We begin by defining what anatomy is.
What is Anatomy?
Anatomy is a field concerned with the identification and description of the body structures of living thingsBritannica, 2023
Anatomy is important mostly in the field of medicine and many students who are in the medical line have to take it as courses. Due to its vastness, a defined collection of descriptive terminology is utilised to efficiently express and comprehend the complexity of the human body. Directional descriptors among these terms are essential for directing anatomists, medical practitioners, and students alike.
What are Directional Descriptors of Anatomy?
Directional descriptors in anatomy are specialised terms used to describe the position, orientation, and relationships of anatomical structures within the human body.
One can efficiently explore and comprehend the intricate three-dimensional structure of the human body using directional anatomical descriptors. Each directional anatomical descriptive term seeks to convey precise information on the direction, location, or connection of a body structure to another body structure or a reference point in the body. The majority of these directional anatomical descriptive terms exist in pairs. They are:
- Supine and Prone
- Anterior and Posterior
- Superior and Inferior
- Medial and Lateral
- Proximal and Distal
- Superficial and Deep
Supine and Prone
These are used to describe the body structure's position while laying down. Unless stated otherwise, a person is assumed to be in an anatomical position.
Anatomical position is the position of a person when they are standing erect with their feet together, their hands at their side, with the palms facing forward.BC Campus, 2023
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| Fig 1: Anatomical Position Source: EZmed |
The Supine position is when a person lies flat on their back. In this position, the palms of the person faces downward, while, their face and abdomen are pointing at the sky or ceiling. The body is horizontal and relaxed in this position due to the symmetry this position provides.
The Prone position is when a person is lying flat on their stomach. In this position, the reverse is the case, as the palms, back and buttocks of the person are pointed upward. Despite being technically horizontal, the body is not considered to be at rest in this position.
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| Fig 2: Supine and Prone Positions Source: MedTrng |
Anterior and Posterior
Anterior can be easily defined as the front or forward-facing aspect of a body structure. While, Posterior is simply the back or rear-facing aspect of a body structure.
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| Fig 3: (a) Anterior and (b) Posterior Source: BC Campus |
Quick note: Anterior is also commonly referred to by its other name: "Ventral". Posterior also has another name which is called "Dorsal". Examples of the use of anterior and posterior are quoted below.
The chest is located anteriorly to the spine.
The shoulder blades are positioned posteriorly to the rib cage.
The sternum (breastbone) is located anteriorly to the heart.
The gluteal muscles (buttocks) are located posteriorly at the hip region.
Superior and Inferior
Superior and Inferior are directional anatomical terms used to describe the vertical orientation of structures within the human body. Superior refers to situations whereby a structure is situated above another in an upright position. Meanwhile, Inferior is where one structure is located below another.
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| Fig 4: Superior and Inferior Position Source: Quizlet |
Since its direction is towards the head, Superior is also known as "Cranial" or "Cephalic" or "Rostral". For Inferior, its direction is usually away from the head and towards the tail end, and so, it is also known as "Caudal". Examples are given below.
The head is superior to the feet.
The ankle is inferior to the nose.
The collarbone is located cranially to the pelvis.
The ulnar head is inferior in the forearm region.
Medial and Lateral
Medial and Lateral are anatomical terminology used to describe the relative position of structures within the body area.
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| Fig 5: Medial and Lateral Position Source: Geeky Medics |
When a structure is closer to the midline or centre of the body, it is said to be medial. While lateral is used to explain when a structure is located further out from the midline. These terms are usually used in relation to another body structure. For example:
The thumb is located on the lateral side of the hand.
The big toe is positioned on the medial side of the foot.
Proximal and Distal
Proximal and distal are directional anatomical terms primarily used to describe the position of structures along the limbs.
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| Fig 6: Proximal and Distal Position Source: RN |
Proximal refers to a situation whereby a structure is closer to the body's trunk or point of origin. While, Distal signifies when a structure is located farther away from the body's trunk or point of origin. Examples of usage below.
The elbow is proximal to the wrist.
The fingers are distal to the wrist.
Superficial and Deep
Superficial and Deep are directional anatomical terms used in describing the depth or layers within the human body.
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| Fig 7: Superficial and Deep Position Source: Quizlet |
Superficial is used to denote that a structure is closer to the surface. Whereas, Deep is used to indicate when a structure is situated further below the surface. Examples of usage below.
The skin is considered superficial to the muscles, which lie deep within the body.
Deep arteries are located deeper within the body than superficial arteries.
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