The lower part of the the trunk. Above, and separated from it bz the diaphragm, lies the thorax or chest and below lies the pelvis, generally described as a separated cavity through continuous with that of the abdomen. Behind are the spinal column and lower ribs, which come within a few inches of the iliac bones. At the sides the contained organs are protected by the iliac bones and down-sloping ribs but in front the whole extent is protected only by soft tissues. The latter consist of the skin, a varying amount of fat, three layers of broad, flat muscle, another layer of fat and finally the smooth, thin peritoneum which lines the whole cavity. These soft tissues allow to necessary distension when food is taken into the stomach and the various important movements of the organs associated with digestion. The shape of the abdomen varies, in children it may protrude considerably, though if this too marked it may indicate disease. In healthy young adults it should be either slightly prominent of slightly indrawn and should show the outline of the muscular layer,especially of the pair of muscles running vertically ( recti), which are divided into four or five sections by transverse lines. In older people fat is ussually deposites on and inside the abdomen. In pregnancy the abdomen enlarges from the 12th week after conception as a the fetus in uterus grows
Contents The principal contents of the abdominal cavity are the digestive organs i.e. the stomach and intestines and the associated glands, the liver and pancreas. The position of the stomach is above and to the left when the individual is lying down, but may be much lower when standing. The liver lies above and to the right, largely under cover of the ribs, and occupying the hollow of the diaphragm. The 2 kidneys lies against the back wall on either side,protected by the last two ribs. From the kidneys run the ureters, or urinary ducts, down along the the back wall to the bladder in the pelvis. The pancreas lies across the spine between the kidneys, and on the upper end of each kidney is a suprarenal gland. The spleen is positioned high up on the left and partly behind the stomach. The great blood vessels and nerves lie on the back wall. And the remainder of the space is taken up by intestines or bowels. The large intestine lies in the flanks on either side in front of the kidneys, crossing below the stomach from right to left, while the small intestine hangs from the back wall in coils which fill up the spaces between the other organs. Hanging down from the stomach in front of the bowels is the omentum, or apron, containing much fat and helping to protect the bowels. In pregnancy the uterus, or womb, as in increases in size, rises up from the pelvis into the abdomen lifting the coils of the small intestine above it.
The pelvis is the part of the abdomen within the bony pelvis and contains the rectum or end part or intestine, the bladder and in the male the prostate , in the female the uterus, ovaries and fallplan tubes