The latissimus dorsi () is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the (trapezius) on the back near the midline. The word latissimus dorsi (plural: latissimi dorsi) comes from Latin and means "broadest [muscle] of the back", from "latissimus" (Latin: broadest) and "dorsum" (Latin: back). The pair of muscles are commonly known as "lats", especially among (bodybuilders). The latissimus dorsi is the largest muscle in the upper body.
Latissimus dorsi | |
---|---|
![]() Latissimus dorsi originates from the mid to lower back | |
Muscles connecting the upper extremity to the (vertebral column). | |
Details | |
(Spinous processes) of (vertebrae) -(L5), (thoracolumbar fascia), (iliac crest), inferior 3 or 4 (ribs) and (inferior angle of) (scapula) | |
Floor of (intertubercular groove) of the (humerus) | |
(Artery) | (Thoracodorsal branch) of the (subscapular artery) |
(Nerve) | (Thoracodorsal nerve (C6, C7, C8)) |
(Actions) | (Adducts), extends and internally rotates the arm when the insertion is moved towards the origin. When observing the muscle action of the origin towards the insertion, the lats are a very powerful rotator of the trunk. |
(Antagonist) | (Deltoid) and (trapezius muscle) |
Identifiers | |
Latin | musculus latissimus dorsi |
(TA98) | A04.3.01.006 |
(TA2) | 2231 |
(FMA) | 13357 |
(Anatomical terms of muscle) [edit on Wikidata] |
The latissimus dorsi is responsible for (extension), (adduction), transverse extension also known as horizontal abduction (or horizontal extension), flexion from an extended position, and (medial) (internal rotation) of the (shoulder joint). It also has a (synergistic) role in extension and lateral flexion of the lumbar spine.
Due to bypassing the scapulothoracic joints and attaching directly to the spine, the actions the latissimi dorsi have on moving the arms can also influence the movement of the scapulae, such as their downward rotation during a (pull up).
Structure
Variations
![image](https://www.viki.en-us.nina.az/image/aHR0cHM6Ly91cGxvYWQud2lraW1lZGlhLm9yZy93aWtpcGVkaWEvY29tbW9ucy90aHVtYi8yLzJhL0JyYXVzXzE5MjFfMTM3LnBuZy8yMDBweC1CcmF1c18xOTIxXzEzNy5wbmc=.png)
![image](https://www.viki.en-us.nina.az/image/aHR0cHM6Ly91cGxvYWQud2lraW1lZGlhLm9yZy93aWtpcGVkaWEvY29tbW9ucy90aHVtYi9iL2I3L0dyYW50XzE5NjJfMjdjLnBuZy8yMDBweC1HcmFudF8xOTYyXzI3Yy5wbmc=.png)
The number of dorsal vertebrae to which it is attached varies from four to eight; the number of costal attachments varies; muscle fibers may or may not reach the crest of the ilium.
A (muscle slip), the (axillary arch), varying from 7 to 10 cm in length, and from 5 to 15 mm in breadth, occasionally springs from the upper edge of the latissimus dorsi about the middle of the posterior fold of the axilla, and crosses the axilla in front of the axillary vessels and nerves, to join the under surface of the tendon of the (pectoralis major), the (coracobrachialis), or the fascia over the (biceps brachii). This axillary arch crosses the (axillary artery), just above the spot usually selected for the application of a ligature, and may mislead a surgeon. It is present in about 7% of the population and may be easily recognized by the transverse direction of its fibers. Guy et al. extensively described this muscular variant using MRI data and positively correlated its presence with symptoms of neurological impingement.
A fibrous slip usually passes from the upper border of the tendon of the Latissimus dorsi, near its insertion, to the long head of the (triceps brachii). This is occasionally muscular, and is the representative of the dorsoepitrochlearis brachii of (apes). This muscular form is found in ~5% of humans and is sometimes termed the latissimocondyloideus.
The latissimus dorsi crosses the inferior angle of the (scapula). A study found that, of 100 cadavers dissected:
- 43% had "a substantial amount" of fibers in the latissimus dorsi originating from the scapula.
- 36% had few or no muscular fibers, but a "soft fibrous link" between the scapula and the latissimus dorsi
- 21% had little or no connecting tissue between the two structures.
Triangles
- The lateral margin of the latissimus dorsi is separated below from the (obliquus externus abdominis) by a small triangular interval, the lumbar triangle of Petit, the base of which is formed by the (iliac crest), and its floor by the (obliquus internus abdominis).
