Body Structures: Body Systems and Anatomical Terminology

Levels of Structural Organization

  • Organ: Structure composed of two or more tissue types.
  • Organ System: Group of organs working together; individual organs can belong to more than one system.
  • Organism: A living being with a cellular structure capable of independently performing all physiologic functions necessary for life.
  • The 11 Human Organ Systems:
    • Integumentary
    • Skeletal
    • Muscular
    • Nervous
    • Endocrine
    • Cardiovascular
    • Lymphatic
    • Respiratory
    • Digestive
    • Urinary
    • Reproductive

Anatomical Orientation and Regional Terminology

  • Anatomical Terminology Roots: Use of precise terms prevents clinical errors. The root specifies the organ, tissue, or condition, while prefixes and suffixes describe the root (e.g., hypertension: hyper = high, tension = pressure).
  • Standard Anatomical Position: The reference body map with the body standing erect, facing forward, arms at sides, and palms facing anteriorly.
  • Body Orientations:
    • Supine: Body lying horizontally on the back, facing upward.
    • Prone: Body lying horizontally on the stomach, facing downward.
  • Specific Regional Designations:
    • Arm (brachium): Strictly reserved for the upper arm (shoulder to elbow).
    • Forearm (antebrachium): Preferred over "lower arm" (elbow to wrist).
    • Thigh (femur): Portion of the lower limb from the hip to the knee.
    • Leg (crus): Strictly reserved for the limb segment between the knee and the ankle.

Directional Terms and Body Planes

Directional Terms Applied to the Human Body

  • Paired Directional Terms:
    • Anterior / Ventral: Toward the front.
    • Posterior / Dorsal: Toward the back.
    • Superior / Cranial: Toward the head or upper body.
    • Inferior / Caudal: Toward the feet or lower body.
    • Medial / Lateral: Toward the midline / away from the midline.
    • Proximal / Distal: Nearer to the limb point of origin / farther from the limb point of origin.
    • Superficial / Deep: Nearer to the surface / farther into the interior of the body.
    • Central / Peripheral: Toward the center / toward the outer edges.
    • Rostral: Toward the nose or beak (the central nervous system follows a curved rostro-caudal axis).

Body Planes

  • Body Planes:
    • Sagittal Plane: Divides the body vertically into right and left portions (midsagittal runs directly down the midline; parasagittal runs parallel to the midline).
    • Frontal (Coronal) Plane: Divides the body vertically into anterior (front) and posterior (back) portions.
    • Transverse (Horizontal) Plane: Divides the body horizontally into superior (upper) and inferior (lower) portions.

Body Cavities and Subdivisions

Dorsal and Ventral Body Cavities

  • Dorsal (Posterior) Body Cavity:
    • Cranial Cavity: Encloses the brain.
    • Spinal (Vertebral) Cavity: Encloses the spinal cord.
  • Ventral (Anterior) Body Cavity:
    • Thoracic Cavity: Superior compartment containing the pleural cavities (lungs), superior mediastinum, and pericardial cavity within the mediastinum (heart). Bounded inferiorly by the diaphragm.
    • Abdominopelvic Cavity: Compartment inferior to the diaphragm, divided into:
    • Abdominal Cavity: Houses digestive viscera.
    • Pelvic Cavity: Houses bladder, reproductive organs, and rectum.

Regions and Quadrants of the Abdominopelvic Cavity

  • Nine Abdominopelvic Regions:
    • Superior row: Right hypochondriac region (1), Epigastric region (2), Left hypochondriac region (3)
    • Middle row: Right lumbar region (4), Umbilical region (5), Left lumbar region (6)
    • Inferior row: Right iliac region (7), Hypogastric region (8), Left iliac region (9)
  • Four Abdominopelvic Quadrants:
    • Right upper quadrant (RUQ)
    • Left upper quadrant (LUQ)
    • Right lower quadrant (RLQ)
    • Left lower quadrant (LLQ)

Serous Membranes

Serous Membrane Layers

  • Structure: Thin double-layered membranes (serosa) lining ventral body cavities and covering organs within them.
    • Parietal Layer: Lines the interior walls of the body cavity.
    • Visceral Layer: Adheres directly to the external surfaces of the organs.
    • Serous Cavity: Fluid-filled potential space between the parietal and visceral layers that reduces organ friction.
  • Specific Serous Membranes:
    • Pleura: Surrounds the lungs within the pleural cavity.
    • Pericardium: Surrounds the heart within the pericardial cavity.
    • Peritoneum: Surrounds multiple internal organs within the abdominopelvic cavity.

Questions & Discussion

  • Question: When you are lying down on your back, facing the sky, you are in which position?
    • Answer: a) Supine
  • Question: Which term describes your fingers relative to your wrist?
    • Answer: d) Distal
  • Question: What is the name of abdominal region number 6?
    • Answer: a) Left Lumbar