Pelvis

From ArticleWorld

The pelvis is a complex combination of bones that forms the base of the human trunk. It is connected to the rest of the body by articulation with the spinal column and is the structure that forms the attachment of the legs to the trunk.

Bony Anatomy

The pelvis is made from the bony fusion of three paired bones that together make the pelvis symmetrical. The broad flat upper aspect of the rear of the pelvis is the ilium. The pubis bone forms the upper half of a loop-like structure that allows for the passage of nerves and blood supply to the leg. The lower half of the loop is formed by the ischium.

The two halves of the pelvis are connected in the front by means of the pubic symphysis, a connective tissue “joint”. Posteriorly, the ilium connects to the sacrum. The result is a wide basin-like structure with a large hole in the base where the pelvic structures reside. It is through that large hole that a fetus passes in childbirth. The female pelvis is shallower, wider and had a more rounded opening at the base which makes it more suited to giving birth.

The inferior lateral aspect of the pelvis on each side has a depression that forms the articular socket or acetabulum for the femur to connect with. Multiple ligaments in the area allow for stability of the joint.

Function

Besides providing solid protection for the pelvic organs, the pelvis functions as an anchoring point for multiple muscles. The rectus abdominis muscle that runs the length of the abdomen attaches along the front of the pelvis. The abductor, adductor, flexion and extension muscles of the upper leg are all connected to the pelvis.

The pelvis also provides room for the blood vessels and some of the nerves to pass through it and to travel down the leg. The sciatic nerve actually passes over the back of the pelvis in a depression called the sciatic notch. This is where the sciatic nerve can become inflamed.

Conditions

The pelvic structure is generally quite solid. In severe injuries or in the elderly, however, the pelvis can become fractured. The most common sites of fracture are the inferior and superior rami, the parts of the pelvis that form the two lateral rings. In childbirth, the pelvis generally widens to allow for the passage of the infant. In some cases, however, the pubic symphysis can dislocate in later pregnancy or in those who have been pregnant more than once. This makes for very difficult ambulation until the infant is born.