Process of urine formation includes all of the following except:?

Question

a. filtration of plasma

b. reabsorption of water

c. reabsorption of certain solutes

d. secretion of waste

e. secretion of excessive glucose molecules

Answer 1

Urine is composed of water, certain electrolytes, and various waste products that are filtered out of the blood system. Remember, as the blood flows through the body, wastes resulting from the metabolism of foodstuffs in the body cells are deposited into the bloodstream, and this waste must be disposed of in some way. A major part of this "cleaning" of the blood takes place in the kidneys and, in particular, in the nephrons, where the blood is filtered to produce the urine.

Urine formation begins with the process of filtration, which goes on continually in the renal corpuscles. As blood courses through the glomeruli, much of its fluid, containing both useful chemicals and dissolved waste materials, soaks out of the blood through the membranes (by osmosis and diffusion) where it is filtered and then flows into the Bowman's capsule. This process is called glomerular filtration. The water, waste products, salt, glucose, and other chemicals that have been filtered out of the blood are known collectively as glomerular filtrate. The glomerular filtrate consists primarily of water, excess salts (primarily Na+ and K+), glucose, and a waste product of the body called urea. Urea is formed in the body to eliminate the very toxic ammonia products that are formed in the liver from amino acids. Since humans cannot excrete ammonia, it is converted to the less dangerous urea and then filtered out of the blood. Urea is the most abundant of the waste products that must be excreted by the kidneys. The total rate of glomerular filtration (glomerular filtration rate or GFR) for the whole body (i.e., for all of the nephrons in both kidneys) is normally about 125 ml per minute. That is, about 125 ml of water and dissolved substances are filtered out of the blood per minute. The following calculations may help you visualize how enormous this volume is. The GFR per hour is:

125 ml/min X 60min/hr= 7500 ml/hr. The GFR per day is:

7500 ml/hr X 24 hr/day = 180,000 ml/day or 180 liters/day.

Now, see if you can calculate how many gallons of water we are talking about. Here are some conversion factors for you to consider: 1 quart = 960 ml, 1 liter = 1000 ml, 4 quarts. = 1 gallon. Remember to cancel units and you will have no problem.

Answer 2

E

Sugar in urine is a sign of poor absorption of glucose in the blood stream or a huge concentration of glucose in the blood. If  insulin-controlled glucose absorption system is working correctly, then glucose should not be secreted.