Body Cavities and Membranes

The body is internally divided into two major body cavities, dorsal and ventral (fig. A.7). The organs within them are called the viscera (VISS-er-uh) (singular, viscus9). Various membranes line the cavities, cover the viscera, and hold the viscera in place (table A.2).

Dorsal Body Cavity

The dorsal body cavity has two subdivisions: (1) the cranial (CRAY-nee-ul) cavity, which is enclosed by the cranium (braincase) and contains the brain, and (2) the verte bral canal, which is enclosed by the vertebral column (backbone) and contains the spinal cord. The dorsal body cavity is lined by three membrane layers called the meninges (meh-NIN-jeez). Among other functions, the meninges protect the delicate nervous tissue from the hard protective bone that encloses it.

Ventral Body Cavity

During embryonic development, a space called the coelom (SEE-loam) forms within the trunk and eventually gives rise to the ventral body cavity. This cavity later becomes partitioned by a muscular sheet, the diaphragm, into a superior thoracic cavity and an inferior abdominopelvic cavity. The thoracic and abdominopelvic cavities are lined with thin serous membranes. These membranes secrete a lubricating film of moisture similar to blood serum (hence the name serous).

Thoracic Cavity

The thoracic cavity is divided into right, left, and medial portions by a partition called the mediastinum10 (ME-dee-ass-TY-num) (fig. A.7). The right and left sides contain the lungs and are lined by a two-layered membrane called the pleura11 (PLOOR-uh) (fig. A.8a). The outer layer, etal12 (pa-RY-eh-tul) pleura, lies against the inside of the

8ante = fore, before + brachi = arm 9 viscus = body organ mediastinum = in the middle

11 pleur = rib, side

12 pariet = wall

Dorsal body cavity

Ventral body — cavity

Abdominopelvic -cavity

Cranial cavity-

Vertebral canal-Spinal cord-

Thoracic cavity

Diaphragm -

Abdominal cavity

Pelvic cavity-

Cranial cavity-

Vertebral canal-Spinal cord-

Thoracic cavity

Abdominal cavity

Body Cavities

Diaphragm

Abdominopelvic Cavity

- Mediastinum

- Pleural cavity Pericardial cavity

Thoracic cavity

Abdominal cavity

Pelvic cavity

Abdominopelvic cavity

Figure A.7 The Major Body Cavities. (a) Left lateral view; (b) anterior view of the ventral body cavity.

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Atlas A General Orientation to Human Anatomy 37

Table A.2 Body Cavities and Membranes

Name of Cavity Associated Viscera Membranous Lining

Dorsal Body Cavity

Cranial cavity

Brain

Meninges

Vertebral canal

Spinal cord

Meninges

Ventral Body Cavity

Thoracic Cavity

Pleural cavities (2)

Lungs

Pleurae

Pericardial cavity

Heart

Pericardium

Abdominopelvic Cavity

Abdominal cavity

Digestive organs, spleen, kidneys

Peritoneum

Pelvic cavity

Bladder, rectum, reproductive organs

Peritoneum

Pleural Pericardial Cavities
Figure A.8 Parietal and Visceral Layers of Double-Walled Membranes. (a) The pleura; (b) the pericardium.

rib cage; the inner layer, or visceral (VISS-er-ul) pleura, forms the external surface of the lung. The narrow, moist space between the visceral and parietal pleurae is called the pleural cavity (see fig. A.19). It is lubricated by a slippery pleural fluid.

The medial portion, or mediastinum, is occupied by the esophagus and trachea, a gland called the thymus, and the heart and major blood vessels connected to it. The heart is enclosed by a two-layered membrane called the pericardium.13 The visceral pericardium forms the heart

,3peri = around + cardi = heart surface, while the parietal pericardium is separated from it by a space called the pericardial cavity (fig. A.8b). This space is lubricated by pericardial fluid.

Abdominopelvic Cavity

The abdominopelvic cavity consists of the abdominal cavity above the brim of the pelvis and the pelvic cavity below the brim (see fig. A.16). The abdominal cavity contains most of the digestive organs as well as the kidneys and ureters. The pelvic cavity is markedly narrower and its lower end tilts posteriorly (see fig. A.7a). It contains the distal part of the large intestine, the urinary bladder and urethra, and the reproductive organs.

Saladin: Anatomy & Physiology: The Unity of Form and Function, Third Edition

38 Part One Organization of the Body

The abdominopelvic cavity contains a moist serous membrane called the peritoneum14 (PERR-ih-toe-NEE-um). The parietal peritoneum lines the walls of the cavity, while the visceral peritoneum covers the external surfaces of most digestive organs. The peritoneal cavity is the space between the parietal and visceral layers. It is lubricated by peritoneal fluid.

Some organs of the abdominal cavity lie between the peritoneum and dorsal body wall (outside of the peritoneal cavity), so they are said to have a retroperitoneal15 position (fig. A.9). These include the kidneys, ureters, adrenal glands, most of the pancreas, and abdominal portions of two major blood vessels—the aorta and inferior vena cava (see fig. A.15).

The intestines are suspended from the dorsal abdominal wall by a translucent membrane called the mesentery16 (MESS-en-tare-ee), a continuation of the peritoneum. The membrane then wraps around the intestines and some other viscera, forming a moist membrane called the serosa (seer-OH-sa) on their outer surfaces (fig. A.10). The mesentery of the large intestine is called the mesocolon. The visceral peritoneum consists of the mesenteries and serosae.

A fatty membrane called the greater omentum17 hangs like an apron from the inferolateral margin of the peri = around + tone = stretched

15retro = behind

1Gmes = in the middle + enter = intestine

17 omentum = covering stomach and overlies the intestines (figs. A.10 and A.13). It is unattached at its inferior border and can be lifted to reveal the intestines. A smaller lesser omentum extends from the superomedial border of the stomach to the liver.

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Responses

  • annika
    Which body cavity contains the pleural and pericardial cavities?
    8 years ago
  • pimpernel burrows
    What is between the parietal and visceral pleura?
    8 years ago
  • vala
    What are the membranes associated with the thoracic cavity?
    8 years ago
  • Quintino
    What is the moist membrane that wraps around the intestines and other viscera?
    8 years ago
  • johan
    What encloses the ventral cavity?
    7 years ago
  • wilcome
    What three membranes (meninges) enclosed in the dorsal cavity?
    7 years ago
  • ambessa
    What 3 membranes enclose dorsal cavities?
    7 years ago
  • lisa
    What membranes line the cranial and bertebral cavities?
    7 years ago
  • URHO
    What major body cavity called the dorsal cavity of the heart?
    7 years ago
  • Trahand
    What is the two layered membrane of the abdominopelvic cavity called?
    7 years ago
  • reijo
    What part of the body is called the pericardium cavity?
    7 years ago
  • stephan
    What organs in the abdominopelvic cavity should have peritoneal serous membranes?
    7 years ago
  • ryan
    What are the two major body cavities?
    2 years ago

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