Talk:Paper - Two anomalies in the construction of the diaphragm (1924)

From Embryology


By FRANCIS R. GUINANE Demonstrator of Anatomy, University of Adelaide

"Tue two examples of anomalous disposition of the muscular fibres of the diaphragm described here were noted during the present session in the dissecting room of this department. The main abnormalities affect the crura in both cases, but in both examples there are associated anomalies which are, from a practical point of view, of more importance than the mere crural variations themselves.

Case 1. Male, aet. 70. .

In this subject the oesophagus and the aorta apparently entered the abdomen by a common opening, the oesophagus lying directly anterior to and upon the aorta. The central tendon extended farther posteriorly than usual, so that the anterior edge of the common opening was mainly tendinous, ’ the anterior decussation being represented by only a few sparse fibres derived from the right crus.

The posterior decussation, which usually separates the oesophageal and the aortic openings, took place upon the anterior surface of the aorta at the level of the first lumbar vertebra, some two inches lower than is usual. Both crura were of approximately equal bulk, and each took an equal share in the formation of the posterior decussation, which was shaped like a flat X upon the aorta. (The right crus contribution was perhaps a little larger than that of the left crus, but the disproportion was not so great as is represented in fig. 1.)

The crura continued wholly muscular to the level of the second lumbar vertebra, and were finally inserted into the anterior common ligament on the anterior surfaces of the bodies of the second and third lumbar vertebrae and the intervening intervertebral disc.

The decussating fibres did not gain insertion with the main parts of their respective crura—instead each became tendinous, and, lying upon the surface of the psoas muscle, picked up another tendinous slip from that muscle immediately distal to the internal arcuate ligament. This formed a Y-shaped band of tendon which at the level of the third lumbar vertebra became continuous with the superficial fibres of the psoas. On the right side only this tendon gave in addition a long tendinous slip, which passed superficially to the fibres of insertion of the main crus, and was inserted into the anterior

6—2 84 F. R. Guinane

common ligament on the anterior surface of the body of the fourth lumbar vertebra.

It is perhaps worthy of note that the coeliac axis artery arose from the aorta below the lower limit of the decussation, and that all the abdominal arteries arose at a lower level than usual. It is evident therefore that the true aortic opening was at the level of the first lumbar vertebra, and that the portion of the aorta visible from the abdomen above the muscular fibres of the posterior decussation, was in reality the lowest portion of the thoracic aorta, and not the upper part of the abdominal aorta.

Fig. 1. Condition of the Crura in Case 1.

It is evident that in this case the abnormally low position of the posterior decussation has brought the aortic opening proper to an unusually low level. The oesophagus therefore, which appears to enter the abdomen by a common orifice with the aorta, is not really in contact with the abdominal aorta, but with an abnormally placed portion of the thoracic aorta.

Case 2. Male, aet. 88.

In this case the muscular separation between the oesophageal and the aortic openings was composed wholly of fibres derived from the right crus. The left crus was insignificant and was confined entirely to the left side. From the posterior edge of the central tendon, on the left side of the oesophageal opening, a rounded cord of muscular fibres, about half-an-inch by an inch in section, passed between the oesophagus and the aorta to join the upper fibres Two Anomalies in the Construction of the Diaphragm 85

of the right crus on the right side of the aorta. The right crus, which was unusually thick and fleshy, was inserted by a short, thick, twisted mass of tendinous fibres into the anterior common ligament on the anterior surface of the body of the third lumbar vertebra. The left crus, much smaller than the right, gained insertion to the anterior surface of the upper border of the second lumbar vertebra.

This interesting variation was accompanied by a further deficiency of the left half of the diaphragm. A semicircular gap of about two inches radius was left in the posterior abdominal] wall above the last rib and the site of the




Fig. 2. Condition of the Crura in Case 2.

external arcuate ligament, which was absent on this side. Muscular fibres were inserted normally on to the internal arcuate ligament, and then arched over to be inserted to the eleventh and twelfth ribs, leaving a semicircular gap lined only by pleura. Directly attached to this “abdominal” layer of the parietal pleura was extra-peritoneal fatty tissue (the so-called “transversalis fascia’”’), Owing to the post-mortem shrinking of the formalin-hardened lungs, the eleventh and twelfth ribs were plainly visible from the abdomen through both layers of the parietal pleura.

The enlarged right crus was pierced by the right renal artery. This vessel arose at a higher level than its fellow of the opposite side and for about an inch was entirely covered by the muscular fibres of the crus. The left renal artery arose at its normal level and passed in front of the small portion of tendon of the left crus which extended to the body of the second lumbar

vertebra. 86 F. R. Guinane

This case therefore appears to be an example of a congenital deficiency of the left side of the diaphragm, which manifested itself by an actual gap in the musculature of the left cupola and in an incomplete development of the left crus. The deficiency in the left side was partly compensated for by an hypertrophy of the diaphragmatic element derived from the right crus. It is rather remarkable that despite the large gap in the musculature of the left cupola, there was no suggestion of visceral displacement: the deficiency had not been accompanied by any hernia.

Figs. 1 and 2 which illustrate this paper have been drawn for the author by Dr Wood Jones, Elder Professor of Anatomy in the University of Adelaide.