Genitalia

Rectum

Topography

Sections

Rectum, radiography

F e m u r. C a p u t fem o ris

Ileu m

F e m u r, C o rp u s fe m o ris

Os pubis, Ramus inferior

Tuber ischiadicum

Canalis analis

Os sacrum

Colon sigmoideum

Ampulla recti

Os coccygis

------ M gluteus maximus

Fig. 1150

Rectum, Rectum;

The transitional zone between the anus and the rectum (arrow!

lateral radiograph in voluntary closure of the anus after filling

is located at the level of the tip of the coccyx (triangle],

with a contrast medium (defaecography).

The angle between the axes of the anus and the rectum (4J

is approximately 90° and depends upon the curvature of the

levator ani muscle (puborectal muscle). Scale in cm.

Femur, Corpus femoris

Os pubis, Ramus inferior

Tuber ischiadicum

x C a n a lis a n alis

Fig. 1151

Rectum, Rectum;

lateral radiograph of the defaecation after filling with a contrast

medium (defaecography).

In comparison to Fig. 1150, the anorectal transitional zone has

descended and the angle (4 ) increased to 137° due to the

relaxation of the curvature of the levator ani muscle. As the

bending acts like a valve, the elongation results in an unimpeded

pressure of the faeces on the anal canal leading to defaecation.