of the acromion of the scapula. The scapular spinal part originates from the lateral 1/3 of the spine of the scapula, on the crest.
The three parts of the deltoid have different functions. The acromial part abducts the arm, while the clavicular and scapular spinal parts play a significant role in stabilization, ensuring a steady plane of abduction. Additionally, the clavicular part (anterior fibers) can act as a flexor and internal rotator of the arm, while the scapular spinal part (posterior fibers) can extend and externally rotate the arm.
When the three parts of the deltoid contract simultaneously, the muscle can assist in abducting the arm past 15 degrees. The deltoid cannot initiate abduction because it contracts parallel to the humeral axis. Throughout abduction, the anterior and posterior parts of the deltoid stabilize the arm, while the lateral segment assists in raising the arm from 15 to 100 degrees.
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Frequently asked questions
The deltoid muscle is a large triangular muscle that covers the top of the shoulder.
The deltoid muscle is named after the inverted Greek letter delta due to its triangular shape.
The deltoid muscle is made up of three distinct parts: the anterior or clavicular, the lateral or acromial, and the posterior or spinal.
The deltoid muscle helps lift your arm to the front, side, and back. It also helps stabilise the shoulder joint.
