Biology π | Excretion | 13 Flashcards
From where is carbon dioxide excreted?
Through the lungs.
What do the kidneys excrete?
Urea, and excess water & ions.
Define excretion.
The process by which waste products from metabolism and other non-useful substances are removed from an organism.
Define transport.
Movement of substances from one part of the body to another.
Define egestion.
The removal of undigested waste material from the intestine. Only for products not produced by the body and that were never digested, such as fiber.
Where are kidneys located?
At the back of the abdomen, on either side.
What is a kidneyβs function?
- To regulate the water content of blood, something important to maintain blood pressure.
- To excrete toxic waste products of metabolism.
What do the ureters do?
They carry urine from the pelvis to the bladder.
What does the bladder do?
It stores urine and contracts to empty urine through the urethra.
What is the function of the sphincter muscles?
It opens so that urine flows along the urethra out of the body.
What is the renal medulla and renal cortex?
The renal cortex is the outer layer of the kidney, and the renal medulla is the inner layer.
What is a nephron?
One of the thousands of tiny tubules in a kidney in which urine is produced.
Where does a tubule begin and end?
It begins in the cortex, loop down to the medulla, back to the cortex, down again to the medulla, and then to the pelvis.
What are the three phases of urine formation?
Filtration, Reabsorption, Formation
What is the glomerulus in a kidney?
A specialized bundle of capillaries situated between two resistance vessels of the nephron.
What is the function of the glomerulus?
Blood brought through a branch of the renal artery has its molecules, water, and substances squeezed into the renal capsule by the glomerulus.
How does filtration occur in urine formation?
Blood is brought to the renal capsule in a branch of the renal artery - molecules, water, and substances, are squeezed out into the renal capsule through the glomerulus walls.
How does reabsorption happen in urine formation?
Blood capillaries wrap around each tubule so that the useful substances can be reabsorbed, passing back into the blood. By the time it reaches the collecting duct, it is mostly water, urea, and some salts.
Why is reabsorption needed in urine formation?
Some of the fluid in the renal capsule (glucose, some water, some salts) need to be reabsorbed into blood.
How does formation happen in urine formation?
Urine from all tubules flows into the ureters, taking it to the bladder.
What is the liverβs role?
The assimilation of amino acids. Urea is formed in the liver by excess ammonia.
Define deamination.
The removal of the nitrogen-containing part of amino acids for urea formation.
Why does the liver split up amino acids?
We cannot store amino acids: yet it would be wasteful to excrete. There is still carbohydrates that can be stored.
What are the products of deamination?
Ammonium and carbohydrates (glycogen)
Why do we convert ammonia to urea?
Ammonia is toxic.
How do amino acids reach the liver?
- They are broken down during digestion into amino acids
- They are absorbed by blood, taken to the liver by the hepatic poral vein
What does the liver do to excess amino acids?
Deaminates it to ammonia and carbohydrates.
What form are carbohydrates stored in the liver?
Glycogen.
