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A body cavity is any space or compartment, or potential space, in an animal body. Cavities accommodate organs and other structures; cavities as potential spaces contain fluid.
The two largest human body cavities are the ventral body cavity, and the dorsal body cavity. In the dorsal body cavity the brain and spinal cord are located.
The membranes that surround the central nervous system organs (the brain and the spinal cord, in the cranial cavity and spinal cavity) are the three meninges. The differently lined spaces contain different types of fluid. In the meninges for example the fluid is cerebrospinal fluid; in the abdominal cavity the fluid contained in the peritoneum is a serous fluid.
In and some the peritoneum lines their largest body cavity called the coelom.
Cavitation in the early embryo is the process of forming the blastocoel, the fluid-filled cavity defining the blastula stage in non-mammals, or the blastocyst in mammals.
The dorsal body cavity includes the cranial cavity, enclosed by the skull and contains the Human brain, and the spinal cavity, enclosed by the Vertebral column, and contains the spinal cord.
The ventral body cavity includes the thoracic cavity, enclosed by the ribcage and contains the and heart; and the abdominopelvic cavity. The abdominopelvic cavity can be divided into the abdominal cavity, enclosed by the ribcage and human pelvis and contains the , , stomach, intestines, liver, gallbladder, and pancreas; and the pelvic cavity, enclosed by the human pelvis and contains urinary bladder, Human anus and reproductive system.
| + Human body cavities and membranes | |||
| Vertebral canal | Spinal cord | Meninges | |
| Abdominopelvic cavity | Abdominal cavity | Digestive organs, spleen, | Peritoneum |
| Pelvic cavity | Urinary bladder, reproductive organs | Peritoneum | |
The abdominopelvic cavity is the largest cavity in the body occupying the entire lower half of the trunk. Although no membrane physically divides the abdominopelvic cavity, it can be useful to distinguish between the abdominal cavity, and the pelvic cavity. The abdominal cavity occupies the entire lower half of the trunk, anterior to the spine, and houses the organs of digestion. Just under the abdominal cavity, anterior to the buttocks, is the pelvic cavity. The pelvic cavity is funnel shaped, and is located inferior and anterior to the abdominal cavity, and houses the organs of reproduction.
In the dorsal cavity, the cranial cavity houses the Human brain, and the spinal cavity encloses the spinal cord. Just as the brain and spinal cord make up a continuous, uninterrupted structure, the cranial and spinal cavities that house them are also continuous. The brain and spinal cord are protected by the bones of the skull and vertebral column and by cerebrospinal fluid, a colorless fluid produced by the brain, which cushions the brain and spinal cord within the dorsal body cavity.
The lateral body wall folds, pulling the amnion in with it so that the amnion surrounds the embryo and extends over the connecting stalk, which becomes the umbilical cord, which connects the fetus with the placenta. If the ventral body wall fails to close, ventral body wall defects can result, such as ectopia cordis, a congenital malformation in which the heart is abnormally located outside the thorax. Another defect is gastroschisis, a congenital defect in the anterior abdominal wall through which the abdominal contents freely protrude. Another possibility is bladder exstrophy, in which part of the urinary bladder is present outside the body. In normal circumstances, the parietal mesoderm will form the parietal layer of serous membranes lining the outside (walls) of the peritoneal, pleural, and pericardial cavities. The visceral layer will form the visceral layer of the covering the lungs, heart, and abdominal organs. These layers are continuous at the root of each organ as the organs lie in their respective cavities. The peritoneum, a serum membrane that forms the lining of the abdominal cavity, forms in the gut layers and in places mesenteries extend from the gut as double layers of peritoneum. Mesenteries provide a pathway for vessels, nerves, and lymphatics to the organs. Initially, the gut tube from the caudal end of the foregut to the end of the hindgut is suspended from the dorsal body wall by dorsal mesentery. Ventral mesentery, derived from the septum transversum, exists only in the region of the terminal part of the esophagus, the stomach, and the upper portion of the duodenum.
Anatomical structures are often described in terms of the cavity in which they reside. The body maintains its internal organization by means of membranes, sheaths, and other structures that separate compartments.
The lungs, heart, stomach, and intestines, for example, can expand and contract without distorting other tissues or disrupting the activity of nearby organs. The ventral cavity includes the thoracic and abdominopelvic cavities and their subdivisions. The dorsal cavity includes the cranial and spinal cavities.
and most Mollusca have a reduced (but still true) coelom, the hemocoel (of an open circulatory system) and the smaller gonocoel (a cavity that contains the ). Their hemocoel is often derived from the blastocoel.
This Wikipedia entry incorporates text from the freely licensed Connexions [1] edition of Anatomy & Physiology [2] text-book by OpenStax College
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