Directional terms and body planes

Hello everyone! This is Megan from Kenhub, and welcome to our tutorial on directional terms and body planes. When you begin to study anatomy, you have to describe the different structures according to the position in the human body. To do this, we have specific directional terms in order to avoid confusion when identifying structures. Anatomical directional terms and body planes are used as a universally accepted language of anatomy allowing precise communication between anatomists and health professionals.

In this tutorial, we will cover the terms and planes you need to know if you wish to study anatomy effectively. The terms used to describe anatomical positioning are described in relation to one standard position. This position is the anatomical position. Therefore, before I begin describing directional terms and body planes, I must first explain the anatomical position.

This position is used to describe body parts and positions of patients regardless of whether they are lying down, on their side or facing down. In the anatomical position, the person is standing upright with their arms to the side, their palms facing forward and their thumbs pointing away from the body. The feet are slightly apart and parallel to each other with the toes pointing forward and the head facing forward with the eyes looking straight ahead.

Now that I've explained the anatomical position, I can move on to talk about some directional terms. Directional terms allow description of one body part in relation to another. The first directional term we're going to talk about is anterior. Anterior indicates that the body part in question is located to the front of the body. For example, in this image, we can see that the toes are in front of the heel, therefore, you could say the toes are located anterior to the heel. Posterior is the directional term which has the opposite meaning to anterior. Posterior indicates that a body part is located to the back of the body. Using the example we used before, we can say that the heel is posterior to the toes.

The term ventral refers to the front of the body or literally towards the abdomen and is, therefore, interchangeable with the term anterior. For example, in this image, we can see transversus abdominis. This muscle is located on the anterior surface of the trunk or the ventral surface of the trunk. Dorsal means towards the back of the body and is thus sometimes used interchangeably with the directional term posterior. For example, in this image, we can see the muscle trapezius which is highlighted in green. This is a muscle of the posterior surface of the trunk or the dorsal trunk.

Dorsal and ventral are common terms used when describing the anatomical positions of other animals. The term dorsal is derived from the Latin word dorsum which literally translates the back and ventral is derived from the Latin term venter which means belly. So, the term ventral refers to the underside of an organism and the term dorsal refers to the back of an organism.

Right is a term used to indicate the right side of. In this image, the right side of the body is highlighted in green. Right is often commonly used when there is more than one body part. For example, the right hand or the right eye are terms used to differentiate which hand or eye one is talking about. Left is a term used to indicate the left side. You can see that the left side of the body is highlighted in green in this image. Like the term right, left can be used to differentiate what body part you are talking about when there's more than one. For example, the left foot or the left ear. It is important to remember especially when you examine the patient that both right and left are used when referring to an individual's left or right side.

The term distal indicates that a body part is located far away from the trunk of the body. This term can also be used to describe regions of a body part. For example, the distal end of a bone is the part of the bone that is located furthest away from the trunk of the body. In this example, we can see that the wrist joint is distal to the elbow joint. Proximal means that a body part is closest to the trunk of the body. Again, like distal, it can be used to describe regions of a body part. For example, the proximal end of a bone is a part of the bone that is located closest to the trunk of the body. Using the example we used in the previous slide, we can say that the elbow joint is proximal to the wrist joint.

A term that often creates confusion is the term median. The term median or midline is the term used to refer to an imaginary line down the middle of the body. It splits the body into equal left and right parts, whereas the term medial is used to refer towards the median or when a body part is closer to the median than another. For example, the right chest is medial to the right arm. The opposite of medial is the term lateral. It's the term used to describe a body part that is away from the median and towards the side of the body. Using the example we used in the previous slide, we can say that the right arm is lateral to the right chest.

Superior is a term used to refer to upwards or towards the vertex or top of the head. For example, we can say that the nose is superior to the mouth. Inferior is a term which indicates the opposite of the term superior. It means below or towards the feet. So, using the previous example, we can say that the mouth is inferior to the nose.

The term external, which is also known as superficial, refers to a structure that's found on the surface of the body. It can also mean open to the external environment. As you can see in the right image, we're showing the outer ear. Highlighted areas can be referred to as external because they are open to the outside environment. Above, we can see a sphere giving a visual representation of what external means. So, you can see the arrows moving towards the exterior. Internal, which is also known as deep, refers to a body part that is away from the body surface or not open to the external environment. For example, the highlighted areas in the right image can be referred to as internal, as they are not open to the outside environment. Again, we have a sphere giving a visual representation of what internal means. Note that the arrows in this image are moving towards the interior.

The final pair of directional terms that we'll talk about is the frontal and occipital regions. Frontal is the term used when talking about structures of the brain and refers towards the frontal bone which is highlighted here in green. For example, the frontal lobe of the brain will be located deep to the frontal bone of the skull. On the other hand, we used the term occipital in order to describe structures of the brain towards the occipital bone such as the occipital lobe.

Now, that we've discussed directional terms, we can move onto the second part of this tutorial which is the body planes. Body planes are imaginary planes or flat surfaces that cut through and section the body in its anatomical position. There are three main body planes used in anatomy. They are referred to as the coronal, sagittal, and transverse planes. Knowing these body planes is very helpful when looking at MRI or CT scans of the brain or other parts of the body as you can often view these images in the different planes.

The coronal plane, which is also referred to as the frontal plane, is a vertical plane that divides the body into anterior and posterior divisions. A way to remember this is that the plane runs parallel to the coronal suture of the skull. The sagittal plane is also a vertical plane that splits the body into right and left parts. A sagittal plane that runs directly through the midline is also called the mid-sagittal plane or the median plane as we saw earlier. A way to remember this plane is that it runs parallel to the sagittal suture of the skull. The transverse plane is a horizontal plane. It divides the body into superior and inferior portions. In anatomy, they are also referred to as the cross-section.

That concludes our tutorial on directional terms and body planes. Thank you for listening.

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Now, good luck everyone, and I will see you next time.