In Depth: Pelvis
The pelvic region is the area between the trunk — or main body — and the lower extremities, or legs.
The male pelvis is different from a female’s. The pelvic bones are smaller and narrower. Evolutionary scientists believe this stems from man’s hunter roots, as a leaner pelvis made running easier.
The bones of the pelvis are the hip bones, sacrum, and coccyx. Each hip bone contains three bones — the ilium, ischium, and pubis — that fuse together as we grow older. The sacrum, five fused vertebral bones, joins the pelvis between the crests of the ilium. Below the sacrum is the coccyx, or tailbone, a section of fused bone that is the end of the vertebral column. The pelvis forms the base of the spine as well as the socket of the hip joint.
The hip joint is a ball-and-socket joint created by the femur and a part of the pelvis called the acetabulum. This joint and its ability to rotate in many angles is one of many pieces of anatomy that allows humans to walk.
The external male genitals include the penis, scrotum, and testicles. The testicles produce sperm cells and the hormone testosterone. The scrotum is a pouch-like sac that hangs below the penis, between the thighs. It pulls the testicles closer to the body to protect them against cold temperatures and potential injury.
The penis is the primary male sexual organ. This tube-shaped, muscular organ fills with blood and becomes firm when a man is sexually aroused. At the point of sexual climax, a healthy penis will ejaculate semen, a mixture of spermatozoa and other fluids that help nourish the sperm and transport it to the female reproductive system for procreation. The penis also holds the urethra, the opening through which urine is expelled from the body.
The pelvic region also contains several digestive organs. These include the large intestine and small intestine. Both are vital to digesting and expelling solid waste. The large intestine ends in the rear of the pelvis at the anus, a sphincter muscle that controls the disposal of solid waste. The intestines are supported by a series of muscles known as the pelvic floor. These muscles also help the function of the anus.