the abdomen, diaphragm and pelvis

The abdomen is that part of the torso that lies between the chest and the legs. The abdominal cavity is a large body region which contains the digestive, urinary and the reproductive organs. The abdominal cavity lies below the diaphragm, and above the pelvis. The abdominal organs include the stomach, small and large intestines, liver and gall bladder, pancreas, spleen, kidneys, adrenal glands, and the urinary bladder, and in females the ovaries and uterus. There are also several arteries, veins and nerves in the abdomen.

Externally, the abdomen is divided into four quadrants or nine regions. The quadrants are the right upper, the left upper, the right lower and the left lower. A more detailed classification is that of the nine regions:

As an example, the gall bladder lies in the right hypochondrium, the appendix in the right iliac fossa, and the right and left kidneys in the right and left lumbar regions.

The diaphragm is a muscle which is shaped like a thick membrane, and is attached lower ribs and adjacent abdominal wall. It forms the the lower limit of the chest cavity and the upper limit of the abdominal cavity. In the resting position is curved with its concavity towards the abdomen. When it contracts it flattens out, and pushes the abdominal organs downwards, causing the lungs above to expand. The diaphragm contracts each time a person breathes. The upper surface of the diaphragm is in contact with the heart and the bases of the lungs. The lower surface of the diaphragm is in contact with the liver, stomach and the spleen. The esophagus and the aorta go through the diaphragm. The diaphragm is susceptible to diseases like hiatus hernia and congenital diaphragmatic hernias.

The food passes along a tract called the alimentary canal, which starts at the mouth and ends at the anus.

The mouth ends at the pharynx.At the pharynx, the respiratory tract and the digestive tract are common. The nasopharynx, the oropharynx and the laryngopharynx are different parts of the pharynx.
The pharynx becomes the esophagus in the upper part of the neck. the esophagus is also known as the foodpipe. It originates behind the mouth at the pharynx,and runs downwards for 30 cm before entering the stomach. Most of the esophagus lies in the chest, close to the left lung, the aorta and the heart. Surrounding the lower end of the esophagus is a circular muscle called the cardiac sphincter (or lower esophageal sphincter), which prevents food in the stomach from refluxing into the esophagus. The function of the esophagus is to transport swallowed food from the mouth into the stomach. Apart from transport, the esophagus serves no digestive function. Diseases of the esophagus therefore mainly present as disorders of swallowing.
The duodenum is the first part of the small intestine. It continues from the pylorus, which is the terminal part of the stomach. It is shaped like a "C", and in the hollow of the "C" lies the head of the pancreas. The function of the duodenum is to digest food, and to absorb a few nutrients, particularly iron. The "bile duct" enters the duodenum by passing through the pancreas. The duodenum is the prime site for development of a peptic ulcer. A bleeding peptic ulcer may present with black stools, or melena.

The pelvis itself is a large bony girdle that is shaped quite like a receptacle. It consists of a set of bones attached to the lower end of the spine, that also provides an articulation for the hip bones. It is formed by three bones, the pubis, the ilium and the ischium.The shape of the pelvis differs in men and women. The pelvic cavity is the area enclosed by the bony pelvis, and contains the urinary bladder, the rectum and the reproductive organs in the female. The pelvic cavity is continuous above with the abdominal cavity, and in a sense forms part of it.

Peritoneum. The peritoneum forms a bag that contains the gastrointestinal organs, and in addition covers them individually. Thus the peritoneum has two layers, the parietal peritoneum and the visceral peritoneum. The peritoneum is a sensitive layer and can become inflamed by disease of the organ just under it. Pain arising from the peritoneum can be severe, unlike pain arising from the visceral organs. The peritoneum secretes fluid called the peritoneal fluid, which keeps the abdominal organs lubricated. Normally there is less than 300-400 ml of fluid in the peritoneal cavity. In certain diseases, such as cirrhosis of the liver, large quantities of peritoneal fluid may accumulate: this is called ascitis. In cancer, a malignant ascitis may form, if cancer cells deposit on the peritoneum. Peritonitis is inflammation of the peritoneum. It usually occurs from a burst in the intestine, and leak of abdominal contents, such as a ruptured appendix, a leaking peptic ulcer or a perforated typhoid ulcer. Peritonitis is a serious and potentially life-threatening illness.

thorax. The part of the body between the neck and the abdomen. The upper border of the thorax is formed by the first ribs, or by the clavicles which are at about the same level as the first ribs. The lower border of the thorax is formed by the diaphragm. The thorax contains the heart, the lungs and the esophagus. The aorta passes through the thorax into the abdomen.

Uterus, Fallopian tubes, ovaries. The womb. It is a thick, muscular, tubular organ, roughly 5 inches long in the nonpregnant woman. The lowermost end of the uterus is called the cervix, and is highly susceptible to the development of cancer. From the sides of the top of the uterus arise the two Fallopian tubes. At the ends of the tubes are the ovaries. The Fallopian tubes conduct the egg from the ovary to the uterus. The egg is usually fertilized in the uterus or in the tube. It implants and grows in the uterus.