Guide to the Urinary System

Complete the paragraph with the correct term listed below (some may be used more than once).

The body gains water by absorbing water form the slurry in the lumen of the small intestine and from (1) ______ during condensation reactions. The mammalian body loses water mostly by excretion of (2) ____, evaporation through the skin and (3) ____, elimination of feces from the gut, and (4) _____ as the body is cooled. (5) ____ behavior, in which the brain compels the individual to seek liquids, influences the gain of water.
The body gains solutes by absorption of substances from the gut, by the secretion of hormones and other substances, and by (6) _______, which produces carbon dioxide and other waste products of degradative reactions. Besides carbon dioxide, there are several other metabolic wastes that must be eliminated: (7) _______, formed when amino groups are detached from amino acids; (8) _____, which is produced in the liver during reactions that link two ammonia molecules to carbon dioxide and release a molecule of water, and (9) ____ _____, which is formed in reactions that break down nucleic acids.

A. uric acid
B. lungs
C. sweating
D. thirst
E. urea
F. ammonia
G. metabolism
H. urine

Complete the paragraph with the correct term listed below (some may be used more than once).

In mammals, urine formation occurs in a pair of (1) ____. Each contains about a million tube-like blood-filtering units called (2) _____. The function of (1) depends on intimate links between (2) and the (3) _____. In every nephron water and reclaimable substances dissolved in blood flow from a(n) (4) ______ into a set of capillaries inside the (5) ____ ____, then into a second set of capillaries that thread around the tubular parts of the nephron, then back to the bloodstream, leaving the kidney. Urine composition and volume depend on three processes: filtration of blood at the (6) _____ _____ of a nephron, with (7) _____ _____ providing the force for filtration; reabsorption, in which water and (8) ______ move out of the tubular parts of the nephron and back into adjacent (9) ______ ______; and (10) _____ ______, in which excess ions and a few foreign substances move out of those capillaries and back into the distal tubule of the nephron so that they are disposed of in the urine. (11) _____ carry the urine away from the kidney to the (12) ____ _____, where it is stored until it is released via a tube called the (13) ____, which carries urine to the outside.

Two hormones, ADH and (14) _____, adjust the reabsorption of water and (15) ____ along the distal tubules and collecting ducts. An increase in the secretion of aldosterone causes (16) _____ sodium to be excreted in the urine. If a person eats an unnecessarily large amount of table salt (sodium chloride) due to taste preferences, the excess sodium must be excreted or it will cause the body to retain excess water, which leads to a rise in (17) ____ _____. Chronically high (17) is called hypertension; it can damage the kidneys, the vascular system, and brain. When the nephrons of both kidneys can no longer perform their excretory and regulatory functions, (18) ____ _____ results. (18) can be caused by (19) _____ ______, by continued high doses of aspirin and other drugs, by ingestion of lead, arsenic, pesticides, and other toxins, or by abnormal retention of metabolic wastes. Increased secretion of ADH enhances water reabsorption at distal tubules and collecting ducts when the body must conserve water. When excess water must be excreted, ADH secretion is (20) ____.

By adjusting the blood's volume and composition, kidneys help maintain conditions in the extracellular fluid.

A. sodium
B. ureters
C. kidneys
D. bloodstream
E. blood pressure
F. less
G. inhibited
H. nephrons
I. solutes
J. urethra
K. Bowman's capsule
L. urinary bladder
M. arteriole
N. renal failure
O. tubular secretion
P. infectious agents
Q. peritubular capillaries
R. glomerular capillaries (renal corpuscle)
S. aldosterone

Thank you.