DISSECTION OF THE ABDOMEN. 



SECTION III. 



Definition, 



and con- 

 tents. 



Dissection 

 to open 

 abdomen. 



Is largest 

 cavity in 

 the body. 



Boundaries 

 above and 



below, 



in front and 

 on sides. 



and behind. 



Depth is 

 altered by 

 action of 

 diaphragm 



levatores 

 ani, 



width by 

 muscles in 

 wall of 

 abdomen. 



How excreta 

 expelled. 



Division of 

 space. 



Abdomen 

 proper. 



Pelvis. 



Abdomen 

 proper here 



CAVITY OF THE ABDOMEN. 



The abdominal cavity comprises the abdomen proper and the pelvis, 

 and is the space included between the spinal column behind and 

 the muscles stretching from the thorax to the pelvis in front. It is 

 lined by a serous membrane (peritoneum), and contains the digestive, 

 urinary, and generative organs, with vessels and nerves. 



Dissection. To prepare the cavity for examination, the remainder 

 of the abdominal wall above the umbilicus is to be divided, along the 

 left side of the linea alba, as far as the ensiform process. The 

 resulting flaps may be thrown to the sides. 



Size and form. This cavity is the largest in the body. It is 

 ovoidal in form, with the ends upwards and downwards, so that it 

 measures more in the vertical than the transverse direction ; and it 

 is much wider above than below. 



Boundaries. Above it is limited by the diaphragm, below by the 

 recto-vesical fascia, the levatores ani muscles and by the other 

 structures closing the outlet of the pelvis. Both these boundaries are 

 concave towards the cavity, and are in part fleshy, so that the space 

 will be diminished by their contraction and flattening. 



In front and on the sides the parietes are partly osseous and 

 partly muscular ; thus, towards the upper and lower limits is the 

 bony framework of the skeleton, viz., the ribs in one direction and 

 the pelvis in the other ; but between these the wall is formed by 

 the broad muscles which have been examined already. 



Behind is placed the spinal column with the muscles contiguous 

 to it, viz., the psoas and the quadratus lumborum. 



Alterations in size. The dimensions of the cavity are influenced 

 by the varying conditions of the boundaries. Its depth is diminished 

 by the contraction and descent of the diaphragm, and the contrac- 

 tion and ascent of the levatores ani ; and the cavity is restored to 

 its former dimensions by the relaxation of those muscles. 



The width is lessened by the contraction of the abdominal muscles ; 

 but it is increased, during their relaxation, by the action of the 

 diaphragm forcing outwards the viscera. The greatest diminution 

 of the space is effected by the simultaneous contraction of all the 

 muscular boundaries, as in the expulsion of the excreta. 



Division of the space. As already intimated a division of the space 

 has been made into the ABDOMEN PROPER and the PELVIS. 



The ABDOMEN PROPER reaches from the diaphragm to the brim 

 of the pelvis, and lodges nearly the whole of the alimentary tube 

 and its appendages, together with the kidneys. 



The PELVIS is situate below the brim of the pelvis, and contains 

 chiefly the generative and urinary organs. 



The following description concerns the part of the cavity between 

 the diaphragm and the brim of the pelvis. After it has been 



