it curves back into the short (2.5 to 4 cm) anal canal. The ANUS is the external opening at the lower end of the digestive system. Except during bowel movement (defecation), it is kept closed by a strong muscular ring, the ANAL SPHINCTER.
The PANCREAS is a large, elongated gland lying posteriorly to the stomach. Its digestive juices amylase, proteinase, and lipase are secreted through the pancreatic duct into the duodenum and act on all types of food. The pancreas contains a special group of cells called the islands of Langerhans, which secrete the hormone insulin needed for use of sugar by the body.
The LIVER is the largest gland in the body. It is located in the upper abdomen on the right side, just under the diaphragm and superior to the duodenum and pylorus.
Of its many functions, the following are important to remember:
The GALLBLADDER is a pear-shaped sac, usually stained dark green by the bile it contains. It is located in a hollow on the underside of the liver. Its duct, the cystic duct, joins the hepatic duct from the liver to form the common bile duct, which enters the duodenum. The gallbladder receives bile from the liver and then concentrates and stores it. It secretes bile when the small intestine is stimulated by the entrance of fats.
The urinary system is the primary filtering system of the body. It consists of two glands, the kidneys, which produce urine; two tubes, the ureters, which drain the urine from the kidneys; a large reservoir, the bladder, where the urine is temporarily stored before it is excreted from the body; and a tube, the urethra, which carries the urine from the bladder to the outside of the body. All these parts, except the length of the urethra, are the same in both sexes.
Figure 3-53.Cross section of the kidney.
The importance of the kidney can be realized only when its structure and function are understood. It is the only part of the urinary system in which any changes occur. The bladder, ureters, and urethra store and pass only the products of the kidneys.
The kidneys are two large, bean-shaped organs designed to filter waste materials from the blood (fig. 3-53). They are located in the upper posterior part of the abdominal cavity, outside the peritoneal sac, one on each side of the spinal column. The upper end of each kidney reaches above the level of the 12th rib. The suprarenal (adrenal) gland sits like a cap on top of each kidney. Each