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Lecture 3 BIOL 211 Chapter 1 Notes (Orientation, Cont.)

Body Planes

  • Plane = a flat surface along which a body or structure is cut for anatomical study.
  • Sagittal plane
    • Divides the body vertically into right and left parts
    • Produces a sagittal section
    • Midsagittal (median) plane lies along the midline
    • Parasagittal plane is not on the midline
    • Median (midsagittal) plane
    • Examples referenced: vertebral column, rectum, intestines (illustrative cross-sections)
  • Frontal (Coronal) plane
    • Vertical plane that divides the body into anterior and posterior parts
    • Examples shown: Right lung, Heart, Left lung, Liver, Stomach, Spleen
  • Transverse (Horizontal) plane
    • Horizontal plane that divides the body into superior (cranial) and inferior (caudal) parts
    • Produces a cross section
    • Examples shown: Liver, Aorta, Pancreas, Spleen, Subcutaneous fat layer, Spinal cord
  • Oblique (Tangential) section
    • Occurs from cuts made diagonally or at a tangent
  • Anatomical Variability
    • Over >90\% of all anatomical structures match textbook descriptions, but:
    • Nerves or blood vessels may be somewhat out of place
    • Small muscles may be missing

Body Cavities and Membranes

  • The body contains internal cavities that are closed to the environment
  • Cavities provide different degrees of protection to organs within them
  • There are 2 sets of cavities:
    • Dorsal body cavity
    • Ventral body cavity
  • Dorsal cavity
    • Protects nervous system
    • Subdivisions:
    • Cranial cavity
      • Encases brain
    • Vertebral cavity
      • Encases spinal cord
  • Ventral cavity
    • Houses internal organs (viscera)
    • Single organ = viscus
    • Two subdivisions (separated by diaphragm):
    • Thoracic cavity
    • Abdominopelvic cavity
  • Ventral Body Cavities
    • Subdivisions of the thoracic cavity:
    • Two pleural cavities (each houses a lung)
    • Mediastinum (surrounds remaining thoracic organs: trachea, esophagus, aorta, etc.)
    • Contains pericardial cavity (which encloses the heart)
    • Subdivisions of the abdominopelvic cavity:
    • Abdominal cavity: contains stomach, intestines, spleen, and liver
    • Pelvic cavity: contains urinary bladder, reproductive organs, and rectum
  • Diaphragm
    • Boundary between thoracic cavity and abdominopelvic cavity
  • Additional notes on body cavity arrangement (from figure descriptions)
    • Cranial cavity (contains brain)
    • Dorsal body cavity
    • Vertebral cavity (contains spinal cord)
    • Abdomino-pelvic cavity
    • Thoracic cavity (contains heart and lungs)
    • Abdominal cavity (contains digestive viscera)
    • Pelvic cavity (contains urinary bladder, reproductive organs, and rectum)
    • Superior mediastinum and pericardial cavity within the mediastinum (illustrative labeling)
    • Pleural cavities and other labeled structures in relation to the thoracic region

Serous Membranes and the Serosa

  • Serous membranes (serosa) are thin, double-layered membranes that cover surfaces in ventral body cavity
  • Components:
    • Parietal serosa lines the surface of internal body cavity walls
    • Visceral serosa covers the surface of internal organs (viscera)
    • The two layers are separated by a slit-like cavity filled with serous fluid
    • Fluid is secreted by both layers
  • Analogy (from clinical discussion):
    • Outer balloon wall = parietal serosa
    • Air between layers = serous cavity
    • Inner balloon wall = visceral serosa
  • Specific serosae associated with the heart and thoracic organs:
    • Pericardial cavity (within the mediastinum) enclosed by the pericardium (a serous membrane around the heart)
    • Pleural cavities (around the lungs) enclosed by pleurae
    • Peritoneum (around abdominal viscera)

Clinical – Homeostatic Imbalance: Serous Membranes

  • Serous membranes can become inflamed due to infection or other causes
  • Normally smooth layers can become rough and can stick together, causing severe pain
  • Examples:
    • Pleurisy = inflammation of the pleurae
    • Pericarditis = inflammation of the pericardium
    • Peritonitis = inflammation of the peritoneum

Abdominopelvic Quadrants

  • Divisions used primarily by medical personnel
  • Right upper quadrant (RUQ)
  • Right lower quadrant (RLQ)
  • Left upper quadrant (LUQ)
  • Left lower quadrant (LLQ)

Abdominopelvic Regions

  • Liver-related mapping (illustrative)
  • The nine regions delineated by four planes (anterior view of the nine regions)
  • Regions:
    • Right hypochondriac region
    • Epigastric region
    • Left hypochondriac region
    • Right lumbar region
    • Umbilical region
    • Left lumbar region
    • Right iliac (inguinal) region
    • Hypogastric (pubic) region
    • Left iliac (inguinal) region
  • Common organ mappings (illustrative):
    • Liver located in the right hypochondriac and epigastric regions
    • Gallbladder nearby in the right hypochondriac region
    • Spleen located in the left hypochondriac region
    • Stomach located in the epigastric region
    • Small intestine and Cecum distributed in multiple adjacent regions
    • Diaphragm forms superior boundary; Urinary bladder, portions of reproductive organs, and rectum lie within the lower regions
  • Practical note: Nine regions provide finer localization beyond the four quadrants for anatomical study and clinical reference

Smaller Cavities Exposed to Environment vs NOT Exposed

  • Exposed to environment:
    • Oral cavity (mouth)
    • Digestive cavity (continues from oral to anus, but discussed separately as a cavity line in some contexts)
    • Nasal cavity
    • Orbital cavities (eye sockets)
    • Middle ear cavities
  • NOT exposed to environment (located within skull or bones):
    • Synovial cavities (joint cavities)

Quick Summary of Key Concepts

  • Planes organize how we study and view the body: sagittal, midsagittal, parasagittal, frontal/coronal, transverse/horizontal, oblique
  • Body cavities (dorsal vs ventral) and their subdivisions protect and compartmentalize organs
  • Ventral cavity contains thoracic and abdominopelvic subdivisions, separated by the diaphragm
  • Serous membranes (serosa) create closed, lubricated environments for organs; parietal vs visceral layers, serous fluid in between
  • Inflammatory diseases of serous membranes have well-known clinical names and implications
  • Quadrants provide a quick method for localization; nine-region plan offers detailed mapping for anatomy education
  • There are additional small cavities not exposed to the environment, alongside synovial cavities in joints