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Latissimus Dorsi Muscle Anatomy

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Origin
  • Spinous processes of thoracic T7–T12
  • Inferior angle of the 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
Innervation
  • Thoracodorsal nerve (C6, C7, C8)
Blood Supply
  • Thoracodorsal artery
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Location & Overview

The latissimus dorsi is a large, flat muscle that occupies a substantial area of the posterior torso, spanning from the lower back to the humerus. Its expansive coverage stretches from left to right across the back, with the upper portion partially hidden by the trapezius muscle in the medial dorsal region. The latissimus dorsi plays a crucial role in various upper-body movements, such as adduction, extension, and internal rotation of the shoulder joint.[1,2]

As one of the superficial extrinsic muscles of the upper back, the latissimus dorsi is part of a group divided into intrinsic and extrinsic categories based on their actions and origins. Extrinsic muscles primarily govern the movement of the humerus and scapula during upper extremity motions. Other superficial extrinsic muscles include the rhomboid major, rhomboid minor, levator scapulae, and the trapezius.[3] Among these, the latissimus dorsi is the largest extrinsic back muscle.[4]

The latissimus dorsi’s extensive attachment points provide the muscle with the leverage and force necessary for its various functions. The latissimus dorsi plays an essential role in various physical activities and sports that involve the upper body, such as swimming, rowing, and climbing. It is also an important muscle for the stabilization and control of the shoulder joint during overhead movements and lifting. Because of its size and function, the latissimus dorsi is an important muscle to target during strength training and rehabilitation programs. Exercises that engage the latissimus dorsi include pull-ups, lat pulldowns, bent-over rows, and Pendlay rows, among others.[5,2]

latissimus dorsi muscle from a posterior view
In this image, we can see the latissimus dorsi muscle from a posterior view.
latissimus dorsi muscle from a posterolateral view
In this image, we can see the latissimus dorsi muscle from a posterolateral view.
latissimus dorsi muscle from an anterior view
Here, we can see the latissimus dorsi muscle from an anterior view.
latissimus dorsi muscle highlighted in red
Here, we can see the latissimus dorsi muscle highlighted in red among the other muscles of the body.

Origin & Insertion

The latissimus dorsi’s origin points include the spinous processes of the thoracic vertebrae T7 to T12, the inferior angle of the scapula, the thoracolumbar fascia (a thick, fibrous sheet connecting the muscle to the lower back), the lower three or four ribs, and the iliac crest of the hip bone.[1,2]

These multiple origin points allow the latissimus dorsi to contribute to a range of upper limb and shoulder movements. The muscle fibers converge as they extend toward the humerus, forming a flat tendon that inserts on the floor of the intertubercular groove, also known as the bicipital groove. This groove is a narrow depression that runs along the anterior surface of the humerus and houses the long head of the biceps tendon. The insertion of the latissimus dorsi on the humerus allows the muscle to exert force on the upper limb during various actions, providing stability and strength in movements that involve the shoulder joint.[1,2]

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 the scapula, the spinous processes of T7–T12, the 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.

Action & Function

The latissimus dorsi plays a crucial role in multiple actions involving the humerus and shoulder joint. When this muscle contracts, it generates movement in three primary directions. First, it adducts the humerus, pulling the arm toward the midline of the body. Second, it extends the humerus, moving the arm backward in a posterior direction. Finally, it causes medial rotation of the humerus, turning the arm inward toward the center of the body.[6,5,2]

In addition to these primary movements, the latissimus dorsi is also involved in lifting the body upward and forward when the arms are positioned above the head. This action is evident during exercises such as pull-ups, where the muscle engages to lift the body by extending and adducting the humerus from an overhead position, helping to pull the torso toward the hands.[6,5,2]

Image of a person demonstrating the movement of shoulder adduction.
This image shows shoulder adduction. Adduction occurs when the arm is brought toward the midline of the body, reducing the angle between the arm and the torso. The opposite of adduction is abduction. Abduction occurs as the arm is moved away from the midline, increasing the angle between the arm and the torso. Shoulder adduction is an action of the latissimus dorsi muscle.
Image of a person demonstrating the movement of shoulder extension.
This image shows shoulder extension. Extension occurs when the arm is moved backward in a posterior direction (toward the back of the body), increasing the angle between the arm and the torso in the sagittal plane. The opposite of this is shoulder flexion, which occurs as the arm is moved forward and upward in an anterior direction. Shoulder extension is an action of the latissimus dorsi muscle.
Image of a person demonstrating the movement of shoulder internal rotation.
This image shows shoulder internal rotation. Internal rotation occurs when the arm is rotated inward toward the center of the body, causing the hand and forearm to move toward the body’s midline. The opposite of this is external rotation, which occurs when the arm is rotated outward away from the center of the body, moving the hand and forearm away from the body’s midline. Internal rotation is an action of the latissimus dorsi muscle.

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.[7]

thoracodorsal nerve and latissimus dorsi
Here, we can see the thoracodorsal nerve, which innervates the latissimus dorsi, with nerve roots from C6, C7, and C8.

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.[8]

References

  1. [1] 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. [2] Moore KL, Agur AMR, Dalley AF. Clinically Oriented Anatomy. 8th ed. Philadelphia: Lippincott Williams & Wilkins; 2017.
  3. [3] Verhaegen F,Debeer P,Moyaert M, The Accessory muscles of the Axilla. Acta orthopaedica Belgica. 2019 Dec; PMID: 32374231
  4. [4] 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. [5] Andersen V, Fimland MS, Wiik E, Skoglund A, Saeterbakken AH. Effects of grip width on muscle strength and activation in the lat pull-down. J Strength Cond Res. 2014 Apr;28(4):1135-42. doi: 10.1097/JSC.0000000000000232. PMID: 24662157.
  6. [6] Donohue BF, Lubitz MG, Kremchek TE. Sports Injuries to the Latissimus Dorsi and Teres Major. Am J Sports Med. 2017 Aug;45(10):2428-2435. doi: 10.1177/0363546516676062. Epub 2016 Dec 20. PMID: 28125914.
  7. [7] 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.
  8. [8] 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.

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