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Anatomy Terms

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Anatomy Terms


 Anatomic terms describe the directions within the body as well as the body’s reference planes, cavities and regions.There are many times in medicine that a doctor has to record information in a medical record or tell another doctor the exact body part or location of disorders or damage to your body or an organ. To do that, there are standard terms for describing human anatomy including the body and it’s organs. The terms used to describe locations and positions reference a person in the standard anatomical position. The standard anatomical position for humans is standing upright as seen in the image below. By using this as a standard posture for anatomical descriptions, we can avoid confusion even when in reality the person is in some other position. For example, suppose the doctor was describing someone lying down? The doctor’s description would be described as if the person were standing up and in the standard anatomical position.

Anatomy is the study of the structure of the human body.The standard anatomical position for humans is the feet together (or slightly apart), and the forearms are rotated with the palms forward and the thumbs pointed away from the body. The arms are usually moved slightly out and away from the body, so that the hands don’t touch the sides of the body. The positions of the arms and legs (and the arms in particular) have important implications for directional terms in those appendages (limbs). The head is upright and facing forward so that certain parts of the eyes and ears are in the same horizontal plane. The penis in men is considered to be erect in the anatomical position, hence the dorsal surface of the penis is actually the anterior surface in the flaccid state.

For “normal” human bodies, the right and left sides are mirror images if divided right down the center by the sagittal plane as shown in the image below. The center line represents an axis or dividing line.

Directional Terms

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In general, directional terms are grouped in pairs of opposites based on the standard anatomical position.

Other directional terms:

There are also terms that describe specific body parts. Palmar describes the palm side of the hand. Dorsal describes the back side of the hand. Plantar describes the bottom of the foot.

Anatomical Reference Planes

A plane is a two-dimensional surface — its dimensions are length and width. The body reference planes are used to locate or describe the location of structures in the body. These terms are often used to describe medical imaging such as CAT scans, PET scans and MRIs where the scans take pictures of the body in flat slices. Brain scans are often of sagittal plane slices (from ear to ear). Abdominal CAT scans are often transverse plane slices (like a stack of coins).

Anatomical Planes

The three basic planes intersect at right angles to each other. When the three basic planes intersect in the center of the body (as seen in the image to the right) they can be used to describe various relationships within the body.

Main Reference Planes

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Body Cavities

Body cavities are areas in the body that contain our internal organs. The dorsal and ventral cavities are the two main cavities. The dorsal cavity is on the posterior (back side) of the body and contains the cranial cavity and spinal cavity. In human anatomy, dorsal, caudal and posterior mean the same thing. The ventral cavity is on the front (anterior) of the body and is divided into the thoracic cavity (chest) and abdominopelvic cavity.

Body Cavities

Dorsal Cavity

The dorsal cavity is further divided into subcavities:

Ventral Cavity

The ventral cavity is on the front of the trunk. The diaphragm (the main muscle of breathing) divides the ventral cavity into two simple subcavities: thoracic and abdominal.

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The thoracic cavity is open at the top and the abdominal cavity is open at the bottom. Both cavities are bound on the back by the spine. Even though their location is defined, the shape of these cavities can change. How they change is very different. Breathing is the main way the shape of these two cavities changes. The abdominal cavity changes shape similar to a water-filled balloon. When you squeeze the balloon, the shape changes as the balloon bulges. When breathing compresses the abdominal cavity it “bulges” into a different shape.  The abdominal cavity can also change shape based on volume—that is how much you eat and drink. The more you eat and drink, the harder it is for the diaphragm to compress the abdominal cavity—which is why it is harder to breathe after a large meal. Also, an increase in volume of the abdominal cavity decreases the volume in the thoracic cavity—you can take in less air. The thoracic cavity changes both shape and volume when you breathe. When you breathe out, the volume decreases; when you breathe in the volume increases. Because of how these two cavities are linked together in shape change, you can see that the quality of breathing affects the health of abdominal organs and the health of our organs affects the quality of our breathing.

Other Cavities

Body Quadrants

Quadrants are another way our bodies are divided into regions for both diagnostic and descriptive purposes.

Body Regions

Body regions describe areas of the body that have a special function or are supplied by specific blood vessels or nerves. The most widely used terms are those that describe the 9 abdominal regions shown in the image to the right. The regions are named below and the corresponding regions are labeled 1-9.

9 Abdominal Regions

Abdominal Regions

Abdominal Quadrants

Quadrants are divide our bodies into regions for diagnostic and descriptive purposes. The quadrants are defined by drawing an imaginary line vertically (top to bottom) and horizontally (sideways) though the umbilicus (belly button). The following is a list of the organs in the four quadrants.

Abdominal quadrants

Body Areas

Anatomical Body Areas

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