The diaphragm in man : a record of our present knowledge of its development, relationships, structure, and mode of action / by J.F. Halls Dally.
- Dally, John Frederick Halls, 1877-1944.
- Date:
- [1908?]
Licence: In copyright
Credit: The diaphragm in man : a record of our present knowledge of its development, relationships, structure, and mode of action / by J.F. Halls Dally. Source: Wellcome Collection.
Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.
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![margin of the central tendon is met by corresponding corn- ])ression-shrinkage which the liver undergoes when subjected to pressure between the diaphragm and the abdominal muscles. B.—As Compressor. One of the chief functions which the diaphragm performs is that of a compressor of the abdominal contents. Jloth functionally and morphologically the triangularis sterni, dia- phragm, transversalis abdominis, and levator ani are portions of one great compressor sheet, and, as such, are capable of acting in unison. The intra-abdominal pressure can be raised enormously by simultaneous contraction of these three latter muscles which in extraordinary expiration push up the dia- phragm. The diaphragm, acting downwards and forwards, causes a corresponding descent of the whole of the abdominal viscera, which is resisted by the corset-action of the transver- salis (Nature’s stays). Contraction of the transversales causes the organs in the upper part of the abdominal cavity to be pressed upwards, the viscera in the lower part of the abdominal cavity to be forced downwards, whilst those intermediate in position are subjected to direct backward pressure against the convex surface of the spinal column and to outward and back- ward pressure away from the middle line into the cavities of the posterior abdominal wall. The powerful downward thrust caused by active contraction of the transversales is opposed by the levatores ani, which, exercising forward traction upon the coccyx, at the same time lift the pelvic floor with the super- imposed pelvic contents, and thus lessen from below upwards the long diameter of the abdomino-pelvic cavity. The develop- ment of the powerful transversalis is directly due to the assumption of the upright position, for, although the homo- logues of the levator ani usually can be recognised, yet this muscle, as it exists in man and some primates, is not present in the lower mammals (®~). Thus combined action of the above muscles compresses the abdomino-pelvic viscera, aids in the evacuation of bladder and bowel, and influences the circulation of blood and lymph. C.—As Compressor and Tractor. Effects u'pon the Circulation of Blood and Lymph. The heart, pericardium, root of lung with the pulmonary vessels, and great vessels of the neck are all depressed by descent of the central tendon which is induced by the in-](https://iiif.wellcomecollection.org/image/b22419226_0034.jp2/full/800%2C/0/default.jpg)
