Maintaining Water & Nitrogen Balance in the Body Flashcards
All 10 cards in this deck
How is water lost from the body, and which of these losses are controlled?
Water is lost via the lungs in exhaled air, and with ions and urea from the skin in sweat — neither is controlled; excess water, ions and urea are removed by the kidneys in urine, which is controlled.
What is the effect on body cells if they lose or gain too much water by osmosis?
They do not function efficiently, because osmotic changes make cells shrink or swell.
What happens to the excess amino acids produced by digesting protein?
They are deaminated in the liver to form ammonia; ammonia is toxic so it is immediately converted to urea for safe excretion.
What effect does ADH have on the kidney tubules, and when is it released?
ADH makes the kidney tubules more permeable to water, so more water is reabsorbed into the blood; it is released by the pituitary gland when the blood is too concentrated, controlled by negative feedback.
What are the steps by which the kidneys produce urine?
e.g. blood flowing through the kidney after a meal
- Filtration: water, ions, glucose and urea are filtered out of the blood.
- Selective reabsorption: all the glucose, plus some ions and water, are taken back into the blood.
- The remaining water, ions and urea leave the body as urine.
What is selective reabsorption in the kidney?
Taking useful substances — all the glucose, some ions and some water — back into the blood from the kidney tubules.
Which substance in blood plasma is not filtered out of the blood in the kidney?
Protein — its molecules are too large to be filtered out.
True or false? In a healthy person, urine contains the same concentration of glucose as the fluid just after filtration.
False. Glucose is filtered out but all of it is reabsorbed, so healthy urine contains no glucose.
What are the basic principles of kidney dialysis?
Blood flows on one side of a partially permeable membrane and dialysis fluid on the other, so urea and excess ions and water pass out of the blood.
Give one advantage and one disadvantage of a kidney transplant compared with dialysis.
Advantage: no need for regular dialysis sessions. Disadvantage: donor kidneys are in short supply and may be rejected.