Abody cavityis any space or compartment, orpotential space,in an animal body. Cavities accommodate organs and other structures; cavities as potential spaces contain fluid.
| Body cavity | |
|---|---|
 Cross-section showingcavities in the human body,the dorsal and ventral body cavities labelled. | |
 Cross-section of anoligochaete worm.The worm's body cavity surrounds the centraltyphlosole. | |
| Identifiers | |
| FMA | 85006 |
| Anatomical terminology | |
The two largest human body cavities are theventral body cavity,and thedorsal body cavity.In the dorsal body cavity the brain and spinal cord are located.
The membranes that surround thecentral nervous systemorgans (thebrainand thespinal cord,in thecranialandspinal cavities) are the threemeninges.The differently lined spaces contain different types of fluid. In the meninges for example the fluid iscerebrospinal fluid;in theabdominal cavitythe fluid contained in theperitoneumis aserous fluid.
Inamniotesand someinvertebratesthe peritoneum lines their largest body cavity called thecoelom.
Mammals
editMammalian embryos develop two body cavities: theintraembryonic coelomand theextraembryonic coelom(orchorionic cavity). The intraembryonic coelom is lined by somatic and splanchnic lateral plate mesoderm, while the extraembryonic coelom is lined by extraembryonic mesoderm. The intraembryonic coelom is the only cavity that persists in the mammal at term, which is why its name is often contracted to simplycoelomic cavity.Subdividing the coelomic cavity into compartments, for example, thepericardial cavity/pericardium,where the heart develops, simplifies discussion of theanatomiesof complex animals.
Cavitationin the early embryo is the process of forming theblastocoel,the fluid-filled cavity defining theblastulastage in non-mammals, or theblastocystin mammals.
Human body cavities
editThedorsal(posterior) cavity and theventral(anterior) cavity are the largest body compartments.
Thedorsal body cavityincludes thecranial cavity,enclosed by theskulland contains thebrain,and thespinal cavity,enclosed by thespine,and contains thespinal cord.[1]
Theventral body cavityincludes thethoracic cavity,enclosed by theribcageand contains thelungsandheart;and theabdominopelvic cavity.The abdominopelvic cavity can be divided into theabdominal cavity,enclosed by theribcageandpelvisand contains thekidneys,ureters,stomach,intestines,liver,gallbladder,andpancreas;and thepelvic cavity,enclosed by thepelvisand containsbladder,anusandreproductive system.[1]
| Name of cavity | Principal contents | Membranous lining | ||
|---|---|---|---|---|
| Dorsal body cavity | Cranial cavity | Brain | Meninges | |
| Vertebral canal | Spinal cord | Meninges | ||
| Ventral body cavity | Thoracic cavity | Heart,lungs | Pericardium Pleural cavity | |
| Abdominopelvic cavity | Abdominal cavity | Digestive organs,spleen,kidneys | Peritoneum | |
| Pelvic cavity | Bladder,reproductive organs | Peritoneum | ||
Ventral body cavity
editThe ventral cavity has two main subdivisions: the thoracic cavity and the abdominopelvic cavity. The thoracic cavity is the more superior subdivision of the ventral cavity, and is enclosed by the rib cage. The thoracic cavity contains thelungssurrounded by thepleural cavity,and theheartsurrounded by thepericardial cavity,located in the mediastinum. Thediaphragmforms the floor of the thoracic cavity and separates it from the more inferior abdominopelvic cavity.
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.[2]
Dorsal body cavity
editThe dorsal body cavity contains thecranial cavity,and thespinal cavity. The cranial cavity is a large, bean-shaped cavity filling most of the upper skull where the brain is located. The spinal cavity is the very narrow, thread-like cavity running from the cranial cavity down the entire length of thespinal cord.
In the dorsal cavity, the cranial cavity houses thebrain,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.[2]
Development
editAt the end of the third week ofgestation,theneural tube,which is a fold of one of the layers of thetrilaminar germ disc,called theectoderm,appears. This layer elevates and closes dorsally, while the gut tube rolls up and closes ventrally to create a "tube on top of a tube". Themesoderm,which is another layer of the trilaminar germ disc, holds the tubes together and thelateral plate mesoderm,the middle layer of the germ disc, splits to form a visceral layer associated with the gut and a parietal layer, which along with the overlying ectoderm, forms the lateral body wall. The space between the visceral and parietal layers of lateral plate mesoderm is the primitive body cavity. When the lateral body wall folds, it moves ventrally and fuses at the midline. The body cavity closes, except in the region of the connecting stalk. Here, the gut tube maintains an attachment to the yolk sac. The yolk sac is a membranous sac attached to the embryo, which provides nutrients and functions as the circulatory system of the very early embryo.[3]
The lateral body wall folds, pulling theamnionin with it so that the amnion surrounds the embryo and extends over the connecting stalk, which becomes theumbilical cord,which connects the fetus with theplacenta.If the ventral body wall fails to close, ventral body wall defects can result, such asectopia 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 theserous membranescovering the lungs, heart, and abdominal organs. These layers are continuous at the root of each organ as the organs lie in their respective cavities. Theperitoneum,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.[4]
Function
editThese cavities contain and protect delicate internal organs, and the ventral cavity allows for significant changes in the size and shape of the organs as they perform their functions.
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.[2]The ventral cavity includes the thoracic and abdominopelvic cavities and their subdivisions. The dorsal cavity includes the cranial and spinal cavities.[2]
Other animals
editOrganisms can be also classified according to the type of body cavity they possess, such aspseudocoelomatesandprotostomecoelomates.[5]
Coelom
editInamniotesand someinvertebrates,thecoelomis the large cavity lined bymesothelium,anepitheliumderived frommesoderm.Organs formed inside the coelom can freely move, grow, and develop independently of the body wall while fluid in theperitoneumcushions and protects them from shocks.
Arthropodsand mostmolluscshave a reduced (but still true) coelom, thehemocoel(of anopen circulatory system) and the smaller gonocoel (a cavity that contains thegonads). Their hemocoel is often derived from theblastocoel.
See also
editReferences
editThis Wikipedia entry incorporates text from the freely licensed Connexions[1]edition of Anatomy & Physiology[2]text-book by OpenStax College
- ^abEhrlich, A.; Schroeder, C.L. (2009), "The Human Body in Health and Disease",Introduction to Medical Terminology(Second ed.), Independence, KY: Delmar Cengage Learning, pp. 21–36
- ^abcd"Anatomy & Physiology".Openstax college at Connexions.RetrievedNovember 16,2013.
- ^Sadler (2012).LANGMAN Embriología médica.Vol. I (12 ed.). Philadelphia, PA: The Point.
- ^Tortora, Gerard; Derrickson, Bryan (2008).Principios de anatomía y fisiología.Vol. I (11 ed.). Buenos Aires: Panamericana.
- ^"Animals III — Pseudocoelomates and Protostome Coelomates".Archived fromthe originalon 2009-04-06.