Excretion Flashcards
(15 cards)
What is excretion?
The removal of waste products of metabolism (that come from metabolic reactions)
How is respiration an example of excretion?
Respiration is the process by which the cells in our body break down glucose to release energy for use. Respiration, (glucose + oxygen -> carbon dioxide + water) along with giving us energy, produces carbon dioxide and water. The CO2 is a waste product, and has been produced through a metabolic reaction, so when we remove (breath) it, it is excretion.
What is urea?
Urea is a waste product produced in the liver, from the breakdown of excess amino acids.
Why is urea constantly removed, and how is it removed?
Too much urea in the blood is toxic, so it is constantly filtered out of the blood by the kidneys.
Describe the process of the production of urea.
First, it starts in the alimentary canal of your digestive system. As you ingest proteins, digestive enzymes (pepsin and trypsin) in your stomach, duodenum, and ileum break down these proteins into amino acids.
These amino acids are now small enough to be absorbed into the blood, so they are absorbed into the capillaries through the villi in the ileum.
These eventually form into the hepatic portal vein, which takes the amino acids to the liver. Obviously, we need some of the amino acids, so they carry on to be assimilated by other cells. But if you have excess, they must be removed from the body. The liver does this in a process called deamination. The excess amino acids are split into carbohydrates (which contain energy and can be used later). The rest is a nitrogen-containing compound, which is then turned into urea, and excreted in the blood, along with the amino acids that can be used.
What is deamination?
The removal of the nitrogen-containing part of amino acids to form urea.
What is the outer layer of tissue on the kidney called?
The cortex
What is the inner layer of tissue in the kidney called?
The medulla
what is a nephron, and where is it located in the kidney?
A nephron is one of thousands of microscopic tubes inside the kidney, where urine is produced. It starts in the cortex (outer), loops down to the medulla, loops back to the cortex, then down through the medulla to the ureter.
What is glomeruli (sing. glomerulus)?
A network of blood capillaries (of the renal artery) where blood is filtered in a kidney.
Describe the formation of urine.
First, blood flows to the artery through the Renal artery. Then, the renal artery divides to form tiny, coiled capillaries called the glomeruli. The blood is then filtered, so small molecules such as urea, water, glucose, and ions can pass through to the kidney (and into the nephron). Urea, which is toxic in the blood, along with excess water and ions, is excreted by the ureter in the form of urine. The useful substances (all of the glucose, most of the water, some ions) are reabsorbed back into the blood to be transported and used.
How is the nephron adapted for urine production?
The glomeruli are very close to the nephron, making absorption and re-absorption easy and fast.
How is urine transported and excreted?
Once urine is formed, it flows out of the kidneys, along the ureters, into the bladder, where it is stored for a while before being released through the urethra.
How efficient are the kidneys at reabsorption?
The kidneys reabsorb 99% of the water that enters (they filter approx. 170 dm³, and produce 1.5 dm³ of urine per day)
What does our urine tell us about our liquid consumption?
The amount of urine produced and what it looks like depends on how much excess water there is in the body. If there is a lot of excess water that has been drunk, large volumes of dilute (clear) urine is produced. Not enough excess liquid, and small amounts of concentrated urine is produced. This can also happen is someone sweats a lot, loosing a lot of water.
