Overview
This lecture introduces the four main body cavities—dorsal, thoracic, abdominal, and pelvic—and describes the location and function of the major organs and blood vessels within each.
Body Cavities: Overview
- The human body contains four main cavities: dorsal, thoracic, abdominal, and pelvic.
- Each cavity houses specific organs and structures critical to bodily function.
Dorsal Cavity
- Contains the brain (cranial cavity) and spinal cord (spinal/vertebral cavity).
- Located at the back of the body.
Thoracic Cavity
- Found above the diaphragm and encased by the rib cage.
- Contains the heart, major blood vessels (aorta, venae cavae, pulmonary arteries/veins), trachea, bronchi, lungs, and oesophagus.
- The heart is in the mediastinum and pumps blood to the body and lungs.
- The lungs are on either side of the thoracic cavity, flanking the heart.
- The trachea and bronchi conduct air to and from the lungs.
Diaphragm
- A dome-shaped muscle separating the thoracic and abdominal cavities.
- Contracts to draw air into the lungs and allows passage of certain blood vessels and the oesophagus.
Abdominal Cavity
- Located between the diaphragm and pelvis, divided into four quadrants for clinical reference.
- Houses the stomach, small and large intestines, liver, gallbladder, pancreas, spleen, and kidneys.
- Large blood vessels like the descending aorta and inferior vena cava run through it.
Digestive and Related Organs
- The oesophagus connects the mouth to the stomach, passing posterior to the trachea.
- The stomach stores and initiates digestion of food, sending contents to the small intestine.
- The small intestine (duodenum, jejunum, ileum) absorbs nutrients and minerals.
- The large intestine (ascending, transverse, descending, sigmoid colons) absorbs moisture and compacts waste.
Major Abdominal Organs
- The liver (upper right quadrant) stores glycogen, manages blood sugar, breaks down fats and toxins, and produces bile.
- The gallbladder stores and releases bile for fat digestion.
- The spleen (upper left quadrant) breaks down old red blood cells, stores and releases blood, and fights infection.
- The pancreas produces digestive enzymes and hormones (insulin, glucagon) to regulate blood sugar.
- The kidneys filter blood, maintain fluid/electrolyte balance, and excrete waste as urine.
Pelvic Cavity
- Contains the rectum, urinary bladder (stores and releases urine), and reproductive organs.
- No physical barrier separates it from the abdominal cavity.
Reproductive Organs
- Female: ovaries (release eggs), fallopian tubes, uterus, vagina, and vulva.
- Male: testicles (produce sperm), scrotum, penis, prostate gland, seminal vesicles, and vas deferens.
Key Terms & Definitions
- Cavity — a hollow space within the body that houses organs.
- Diaphragm — a muscle separating thoracic and abdominal cavities, vital for breathing.
- Mediastinum — central compartment of thoracic cavity containing the heart.
- Venae cavae — major veins returning blood to the heart.
- Aorta — largest artery, carries blood from heart to body.
- Oesophagus — muscular tube connecting mouth to stomach.
- Duodenum, Jejunum, Ileum — sections of the small intestine.
- Colon — sections of the large intestine.
Action Items / Next Steps
- Review the structure and function of each body cavity and its organs.
- Watch recommended videos on the respiratory system and kidney function as additional resources.