ABDOMINAL CAVITY 



427 



UMBILICUS) 



posterior surface of the anterior abdominal wall, taking with 

 it a fold of peritoneum termed the falciform ligament of the 

 liver. 



Shape and Boundaries of the Abdominal Cavity. The 

 abdominal cavity is ovoid in shape, its vertical diameter 

 being the longest. Superiorly, it is roofed by the dome- 

 shaped diaphragm, which presents a deep concavity towards 

 the abdomen. Inferiorly, it is floored by the pelvic 

 diaphragm, formed by 

 the levatores ani and 

 the coccygei muscles, 

 which is also concave 

 towards the abdominal 

 cavity. Neither the 

 roof nor the floor is 

 complete and unbroken. 

 The diaphragm is per- 

 forated by certain struc- 

 tures which pass between 

 the thorax and the ab- 

 domen. The continuity 

 of the pelvic diaphragm 

 is broken by the passage 

 of certain structures be- 

 tween the pelvic division 

 of the abdominal cavity 

 and the perineum. The 

 upper part of the ab- 

 dominal cavity extends 

 upwards for a consider- 

 able distance Under the FlG " '6o.-Outline of the Abdominal Cavity 

 , ., as se.en in medial section. The planes of 



Shelter Ot the lower ribs subdivision are indicated by dotted lines. 

 and their costal cartil- 

 ages. The protection which is thus afforded to the viscera in 

 this portion of the cavity is most complete laterally and behind. 

 In front, as the costal cartilages ascend towards the sternum, a 

 wide A-shaped gap is left between those of opposite sides. The 

 level to which the costal arches descend on either side varies 

 greatly in different subjects, but, in the great majority of cases, 

 a narrow belt of abdominal wall, from one to two inches 

 wide, is left between the lower border of the chest wall and 

 the highest point of the iliac crest. This receives no skeletal 



NTERTUBERCULAR 

 PLANE 



LINE 



OF 

 PELVIC BRIM 



