For their anterior three-fourths the
corpora cavernosa penis lie in intimate apposition with one another, but behind they diverge in the form of two tapering processes, known as the crura, which are firmly connected to the ischial rami.
Traced from behind forward, each crus begins by a blunt-pointed process in front of the
tuberosity of the ischium
The ischial tuberosity (or tuberosity of the ischium, tuber ischiadicum), also known colloquially as the sit bones or sitz bones, or as a pair the sitting bones, is a large swelling posteriorly on the superior ramus of the ischium. It marks ...
, along the perineal surface of the conjoined (ischiopubic) ramus.
Just before it meets its fellow it presents a slight enlargement, named by
Georg Ludwig Kobelt (1804–1857) the
bulb of the corpus cavernosum penis.
Beyond this point the crus undergoes a constriction and merges into the corpus cavernosum proper, which retains a uniform diameter to its anterior end.
Additional images
File:Gray1142.png, Male urethra.
References
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Mammal male reproductive system
Human penis anatomy