22 Bony Pelvis – Male and Female

The Pelvis:

Like the foundation of a building, the pelvis is the load-bearing structure of the body which keeps humans upright. The hip or pelvis is composed of 3 bones that form a ring-like structure which supports the weight of the upper body and provides attachment points for the lower limbs. The pelvis also helps protect the reproductive organs and other visceral peritoneum.

The pelvis is made of 3 other bones fused together:

• Ilium: The largest bone which forms the acetabulum, the socket head for the head of the femur. The superior part of the ilium forms the iliac crest which ends anteriorly forming the anterior superior iliac spine
• Ischium: The ischium is the inferior and posterior part of the pelvis which connects with the pubis to form the obturator foramen – an opening through which vasculature and nerves flow
• Pubis: The anterior and inferior part of the pelvis, which fuses together with each other to form the pubic symphysis.

The sacrum is a fusion of 5 sacral vertebrae (S1-S5), positioned at the posterior end of the pelvis, the two ilium. View the diagram below to get a visual representation of the hip bone and pelvic structure:

Pelvic Foramina:

The pelvic bones –mentioned above – can come together to form several openings known as foramen:

 figure x. Anterior View; Bony Pelvis foramen

• The Greater Sciatic Foramen (red arrow) is situated between the ilium and ischium formed by the sacrospinous ligament allowing the sciatic nerve – the largest nerve in the body – to pass from the pelvis to the gluteal region and down the leg.
• The Lesser Sciatic Foramen (green arrow) located just below the greater sciatic foramen allows the passage of the pudendal nerve, and internal pudendal vessels.
• The Obturator Foramen (blue arrow) is the largest foramen in the body located between the pubis and ischium covered by the obturator membrane allowing the obturator nerve, artery and vein to pass through into the thigh.

Pelvic Brim (Pelvic inlet):

The pelvic brim forms the upper opening into the pelvic cavity and divides the true pelvis (above the brim) from the false pelvis (below the brim).

The pelvic brim is the circular shaped ring surrounding the top end of the sacrum, the ilium, pubis and the pubic symphysis.

The false pelvis is located above the pelvic brim. Without the false pelvis your internal organs would have no inferior support and fall.

The true pelvis is located below the pelvic brim. It encloses the pelvic cavity and contains the pelvic organs. The true pelvis forms the bony passage from which the baby descends during delivery.

 figure x. Anterior View; True and False Pelvis

Pelvic Sexual Dimorphism:

While both male and female pelvises share the same bones and basic structure, there are several key differences which differentiate males from females, such as shape, bone density and other features.

Check out this meme!

Hint: This meme is referencing the fact that many perceive pelvic anatomy to be complicated, while the bony pelvis is composed of only three bones. Looks like those assumptions don’t have a leg to stand on!