Cavities provide different degrees of protection to organs within them Two sets

Cavities provide different degrees of protection to organs within them • Two sets of cavities • Dorsal body cavity • Ventral body cavity Dorsal Body Cavity • Protects fragile nervous system • Two subdivisions • Cranial cavity • Encases brain • Vertebral cavity • Encases spinal cord Ventral Body Cavity • Houses the internal organs (collectively called viscera ) • Two subdivisions, which are separated by the diaphragm • Thoracic cavity • Abdominopelvic cavity Ventral Body Cavity (cont.) • Thoracic cavity • Two pleural cavities • Each cavity surrounds one lung • Mediastinum • Contains pericardial cavity • Surrounds other thoracic organs, such as esophagus, trachea, etc. • Pericardial cavity • Encloses heart Ventral Body Cavity (cont.) • Abdominopelvic cavity 6

• Abdominal cavity • Contains stomach, intestines, spleen, and liver • Pelvic cavity • Contains urinary bladder, reproductive organs, and rectum Clinical – Homeostatic Imbalance 1.1 • Whereas the pelvic bones provide limited protection to the pelvic cavity, the walls of abdominal cavity are formed by muscle only, so organs in this area are most vulnerable to trauma Ventral Body Cavity (cont.) • Membranes in ventral body cavity • Serosa (also called serous membrane ) • Thin, double-layered membranes that cover surfaces in ventral body cavity Parietal serosa lines internal body cavity walls Visceral serosa covers internal organs (viscera) • Double layers are separated by slit-like cavity filled with serous fluid • Fluid secreted by both layers of membrane Ventral Body Cavity (cont.) • Named for specific cavity and organs that they are associated with • Pericardium • Heart • Pleurae • Lungs • Peritoneum • Abdominopelvic cavity Clinical – Homeostatic Imbalance 1.2 • Serous membranes can become inflamed as a result of infection or other causes • Normally smooth layers can become rough and even can stick together, resulting in excruciating pain • Examples: pleurisy and peritonitis Ventral Body Cavity (cont.) • Abdominopelvic quadrants and regions • Quadrants are divisions used primarily by medical personnel • Abdominopelvic region is sectioned into quarters – Right upper quadrant (RUQ) – Left upper quadrant (LUQ) – Right lower quadrant (RLQ) – Left lower quadrant (LLQ) Ventral Body Cavity (cont.)  Abdominopelvic quadrants and regions (cont.) • Nine divisions called regions , resembling a tic-tac-toe grid, are used primarily by anatomists • Right hypochondriac region • Epigastric region 7

• Left hypochondriac region • Right lumbar region • Umbilical region • Left lumber region • Right Iliac (inguinal) region • Hypogastric region • Left iliac (inguinal) region Other Body Cavities • In addition to the two main body cavities, the body has several smaller cavities that are exposed to environment • Oral and digestive cavities • Nasal cavity • Orbital cavities • Middle ear cavities • Not exposed to environment • Synovial cavities : joint cavities 8