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.
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.
If you have already studied the ventral cavity, or front cavity of the body, then you will find studying the dorsal cavity, or back side 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: the cranial cavity and the spinal cavity, sometimes called the vertebral 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 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.
Next, Margie tells Sabrina about the diencephalon, which is the division below the cerebrum. There are two parts to the diencephalon. The upper portion of the diencephalon is the thalamus, and the lower part of the diencephalon 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 of the brainstem is the pons, and the bottom structure of the brainstem is the medulla oblongata.
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 they go 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 five 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.
The last things they cover that are located within the dorsal cavity are the membranes that surround the brain and spinal cord called the meninges. The meninges are tough and contain fluid to help protect and increase the function of the brain and spinal cord. There are three membranes that make up the meninges. Sabrina tells Margie that the innermost membrane of the meninges is the pia mater, the middle membrane of the meninges is the arachnoid mater, and the outermost membrane of the meninges is the dura mater.
Let's recap what we learned from Margie and Sabrina. The ventral cavity is the front cavity of the body, and the dorsal cavity is the back side of the body. There are two main cavities that make up the dorsal cavity: the cranial cavity and the spinal cavity.
The cranial cavity is the skull cavity of the head that houses the entire brain. The major divisions of the brain include:
- The cerebrum, which is the uppermost and largest division of the brain
- There are four lobes that make up this division of the cerebrum:
- Frontal lobe - top front of the cerebrum
- Parietal lobe - top middle of the cerebrum
- Occipital lobe - back of the cerebrum
- Temporal lobe - bottom of the cerebrum
- The diencephalon is the division below the cerebrum
- There are two structures of the diencephalon: the thalamus and the hypothalamus
- The thalamus is the upper structure of the diencephalon
- The hypothalamus is the lower structure of the diencephalon
- The cerebellum is the division under the back portion of the cerebrum
- The brainstem is the portion that hangs down from the brain
- There are three structures of the brainstem:
- Midbrain - uppermost structure of the brainstem
- Pons - middle structure of the brainstem
- Medulla oblongata - bottom structure of the brainstem
The spinal cavity is the cavity for the spinal cord. Divisions of the spinal cavity include:
- Cervical region - the top eight nerves in the neck area
- Thoracic region - the twelve nerves in the chest
- Lumbar region - the five nerves in the lower back
- Sacral region - the five nerves in the pelvis
The meninges are the membranes surrounding the brain and spinal cord. The innermost membrane is the meninges is the pia mater, the middle membrane of the meninges is the arachnoid mater, and the outermost membrane of the meninges is the dura mater.