Directional Terms: Body Sides: Videos & Practice Problems

Understanding body orientation involves recognizing bilateral symmetry, where the right and left sides are mirror images. Key terms include medial (toward the midline) and lateral (away from the midline), with examples like the hip being lateral to the navel. Additionally, ipsilateral refers to structures on the same side, while contralateral indicates opposite sides. For instance, the left knee is ipsilateral to the left hand and contralateral to the right hand. These concepts are essential for accurately describing anatomical relationships in the body.

Medial and Lateral

Understanding the directional terms related to the human body is essential for accurately describing anatomical locations and relationships. The concept of bilateral symmetry is fundamental, as the body can be divided into right and left halves, which are mirror images of each other. It is crucial to remember that when referring to the right and left sides, these terms pertain to the subject's perspective, not the observer's. For instance, what is the right side of the body from the subject's viewpoint may appear as the left side from the observer's perspective.

In anatomical terminology, two key terms describe proximity to the midline: medial and lateral. Medial indicates a position closer to the midline, while lateral refers to a position further away. For example, the hip is lateral to the navel, and conversely, the navel is medial to the hip. This relationship is always comparative, meaning that the position of one structure is defined in relation to another.

Additionally, the term intermediate is used to describe a position between medial and lateral. For instance, the eye is intermediate to the ear and the nose, while the collarbone is intermediate to the shoulder and the sternum. It is important to note that the term intermediate is specific to the medial-lateral axis and should not be confused with the inferior-superior axis.

When discussing structures in relation to each other, the terms ipsilateral and contralateral are used. Ipsilateral means on the same side of the body, while contralateral refers to the opposite side. The root "ipsa" signifies "same," and "contra" indicates "opposite." For example, the left knee is ipsilateral to the left hand, while it is contralateral to the right hand. Understanding these terms enhances clarity in anatomical discussions and is vital for effective communication in medical contexts.

Directional Terms: Body Sides Example 1

Understanding directional terms is essential for accurately describing the location of body parts. In this exercise, we will apply these terms to mark specific locations on a body diagram.

First, we identify the term lateral, which refers to a position away from the midline of the body. For example, placing an asterisk lateral to the left of the navel means we mark a point slightly to the left of the navel, which is centrally located on the body.

Next, we consider the term intermediate, which indicates a position between two structures. When asked to mark a point intermediate to the nose and the right ear, we find the location that lies directly between these two points along the left-to-right axis.

We then encounter the term contralateral, which combines the concepts of lateral (side) and contra (opposite). To mark a point contralateral to the right knee, we identify the hip on the opposite side of the body from the right knee, placing a plus sign there.

Finally, we address the term medial, which refers to a position closer to the midline of the body. When marking the medial side of the left wrist, we focus on the side of the wrist that is closest to the body’s midline, placing an x there.

By applying these directional terms—lateral, intermediate, contralateral, and medial—we can accurately describe and mark the locations of various body parts in relation to one another.

Imagine you are a surgeon about to perform a procedure on the liver, which is located on the right side of body just below the ribs. Relative to the navel (belly button) where would you prepare the incision?

• A. Medial and ipsilateral to the right.
• B. Inferior and medial to the left.
• C. Contralateral and superior to the left.
• D. Superior and lateral to the right.

Answer: (D)

According to anatomical position, what is the most lateral part of the body?

• A. Anywhere on the midline
• B. The hips or shoulders
• C. The thumbs
• D. The feet

Answer: (C)

The left knee and the left ankle are _______________.

• A. Ipsilateral
• B. Intermediate
• C. Contralateral
• D. Medial

Answer: (A)

The right hemisphere of the brain processes signals from sensory nerves on the left side of the body. Another way to say this is that sensory neurons are located ________________ to the hemisphere of the brain that processes them.

• A. Ipsilateral
• B. Medial
• C. Contralateral
• D. Lateral

Answer: (C)

Here’s what students ask on this topic:

What is the difference between medial and lateral in anatomical terms?

In anatomical terms, 'medial' refers to a position closer to the midline of the body, while 'lateral' refers to a position farther from the midline. For example, the navel (belly button) is medial to the hip because it is closer to the midline, whereas the hip is lateral to the navel because it is farther from the midline. These terms help describe the relative positions of structures within the body.

How do ipsilateral and contralateral differ in describing body sides?

'Ipsilateral' means that structures are on the same side of the body, while 'contralateral' means that structures are on opposite sides. For instance, the left hand is ipsilateral to the left knee because they are on the same side. Conversely, the left hand is contralateral to the right knee because they are on opposite sides. These terms are crucial for accurately describing anatomical relationships and movements.

Can you provide examples of structures that are intermediate in the body?

In anatomical terms, 'intermediate' refers to a structure that is between two other structures on the medial-lateral axis. For example, the eye is intermediate to the ear and the nose. Another example is the collarbone (clavicle), which is intermediate to the shoulder and the sternum. This term helps specify the relative position of structures more precisely.

Why is it important to understand bilateral symmetry in anatomy?

Understanding bilateral symmetry is crucial in anatomy because it helps in accurately describing the positions and relationships of body structures. Bilateral symmetry means that the right and left sides of the body are mirror images of each other. This concept is foundational for using directional terms like medial, lateral, ipsilateral, and contralateral, which are essential for clear and precise communication in medical and anatomical contexts.

How do you determine the right and left sides of the body in anatomical terms?

In anatomical terms, the right and left sides of the body are determined from the perspective of the body being described, not the observer. This means that the right side of the body is the body's own right side, and the left side is the body's own left side. This distinction is important to avoid confusion, especially when describing anatomical positions and relationships.