What is the origin, insertion, action, blood supply, and nerve innervation of the Pectoralis Major?
Understand the Problem
The question is asking for a detailed anatomical description of the Pectoralis Major muscle group, including its origin, insertion, action, blood supply, and nerve innervation. This requires knowledge of human anatomy.
Answer
The Pectoralis Major originates from the clavicle and sternum, inserts on the humerus, and is responsible for flexion, adduction, and medial rotation of the arm. It is supplied by the pectoral branch of the thoracoacromial artery and innervated by the lateral and medial pectoral nerves.
Here is information about the Pectoralis Major:
- Origin: Clavicular head: anterior surface of the medial half of the clavicle; Sternocostal head: anterior surface of the sternum, superior six costal cartilages.
- Insertion: Lateral lip of the intertubercular groove of the humerus.
- Action: Flexes, adducts, and medially rotates the arm at the shoulder joint.
- Blood Supply: Pectoral branch of the thoracoacromial artery, superior thoracic artery, lateral thoracic artery.
- Nerve Innervation: Lateral and medial pectoral nerves (C5-T1). The clavicular head is innervated by the lateral pectoral nerve, and the sternocostal head is innervated by the medial pectoral nerve.
Answer for screen readers
Here is information about the Pectoralis Major:
- Origin: Clavicular head: anterior surface of the medial half of the clavicle; Sternocostal head: anterior surface of the sternum, superior six costal cartilages.
- Insertion: Lateral lip of the intertubercular groove of the humerus.
- Action: Flexes, adducts, and medially rotates the arm at the shoulder joint.
- Blood Supply: Pectoral branch of the thoracoacromial artery, superior thoracic artery, lateral thoracic artery.
- Nerve Innervation: Lateral and medial pectoral nerves (C5-T1). The clavicular head is innervated by the lateral pectoral nerve, and the sternocostal head is innervated by the medial pectoral nerve.
More Information
Knowing the origin, insertion, and nerve innervation can explain the actions of the Pectoralis Major. Injury to the nerves that innervate the muscle can affect its function.
Tips
A common mistake is confusing the origin and insertion points. Remember, the origin is generally the more stable attachment site, while the insertion is on the bone that moves more during muscle contraction.
Sources
- Pectoralis major - Physiopedia - physio-pedia.com
- Pectoralis Major - UW Radiology - University of Washington - rad.washington.edu
- Pectoralis Major - Attachments - Actions - TeachMeAnatomy - teachmeanatomy.info
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