Anatomy and Physiology: Body Regions and Directional Terms

Anatomical Position and Fundamental Principles

• Definition and Purpose of Anatomical Position

  • Anatomical position is a standardized reference posture agreed upon to orient the body or any organ when identifying, naming, and describing its components.

  • It ensures a uniform frame of reference regardless of whether an organ is examined inside a body, displayed in a textbook diagram, or observed directly on a patient.

• Specific Postural Criteria for Anatomical Position

  • Eyes and Face: Facing directly forward.

  • Body/Trunk: Facing directly forward.

  • Upper Limbs: Positioned out to the sides with palms facing directly forward.

  • Lower Limbs and Feet: Extended down to the feet with toes facing directly forward.

• Right vs. Left Orientation Rule

  • When looking at a patient head-on or viewing an anatomical diagram on a page, the subject's right side is across from the observer's left side, and the subject's left side is across from the observer's right side (analogous to shaking hands with someone).

  • Example: The right side of a heart in a textbook or patient is located on the side opposite the observer's right hand.

• Surface Regions and Anatomical Landmarks

  • Anatomy and physiology renames everyday body structures into formal surface regions or anatomical landmarks.

  • Mastering surface regions early builds a foundational vocabulary that directly corresponds to underlying skeletal, muscular, nervous, and organ systems across future studies.

  • Example: The forehead surface region is designated as the frontal area. This single anatomical term prepares students to learn the underlying frontal bone, the overlying frontalis muscle, and the frontal lobe of the brain.

• Primary Subdivisions of the Body

  • Axial Region: Encompasses the central axis of the body: the head, neck, and trunk.

  • Appendicular Region: Encompasses the limbs (upper and lower extremities) attached to the axial body.

  • Anterior Surface: Refers to the front side of the body.

  • Posterior Surface: Refers to the back or backside of the body.

Axial Surface Regions: Head, Neck, Trunk, and Dorsum

• Cephalic Region (Head)

  • Term pertains to the head as a whole on both anterior and posterior views.

  • Anterior/Facial Landmarks:

    • Frontal Region: Pertaining to the forehead.

    • Orbital Region: Pertaining to the area around the eye.

    • Nasal Region: Pertaining to the nose.

    • Oral Region: Pertaining to the mouth and the area around the lips.

    • Buccal Region: Pertaining to the cheek area.

    • Mental Region: Pertaining to the chin.

  • Posterior Cephalic Landmark:

    • Occipital Region: Pertaining to the lower posterior area of the head (overlying the occipital bone and occipital lobe of the brain).

• Cervical Region (Neck)

  • Pertaining to the neck area on both anterior and posterior views.

• Thoracic Region (Chest - Anterior Trunk)

  • Pertaining to the chest area.

  • Sternal Region: Pertaining to the central breastbone area along the anterior midline.

  • Auxiliary Region: Pertaining to the armpit area (visible on both anterior and posterior perspectives).

  • Mammary Region: Pertaining to the area where the breasts are located.

• Dorsum or Dorsal Region (Back - Posterior Trunk)

  • Pertaining to the back of the body.

  • Scapular Region: Pertaining to the shoulder blade area defined by the outline of the scapular bone.

  • Vertebral Region: Pertaining to the spinal column running along the posterior midline.

  • Lumbar Region: Pertaining to the lower back area situated between the lower ribs and the hips (commonly called the loins).

  • Sacral Region: Pertaining to the area directly below the lumbar region, overlying the sacral bone.

  • Gluteal Region: Pertaining to the buttocks area (commonly referred to as glutes).

  • Perineal Region: Pertaining to the specific regional area located between the external genitals and the anus.

    • Critical Spelling Warning: Spelled p e r I n e a l (with an I). This must never be confused with peroneal (with an o), which pertains strictly to the lower leg.

• Abdominal and Pelvic Regions (Anterior Trunk)

  • Abdominal Region: Pertaining to the stomach area.

  • Umbilical Region: Pertaining to the navel or belly button area.

  • Inguinal Region: Pertaining to the groin area where the trunk joins the thigh.

  • Pubic Region: Pertaining to the genital area located inferior to the abdominal region and medial to the hips.

Appendicular Surface Regions: Upper and Lower Limbs

• Upper Limb Regions (Anterior and Posterior Views)

  • Acromial Region: Pertaining to the point of the shoulder (a prominent landmark of the scapula).

  • Brachial Region: Pertaining to the upper arm (contains the major brachial artery).

  • Antecubital Region: Pertaining to the anterior surface/bend of the elbow.

  • Oleocranal Region: Pertaining to the posterior surface of the elbow.

  • Antebrachial Region: Pertaining to the forearm (lower arm).

  • Carpal Region: Pertaining to the wrist area.

  • Manus: Term pertaining to the hand as a whole.

    • Palmar Region: Pertaining to the palm of the hand.

    • Pollux: Term specifically referring to the thumb.

    • Digital Region: Pertaining to the fingers (visible on both anterior and posterior views).

• Lower Limb Regions (Anterior and Posterior Views)

  • Coxal Region: Pertaining to the hips or hip bones.

