Without its organs, your body is nothing but a collection of empty spaces called cavities. There are two major cavity regions with their own unique subdivisions, and they'll be defined here.
What's a fireplace that's not filled with logs, or a fridge that's not filled with food, but a cavity? It's just empty space waiting to be filled with something.
If you could extract the organs of your body, you'd find that it, too, has many cavities that were once filled with one organ or another. A cavity, in our lesson's context, is a hollow space within the body. How about we go over the major ones?
The Dorsal Cavity
The dorsal cavity is one of the two largest body cavities, located at the posterior aspect of the body. By posterior, I mean that it runs along the back of the body.
It's called dorsal, because dorsal is a term for the back of an animal, including a human. Sort of like dorsal fins are found along a fish's or dolphin's back.
This dorsal body cavity is, itself, composed of two different cavities. One is known as the cranial cavity, and it's a cavity located within the skull. Cranial comes from cranium, which refers to the bones encasing the brain. It's a brain case!
So if, like the ancient Egyptians, you could extract the brain through the nose, you'd be left with nothing but an empty space inside the cranium, the cranial cavity. The other constituent of the dorsal cavity is the spinal (vertebral) cavity, which is the vertebral canal, the space located within the spinal (vertebral) column that houses the spinal cord.
The Ventral Cavity
The other major body cavity is called the ventral cavity, and it's the cavity located along the anterior aspect of the body. Ventral is a word that refers to the abdomen or belly of the animal, which is obviously, in humans, at the front (anterior) part of the body. It's the opposite of dorsal. Like the dorsal cavity, the ventral cavity can be broken apart into smaller cavities.
The thoracic cavity is the chest cavity. The term thoracic comes from thorax, which is just another word for chest. (Remember, thorax sounds like Lorax, the character who speaks for the trees.) Your speaking voice is made possible, in part, thanks to the lungs, located in the thorax. The chest also contains the heart, of course.
Breathing and speaking is also made possible thanks to a big muscle called the diaphragm, which separates the thoracic cavity from the abdominal cavity, the body cavity that houses the organs of digestion (such as the stomach and intestines), the liver, spleen, and kidneys, among others. The abdominal cavity is sometimes simply referred to as the abdomen.
Another important division of the ventral cavity is the pelvic cavity, the space formed by the hipbones, which contains the organs of reproduction and the bladder. Unlike the division between the thoracic cavity and abdominal cavity, there is no clear division between the abdominal and pelvic cavity. This is why they are sometimes referred to as a single unit, the abdominopelvic cavity.
Let's clearly divide up our body into its major cavities one more time.
A cavity is a hollow space within the body. The first overarching body cavity is the dorsal cavity, one of the two largest body cavities, located at the posterior aspect of the body. Remember that posterior means along the back of the body. It is subdivided into the cranial cavity, a cavity located within the skull, and the spinal cavity, the vertebral canal, the space located within the spinal (vertebral) column that houses the spinal cord.
The other major body cavity is the ventral cavity, the cavity located along the anterior aspect of the body. Anterior, of course, means along the front of the body. It is broken mainly into the thoracic cavity, which is just the chest cavity, the abdominal cavity, the body cavity that houses the organs of digestion (such as the stomach and intestines), the liver, spleen, and kidneys and the pelvic cavity, the space formed by the hipbones.
When this lesson on major body cavities ends, you can expect to be able to:
- Define body cavity
- Detail what a dorsal cavity is
- Highlight the cranial and spinal cavities
- Locate the ventral cavity
- Break down the main cavities: thoracic, abdominal and pelvic