Sections, Planes, and Body Cavities

3D verses 2D

We can use the anatomical positionA standard reference position where the body stands upright, facing forward, with arms at the sides to visualize our patient from the outside of their body.  If we want to refer to internal structures, we must consider sections or planes of division. These are viewable with imaging techniques.  We need to understand the direction in which the body is divided. We also need to know what the resulting image would look like.  Consider a banana. Dividing it into top and bottom sections yields a completely different outline than a side-to-side cut. This helps us realize how planes of division can produce unexpected outlines.  In this class, it will be important for you to develop a mental 3D structure from looking at 2D pictures.  This is what radiologists do all day long!  For example, look at how diving a blood vessel. A blood vessel is basically just a tube. It can yield an oval or a circle. This depends on the plane through which it is cut.  Cutting the vessel longways produces a completely different impression than cutting it in a transverse or oblique section A cut or slice of the body or an organ for study..

Sagittal Sections

Sagittal sections Cut the body into left and right sections. The term sagittal comes from a crest that that runs right down the midline of your skull. Therefore amid sagittal section cuts the body into two perfectly equal right and left halves. Paris sagittal section divides the body into right and left halves However those two halves are not equal. In this class, we will most likely just say sagittal. You will need to determine if it is a mid or a pair of sagittal sections. Think of the outline that is produced from a sagittal section. It looks much like the outline of someone if you were viewing them from the side.

Frontal Sections

Frontal sections are also called Coronal sections. The word coronal means crown. Connecting your forehead to the rest of your skull is a suture called the coronal sutureRuns across top of skull between frontal and parietal bones (like a headband).. Frontal sections run along a coronal or frontalForehead bone; forms the front part of the skull and roof of the orbits. Smooth and curved. axisSecond cervical vertebra; has the odontoid process (dens) for pivoting head (“no” motion).. They divide the body into a front and back, also known as anteriorThe front of the body or toward the front when standing in the anatomical position. and posterior sections. The term coronal usually indicates two equal sections of division. In contrast, the term frontal often refers to two unequal sections of division. In our class we will most often use the term frontal. Think of the outline a frontal section can make. If a patient is standing in the anatomical position and you cut them into a frontal section,

Transverse Sections

Transverse sections cut the body into a superiorAbove or toward the upper part of the body. and inferiorBelow or toward the lower part of the body. section. These tend to be the most mystifying types of cuts for students.  These section usually depict organs with shapes that seem unrecognizable by students.  For example, you may visualize your kidneys by comparing them to a kidney bean’s shape.  But the shape of your kidney in a transverse section looks nothing like a kidney bean.  When we receive transverse sections from imaging such as an MRI or a CT, the image is shown from the bottom. It looks up, not from the top looking down.  Transverse sections also include a category called oblique sections which are just a slanted transverse section. 

Body Cavities

Anatomical directions help us refer to a patient’s body verbally. However, more specificity might be needed when referring to internal organs. For your squishy organs, we can use internal body cavities to refer to their general area.  You have these compartments in your body. Organs are encased in a sac, a membrane, or a fluid filled bubble within them.  The thoracic or chest cavity contains two bubbles. One contains the heart and is called the pericardiumThe membrane surrounding the heart.. The other contains the lungs and is called the pleuraThe double-layered membrane surrounding the lungs and lining the thoracic cavity..  The thoracic cavityThe body cavity housing the heart and lungs. is separated from the more inferior abdominal cavityThe body cavity containing the stomach, intestines, liver, and other digestive organs. by the diaphragm, the parachute muscle used in inhalation.

The abdominal cavity and your digestive organs are contained by the peritoneumThe membrane lining the abdominal cavity and organs. whereas your pelvic organs have their own covering.  Some people prefer to consider the abdominal and pelvic cavities separately, some don’t.  The additional cavity can sometimes be called the dorsalRelating to the back side of the body. cavity. It is the sac containing your brain and spinal cordThe central nervous system structure that relays signals between the brain and body..  This sac completely separates your central nervous systemComposed of the brain and spinal cord; integrates and processes information.  (the brain and spinal cord) from other tissues.  A spinal tapA procedure to collect cerebrospinal fluid from the subarachnoid space. is necessary to see the fluids surrounding your brain. This cannot be done with a blood draw.

Imaging Techniques

Many of us are very familiar with imaging techniques from our own experiences as a patient with health care. People are usually very familiar with X-rays that are excellent in looking at solid structures within the body. This dental X-ray is excellent for looking at the teeth embedded in the maxillaUpper jaw bones; form upper teeth sockets, hard palate front, and parts of the nose and orbit. and mandibleLower jawbone; only movable bone of the skull; U-shaped and largest facial bone.. MRI and CT scans are often confused with each other. Both provide similar resolution or sharpness in viewing the soft mushy structures of the body. One of the big differences between an MRI and a CT scan is the amount of radiation received in either. With an MRI there is none. With a CT scan there’s about a third of the radiation that you should receive in one full year. Spiral scans are special methods for taking CT images. They are usually used to image areas with a high surface area, like the lungs. PET scans are usually combined with CT scans. The PET portion uses a radioactive dye. This dye helps radiologists visualize very specific structures.

Other Techniques

These techniques are used to internally image body parts.  Pictures are taken from an internal vantage point.  An echocardiogram is usually taken from within the esophagusThe muscular tube that transports food from the pharynx to the stomach via peristalsis. and is effective at visualizing the heart muscle.  An angiogram is a visualization of the coronary vessels that lie on the superficialNear the surface of the body. aspect of the heart.  Endoscopies and colonoscopies are both used to visualize the digestive system, just from different ends.  A colposcopy visualizes the lining of the uterusThe muscular organ where a fertilized egg implants and develops. and/or cervix and an angiogram shows us the routes of blood vessels.