|Origin||Coracoid process of the scapula|
|Insertion||Midshaft of humerus (distal to the crest of the lesser tubercle)|
|Nerve||Musculocutaneous nerve (C5, C6, C7)|
Location & Overview
The coracobrachialis muscle is a prominent muscle situated in the upper arm region. It is one of the three muscles which attaches to the coracoid process of the scapula. The other two are: the short head of the biceps brachii muscle and the pectoralis minor muscle. The coracobrachialis is the smallest of these three muscles. The coracobrachialis muscle is part of the anterior compartment of the arm, it is located medially to the biceps brachii and brachialis muscles. The primary roles of the coracobrachialis include flexion and adduction of the arm at the glenohumeral joint. It also contributes to maintaining the arm’s alignment in the frontal plane during abduction  .
Origin & Insertion
The coracobrachialis originates from the coracoid process of the scapula, a small hook-like structure on the lateral edge of the superior and anterior portion of the scapula. The coracobrachialis shares the coracoid process’s apex as its origin point with the short head of the biceps brachii muscle  .
The muscle’s insertion point is located on the medial surface of the humerus. It inserts around the midshaft of the humerus. Specifically, it attaches between the insertions of the triceps brachii and brachialis muscles, anchoring itself by means of a short, flat tendon  .
The primary actions of the coracobrachialis are flexing and adducting the arm at the glenohumeral joint (shoulder). Shoulder flexion involves reducing the angle between the arm and the body’s frontal plane, such as lifting the arm forward. As for adduction, this involves drawing the arm closer to the body’s midline, moving it away from the lateral side. Another significant function of the coracobrachialis is to stabilise the arm during abduction, preventing deviation from the frontal plane   .
The coracobrachialis is innervated by the musculocutaneous nerve. This nerve originates from the lateral cord of the brachial plexus. The musculocutaneous nerve carries its fibers from the ventral rami of the spinal nerve roots C5-C7. As it decends, the musculocutaneous nerve passes through the coracobrachialis muscle, piercing it and also providing the innervation that allows for its contractions and movements. It is also worth noting that the musculocutaneous nerve also innervates the biceps brachii and the brachialis muscles, which are closely related in terms of their functions  .
The blood supply of the coracobrachialis muscle is primarily assured by branches of the brachial artery, ensuring the muscle receives adequate oxygen and nutrients necessary for its function. The brachial artery is the major blood vessel of the upper arm and continues from the axillary artery at the lower margin of the teres major muscle  .
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|↑1, ↑7||Moore KL, Agur AMR, Dalley AF. Clinically Oriented Anatomy. 8th ed. Philadelphia: Lippincot Williams & Wilkins; 2017.|
|↑2, ↑3, ↑5, ↑9||Szewczyk B, Polguj M, Paulsen F, Podgórski M, Duparc F, Karauda P, Olewnik Ł. A proposal for a new classification of coracobrachialis muscle morphology. Surg Radiol Anat. 2021 May;43(5):679-688. doi: 10.1007/s00276-021-02700-1. Epub 2021 Feb 9. PMID: 33564931; PMCID: PMC8105249.|
|↑4, ↑6, ↑12||Standring S. (2015). Gray’s Anatomy: The Anatomical Basis of Clinical Practice, 41st Edn. Amsterdam: Elsevier.|
|↑8, ↑13||Georgiev GP, Landzhov B, Tubbs RS. A Novel Type of Coracobrachialis Muscle Variation and a Proposed New Classification. Cureus. 2017;9(7):e1466. Published 2017 Jul 13. doi:10.7759/cureus.1466|
|↑10||Chouke, K. S. (1924). Variation of the coracobrachialis muscle. The Anatomical Record, 27(3), 157-163.|
|↑11||Desai SS, Arbor TC, Varacallo M. Anatomy, Shoulder and Upper Limb, Musculocutaneous Nerve. [Updated 2022 Sep 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK534199/|