The American cyclopedia of practical medicine and surgery: a digest of medical literature (Volume 1).

  • Hays, Isaac, 1796-1879.
Date:
1834-1836
Catalogue details

Licence: Public Domain Mark

Credit: The American cyclopedia of practical medicine and surgery: a digest of medical literature (Volume 1). Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

    17/572
    siderable support to those organs, and con- tribute to fortify those points at which they are most liable to be protruded. This lozenge-like stratum is attached posteriorly, on each side, to the transverse processes of the lumbar vertebrae; superi- orly, to the lower ribs and the ensiform cartilage of the sternum; inferiorly and laterally, to the crista of the ilium and Poupart's ligament, and upon the median line to the spine and symphisis pubis. It is composed, besides the structures which have been enumerated, of five pairs of muscles and their aponeuroses, three of which are broad and expanded, while the other two are narrow and of more limited extent. The three first are spread out upon the whole extent of the region, on each side, and unite by their aponeuroses upon the median line of the abdomen : the two last are placed in a vertical direction on each side of that line, one of them ex- tending from the pubis to the sternum and ribs; the other, merely from the former point to about one third the distance to the umbilicus, where it terminates in the linea alba. (See Muscles). The thin broad muscles, consisting of the external and internal oblique, and the transversales, form a thick and strong stra- tum, partly fleshy, and partly aponeurotic, which not only affords a powerful support to the abdominal organs, but also acts upon them with great energy in the execution of different functions. At the extreme posterior part, two of these muscles, the internal oblique and transversalis, present a strong aponeurosis by which they are at- tached to the transverse processes of the lumbar vertebrae, between the layers of which are included the spinal and quad- ratus lumborum muscles. This region of the abdomen is therefore so well fortified, that a protrusion of the organs cannot take place, except in consequence of some de- fect of the arrangement. Anterior to this point, the three muscles in question form a thick fleshy stratum, composed of three layers, the fibres of which pursue different directions, those of the external oblique running downwards and forwards, those of the internal upwards and forwards, while those of the transversalis are ranged nearly horizontally. The extent of this fleshy portion varies in the different mus- cles ; in all of them, however, it is ter- minated anteriorly in a strong expanded aponeurosis, which closes up the whole ex- tent of the anterior portion of the abdomen, from the sternum to the pubis and Poupart's ligament, and from the fleshy portion of the muscle, on one side, to their corre- sponding portion on the other. The de- cussation of the fleshy fibres, while it in- creases the strength of the walls of the abdomen where it exists, enables the mus- cles to act to greater advantage in depress- ing the ribs, elevating the pelvis, narrow- ing the capacity of the cavity of the ab- domen, and supporting and compressing its various organs. It is principally in virtue of the ready contraction and relaxation of this fleshy portion of the muscles, that the walls of the abdomen are enabled to ac- commodate themselves to the distension or vacuity of the viscera, and to impress upon them that influence which is requisite in the performance of some of their functions. The tendinous, or aponeurotic portion just alluded to, is composed, on each side of the median line, of four strong layers, between two of which are placed the recti and pyramidal muscles, which are thus furnished with a strong sheath, by which they are firmly maintained in their situa- tion, and at the same time have their power very much increased. The aponeurosis of the external oblique comes off from the fleshy portion of the muscle, in the direc- tion of a curved line which extends from the inferior margin of the cartilages of the ribs, to the anterior superior spinous pro- cess of the ilium. It is strong, and is composed of conspicuous fibres of a pearly lustre, which are closely bound together by other fibres, which intersect them at oblique angles. Beneath this, we come to the tendon of the internal oblique, which is also strong, but which is divided into an anterior and a posterior layer, the first passing with the aponeurosis of the exter- nal oblique in front of the rectus, to form the anterior portion of the sheath; while the second glides behind that muscle, in company with the aponeurosis of the trans- versalis, to form the posterior portion of the same sheath. Midway between the umbilicus and the pubis, however, all these layers pass in front of the rectus muscle, so that from that point to the symphisis pubis, the posterior portion of the sheath is deficient, or is merely supplied by the fas- cia transversalis and the peritonaeum. The aponeurosis of the three muscles of each side finally meet upon the median line of the abdomen, where an intricate interlace- ment of their fibres takes place, by which a compact, resistant, white line or band is formed, which extends from the ensiform cartilage of the sternum to the pubis. This narrow band, generally denominated linea alba, is perforated towards its inferior third by the umbilicus already described, which in the adult forms a firm compact cicatrix.