Anatomical Orientation and Directions

Information

To be able to direct others to specific anatomical structures, or to find structures based on someone else’s directions, it is useful to have specific pairs of terms that allow you to orient your search with respect to the location of another, known structures. The following pairs of terms are used to make comparisons. Each term is used to orient a first structure or feature with respect to the position of a second structure or feature.

  • Superior/Inferior–Equivalent to above and below when moving along the long axis of a body in anatomical position. The structure that is superior to another is above the second structure when the body is in anatomical position. A feature that is inferior to another is below the second feature when the body is in anatomical position.
  • Proximal/Distal–Equivalent to near and far. Usually used to orient the positions of structures and features along the limbs with respect to the trunk of the body. A feature that is proximal to something else is closer to the limb’s point of attachment to the trunk. A structure that is distal to something else is farther away from the limb’s point of attachment. Less precisely but still occasionally used in the trunk of the body itself to indicate whether something is closer to (proximal) or farther away from (distal) something else.
  • Medial/Lateral–Equivalent to towards the middle or towards the edge. Used with respect to the midline of the trunk of a body in anatomical position. A structure that medial to another is closer to the midline of the body’s trunk. A feature that is lateral to another is farther away from the midline of the trunk.
  • Anterior/Posterior–Equivalent to the front and back of a body in anatomical position. A structure that is anterior to another is closer to the front of the body when the body is in anatomical position. A feature that is posterior to another is closer to the back of the body when the body is in anatomical position.
  • Ventral/Dorsal–Equivalent to belly-side and back-side of a body in anatomical position. For a human in anatomical position, this pair of terms is equivalent to anterior and posterior. However, for four-legged animals in what is considered their anatomical position, the belly-side is not equivalent to the front of the animal. A structure that is ventral to another is closer to the belly-side of the body. A feature that is dorsal to another is closer to the back of the body.
  • Superficial/Deep–Equivalent to closer to the surface and farther from the surface.
  • Cephalic/Caudal–Equivalent to closer to the head and closer to the tail. This is more useful for four-legged animals with tails than for upright humans with only a vestigial tail.

 

Figure 1-5. Pairs of terms providing anatomical direction or orientation.

 

 

 

cross-section of a bone showing deep (in the center) and superficial areas on the perimeter.

Figure 1-6. Cross-section of the thigh.

 

 

Lab 1 Exercises 1.3

1. Fill in the blank with the appropriate directional term to complete the following sentences. More than one answer may be correct.

  • The heart is ____________ to the lungs.
  • The knee is ____________ to the hip.
  • The wrist is ____________ to the hand.
  • The mouth is ____________ to the nose.
  • The thorax is ____________ to the abdomen.
  • The thumb is ____________ to the ring finger.
  • The sternum is ____________ to the heart.
  • The skull is ____________ to the scalp.
  • The ears are ____________ to the nose.
  • Dorsal refers to the ____________ of the human body, while ventral refers to the ____________ of the human body.

 

2. Find the indicated structures in the diagrams provided, based on the directional terms given. The structure to find will be one of those at the end of an unlabeled line.

A. Label the extensor digitorum muscle in the figure below. It is:

  • Distal to the anconeus muscle
  • Lateral to the extensor digiti minimi muscle
  • Superficial to the Extensor pollicis brevis muscle
Muscles of the forearm depicting the anconeus, extensor pollicis brevis, and the extensor digiti minimi

Figure 1-7. Muscles of the forearm.

 

B. Label the Incus in the figure below. It is:

  • Superior to the lateral end of the cochlear nerve
  • Medial to the malleus
  • Lateral to the stapes
Image of the inner ear showing the malleus, stapes, and cochlear nerve.

Figure 1-8. Anatomy of the human ear.

 

3. Using your knowledge of the different body planes shown in Figure 1-2 (shown again below), fill in the blanks with the appropriate body plane for each of the following descriptions.

  1. The plane that divides the body into anterior and posterior parts is the ________________ plane.
  2. A transverse plane divides the body into ________________ and ________________ regions.
  3. A ________________or ________________ plane divides the body into right and left parts.
Computer generated image of a person's head, showing the transverse cut as a sheet of paper going from the nose out the back of the head, the frontal (coronal) plane as a paper slicing from the tip of the skill down towards the center of the neck and between the ears, the midsagittal plane as a slice from the tip of the head through the neck but cutting along the nose line, and a parasagittal plane as a similar slice (from the tip of the head down to the neck, but through the eye and cheek)

Figure 1-2. The different sectional planes used to expose internal structures.