Bones of the Pelvis: Definition and Function

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  • 0:05 Pretzels and Hips
  • 0:50 The Ilium, Ischium, and Pubis
  • 1:45 The Sacrum
  • 2:14 The Pelvic Cavity
  • 2:44 The Acetabulum
  • 3:07 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

In this lesson, you will learn about your hips and the important structures involved in their formation. The ilium, ischium, pubis, acetabulum, pelvic cavity, and sacrum will all be covered.

Pretzels and Hips

My hips don't lie around much. I like to get moving and be active. This is really good in a sense but can also be dangerous if I were to do something that causes a fracture to my pelvis, the structure that does things like protecting my bladder and joining to my spine and legs to provide stability within my body.

The pelvis is like a hard pretzel; it is usually not possible to fracture it in only one spot.
Pelvis Fractures

The reason that even one fracture in the pelvis is really bad is because your pelvis, which the hips are a part of, are like a hard pretzel. Go ahead and try breaking a hard pretzel in one spot without having it crack in another. It's not possible! Likewise, a fracture of the pelvic ring usually leads to an automatic fracture, free of charge, in another spot.

The Ilium, Ischium, and Pubis

Your hip bones are made of paired bones, one on either side of your body, called the ilium, ischium, and pubis. The ilium is the largest and uppermost bone of the pelvis and accounts for the width of your pelvis. This is the bone on which you actually place your hands when you place your hands on your hips.

The ischium is at the very bottom of the pelvis, and when you sit, the weight of your body falls onto this part of the pelvis. So, if you ever sit in someone's lap and they say you have a bony ol' behind, it's because the ischium is digging into the other person's leg!

Finally, the pubis, or pubic bone, is at the bottom and front of your pelvis in your pubic area and helps to connect the two hip bones at the front of your body at a location called the pubic symphysis.

The arrow points to the pubis bone at the bottom and front of the pelvis.

The Sacrum

The hip bones also unite together at the back of the pelvis thanks to an axial skeletal structure called the sacrum, which is a bone composed by a fusion of five vertebrae that connects the two hip bones and forms the back, or posterior, portion of the pelvis. The sacrum, along with the coccyx, or tailbone, which attaches to the sacrum, are not only part of the pelvis but also make up the pelvic portion of your lower spine.

The Pelvic Cavity

The parts of your pelvis, including the sacrum, coccyx, and the three bones which make up your hips, combine together to form a cavity formed by the bones of the pelvis that we call the pelvic cavity. If it wasn't for this space, you would've never been born because it is here where the birth canal passes through! In addition, the bones surrounding the pelvic cavity form a ring around it, called the pelvic ring, that often breaks in more than one spot if fractured.

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