The deltoid muscle is a large, triangular muscle located in the shoulder region. It is named after its shape, which resembles the Greek letter “delta” (Δ). The deltoid muscle covers the shoulder joint and is responsible for several important movements of the arm.
Key features of the deltoid muscle:
1. Origin: The deltoid muscle originates from three separate sites: the lateral third of the clavicle (anterior fibers), the acromion process of the scapula (middle fibers), and the spine of the scapula (posterior fibers).
2. Insertion: The deltoid muscle inserts onto the deltoid tuberosity of the humerus, a bony prominence on the lateral side of the upper arm.
3. Three Parts: The deltoid muscle is divided into three parts, or heads, based on its origin and fiber orientation: anterior (clavicular), middle (acromial), and posterior (spinal) heads. These heads work together to produce various movements.
4. Nerve Supply: The deltoid muscle is innervated by the axillary nerve, which arises from the brachial plexus. The axillary nerve provides both motor innervation and sensory innervation to the deltoid muscle and the skin overlying it.
5. Actions: The deltoid muscle has several important actions on the shoulder joint. It acts as the primary abductor of the arm, meaning it raises the arm away from the body laterally. It also assists in other movements, such as flexion, extension, and rotation of the shoulder joint.
6. Synergistic Muscles: During shoulder abduction, the deltoid muscle works synergistically with other muscles, including the supraspinatus muscle, which initiates the movement, and the rotator cuff muscles (subscapularis, infraspinatus, and teres minor), which provide stability.
7. Common Injuries: The deltoid muscle can be strained or torn due to various reasons, such as overuse, trauma, or repetitive stress. Injuries to the deltoid muscle can result in pain, weakness, and limited shoulder movement.
Understanding the anatomy and function of the deltoid muscle is important in fields such as anatomy, orthopedics, sports medicine, and physical therapy.
Deltoid Muscle MCQS:
1. Which of the following is the primary action of the deltoid muscle?
a) Flexion of the shoulder
b) Extension of the shoulder
c) Abduction of the shoulder
d) Adduction of the shoulder
2. The deltoid muscle is innervated by which nerve?
a) Axillary nerve
b) Radial nerve
c) Median nerve
d) Ulnar nerve
3. The deltoid muscle is divided into three parts. Which of the following is not one of the deltoid muscle parts?
a) Anterior deltoid
b) Middle deltoid
c) Posterior deltoid
d) Superior deltoid
4. The deltoid muscle is located in which region of the upper limb?
a) Upper arm (brachium)
b) Forearm (antebrachium)
c) Shoulder (scapular region)
d) Hand (manus)
5. Which of the following movements is primarily performed by the anterior deltoid?
a) Shoulder flexion
b) Shoulder extension
c) Shoulder abduction
d) Shoulder adduction
6. The deltoid muscle is responsible for the initiation of which joint movement?
a) Glenohumeral joint
b) Elbow joint
c) Wrist joint
d) Hip joint
7. Which of the following muscles works synergistically with the deltoid muscle during shoulder abduction?
a) Pectoralis major
b) Latissimus dorsi
c) Supraspinatus
d) Rhomboids
8. The deltoid muscle gets its name from its shape, which resembles which letter of the Greek alphabet?
a) Alpha (Α)
b) Beta (Β)
c) Gamma (Γ)
d) Delta (Δ)
Answers:
1. c) Abduction of the shoulder
2. a) Axillary nerve
3. d) Superior deltoid
4. c) Shoulder (scapular region)
5. a) Shoulder flexion
6. a) Glenohumeral joint
7. c) Supraspinatus
8. d) Delta (Δ)
Anatomy MCQS books PDF:
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