THE ABDOMEN 689 



ABDOMINAL CAVITY. 



The abdominal cavity is somewhat ovoid, the vertical measm^e- 

 ment greatly exceeding the transverse. Its superior boundary is 

 formed by the diaphragm, which here presents a concave surface. 

 The inferior boundary is formed by the levatores ani and coccygei 

 muscles, covered superiorly by the visceral pelvic fascia and inferiorly 

 by the anal fascia. This boundary is concave on its upper aspect. 

 The superior and inferior boundaries, being fleshy, are capable of con- 

 tracting and relaxing alternately. During contraction the diaphragm 

 descends on each side, and the levatores ani ascend, thus diminishing 

 the vertical measurement of the cavity. During relaxation the 

 reverse takes place, the diaphragm ascending and the levatores ani 

 descending, and so the cavity is increased in its vertical measure- 

 ment. The anterior and lateral boundaries are partly osseous and 

 partly musculo-aponeurotic. The osseous boundaries are formed by 

 the lower ribs above, and the pelvis below. Elsewhere these boun- 

 daries are formed by the musculo-aponeurotic planes of the abdominal 

 muscles. The posterior boimdary is formed by the bodies and 

 discs of the lumbar vertebrse, psoas magnus and quadratus lum- 

 borum muscles with their fascial investments, sacrum, and coccyx. 

 The cavity is divided into two regions, the abdomen proper and the 

 pelvis. The abdomen proper is limited below by the brim of the 

 pelvis, and its visceral contents are the abdominal portion of the 

 alimentary canal, with the exception of the pelvic colon and rectum, 

 the liver, pancreas, spleen, kidneys, and suprarenal bodies. The 

 pelvis is situated below the level of the brim, and contains the 

 pelvic colon, rectum, and internal uro-genital organs. 



Abdomen Proper. 



Division into Regions. — The abdomen proper is divided into .nine 

 regions by means of two horizontal and two vertical lines, with their 

 corresponding planes. The horizontal lines are called subcostal 

 and intertubercular. The subcostal line encircles the abdomen 

 proper on a level with the lowest parts of the tenth costal cartilages, 

 and the plane corresponding to it is called the subcostal plane. 

 The intertubercular line connects the highest points of the iliac 

 crests which can be felt from the front, where there is usually a 

 tubercle on the outer lip about 3 inches from the anterior superior 

 iliac spine. The plane corresponding to this line is called the 

 intertubercular plane. The vertical lines are called the Poupart 

 lines, right and left, and each extends vertically upwards from the 

 centre of Poupart's ligament. The planes corresponding to these 

 lines are known as the Poupart planes. The subcostal and inter- 

 tubercular lines, with their corresponding planes, map out the 

 abdomen proper into three horizontal zones, called subcostal, 

 umbilical, and hypogastric. The two Poupart lines, with their 



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