Anatomical Body Regions and Directional Terms

Introduction to Body Regions and Directional Terms
  • Purpose of Body Regions: These regions help identify specific locations on the body to locate structures.
  • Interrelation: Body regions are interrelated using specific directional terms.
Directional Terms
  • Anterior / Posterior:
    • Anterior: Refers to the front of the body or a structure. Also known as ventral.
    • Posterior: Refers to the back of the body or a structure. Also known as dorsal.
  • Medial / Lateral:
    • Medial: Implies movement or position towards the midline of the body or a structure.
    • Lateral: Implies movement or position away from the midline of the body or a structure.
  • Visceral / Parietal:
    • Visceral: Describes a membrane or covering that is directly on the surface of an organ.
      • Example: A membrane covering the outside of the stomach is visceral. The term "eviscerate" means to remove organs, reinforcing that "visceral" relates to organs.
    • Parietal: Describes a membrane or covering that lines the body wall or structures forming the body wall, but is not directly on the organ itself.
      • Example: The peritoneum has a visceral portion covering the stomach, but it also wraps around and lines the internal surface of the body wall's muscles; this lining portion is parietal.
  • Superficial / Deep:
    • Superficial: Towards the surface of the body or a structure.
    • Deep: Underneath the surface, further away from the surface.
    • Significance: These terms are crucial because the human body is three-dimensional.
      • Example: Skin is superficial to muscles. Muscles are deep to the skin.
      • Application to Blood Vessels: Superficial veins are visible just under the skin (e.g., medial antebrachial cutaneous vein). Deeper veins and arteries (e.g., ulnar and radial arteries) are located inside the muscle.
      • Pulsations: The radial artery becomes somewhat superficial near the wrist, allowing for a radial pulse to be taken. Similarly, an ulnar pulse can be felt on the other side of the wrist. While relatively deep in the forearm, these arteries adopt a more superficial position closer to the wrist.
  • Inferior / Superior:
    • Inferior: Away from the head end; lower.
    • Superior: Towards the head end; upper.
  • Ipsilateral / Contralateral:
    • These terms relate to the midsagittal plane (an imaginary line dividing the body into equal left and right halves).
    • Ipsilateral: Refers to structures or occurrences on the same side of the midsagittal plane.
      • Example: A right kidney and a right lung are ipsilateral.
    • Contralateral: Refers to structures or occurrences on opposite sides of the midsagittal plane.
      • Example: A left kidney and a right testicle are contralateral. Ovaries (one on each side) are contralateral. Any right and left paired structures are considered contralateral.
Importance of Directional Terms
  • Foundation for Description: Mastering these terms is essential as they are continuously used to describe anatomical structures throughout the course.
  • Vast Usage: Unlike some informational points that are seasonal, directional terms will be used consistently for the entire quarter and are fundamental for understanding anatomy.