Overview
This lecture introduces body cavities, the organs they contain, and the membranes that protect and separate these organs within the human body.
Types of Body Cavities
- The body has sinuses (empty or fluid/air-filled spaces) and cavities (contain organs).
- Main body cavities are the dorsal (back) and ventral (front) cavities.
Dorsal Cavity
- Located at the back, containing the brain (in the cranial cavity) and spinal cord (in the vertebral cavity).
- Protected by hard bones, three layers of meninges, and cerebrospinal fluid for cushioning.
Ventral Cavity
- Located at the front, contains soft organs like lungs, liver, intestines, and reproductive organs.
- Has less bony protection and more flexibility to accommodate changing organ sizes.
- Divided by the diaphragm into the thoracic cavity (above) and abdominopelvic cavity (below).
Thoracic and Abdominopelvic Cavities
- Thoracic cavity contains two pleural cavities for the lungs and a pericardial cavity for the heart.
- Abdominopelvic cavity holds most digestive and immune organs and extends from rib cage to pelvic floor.
Other Cavities
- Includes orbital cavities (eyes) and the oral cavity (mouth).
Serous Membranes
- Serous membranes are epithelial tissue layers that reduce friction between organs.
- Each membrane has a parietal layer (lines cavity walls) and visceral layer (wraps organs), separated by serous fluid.
- Membranes are named by location: pericardium (heart), pleura (lungs), etc.
- Heart membranes have an extra fibrous outer layer; visceral heart membrane is called epicardium.
Key Terms & Definitions
- Sinus — an empty or fluid/air-filled space in the body.
- Body cavity — a space in the body containing organs.
- Dorsal cavity — cavity at the back, housing brain and spinal cord.
- Ventral cavity — cavity at the front, housing organs like lungs, heart, and digestive system.
- Thoracic cavity — upper ventral cavity housing lungs (pleural) and heart (pericardial).
- Abdominopelvic cavity — lower ventral cavity containing digestive and pelvic organs.
- Serous membrane — tissue lining cavities/organs, produces lubricating serous fluid.
- Parietal layer — membrane lining the cavity wall.
- Visceral layer — membrane covering an organ.
Action Items / Next Steps
- Watch the upcoming video on tissue types and learn to distinguish epithelial and connective tissues.
- Review anatomy basics in the recommended playlist.