Anatomical Terms of Location: Anterior vs Posterior and Dorsal vs Ventral


Anterior Posterior Dorsal Ventral Anatomical Terms of Location

Anatomical terms of location are precise descriptors used in biology and medicine that describe the location or direction of structures within the body. Understanding these terms is crucial for clear communication among healthcare professionals, veterinarians, and scientists.

Importance Across Species

The terms adapt depending on the organism’s body structure, especially between bipeds (like humans), quadrupeds (like dogs), and organisms that are neither (like fish, starfish, and clams). For example, anterior and posterior depend on an organisms usual direction of motion. So, in bipeds, terms like “anterior” and “posterior” refer to the front and back, respectively. In quadrupeds and fish, the anterior is toward the head, while posterior is toward the back or tail.

Standard Anatomical Position

This is a baseline posture that describes anatomical structures and directions. In humans, it involves standing upright, facing forward, with arms at the sides and palms facing forward. For quadrupeds, it’s standing on all four limbs, with the head facing forward.

Key Anatomical Terms of Location and Their Differences

Anterior and Posterior

These terms describe positions towards the front (anterior) and back (posterior) of the body, with respect to the organism’s forward motion. In humans, the chest is anterior, while the back is posterior. In cats, for example, the head is anterior while the tail is posterior.

Dorsal and Ventral

“Dorsal” refers to the back or vertebral side, while “ventral” refers to the belly side. In a fish, the dorsal fin is on the back, and the belly is the ventral side. A person’s back is their dorsal surface, while the belly is the ventral surface. But, in humans, these terms more often describe relative positions within the brain and spinal cord.

Superior and Inferior

“Superior” means above, and “inferior” means below. The head is superior to the neck, and the feet are inferior to the knees.

Medial and Lateral

“Medial” means towards the midline of the body, while “lateral” means away from the midline. The nose is medial, while the ears are lateral.

Proximal and Distal

These terms are primarily for limbs. “Proximal” means closer to where the limb attaches to the body, and “distal” means further away. The elbow is proximal to the wrist.

Central and Peripheral

“Central” refers to locations near the center of the body or an organ, while “peripheral” means towards the outer edges. The brain is central, while the nerves extending into the limbs are peripheral.

Superficial and Deep

“Superficial” means closer to the surface of the body, while “deep” refers to structures further inside. Skin is superficial, while muscles are deeper.

Rostral, Cranial (Cephalic), and Caudal

“Rostral” refers to the nose or beak, “cranial” or “cephalic” to the head, and “caudal” to the tail region.

Clarifying Dorsal/Ventral and Anterior/Posterior

In humans, “dorsal” and “posterior” are similar but are used in different contexts. “Dorsal” is often used for the back of the hand or the top of the foot, distinct from “posterior,” which refers to the back of the body.

Prefixes and Suffixes for Anatomical Terms of Location

Prefixes and suffixes describe the position of one body part relative to another:

  • Sub- (e.g., subcutaneous): beneath or under. For example, subcutaneous refers to a position below the skin.
  • Hypo- (e.g., hypodermic): below or less than normal.
  • Infra- (e.g., infraspinatus): below a certain part.
  • Inter- (e.g., intercostal): between.
  • Supra- (e.g., supraorbital): above or over.
  • Super- (e.g., superficial): above or more than normal.
  • -ad (e.g., cephalad): toward a certain direction.

Axes

An organism that has bilateral symmetry, like humans and other vertebrates, has three axes that intersect at right angles.

  • Anteroposterior Axis: From front to back.
  • Cephalocaudal Axis: From head (cephalic) to tail (caudal).
  • Dorsoventral Axis: From back (dorsal) to belly (ventral).

These axes apply to most invertebrates too (e.g., insects and crustaceans), but get a bit more tricky when discussing organisms with radial or else no symmetry.

Anatomical Planes

The axes divide the body into various planes:

Human Anatomy Planes
(image: David Richfield and Mikael Häggström, M.D. and cmglee, CC 4.0)

Median Plane

The median plane divides the body into equal left and right halves. It passes through the head, spine, navel, and tail (when applicable).

Sagittal Plane

The sagittal plane or longitudinal plane is similar to the median plane but doesn’t necessarily divide the body into equal halves.

Frontal Plane (Coronal Plane)

The frontal plane or coronal plane divides the body into anterior and posterior (front and back) parts.

Horizontal Plane (Transverse Plane)

The horizontal plane or transverse plane divides the body into superior and inferior (upper and lower) parts.

References

  • Dyce, K.M.; Sack, W.O.; Wensing, C.J.G. (2010). Textbook of Veterinary Anatomy (4th ed.). St. Louis, Missouri: Saunders/Elsevier. ISBN 9781416066071.
  • Kardong, Kenneth (2019). Vertebrates: Comparative Anatomy, Function, Evolution (8th ed.). New York: McGraw-Hill. ISBN 9781260092042.
  • Smith, J. B.; Dodson, P. (2003). “A proposal for a standard terminology of anatomical notation and orientation in fossil vertebrate dentitions”. Journal of Vertebrate Paleontology. 23 (1): 1–12. doi:10.1671/0272-4634(2003)23[1:APFAST]2.0.CO;2
  • Standring, Susan, ed. (2016). Gray’s Anatomy: The Anatomical Basis of Clinical Practice (41st ed.). Philadelphia: Elsevier Limited. ISBN 9780702052309.