  • Femoral Region: Pertaining to the thigh area below the hip (present on both anterior and posterior views).

  • Patellar Region: Pertaining to the anterior kneecap area.

  • Popliteal Region: Pertaining to the posterior area behind the knee.

    • Memory Aid: Remembered by the phrase "pop a cap," indicating that the popliteal region sits on the side opposite the kneecap (patella).

  • Curl Region: Pertaining to the anterior lower leg.

  • Fibular Region (also termed Peroneal Region): Pertaining to the lateral side of the lower leg.

    • Spelling Note: Spelled p e r o n e a l (with an o), referring to the lateral lower leg, contrasting with the perineal region of the pelvic floor.

  • Sural Zone/Region: Pertaining to the posterior surface of the lower leg (the calf region).

  • Pedal Region: Pertaining to the foot as a whole.

    • Memory Aid: Pedaling a bicycle is done with the feet.

    • Tarsal Region: Pertaining to the ankle area.

    • Digital Region: Pertaining to the toes.

    • Holox: Term specifically referring to the great toe (big toe).

    • Calcaneal Region: Pertaining to the heel of the foot.

    • Plantar Region: Pertaining to the sole (underside) of the foot.

Orientation and Directional Terms

• Purpose of Directional Terms

  • Directional terms provide exact descriptions of relative position, allowing precise localization of structures on an individual organ or comparisons between two separate anatomical organs.

• Superior vs. Inferior

  • Superior: Directed towards the head or upper part of a structure/organ.

    • Example: The superior portion of the heart is the top region closest to the head.

  • Inferior: Directed away from the head or toward the lower part of a structure/organ.

    • Example: The inferior portion of the heart is the bottom region farthest from the head.

  • Critical Rule: Do NOT use superior or inferior when describing locations on the limbs. Superior and inferior are reserved strictly for the axial body (head, neck, trunk) and organs contained within the axial region.

• Anterior vs. Posterior

  • Anterior: Towards or facing the front of the body.

    • Example: The anterior surface of the heart faces the front chest wall.

  • Posterior: Towards or facing the back of the body.

    • Example: The posterior surface of the heart faces the spine.

• Medial, Lateral, and Intermediate

  • Medial: Positioned toward the midline of the body.

  • Lateral: Positioned away from the midline toward the outer side of the body.

  • Intermediate: Positioned between a more medial structure and a more lateral structure.

    • Example: The collarbone (clavicle) is intermediate between the medial sternum and the lateral acromial region of the shoulder.

• Proximal vs. Distal

  • Requirement: These terms require a designated point of origin.

  • Primary Application (Limbs): Applied to the appendicular limbs, where the point of origin is the shoulder junction (for upper limbs) or hip junction (for lower limbs).

    • Proximal: Nearer to the point of attachment or origin.

      • Examples: The elbow is proximal to the wrist. The knee is proximal to the ankle.

    • Distal: Farther from the point of attachment or origin.

      • Examples: The wrist is distal to the elbow. The ankle is distal to the knee.

  • Secondary Application (Internal Organs): Used for tubular organs with an origin point, such as blood vessels relative to the heart or sections of the gastrointestinal tract.

    • Examples: The proximal component of the small intestine; the distal portion of the colon.

• Superficial vs. Deep

  • Superficial: Located toward or on the outer surface of the body or an organ.

    • Example: The external surface of the skin or outer wall of an organ.

  • Deep: Located away from the surface and toward the interior/inside of the body or organ.

    • Example: Tissue layers situated deep within an organ body accessed by cutting into it.

• Anatomical position is a standardized reference posture to orient the body or organs, ensuring uniformity when identifying and describing anatomical components.

• Specific Postural Criteria:

  • Eyes and Face: Forward

  • Body/Trunk: Forward

  • Upper Limbs: Out to sides, palms forward

  • Lower Limbs: Extended with toes forward

• Right vs. Left Orientation Rule:

  • Subject's right side corresponds to observer's left and vice versa, such as the heart's right side being opposite the observer's right hand.

• Surface Regions and Anatomical Landmarks:

  • Mastering these terms underpins understanding skeletal, muscular, and organ systems. Example: The forehead is called the frontal area.

• Body Subdivisions:

  • Axial Region: Head, neck, trunk

  • Appendicular Region: Limbs

  • Anterior Surface: Front

  • Posterior Surface: Back

• Axial Surface Regions:

  • Cephalic Region: Whole head

  • Cervical Region: Neck

  • Thoracic Region: Chest area

  • Lumbar Region: Lower back

  • Abdominal Region: Stomach

  • Pelvic Region: Genital area

• Appendicular Regions:

  • Upper Limb Regions: Shoulder to hand

  • Lower Limb Regions: Hip to foot

• Directional Terms:

  • Superior/Inferior: Headward/footward, reserved for axial structures.

  • Anterior/Posterior: Front/back orientations.

  • Medial/Lateral: Toward/away from the midline.

  • Proximal/Distal: Closer to/further from the point of attachment, mainly for limbs.

  • Superficial/Deep: Outer surface/inner layers of body or organ.