Waste disposal Flashcards
What happens to amimo acids?
Excess and unwanted amino acids are broken down in the liver, forming urea, which is taken in the blood to the kidneys.
How does waste enter the kidney?
- Blood containing waste such as urea enters each kidney by the renal artery. Blood without waste leaves by the renal vein. Each kidney has an outer cortex and an inner medulla. Waste removed from the kidney leaves through the ureters as urine.
- The blood flows through the kidney under high pressure so filtration to remove wastes also take place under high pressure. Useful materials such as water, glucose and salt are reabsorbed back into the blood.
Each kidney has:
has millions of microscopic kidney tubules (nephrons) where filtration takes place to form urine.
Each nephron has:
- A small network of capillaries (the glomerulus) surrounded by a capsule: this forms the filtration unit.
- A region where some materials such as glucose are selectively reabsorbed.
- A region where reabsorbation of some salt and water takes place.
When is a blood dialysis machine used?
A dialysis machine is used when someone has kidney failure. The machine has many tubes containing blood, surrounded by a liquid. The machine acts as an artificial kidney and removes urea from the blood. As urea molecules are small, they diffuse through the membrane. A dialysis machine also uses different sizes of tubes, so it slightly increases pressure during diffusion.
What does dialysis fluid contain.
The dialysis fluid contains sodium salt, so it the same or slightly lower than the desired concentration. This maintains the sodium levels in the blood.
When does urine concentration decrease and increase?
- After drinking a large quantity of water, the quantity of urine produced increases and the urine concentration decreases.
- During strenuous exercise or in hot conditions the body produces more sweat to cool down, so the quantity of urine produced decreases and the urine concentration increases.
What does the pituitary glands produce?
- The pituitary gland produces the anti-diuretic hormone (ADH) which controls the concentration of urea by:
- Increasing the permeablity of kidney tubules so that more water is reabsorbed.
- Using a negative feedback mechanism to control ADH production.
Carbon dioxide concentration.
- Carbon dioxide at high concentrations is toxic and must be removed from the body.
- The body is more sensitive to the level of carbon dioxide than to that of oxygen. An increase in carbon dioxide in the blood is detected by receptors in the carotid artery. Nerve impulses inform the brain, which causes the rate of breathing to increase to remove more carbon dioxide via the lungs.
