Abdominopelvic Cavity: Bony Landmarks, Organs & Regions

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  • 0:00 What is the…
  • 2:12 The Nine Regions
  • 4:29 Lesson Summary
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Lesson Transcript
Instructor: Sarah Phenix
In this lesson, we'll explore the abdominopelvic cavity. We'll learn what it is, where it is, and what it houses. Also, we'll learn about the location of the nine regions that make up the abdominopelvic cavity and the organs within each one.

What is the Abdominopelvic Cavity?

Have you ever played the board game Operation, where you use an instrument to remove organs from a 'patient' without touching the side of the cavities they sit it? Unlike the game, our organs do not lie in individual little cavities. There are three major organ cavities: our cranial cavity, housing our brain; our thoracic cavity, housing our heart and lungs; and our abdominopelvic cavity, housing everything else. So, what does this mean? Well, let's take a look.

The abdominopelvic cavity is separated from the thoracic cavity by our diaphragm muscle. The purpose of this muscle is more than just a mere divider. It helps maintain the pressure gradient in our thoracic cavity, which eases the work required by the lungs as they draw air into the body. The back of the cavity is framed by our spinal cord, while the front is cinched together by a series of muscles that envelope our organs and ensures they sit nice and tight in our bodies.

The rectus abdominis (also known as the 6-pack muscles) runs from the base of the sternum to the crest of the pelvic pubis bone, keeping our abdomens tight from top to bottom. Our 'girdle-like' transverse abdominis muscle transects our bodies around the waist to keep our organs laterally nestled together. Then a set of internal and external oblique muscles criss-cross our sides, from top to bottom by connecting our ribs down to the pelvis and the sides of the rectus abdominis.

Our pelvic bones form the lower boundaries of our abdominopelvic cavity. Like an ice cream cone, it cups our organs, some of which sit on top of the cone while others funnel down into our pelvic opening. Did you know that our pelvis is actually formed by three different bones fused together? Our ilium is the upper-most blade-like bone that forms the frontal protrusions called hip bones. The ischium is the lower, posterior butt bone, while the pubis is the lower anterior bone. The sacrum is the bottom portion of our spinal vertebrae and is fused with the ilium, that essentially holds the top part of our skeleton with the lower limb portion.

The Nine Regions

As mentioned above, your abdominopelvic cavity houses all of your organs other than your brain, heart, and lungs. The liver, gallbladder, kidneys, spleen, pancreas, stomach, small intestines, large intestines, bladder, and internal reproductive organs are all contained in this region. For the sake of illness and pain assessment, doctors have divided the abdomen into nine functional areas to aid in localizing the discussion of pain and illness as the abdominopelvic cavity is quite large.

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