The language of anatomy relies on a system of imaginary flat surfaces, known as anatomical planes, that pass through the body to provide a universal frame of reference. These conceptual slices are foundational tools used by medical professionals to map the complex geography of the human body consistently. By defining specific relationships between structures, these planes allow for precise communication about the location of organs, the direction of movement, or the orientation of a medical image. This established terminology ensures that descriptions are understood universally across the medical field.
The Plane That Divides Right and Left
The plane responsible for separating the body into right and left portions is called the sagittal plane. This plane runs vertically, parallel to the long axis of the body, moving from front to back. The term “sagittal” is derived from the Latin word for arrow, referencing how the plane splits the body.
A specific type, the midsagittal or median plane, runs directly down the exact center of the body, dividing it into two perfectly equal halves. Any sagittal plane situated off-center is referred to as a parasagittal plane, creating unequal right and left sections. The sagittal plane defines the directional terms medial (closer to the midline) and lateral (further away from the midline).
Dividing Front and Back
The plane that divides the body into front and back sections is known as the coronal plane, also called the frontal plane. This plane is oriented vertically, running perpendicular to the sagittal plane, separating the body into anterior (front) and posterior (back) sections. The anterior section is also described using the directional term ventral, while the posterior section is known as dorsal. A coronal slice provides an excellent view of internal organs and is useful for studying the relationship between surface and deeper structures.
Dividing Top and Bottom
The transverse plane, also known as the horizontal or axial plane, divides the body into upper and lower portions. Unlike the coronal and sagittal planes, the transverse plane runs parallel to the ground and is perpendicular to both of them, creating a cross-sectional view. This plane separates the superior (upper) structures from the inferior (lower) structures. Superior is sometimes referred to as cranial (toward the head), and inferior is sometimes called caudal (toward the tail end). Medical imaging techniques like Computed Tomography (CT) scans often capture images in the transverse plane.
The Importance of Standard Positioning
All descriptions of anatomical planes and directional terms rely on a single fixed posture called the anatomical position. This standardized reference point is defined as a person standing upright, with the feet flat on the floor and slightly apart. The arms hang at the sides with the palms facing forward, and the head and eyes are directed straight ahead. Using this universal starting point prevents confusion, regardless of the actual position a patient may be in, such as lying down for an exam or surgery. The anatomical position establishes a non-moving coordinate system, ensuring that descriptive terms like medial, lateral, superior, and inferior always have the same meaning.