- Another triangle is situated behind the scapula. It is bounded above by the (trapezius), below by the latissimus dorsi, and laterally by the vertebral border of the scapula; the floor is partly formed by the (rhomboideus major). If the (scapula) is drawn forward by folding the arms across the chest, and the trunk bent forward, parts of the sixth and seventh ribs and the interspace between them become subcutaneous and available for (auscultation). The space is therefore known as the (triangle of auscultation).
- The latissimus dorsi can be remembered best for insertion as "A Miss Between Two Majors". As the latissimus dorsi inserts into the floor of the intertubercular groove of the (humerus) it is surrounded by two major muscles. The teres major inserts medially on the medial lip of the intertubercular groove and the pectoralis major inserts laterally onto the lateral lip.
Nerve supply
The latissimus dorsi is innervated by the sixth, seventh, and eighth cervical nerves through the (thoracodorsal (long subscapular)) nerve. (Electromyography) suggests that it consists of six groups of muscle fibres that can be independently coordinated by the (central nervous system).
Function
The latissimus dorsi assists in depression of the arm with the (teres major) and (pectoralis major). It adducts, extends, and internally rotates the shoulder. When the arms are in a fixed overhead position, the latissimus dorsi pulls the trunk upward and forward.
It has a (synergistic) role in extension (posterior fibers) and lateral flexion (anterior fibers) of the lumbar spine, and assists as a muscle of both forced expiration (anterior fibers) and an accessory muscle of inspiration (posterior fibers).
Most latissimus dorsi exercises concurrently recruit the (teres major), posterior fibres of the (deltoid), long head of the (triceps brachii), among numerous other stabilizing muscles. Compound exercises for the 'lats' typically involve elbow flexion and tend to recruit the (biceps brachii), (brachialis), and (brachioradialis) for this function. Depending on the line of pull, the (trapezius) muscles can be recruited as well; horizontal pulling motions such as rows recruit both latissimus dorsi and trapezius heavily.
Training
The power/size/strength of this muscle can be (trained) with a variety of different exercises. Some of these include:
- Vertical pulling movements such as (pull-downs) and (pull-ups) (including (chin-ups))
- Horizontal pulling movements such as (bent-over row), and other (rowing exercises)
- Shoulder extension movements with straight arms such as straight-arm lat pulldowns and (pull-overs)
- (Deadlift)
Clinical significance
Tight latissimus dorsi has been shown to be a contributor to chronic shoulder pain and chronic back pain. Because the latissimus dorsi connects the spine to the (humerus), tightness in this muscle can manifest as either sub-optimal (glenohumeral joint) (shoulder) function which leads to chronic pain or (tendinitis) in the tendinous fasciae connecting the latissimus dorsi to the thoracic and (lumbar spine).
The latissimus dorsi is a potential source of muscle for (breast reconstruction) surgery after mastectomy (e.g., Mannu flap) or to correct pectoral (hypoplastic) defects such as (Poland's syndrome). An absent or hypoplastic latissimus dorsi can be one of the associated symptoms of Poland's syndrome.
Cardiac support
For heart patients with low cardiac output and who are not candidates for cardiac transplantation, a procedure called (cardiomyoplasty) may support the failing heart. This procedure involves wrapping the latissimus dorsi muscles around the heart and electrostimulating them in synchrony with ventricular systole.
Injury
Injuries to the latissimus dorsi are rare. They occur disproportionately in baseball pitchers. Diagnosis can be achieved by visualization of the muscle and movement testing. MRI of the shoulder girdle will confirm the diagnosis. Muscle belly injuries are treated with rehabilitation while tendon avulsion injuries can be treated surgically, or with rehab. Regardless of treatment, patients tend to return to play without any functional losses.
Additional images
- Position of the latissimus dorsi muscle (shown in red). Animation.
- Lumbar triangle
- Latissimus dorsi
- Clearly visible latissimus dorsi muscle of an (artistic gymnast) on (pommel horse).
- (Contraction) of the latissimus dorsi muscle of another artistic gymnast on (still rings).
See also
![image](https://www.viki.en-us.nina.az/image/aHR0cHM6Ly91cGxvYWQud2lraW1lZGlhLm9yZy93aWtpcGVkaWEvZW4vdGh1bWIvNC80YS9Db21tb25zLWxvZ28uc3ZnLzMwcHgtQ29tbW9ucy1sb2dvLnN2Zy5wbmc=.png)
- (Muscle energy techniques)
References
This article incorporates text in the public domain from the 20th edition of (Gray's Anatomy) (1918)
- Kinematic Concepts for Analyzing Human Motion. In: Hall SJ. eds. Basic Biomechanics, 7e. McGraw-Hill; Accessed January 25, 2021. https://accessphysiotherapy-mhmedical-com.libaccess.lib.mcmaster.ca/content.aspx?bookid=1586§ionid=99981270
- Guy, MS; Sandhu, SK; Gowdy, JM; Cartier, CC; Adams, JH (January 2011). "MRI of the axillary arch muscle: prevalence, anatomic relations, and potential consequences". AJR Am J Roentgenol. 196 (1): W52–7. (doi):10.2214/ajr.10.4380. (PMID) 21178031.
