219. END PRODUCTS OF DIGESTION
a. Carbohydrates. Carbohydrates are finally absorbed as simple sugars, or
b. Proteins. Proteins are broken down and absorbed as amino acids.
c. Fats. Fats are absorbed by the body in the form of fatty acids and glycerol.
Absorption occurs through the gastrointestinal mucosa by active transport and
also by diffusion.
a. Stomach. Only small amounts of simple salts, alcohol, water, and glucose
can be absorbed by the stomach.
b. Small Intestine. Over 90 percent of all digestion occurs in the small
intestine. At the beginning of the small intestine are located numerous small villi. Since
these structures are extremely vascular, they are able to absorb fluid and dissolved food
material into the blood and the lymphatics.
c. Large Intestine. Though the small intestine is the site of most absorption in
the gastrointestinal tract, about 500 mL of chyme passes into the large intestine each
day. Of this, most of the water and electrolytes are absorbed in the colon. Only 50100
mL of fluid is excreted in the feces. The main functions of the large intestine are to
absorb water and electrolytes to form and store feces for elimination. In addition,
bacterial activity in the large intestine is a source of vitamin K, vitamin B12, thiamin,
riboflavin, and gases. The formation of vitamin K is particularly important since there is
an insufficient amount in the ordinary diet for adequate blood coagulation.
Section IV. THE URINARY SYSTEM
221. GROSS ANATOMY
a. Location of The Kidneys. The kidneys are flattened, beanshaped,
glandular organs about 4 inches long by 2 inches wide by 1 inch thick. They lie against
the muscles of the back on each side of the vertebral column on the posterior wall of the
abdomen, beneath the diaphragm, and behind the peritoneum (retroperitoneal). The
right kidney is usually lower than the left. The kidney is supported by peritoneum
anteriorly and by perirenal connective tissue posteriorly and laterally. Since the kidneys
are under the dome of the diaphragm, they are afforded protection by the ribs.
b. Gross Kidney Structure (figure 210). The large renal artery and renal vein
enter the kidney at its central notch, the hilus. The kidney is composed of an outer shell
called the cortex, and a hollow inner chamber called the pelvis. The cortex is firm, and