Body Cavities and Membranes Overview

Overview

This lecture covers the major body cavities and membranes in the human body, focusing on their locations, subdivisions, and protective functions.

The body has two major cavities: the dorsal (back) and ventral (front) cavities.
The dorsal cavity houses the central nervous system (brain and spinal cord).
The dorsal cavity is subdivided into the cranial cavity (brain) and vertebral cavity (spinal cord).
The ventral cavity contains the visceral organs (internal "guts").
The ventral cavity is subdivided into the thoracic and abdominopelvic cavities, separated by the diaphragm.

The thoracic cavity (chest) lies above the abdominopelvic cavity and contains heart, lungs, trachea, and esophagus.
The thoracic cavity is divided into left pleural cavity (left lung), mediastinum (heart, thymus, esophagus, trachea), and right pleural cavity (right lung).
The heart is located in the mediastinum and surrounded by the pericardial cavity.
The abdominopelvic cavity includes the abdominal cavity (liver, stomach, pancreas, spleen, gallbladder, intestines, kidneys) and pelvic cavity (bladder, reproductive organs, lower intestine).

Other small cavities include oral, orbital, nasal, middle ear, and synovial (joint) cavities.

Major body cavities are lined with membranes that protect and cover organs.
The dorsal cavity is lined by three meninges: dura mater, arachnoid, and pia mater.
Meningitis is inflammation of the meninges and presents with a stiff neck.
The ventral cavity is lined by serous membranes, which secrete serous fluid for organ lubrication.

The pleura covers each lung and lines the pleural cavities.
The pericardium covers the heart and lines the pericardial cavity.
The peritoneum covers abdominal organs and lines the peritoneal cavity.
The visceral layer of a serous membrane touches the organ; the parietal layer lines the cavity wall.

Visceral (touches organ/viscera), Parietal (lines cavity wall).
Retroperitoneal = behind the peritoneal space; intraperitoneal = within; subperitoneal = below.

Dorsal cavity — Cavity at the back of the body containing the brain and spinal cord.
Ventral cavity — Front cavity containing visceral organs.
Thoracic cavity — Upper ventral cavity, above the diaphragm, housing lungs and heart.
Abdominopelvic cavity — Lower ventral cavity, subdivided into abdominal and pelvic.
Pleura — Serous membrane covering the lungs.
Pericardium — Serous membrane surrounding the heart.
Peritoneum — Serous membrane lining the abdominopelvic organs.
Meninges — Three protective membranes of the brain and spinal cord.
Visceral layer — Membrane layer touching the organ surface.
Parietal layer — Membrane layer lining the cavity wall.