Anatomy and Physiology: Body Positions, Planes, and Cavities

Anatomical Position

Standing upright, facing forward, arms at sides, palms forward — the reference for all anatomical descriptions.

Supine Position

Lying on the back, face upward.

Prone Position

Lying on the stomach, face downward.

Etymology

Study of word origins; helps decode medical terms (e.g., "isch-" = restraint; "-emia" = blood condition).

Ischemia

Restricted blood flow to tissue ("isch-" = restraint + "heme" = blood + "-ia" = condition).

Hypoxemia

Low oxygen level in the blood ("hypo-" = below; "oxys" = oxygen; "-emia" = blood condition).

Hypoxia

Low oxygen level in tissues; causes fatigue, cyanosis, confusion.

Anoxia

Absence of oxygen supply.

Sagittal Plane

Divides the body into left and right halves (mid-sagittal = equal halves).

Coronal (Frontal) Plane

Divides body into anterior (front) and posterior (back) sections.

Transverse (Horizontal) Plane

Cuts body into superior (upper) and inferior (lower) parts.

Oblique Plane

Cuts the body at an angle other than 90 degrees.

Anterior (Ventral)

Toward the front of the body.

Posterior (Dorsal)

Toward the back of the body.

Superior (Cranial)

Toward the head or upper part.

Inferior (Caudal)

Toward the feet or lower part.

Medial

Toward the midline.

Lateral

Away from the midline.

Proximal

Closer to the point of limb attachment.

Distal

Farther from the point of limb attachment.

Superficial

Near the body surface.

Deep

Farther from the body surface.

Ipsilateral

On the same side of the body.

Contralateral

On the opposite side of the body.

Dorsolateral

Toward the back and side.

Protraction

Moving a body part forward (e.g., jaw forward).

Retraction

Moving a body part backward (e.g., jaw backward).

Flexion

Decreasing the angle of a joint.

Extension

Increasing the angle of a joint.

Abduction

Movement away from the midline.

Adduction

Movement toward the midline.

Rotation

Turning movement around a longitudinal axis.

Circumduction

Circular motion of a limb that traces a cone.

Elevation

Raising a body part (e.g., shrugging shoulders).

Depression

Lowering a body part (e.g., relaxing shoulders).

Dorsal Body Cavity

Cranial + Spinal cavities.

Ventral Body Cavity

Thoracic + Abdominopelvic cavities.

Thoracic Cavity

Contains mediastinum and left/right pleural cavities.

Abdominal Subregions

Nine-region method using mid-clavicular and trans-umbilical lines.

Axial Skeleton

Skull, ribs, vertebral column.

Appendicular Skeleton

Limbs and girdles (attachments).

Intra-individual Variation

Differences within one person (time of day, posture, diet).

Inter-individual Variation

Differences between people (age, sex, genetics, lifestyle).

Environmental Variation

Differences caused by surroundings (altitude, temperature, chemicals).

Anatomical Variation Examples

Extra rib, missing pyramidalis muscle, varied blood vessel paths.

X-inactivation

Random shutting off of one X chromosome in females → mosaic traits.

MHC Diversity

Genetic immune variation affecting mate preference ("sweaty T-shirt test").

Gut & Skin Microbiota

Microbes that affect digestion, immunity, mood ("human ecosystem").

Telomeres

Chromosome end caps that shorten with each cell division; linked to aging and cancer.