Contents of the cavities of the chest and abdomen
Contents of the cavities of the chest and abdomen (fig 2.11)
The interior of the trunk houses the cavities of the chest and abdomen, which are separated from each other at the level of the lower ribs by a dome-shaped muscular partition called the diaphragm.
The chest cavity is enclosed and protected by the doralventebrae at the back and the ribs and breastbone at the sides and in front.
It contains the following organs, most of which are involved in the circulation of the blood or breathing:
· On either side are the right and left lungs, which together fill the greater part of the chest cavity.
· The windpipe or trachea lies along the vertical middle of the neck and divides into two smaller tubes, the right and left bronchus, each of which enters the corresponding lung.
· The central portion of the chest is occupied by the heart and the great blood vessels which issue from it or enter it, namely the aorta and pulmonary artery, and the corresponding great veins.
· Behind the heart the gullet runs down from the neck where is lies behind the windpipe, to the diaphragm through which it passes to enter the stomach.
The abdominal cavity contains a large number of important organs most of which are involved in the digestion of food. It is protected at the back by the backbone, above by the lower ribs, and at its lowest portion by the pelvic bones. This portion lies wholly within the pelvis and is called the pelvic cavity.
· The stomach lies in the upper part of the abdomen immediately below the diaphragm, and mainly to the left side of the middle line. It is continuous with the gullet at the top and with the small intestine at its lower part.
· The coils of the small intestine form a tube some six metres long, and occupy the central portion of the abdomen.
· In the right lower corner of the abdomen the small intestine joins the large intestine, which passes up the right side of the abdomen, then across it just below the stomach, and finally down the left side, and through the cavity of the pelvis to end at the anus. The large intestine is about 1,5 m long.
· A small worm-like blind tube about 10 cm long called the appendix is affixed to the large intestine close to the point where the small intestine enters it.
· The mouth, throat, gullet, stomach, small intestine and large intestine together form a continous tube, the digestive canal, through which the food passes in digestion (fig 2.11, 2.12). Connected with the digestive canal in the abdomen are two organs, the liver and the pancreas.
· The liver occupies the right upper part of the abdomen, immediately below the diaphragm, and extends across the middle line to the left. It lies almost wholly under the lower ribs. This large organ produces the bile which, after being stored in the gall bladder (a small sac at the lower end of the liver) enters the small intestine not far from where the intestine begins by a duct or tube (fig 2.12).
· The pancreas lies in the angle between the stomach and the small intestine. It produces an important digestive juice, and the duct which conveys this juice to the small intestine enters the bowel at the same point as the duct which carries the bile from the liver (fig 2.12).
· To the left of the stomach, in the upper part of abdomen, covered by the lower ribs, lies the spleen, an organ which inter alia helps with the formation and break-down of blood.
· The kidneys (fig 2.14) lie at the back of the abdominal cavity, one on either side of the spine, with upper halves covered by the ribs. They are not involved in digestion; their function is removal of waste matter from the body. They withdraw water and other waste matter from the blood passing through them, and this forms urine. The urine leaves each kidney through a tube (the ureter), and both tubes enter the bladder, which lies in the pelvic cavity at front.
· The abdomen also contains the lower part of the aorta and its branches, the corresponding great veins, and many important nerves, especially sympathetic nerves.