The bilateral further origin of pectoralis main muscle: A case report.OA Anatomy

For quotation functions:
Vallabhajosyula R, Babu CS. The bilateral further origin of pectoralis main muscle: A case report. OA Anatomy 2014 Jul 18;2(2):18.

Gross Anatomy

R Vallabhajosyula1*, CS Babu2


Authors affiliations

(1) Newcastle College Medication Malaysia, Nusajaya, Johor, Malaysia

(2) Sri Venkateswara Medical Faculty, Tirupati, Andhra Pradesh, India

* Corresponding creator E-mail:



Within the routine dissection of pectoral area of higher limb anatomy, an extra slip of pectoralis main was noticed. The origin of the additional slip was from
6[th] rib and the costal cartilage. The fibers
of the slip have been directed upwards and medially and joined with the deep fibers of pectoralis main and eventually inserted to the lateral lip of intertubercular sulcus. The nerve provide was much like that of pectoralis
main. Earlier research named the additional slip of pectoralis
main as costohumeralis, the place the origin was from the 6[th] rib and the costal cartilage. Nonetheless, the insertion of the additional slip was discovered to be variating.
In response to the literature overview, the slip runs both along with the pectoralis main or runs as a separate slip. Variations within the muscular fibers is probably not symptomatic however are of educational curiosity. If symptomatic could also be related
be altered kinetics of the joints which influences the actions of the joint or nerve entrapment.


Within the current examine, the additional origin of pectoralis main, was noticed to asymptomatic and couldn’t be related to any
medical utility, however is of educational curiosity.


Variations are fairly widespread in several areas of anatomy. Higher limb anatomy usually exhibits quite a few
variations as regards to brachial plexus or the person nerves, the place totally different nerves share the roots of origin. Though, muscular variations are much less widespread, experiences on additional
origin or poor origin of muscle and variable positions of insertion are being reported. The muscular variations, most of
time, are asymptomatic and generally are symptomatic. Symptomatic circumstances might affiliate with comfortable tissue tumors, that are troublesome to distinguish precisely. The pectoral muscle mass present extraordinarily uncommon muscular variations akin to chondroepitrochlearis, costoepitrochlearis or costohumeralis that extends from costal cartilage or from the ribs. The suitable insertion of those muscle mass was reported to be variable. The research which might be reported on these muscular variations indicated that the muscle could also be inserted to totally different components of the humerus akin to medial
epicondyle or medial inter muscular septa of the
humerus. Within the current case, we noticed a muscular slip that originated from 6[th] rib close to the costochondral junction, ran alongside the inferior margin of the pectoralis main, continued as anterior fold of axilla and received additional joined
with stomach fibers and eventually inserted as similar classical sample. These variations carry appreciable morphological significance. These muscular variations would be the analogs of pectoral muscle extensions in decrease mammals.

Case Report

Throughout the routine dissection schedule for 1[st] yr MBBS graduates, in a feminine cadaver of unknown age and medical historical past, which was obtained for the
educating and analysis work, the pores and skin, superficial fascia and deep fascia of pectoral area have been dissected as per the
tips of Cunningham’s guide of human anatomy. No particular pathological circumstances are noticed within the cadaver.
The pectoral fascia, which varieties the deep fascia of the pectoral area, was rigorously eliminated. Whereas observing the origin of the muscle, on left facet, 2.5 cm width muscle strip was recognized originating from the
6[th] rib. The size of muscle strip was 6 cm, continued with the inferior margin of pectoralis main. On the fitting facet, the size of muscle strip was 4 cm, width was 1cm. On the left facet, the muscle strip was thick and distinguished, whereas on the fitting, it was skinny and never distinguished.
On each the perimeters, the muscle strip was directed upward and backwards, continued alongside the inferior border of pectoralis main. On the inferior border, the fibers joined with stomach
fibers and inserted as the identical classical sample (Determine 1).

The examine doesn’t have any monetary assist from any group; nevertheless, there was consent from the administration to report the

{Photograph} displaying the additional origin of pectoralis main muscle. Arrows point out the fitting and left origin. The appropriate strip of muscle is skinny, the place because the left one is thick and distinguished.


