Online Encyclopedia

Search over 40,000 articles from the original, classic Encyclopedia Britannica, 11th Edition.

MMMMM

Online Encyclopedia
Originally appearing in Volume V08, Page 167 of the 1911 Encyclopedia Britannica.
» Make a correction to this article.
» Add information or comments to this article.
Spread the word: del.icio.us del.icio.us it!

MMMMM ms ms nos _mom m ^u . Is.^...' . u less mom See also:

sus See also:ems nms See also:mow sm. A The fleshy See also:fibres on each See also:side of this opening See also:act as a sphincter. Passing between the xiphoid and costal origins in front are the See also:superior epigastric See also:arteries, while the other terminal branches of the See also:internal mammaries, the musculo-phrenics, pass through between two costal origins. Through the crura pass the splanchnic nerves, and in addition to these the See also:left crus is pierced by the vena azygos See also:minor. The sympathetic nerves usually enter the See also:abdomen behind the internal arcuate ligaments. 'The phrenic nerves, which are the See also:main See also:supply of the See also:diaphragm, See also:divide before reaching the muscle and See also:pierce it in a number of places to enter its abdominal See also:surface, but some of the See also:lower intercostal nerves assist in the supply. The last thoracic or subcostal nerves pass behind the See also:external arcuate See also:ligament. For the See also:action of the diaphragm see See also:RESPIRATORY See also:SYSTEM. See also:Embryology.--The diaphragm is at first See also:developed in the See also:neck region of the embryo, and this accounts for the phrenic nerves, which supply it, rising from the See also:fourth and fifth cervical. From the mesoderm on the caudal side of the pericardium is developed the septumtransversum, and in this the central tendon is formed. The fleshy portion is developed on each side in two parts, an anterior or sterno-costal which is derived from the See also:longitudinal neck musculature, probably the same layer front which the sternothyroid comes, and a See also:spinal See also:part which is a derivative of the transversalis See also:sheet of the See also:trunk.

Between these two parts is at one See also:

time a See also:gap, the spino-costal See also:hiatus, and this is obliterated by the growth of the pleuro-peritoneal membrane, which may occasionally fail to See also:close and so may See also:form the site of a phrenic See also:hernia. With the growth of the See also:body and the development of the lungs the diaphragm shifts its position until it becomes the septum between the thoracic and abdominal cavities. (See A. See also:Keith,"On the Development of the Diaphragm," Jour, of Anat. and Phys. vol. 39.) A. See also:Paterson has recorded cases in which the left See also:half of the diaphragm is wanting (Proceedings of the Anatomical Society of Gt. See also:Britain, See also:June 1900; Jour. of Anat. and Phys. vol. 34), and occasionally deficiencies are found elsewhere, especially in the sternal portion. For further details see See also:Quain's See also:Anatomy, vol. i. (See also:London, 1908). See also:Comparative Anatomy.—A See also:complete diaphragm, separating the thoracic from the abdominal parts of the coelom, is characteristic of the See also:Mammalia; it usually has the human structure and relations exceptthat belowthe Anthropoids it is separated from the pericardium by the azygous See also:lobe of the See also:lung. In some Mammals, e.g.

See also:

Echidna and Phocoena, it is entirely See also:muscular. In theCetacea it is remarkable for its obliquity; its vertebral See also:attachment is much nearer the tail than its sternal or ventral one; this allows a much larger lung space in the dorsal than in the ventral part of the See also:thorax, and may be concerned with the equipoise of the See also:animal. (See also:Otto See also:Muller, " Untersuchungen fiber See also:die Veranderung, welche die Respirationsorgane der Saugetiere durch die Anpassung an das Leben See also:im Wasser erlitten haben," fen. Zeitschr. f. Naturwiss., 1898, p. 93.) In the See also:Ungulata only one crus is found (Windle and See also:Parsons, " Muscles of the Ungulata," Proc. Zool. See also:Soc., 1903, p. 287). Below the Mammals incomplete partitions between the pleural and peritoneal cavities are found in Chelonians, Crocodiles and Birds, and also inAmphibians (Xenopus and Pipa). (F. G.

End of Article: MMMMM

Additional information and Comments

There are no comments yet for this article.
» Add information or comments to this article.
Please link directly to this article:
Highlight the code below, right click, and select "copy." Then paste it into your website, email, or other HTML.
Site content, images, and layout Copyright © 2006 - Net Industries, worldwide.
Do not copy, download, transfer, or otherwise replicate the site content in whole or in part.

Links to articles and home page are always encouraged.

[back]
MLL 		[next]
MNEMONICS (from Gr. /IvaoBat, remember; whence ,uvi...

Site © 2006 - Net Industries