Dorsal and ventral cavities are sealed (closed off) from the external environment • Dorsal Body Cavity – Houses and protects nervous system – Two subdivisions: • Cranial cavity • Encases brain • Vertebral cavity • Encases spinal cord • Ventral Body Cavity – Houses and protects the internal visceral organs ( viscera ) – Can be divided into two subdivisions (separated by diaphragm) • Thoracic cavity • Abdominopelvic cavity – Thoracic cavity subdivisions • Two pleural cavities • Each surround a lung • Mediastinum
• Contains pericardial cavity • Surrounds some thoracic organs • Pericardial cavity • Encloses heart – Abdominopelvic cavity subdivisions • Abdominal cavity • Contains stomach, intestines, spleen, and liver • Pelvic cavity • Contains urinary bladder, reproductive organs, and rectum • Membranes in Ventral Body Cavity – Thoracic and abdominal body cavities are lined by thin, slippery, double-layered membranes called serous membranes. These membranes adhere to the outer surface of the organs or “viscera”, and then double-back on themselves to line the body cavity wall. – Serous membrane or serosa • Thin, double-layered membranes • Parietal serosa - lines internal body cavity walls • Visceral serosa - covers internal organs (viscera) • Layers separated by slit-like cavity filled with serous fluid • Fluid secreted by both layers of membrane • Serous Membranes – Named for specific cavity and organs with which associated –
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