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Anatomy Atlases: Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: T: Transversus Thoracis Anterior (Sternocostalis) and Subcostalis

Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: T

Transversus Thoracis Anterior (Sternocostalis) and Subcostalis

Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD

Peer Review Status: Internally Peer Reviewed


Transversus thoracis arises from the posterior surface of the sternum and xiphoid (to the level of the third costal cartilage) and extends onto the internal surface of the second (third) to sixth costal cartilages. Transversus thoracis may extend to the first rib. Absence on one or both sides has been recorded. It is sometimes divided into separate fasciculi which may number from two to six, and its division into two lamellae has also been observed. This muscle was Hyrtl's candidate for the most variable in the body.

 

Mori provides a statistical report of 310 sides, 155 cadavers:

Highest Rib of Insertion

Rib

Number of sides

%

I

7

2.2

II

122

39.3

III

155

50.0

IV

23

7.4

V

3

0.9

 

Lowest Rib of Insertion

Rib

Number of sides

%

V

50

16.1

VI

237

76.4

VII

23

7.4

 

The Extent of Transversus Thoracis on Inner Surface of Thoracic Wall

Highest Rib

Lowest Rib

V

VI

VII

I

1 (0.3%)

6 (3.9%)

9 (2.9%)

II

27 (8.74%)

86 (27.7%)

-

III

21 (6.7%)

121 (39.3%)

13 (4.1%)

IV

1 (.3%)

21 (6.7%)

1 (0.3%)

V

3 (0.9%)

 

The subcostales are usually better developed on the inner surface of the thorax and are variable in number.

Syn.: Tr. Th.: m. triangularis sterni s. sternocostalis (Henle), transversus pectoris (Arnold), Sternoabdominalis (Rosenmüller), Dreieckiger or innerer Brustmuskel, Petit dentelé anterieur (Cruveilheir).

Image 149

Varieties of Chest, Neck, and Shoulder Muscles-Sternocostalis.
modified and redrawn from Wood.


References

Anson, B.J., Ed. (1966) Morris' Human Anatomy, 12th ed. The Blakiston Division, McGraw-Hill Book Company, New York.

Macalister, A. (1875) Observations on the muscular anomalies in the human anatomy. Third series with a catalogue of the principal muscular variations hitherto published. Trans. Roy. Irish Acad. Sci. 25:1-134.

Mori,M. (1964) Statistics on the musculature of the Japanese. Okajimas Fol. Anat. Jap. 40:195-300.

de Pina, L. (1933) Le muscle petit dentele postieur et superieur chez l'homme et les primates. L'Assoc. Anatomistes, Comptes rendus 28:523-531.

Wood, J. (1870) On a group of varieties of the muscles of the human neck, shoulder, and chest, and their transitional forms and homologies in the mammalia. Phil. Trans. R. Soc. (Lond.) 160:83-116.

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