Dorsal Body Cavity: Definition, Organs & Membranes

Instructor: Adrianne Baron

Adrianne has taught high school and college biology and has a master's degree in cancer biology.

The dorsal cavity of the body is simpler than the ventral, but still detailed. We will discuss the dorsal cavity by looking at the organs, divisions, and membranes that make up this cavity.

Dorsal Cavity

Scientists realized a very long time ago that it is easier to study the body if they divide it up in different ways. One way they chose to divide the body is by cavities. There are two main cavities of the body.

The dorsal cavity is on the backside and the ventral is the belly side
Diagram showing the dorsal and ventral cavities

If you have already studied the ventral cavity, or front cavity of the body, then you will find studying the dorsal cavity, or backside of the body, much easier and much less involved. Let's follow Margie and Sabrina as they study the dorsal cavity.

Margie starts off discussing the fact that the dorsal cavity is divided up just like the ventral cavity was divided. There are two cavities within the dorsal cavity: cranial cavity and spinal cavity sometimes called the vertebral cavity.

Cranial Cavity

Sabrina explains that the cranial cavity is the skull cavity that houses the brain. The cranial cavity has four major divisions with a few subdivisions.

The cranial cavity is divided into 4 major divisions
Diagram of the divisions of the cranial cavity

The uppermost division of the brain is the cerebrum. This is by far the biggest division of the brain. Margie explains that there are four lobes that make up this division of the brain. The top front of the cerebrum is the frontal lobe, the top middle of the cerebrum is the parietal lobe, the back of the cerebrum is the occipital lobe and the bottom of the cerebrum is the temporal lobe.

Margie tells Sabrina that the next division is the one below the cerebrum called the diencephalon. There are two parts to the diencephalon. The upper portion of the diencephalon is the thalamus and the lower part is the hypothalamus. Sabrina thinks that is easy to remember since 'hypo-' means under.

Sabrina mentions that the next division is the one that is under the back portion of the cerebrum. That division is called the cerebellum. Margie tells Sabrina that it is probably the easiest one to remember since it is not divided into parts, regions or anything else.

They go on to the last division, which is the brainstem. The brainstem is the portion that hangs down from the brain. Sabrina tells Margie that she thinks of it the same way as a stem hanging down from a flower. That makes it easier to remember the brainstem's location. The brainstem is divided into three structures. The uppermost structure of the brainstem is the midbrain, the middle structure is the pons and the bottom structure is the medulla oblongata.

Spinal Cavity

Margie starts on the spinal cavity, which as its name suggests, is the cavity where we find the spinal cord. Sabrina admits that she used to think about the spinal cord as simply being one, long organ in the body, but now she is learning that there are divisions to the spinal cord and nerves that stem from the spinal cord.

The spinal cord is divided based on the nerves that come off of the spinal cord and what area of the body that goes into. There are four divisions of the spinal cord. The section of the spinal cord with the first eight nerves is called the cervical region. Margie tells Sabrina to just remember that cervical is the medical term for neck and this will help her to remember the location of the cervical region.

The next lower region is the thoracic region, which extends through the next twelve nerves below the cervical nerves. Sabrina chimes in that she can remember that too since she already learned that thoracic means chest. So, this is the chest region of the spinal cord.

The section of the spinal cord with the next 5 nerves below the thoracic region is the lumbar region. Margie remembers that lumbar means lower back, so she knows that this region of the spinal cord is the region located in the lower back area of the body.

Sabrina finishes the spinal cord divisions by telling that the section with the last five nerves located at the back of the pelvic area is the sacral region of the spinal cord. The best way Margie can think to remember this is by recalling that back area of the pelvis is called the sacrum.

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