Biology- Excretion in humans

  • Created by: Kitsune
  • Created on: 13-02-17 08:30
What is the need for excretion?
Waste materials are toxic
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Where is carbon dioxide excreted?
In the lungs
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How is CO2 toxic?
It dissolves in plasma and tissue fluid to form carbonic acid which can denature enzymes and other proteins
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How is urea toxic?
It can denature enzymes
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What harm can salts do?
They affect water potential of the blood
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What are the two roles of kidneys?
To carry out excretion and osmoregulation
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How are kidneys adapted to their functions?
Each kidney: receives blood from the renal artery, has 1000s of nephrons, has a ureter to take away urine and is close to a feedback system
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What is the functional unit of a kidney called?
A nephron
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What is the ball of capillaries in the nephron called?
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What holds the glomerulus?
Bowman's capsule
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What diffuses through the Bowman's capsule?
Waste, blood and water
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What happens in the first coiled tubule?
Water and useful molecules are selectively reabsorbed
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What happens in the Loop of Henle?
Salt concentrations in the medulla are altered to aid reabsorption of water from the collecting ducts
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What happens in the collecting ducts?
Kidneys reabsorb water and return it to the blood under the influence of the antidiuretic hormone
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What blood flows in the renal vein?
Blood with useful molecules and water but no wastes
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What parts of the nephron does the medulla contain?
Collecting ducts and loop of Henle
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What parts of the nephron does the cortex contain?
Coiled tubules and Bowman's capsule
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What organ carries out deamination?
The liver
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What is deamination?
Removal of the nitrogen containing part of the amino acid to form urea and excreting it into urine
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What does the volume of urine depend on?
Water intake, temperature, exercise
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What happens to the volume of urine if a person sweats a lot?
It decreases greatly
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What is osmoregulation?
The control of the amount of water in blood taken from the kidneys
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How can kidney failure lead to death?
The body can't control the amount of urine formed so the content of blood and tissue fluid isn't optimum.
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From where does blood leave into the kidney dialysis machine?
From the artery
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What does a pump do in a dialysis machine?
It controls the flow and pressure of blood
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What aids diffusion of urea out of blood in a dialysis machine?
The countercurrent flow of plasma and the dialysis fluid
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Why can only urea diffuse out of blood in a dialysis machine?
Because there is a partially permeable membrane and the dialysis fluid has a special composition
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What does the chamber in the dialysis machine do?
It removes blood clots and rewarms blood
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Why does blood need to be rewarmed in a dialysis machine?
To avoid shocking the body
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Where does blood return to from the dialysis machine?
Into the vein where the pressure is low
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Why do kidney donors have to be carefully selected?
To avoid tissue rejection
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What is better- a kidney transplant or kidney dialysis?
A transplant
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What are the advantages of a kidney transplant?
It is much cheaper and the person's life isn't disrupted
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How long can kidney dialysis take?
6-8 hours
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Other cards in this set

Card 2


Where is carbon dioxide excreted?


In the lungs

Card 3


How is CO2 toxic?


Preview of the front of card 3

Card 4


How is urea toxic?


Preview of the front of card 4

Card 5


What harm can salts do?


Preview of the front of card 5
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