The pectoral muscle mass, develop from primitive muscle mass, constituting, the higher limb, derived from
5[th] to 7[th] cervical myotomes, throughout 5[th] week of intra uterine life. A mixture of migration, fusion and apoptosis offers the ultimate form
[1]. It was opined that stomach origin of pectoralis main was thought-about as spinoff of panniculus carnosus. The stomach portion could also be fused with rectus abdominis or with exterior
indirect. Typically, a slip from pectoralis main extends
to biceps, pectoralis minor, coracoid course of, capsule of
the shoulder joint or the brachial fascia [2].
In 12-20% of the our bodies, a muscular strip, costoepitrochlearis, chondroepitrochlearis or chondrohumeralis has been described arising from a number of ribs, crosses the axilla, attaches to medial intermuscular septum or to the medial epicondyle of the humerus[3]. Data of those anatomical variations is of vital in
the surgical interventions of axillary and head and neck reconstructive surgical procedures[4]. Variability within the musculature sample within the pectoral area is reported in a number of the earlier research. The pectoralis main slip that originates from aponeurosis of exterior indirect abdominis
could also be generally absent. The costal attachments, the extent of clavicular half might fluctuate. Typically, the muscle mass on both facet might decussate and be a part of with the alternative or generally, the muscle
might type a steady sheet from rectus abdominis,
pectoralis main and sternocleidomastoid indicating the
sternalis muscle formation [5]. Within the current case, the origin was much like earlier reported variable observations which might be from the 6[th] rib and the costal cartilage, however the insertion was instantly with the
stomach fibers which additional inserted to lateral lip of intertubercular sulcus. Unilateral presence
of costohumeralis in a 66 yr previous male cadaver, which
originated from 6[th] rib, close to the
costochondral junction, coursed alongside the decrease border of
pectoralis main and received inserted to medial epicondyle of
humerus[6]. Unilateral presence of
epitrochlearis muscle was reported in a Indian cadaver[7]. Vasculaity and innervations in chondroepitrochlearis was additionally reported in a Indian cadaver[8]. Within the current examine, no variable vascular provide and nerve provide was noticed for the strip muscle. Compared with the earlier observations, the
distinction that was noticed was on the level of insertion, the place, the additional slip can referred to as as thoracohumeralis
muscular flap.


Familiarity on the anatomic variations of pectoral musculature is of utmost significance and to proceed for a definitive dissection aircraft throughout surgical procedure of chest wall. The variations
could also be advantageous for beauty reconstructive surgical procedures and radiological anatomy.


1- Carlson BM. Human embryology and developmental biology. Mosby, 2004. Pp 224-5.

2-Anson BJ. Morris’ Human Anatomy. Mc Graw-Hill. 1966. Pp. 478-9.

3- Bergman RA, Thomson SA,
Afifi AK, Miyauchi R. Compendium of Human Anatomic variations. City and Schwarzenberg, 1988. Pp. 7-8.

4-Rai R, Ranade
AV, Prabhu LV, Pai MM,
Nayak SR. Accent lateral pectoral nerves supplying the pectoralis main. Romanian Journal of Morphology and Embryology. 2008; 49 (4): 577-9.

5-Standring S. Grays
Anatomy. fortieth version. Elsevier Churchill-Livingstone, 2008. Pp. 808.

6-Rao TR, Shetty PC, Rao S. Further slip of pectoralis main muscle – the costohumeralis. Worldwide journal of Anatomical variations. 2009; 2:35-7.

7-Jaijesh P. Unilateral look of chondro-epitrochlearis muscle – a case report. Indian journal of cosmetic surgery. 2005; 38:

8-Samuel VP, Vollala VR. Uncommon pectoralis main muscle: The chondroepitrochlearis. Anatomical Science worldwide. 2008; 83:277-79.

Licensee to OAPL (UK) 2014. Inventive Commons Attribution License (CC-BY)

Click to comment

You must be logged in to post a comment Login

Leave a Reply

Most Popular

To Top