Anatomy and Physiology: Key Terminology

Understanding the Body: A Simple Guide

  • We use specific words to describe body parts, their positions, and how they relate to each other. Think of it as a universal language for anatomy.
  • Our main reference point for all descriptions is the Anatomic Position.
Anatomic Position and Directional Words
  • Anatomic Position: Imagine someone standing straight up, feet together or slightly apart, arms at their sides with palms facing forward, and thumbs pointing away from the body.
  • Directional Terms (words to describe location):
    • Anterior (Ventral): Towards the front of the body.
    • Posterior (Dorsal): Towards the back of the body.
    • Superior (Cranial): Towards the head or upper part.
    • Inferior (Caudal): Towards the feet or lower part.
    • Medial: Towards the middle of the body.
    • Lateral: Away from the middle of the body (towards the sides).
    • Proximal: Closer to the point where a limb attaches to the body (e.g., shoulder is proximal to the elbow).
    • Distal: Further from the point where a limb attaches to the body (e.g., fingers are distal to the wrist).
    • Superficial: Towards the body's surface.
    • Deep: Away from the body's surface (more internal).
    • Ipsilateral: On the same side of the body.
    • Contralateral: On the opposite side of the body.
Imaginary Slices of the Body (Planes)
  • These are imaginary flat surfaces that divide the body.
    • Sagittal: Divides the body into left and right parts.
    • Midsagittal (Median): A special sagittal plane that divides the body into equal left and right halves.
    • Frontal (Coronal): Divides the body into front (anterior) and back (posterior) parts.
    • Transverse (Horizontal): Divides the body into upper (superior) and lower (inferior) parts.
    • Oblique: Any slice that isn't parallel to the sagittal, frontal, or transverse planes.
Body "Rooms" and Their Linings
  • Body Cavities: Spaces within the body that hold organs.
    • Dorsal Body Cavity (towards the back):
    • Cranial cavity: Contains the brain.
    • Vertebral (Spinal) cavity: Contains the spinal cord.
    • Ventral Body Cavity (towards the front):
    • Thoracic cavity: Contains the chest organs.
      • Pleural cavities: Each holds a lung.
      • Pericardial cavity: Holds the heart.
    • Abdominopelvic cavity: Contains organs in the abdomen and pelvis.
      • Abdominal subdivision: Upper part (stomach, intestines, etc.).
      • Pelvic subdivision: Lower part (bladder, reproductive organs).
      • Peritoneal cavity: A space within the abdominopelvic cavity.
  • Serous Membranes: Thin, double-layered membranes that line these cavities and cover organs, reducing friction.
    • They have a parietal layer (lining the cavity wall) and a visceral layer (covering the organ).
    • Pericardium: Around the heart.
    • Pleura: Around the lungs.
    • Peritoneum: In the abdominopelvic cavity.
Mapping the Abdomen
  • We divide the abdomen in two ways to easily describe organ locations or pain:
    • Quadrants (simpler, 4 sections):
    • Right Upper (RUQ)
    • Left Upper (LUQ)
    • Right Lower (RLQ)
    • Left Lower (LLQ)
    • Nine-Region Method (more detailed, 9 sections):
    • Epigastric (upper middle)
    • Right hypochondriac (upper right)
    • Left hypochondriac (upper left)
    • Umbilical (middle, around belly button)
    • Right lumbar (middle right)
    • Left lumbar (middle left)
    • Right iliac (inguinal) (lower right)
    • Left iliac (lower left)
    • Hypogastric (lower middle)
How the Body is Built (Levels of Organization)
  • The body is organized from simplest to most complex:
    1. Chemical: Atoms and molecules.
    2. Cellular: Cells are the basic units of life.
    3. Tissue: Groups of similar cells working together.
    4. Organ: Structures made of different tissues working together (e.g., heart, brain).
    5. Organ System: A group of organs working together for a major function (e.g., digestive system).
    6. Organism: A complete living being.
The Eleven Organ Systems (Teams of Organs)
  1. Integumentary: Skin, hair, nails (protection, temperature regulation).
  2. Skeletal: Bones, joints (support, protection, movement).
  3. Muscular: Muscles (movement, posture, heat production).
  4. Nervous: Brain, spinal cord, nerves (control, communication).
  5. Endocrine: Glands (hormones for regulation).
  6. Cardiovascular: Heart, blood vessels (transport of blood).
  7. Lymphatic/Immune: Lymph nodes, spleen (fluid balance, defense against disease).
  8. Respiratory: Lungs, airways (gas exchange).
  9. Digestive: Stomach, intestines (food breakdown, nutrient absorption).
  10. Urinary: Kidneys, bladder (waste removal, fluid balance).
  11. Reproductive: Ovaries/testes (producing offspring).
How the Body Stays in Balance (Feedback Loops)
  • Negative feedback: This is the most common type. It works to reverse a change and bring the body back to its normal state (homeostasis). Think of a thermostat: if it gets too hot, the AC turns on to cool it down.
  • Positive feedback: This is less common. It amplifies or intensifies a process. It usually needs an external event to stop it. Examples include childbirth (contractions get stronger) and blood clotting (platelets attract more platelets).