- Haninec, P; Tomás, R; Kaiser, R; Cihák, R (2009). "Development and clinical significance of the musculus dorsoepitrochlearis in men". Clin. Anat. 22 (4): 481–8. (doi):10.1002/ca.20799. (PMID) 19373904. (S2CID) 221547558.
- Edwards, William E., The Musculoskeletal Anatomy of the Thorax and Brachium of an Adult Female Chimpanzee,6571st Aeromedical Research Laboratory, New Mexico, 1965.
- "Anatomy Atlases: Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: L:Latissimus Dorsi". www.anatomyatlases.org.
- Giacomo, Giovanni Di; Pouliart, Nicole; Costantini, Alberto; Vita, Andrea de (September 25, 2008). Atlas of Functional Shoulder Anatomy. Springer Science & Business Media. ISBN .
- Brown, JM; Wickham, JB; McAndrew, DJ; Huang, XF (2007). "Muscles within muscles: Coordination of 19 muscle segments within three shoulder muscles during isometric motor tasks". J Electromyogr Kinesiol. 17 (1): 57–73. (doi):10.1016/j.jelekin.2005.10.007. (PMID) 16458022.
- George, Michael S.; Khazzam, Michael (February 2019). "Latissimus Dorsi Tendon Rupture". Journal of the American Academy of Orthopaedic Surgeons. 27 (4): 113–118. (doi):10.5435/JAAOS-D-17-00581. (ISSN) 1067-151X. (PMID) 30278013. (S2CID) 52910621.
- Kendall, Florence Peterson; McCreary, Elizabeth Kendall; Provance, Patricia Geise (2005). Muscles Testing and Function With Posture and Pain. p. 238. ISBN .
- Arnheim, D.D., Prentice, W.E., Principles of athletic training. 9th ed. McGraw Hill, pp 570-574, 1997.
- Francis, P., Applied anatomy and kinesiology, supplemental materials. KB Books., p 19-25, 1999.
- Mannu, G. S., Farooq, N., Down, S., Burger, A. and Hussien, M. I. (2013), Avoiding back wound dehiscence in extended latissimus dorsi flap reconstruction. ANZ J Surg, 83: 359–364. http://onlinelibrary.wiley.com/doi/10.1111/j.1445-2197.2012.06292.x/full
- Yang CE, Roh TS, Yun IS, Kim YS, Lew DH (2014). "Immediate partial breast reconstruction with endoscopic latissimus dorsi muscle flap harvest". Arch Plast Surg. 41 (5): 513–9. (doi):10.5999/aps.2014.41.5.513. (PMC) 4179355. (PMID) 25276643.
- Lantzsch T, Lampe D, Kantelhardt EJ (2013). "Correction of Poland's Syndrome: Case Report and Review of the Current Literature". Breast Care (Basel). 8 (2): 139–42. (doi):10.1159/000350778. (PMC) 3683949. (PMID) 24419214.
- Masia J, Pons G, Loschi P, Sanchez Porro-Gil L, Nardulli ML, Olivares L (2015). "Autologous reconstruction of a complex form of Poland syndrome using 2 abdominal perforator free flaps". Ann Plast Surg. 74 (5): 580–3. (doi):10.1097/SAP.0b013e31829a39b1. (PMID) 24322640.
- Beer GM, Kompatscher P, Hergan K (1996). "Poland's syndrome and vascular malformations". Br J Plast Surg. 49 (7): 482–4. (doi):10.1016/S0007-1226(96)90037-5. (PMID) 8983554.
- Donohue, Benjamin; Lubitz, Marc (December 20, 2016). "Sports Injuries to the Latissimus Dorsi and Teres Major". The American Journal of Sports Medicine. 45 (10): 2428–2435. (doi):10.1177/0363546516676062. (PMID) 28125914. (S2CID) 3872258.
External links
- Anatomy figure: 01:03-08 at Human Anatomy Online, SUNY Downstate Medical Center - "Superficial layer of the extrinsic muscles of the back."
- Cross section image: pembody/body8a—Plastination Laboratory at the Medical University of Vienna
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