Latissimus Dorsi Muscle Anatomy

Overview
Origin Spinous processes of thoracic T7–T12
Inferior angle of scapula
Inferior 3 or 4 ribs
Thoracolumbar fascia
Iliac crest
Insertion Floor of the intertubercular groove of the humerus
Action Humeral adduction
Humeral extension
Humeral medial rotation
Nerve Thoracodorsal nerve (C6, C7, C8)
Artery Thoracodorsal artery

Location & Overview

The latissimus dorsi is a large muscle that covers a big portion of the posterior of the torso. It spans from left to right across the posterior of the body and its upper portion is partly covered by the trapezius muscle on its medial dorsal region[1]. The latissimus dorsi is one of the extrinsic muscles of the upper back. The upper back muscles are divided into intrinsic and extrinsic parts. This division is based on their movement actions and origins. The extrinsic muscles primarily control the movement of the humerus and scapula during movement of the upper extremities. The other extrinsic muscles are: the rhomboid major, rhomboid minor, levator scapulae and the trapezius [2]. The latissimus dorsi is the largest extrinsic back muscle [3].

latissimus dorsi muscle from a posterior view

Here we can see the latissimus dorsi muscle in isolation from a posterior view.

Origin & Insertion

The latissimus dorsi originates from the spinous processes T7–T12, the inferior angle of scapula, the thoracolumbar fascia, the inferior 3 or 4 ribs and the iliac crest. It then inserts on the floor of the humerus’ intertubercular groove (also known as the bicipital groove)[4].

the origin points of the latissimus dorsi muscle marked in red

Here we can see the origins of the latissimus dorsi muscle marked in red. The latissimus dorsi origins marked here are: the inferior angle of scapula, the spinous processes of T7–T12, inferior 3 or 4 ribs and the iliac crest.

thoracolumbar fascia highlighted in green

The final origin point of the latissimus dorsi muscle is the thoracolumbar fascia which is marked here in green.

latissimus dorsi insertion on the intertubercular groove of the humerus

Highlighted here in blue we can see the insertion of the latissimus dorsi on the intertubercular groove of the humerus.

Actions

Contraction of the latissimus dorsi results in adduction, extension and medial rotation of the humerus. When the arms are placed above the head, it can then lift the body upwards and forward (such as during a pull up) [5].

Innervation

The latissimus dorsi is innervated by the thoracodorsal nerve (C6, C7, C8), which is sometimes also referred to as the middle subscapular nerve. The thoracodorsal nerve branches from the brachial plexus’ posterior cord [6].

Blood Supply

Blood is supplied to the latissimus dorsi via the thoracodorsal artery. This artery is a continuation of the subscapular artery. The subscapular artery branches off the axillary artery [7].

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Latissimus Dorsi Flashcards

References

References
1, 4 Bhatt CR, Prajapati B, Patil DS, Patel VD, Singh BG, Mehta CD. Variation in the insertion of the latissimus dorsi & its clinical importance. J Orthop. 2013;10(1):25-28. Published 2013 Mar 7. doi:10.1016/j.jor.2013.01.002.
2 Verhaegen F,Debeer P,Moyaert M, The Accessory muscles of the Axilla. Acta orthopaedica Belgica. 2019 Dec; PMID: 32374231
3 Mitchell B, Imonugo O, Tripp JE. Anatomy, Back, Extrinsic Muscles. [Updated 2021 Aug 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537216/
5 Donohue BF,Lubitz MG,Kremchek TE, Sports Injuries to the Latissimus Dorsi and Teres Major. The American journal of sports medicine. 2017 Aug PMID: 28125914.
6 Anthony DJ, Basnayake BMOD, Ganga NMG, Mathangasinghe Y, Malalasekera AP. An improved technical trick for identification of the thoracodorsal nerve during axillary clearance surgery: a cadaveric dissection study. Patient Saf Surg. 2018 Jun 26;12:18. doi: 10.1186/s13037-018-0164-2. PMID: 29983745; PMCID: PMC6020335.
7 Kumar N,Aithal AP,Nayak SB,Bhaskar R, A rare case of atypical thoracodorsal artery: a challenge for flap reconstruction. Surgical and radiologic anatomy : SRA. 2018 Aug PMID: 29594336.