Excretion In Humans. Flashcards
Where is carbon dioxide excreted through?
Carbon dioxide is made by all cells during respiration and dissolves in blood plasma to form a weak acid which lowers the pH and can denature enzymes. Carbon dioxide is transported to the alveoli and excreted through the lungs.
What do the kidneys excrete?
Urea is produced in the liver during the deamination of excess amino acids and can denature enzymes. It is carried in the blood plasma from the liver to the kidneys where it is excreted in the urine, along with excess water and ions (substances in excess of requirements).
What is excretion?
The removal of the waste products of metabolism and substances in excess of requirements.
What is deamination?
The removal of the nitrogen-containing part of amino acids to form urea. The ammonia is carried to the kidneys in the blood and excreted in the urine as urea while the second part of the molecule is converted to carbohydrate or fat and used as a source of energy.
What is the role of the glomerulus?
The role of the glomerulus in the filtration from the blood of water, glucose, urea, and ions.
What is the role of the nephron?
The role of the nephron in the reabsorption of all of the glucose, some of the ions, and most of the water back into the blood.
Describe the formation of urine.
The formation of urine containing urea excess water and excess ions.
What is ultrafiltration?
Blood in the glomerulus is under high pressure and this forces substances out of the blood and is known as ultrafiltration.
From the substances forced out of the blood into the nephron, which ones are reabsorbed, and how are they reabsorbed along the nephron tubule (loop of Henle)?
All glucose is reabsorbed by diffusion and active transport, some water is reabsorbed by osmosis and some salts are reabsorbed by diffusion.
What is transported down the collecting duct to the ureter to be excreted?
Excess water, urea and excess salts.
What are the seven processes that take place in the nephron?
- The blood is delivered to the glomerulus under high pressure by branches of the renal artery.
- The blood is filtered by ultrafiltration and water, glucose, urea, and ions are forced into the renal capsule (proteins and blood cells are too big to be filtered).
- In the first tubule of the nephron, all glucose, some ions, and some of the water are reabsorbed back into the blood.
- The collecting tube further reabsorbed water by osmosis and returns it to the blood leaving concentrated urea in the urine.
- The filtered blood is returned to the circulatory system by the renal vein.
- Urea and excess ions are dissolved in excess water from the urine which is carried from the kidneys to the bladder in the ureter.
- The urine is stored in the bladder and when the bladder is full, the urine is excreted out through the urethra.
Where is urea formed?
Urea is formed in the liver from excess amino acids.
What are the three main functions of the kidneys?
- Controlling ion levels.
- Excreting urea.
- Osmoregulation.
Define osmoregulation.
Osmoregulation is the process by which organisms regulate the balance of water and salt in their bodies to maintain proper fluid balance and prevent dehydration or overhydration.
What are the main functions of the liver?
- Makes bile to emulsify fats.
- Stores glucose as glycogen.
- Uses amino acids to make proteins e.g. fibrinogen.
- Excess amino acids are deaminated.
- Converts fatty acids and glycerol into fat or cholesterol.
- Processes unwanted substances from the blood e.g. alcohol and poisons.
- Generates heat to keep the body internal temperature at 37C.
