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Cavities of the Body
A cavity is a structure surrounded by bones and muscles within a space or soft organs and glands. There are four main cavities in the human body, they include
(1) Cranial cavity
(2) Thoracic cavity
(3) Abdominal cavity
(4) Pelvic cavity
The cavities in the human body can be discussed under the axial portion of the human organism. The axial portion includes the cranial cavity, which houses the brain, and the bones of the skull form its boundaries. They are formed anteriorly by the fronter bone, posteriorly by the occipital bone, laterally by two temporal bones, superiorly by the two parietal bones, inferiorly by the sphenoid, ethimoid, and parts of the occipital, temporal and frontal bone. The axial portion also contains the vertebral canal, which contains the spinal cord within the sections of the backbone.
Other cavities in the head are:
(1) Oral cavity: this contains the teeth and tongue.
(2) Nasal cavity: this cavity is located within the nose and are divided into right and left portion by a nasal septum. The frontal and the sphenoidal sinus connects to the nasal cavity.
(3) Orbital cavity: it contains the eyes and associated muscles and nerves.
(4) Middle ear cavities: contains the middle ear bones.
The trunk in the axial portion includes two large cavities. The thoracic cavity and the abdominopelvic cavity, which are separated by the diaphragm. The thoracic cavity is located at the upper part of the trunk and bones and muscles form its boundaries. anteriorly the are formed by the sternum and coastal cartilages of the ribs, posteriorly by the thoracic vertebrae and intercostal disc, laterally by the twelve pairs of ribs and intercostal muscles, superiorly by the structure that forms the root of the neck, and inferiorly by the diaphragm. the thoracic cavity is also broken down into two smaller cavities, it includes the right and left pleural cavity holding the lungs, pericardial cavity holding the heart and the mediastinum which is the space between the lungs houses the structures found there such as the esophagus, the trachea, heart and blood vessels. The reason why there are several cavities in the thoracic cavity is that the lungs and the heart are surrounded by its own serous membrane. The serous membrane coutions the organs found in it and reduce friction between the organs. In the pleural cavity, the wall of the right and left thoracic compartments containing the lungs are lined with a membrane called parietal pleura and a membrane called the visceral pleura covers the lungs. A thin film of watering fluid, which they secrete, separates these two membranes. In the pericardial cavity, the heart is located at the broad portion of the mediastinum, its wall is lined with a membrane called parietal pericardium, and a membrane called visceral pericardium covers the heart itself. A thin volume of fluid separates the two membrane and the potential space between the membranes is called the pericardial cavity. contents found in the thoracic cavity includes the trachea, two bronchi, two lungs, heart, aorta, lymph vessels, nerves, several blood vessels and the esophagus.
The abdominopelvic cavity: this is also broken down into the abdominal cavity and pelvic cavity. The abdominal cavity, which is the largest cavity of the body, is located at the lower part of the trunk. Muscle of the abdominal wall, posteriorly by the lumber vertebrae and the muscles of the posterior abdominal wall, laterally by the lower ribs and the muscles of the abdominal wall bound the abdominal cavity anteriorly, and inferiorly it continues with the pelvic cavity. The organs within the abdominal cavity are the stomach, liver, spleen, kidney, gall bladder, pancreas, and upper part of the ureter, small intestine, most of the large intestine, blood vessels, nerves, lymph nodes, and the bile duct. The wall of the abdominal cavity is lined with a membrane called parietal peritoneum while each organs in the abdominal cavity are covered with a peritoneum membrane called the visceral peritoneum.
Pelvic cavity: this is an extension of the lower abdomen; it is a funnel shaped region. The boundaries are formed anteriorly by the pubic bones, posteriorly by the sacrum and coccyx, superiorly it continues with the abdominal cavity and inferiorly by the muscles of the pelvic floor. The wall of the pelvic cavity is lined with a peritoneal membrane called parietal peritoneum, while each organs within the pelvic cavity is covered with a membrane called visceral peritoneum. the content within the pelvic cavity are sigmoid Colum, rectum, anus, some loops of the small intestine, the urinary bladder, lower part of the ureter, the urethra.
In female the content found are the uterus, uterine tube, ovary and vagina, while In male the content found are the prostate gland, seminal vesicles, spermatic cord, ejaculatory duct and the urethra.