Anatomical Position, Regional Terms, and Body Planes: Foundations of Human Anatomy

Anatomical Position and Directional Terms

Standard Anatomical Position

The anatomical position is the universally accepted starting point for describing locations and directions on the human body. It ensures consistency in anatomical terminology.

• Body erect

• Feet slightly apart

• Palms facing forward

• Thumbs point away from the body

• Directional terms are always used as if the body is in anatomical position, regardless of its actual posture.

• Right and left refer to the body being viewed, not the observer's right and left.

Directional Terms

Directional terms are used to describe the locations of structures relative to other structures or locations in the body.

Term	Definition	Example
Superior (cranial)	Toward the head or upper part of a structure	The head is superior to the abdomen.
Inferior (caudal)	Away from the head or toward the lower part of a structure	The navel is inferior to the chin.
Anterior (ventral)	Toward or at the front of the body	The breastbone is anterior to the spine.
Posterior (dorsal)	Toward or at the back of the body	The heart is posterior to the breastbone.
Medial	Toward the midline of the body	The heart is medial to the arm.
Lateral	Away from the midline of the body	The arms are lateral to the chest.
Proximal	Closer to the origin of the body part or point of attachment	The elbow is proximal to the wrist.
Distal	Farther from the origin of a body part or point of attachment	The knee is distal to the thigh.
Superficial (external)	Toward or at the body surface	The skin is superficial to the skeletal muscles.
Deep (internal)	Away from the body surface; more internal	The lungs are deep to the skin.

Regional Terms and Body Divisions

Major Body Divisions

Regional terms are used to designate specific areas within the major divisions of the body.

• Axial division: Includes the head, neck, and trunk.

• Appendicular division: Includes the limbs (arms and legs).

Regional terms help in precisely locating and describing anatomical structures.

Examples of Regional Terms

Region	Location
Cephalic	Head
Cervical	Neck
Thoracic	Chest
Abdominal	Belly
Pelvic	Pelvis
Brachial	Arm
Femoral	Thigh
Crural	Leg
Antebrachial	Forearm
Carpal	Wrist
Tarsal	Ankle

Anatomical Variability

Individual Differences

Humans differ both externally and internally. Not all anatomical structures are identical in every individual.

• About 90% of anatomical structures match textbook descriptions.

• Nerves or blood vessels may be out of place.

• Small muscles may be missing.

• Extreme anatomical variations are usually incompatible with life.

Example: The branching pattern of arteries in the arm may differ between individuals.

Body Planes and Sections

Body Planes

Body planes are imaginary flat surfaces that divide the body into sections. They are used to describe locations of structures and to make anatomical cuts for study.

• Sagittal plane: Divides the body vertically into right and left parts.

• Frontal (coronal) plane: Divides the body vertically into anterior (front) and posterior (back) parts.

• Transverse (horizontal) plane: Divides the body horizontally into superior (upper) and inferior (lower) parts.

• Oblique section: Cuts made at angles other than 90° to the vertical plane.

Sagittal Plane

• Median (midsagittal) plane: Lies exactly along the midline, dividing the body into equal right and left halves.

• Parasagittal plane: Divides the body into unequal right and left parts, parallel to the midsagittal plane.

Frontal (Coronal) Plane

• Divides the body into anterior and posterior parts.

• Produces a frontal or coronal section.

Transverse (Horizontal) Plane

• Divides the body into superior and inferior parts.

• Produces a cross section.

Oblique Section

• Results from cuts at angles other than 90° to the vertical plane.

Summary Table: Body Planes

Plane	Direction	Resulting Section
Sagittal	Vertical; right and left parts	Midsagittal (equal halves), Parasagittal (unequal halves)
Frontal (Coronal)	Vertical; anterior and posterior parts	Frontal section
Transverse (Horizontal)	Horizontal; superior and inferior parts	Cross section
Oblique	Any angle other than 90°	Oblique section

Example: MRI and CT scans often use transverse sections to visualize internal organs.

*Additional info: The study notes have expanded on the brief points and tables from the slides, providing definitions, examples, and context for each anatomical term and concept.*