Chapter 11 - Excretion Flashcards
Why do larger organisms need excretory organs for excretion?
They have impermeable skin and waste products cannot be excreted via diffusion into the surrounding environment.
What is in the filtrate of ultrafiltration? (2) (filtered out)
1) water
2) small molecules such as glucose, amino acids, mineral salts, urea
What is the urethra?
It is the duct through which urine discharges from the bladder to outside of the body
What is not filtered out (residue) of ultrafiltration?
Large molecules such as plasma proteins and red/white blood cells
What is the hilus?
A concave depression where the renal artery, renal vein and nerves are connected to the kidney.
Why is blood pressure indirectly regulated by osmoregulation?
Kidneys control water and solute levels in blood plasma by controlling amount of water reabsorbed at nephrons. The amount of water reabsorbed affects blood volume, which affects blood pressure. If the blood volume increases, blood pressure rises.
What is the cortex?
It is the outer dark red region that is covered and protected by a fibrous capsule.
Define osmoregulation.
It is the regulation of water and solute concentrations in the blood plasma to maintain a constant water potential in the body.
What is the sphincter muscle and what is its function?
It is located at the bottom of the bladder where it controls urination.
How does dialysis work? (6)
1) blood is drawn from a vein in patient’s arm
2) blood is pumped into dialysis machine through tubing
3) the partially permeable tubing is bathed in dialysis fluid
4) small molecules like urea and metabolic waste products diffuse out of tubing
5) larger molecules like platelets and blood cells remain in tubing
6) the filtered blood is returned to a vein in patient’s arm
Define excretion.
Excretion is the removal of metabolic waste products from the body which when left accumulated in excess will be toxic to the body.
What happens during osmoregulation when there is too much water? (7)
1) large intake of water causes water potential in blood plasma to increase
2) increase STIMULATES hypothalamus in brain,
3) which causes pituitary gland to secrete less ADH into bloodstream
4) cells in walls of collecting ducts become less permeable to water
5) less water reabsorbed from collecting duct into blood capillaries surrounding kidney tubule
6) larger volume of urine&urine more diluted
7) water potential of blood returns to normal
Describe the blood circulation at the kidney tubule. (7)
1) blood enters the kidney via the renal artery
2) renal artery branches out into many arterioles
3) arterioles branch into a mass of blood capillaries called the glomerulus.
4) blood leaves the glomerulus and enters blood capillaries surrounding the kidney tubule
5) blood capillaries unite to form venules
6) venules join to form renal veins
7) blood exits kidneys via renal vein.
What is the bowman’s capsule?
It is a cup-like structure found at the beginning of the kidney tubule.
What is reabsorbed at the loop of Henlé?
Some water is reabsorbed from the filtrate back into the blood vessels.
What is a fistula?
It is a direct connection of an artery to a vein.
How is carbon dioxide excreted? (1)
By lungs as expired air.
What are the two conditions required for ultrafiltration?
1) high hydrostatic blood pressure at the glomerulus due to afferent arteriole being wider than the efferent arteriole
2) partially permeable basement membrane around glomerular blood capillaries (has very small pores)
NOT BY DIFFUSION OR ACTIVE TRANSPORT
What happens if there is a large increase in blood pressure and what can be done to prevent it?
A large increase can cause blood vessels in the brain to burst, causing a stroke.
To prevent, diuretics (drug) can be prescribed to reduce production of ADH. Large amount of dilute urine will be produced and volume of water in blood decreases
Describe how urea is produced and excreted.
During ultrafiltration, urea, being a small molecule, will pass through the basement membrane of the glomeruli in the Bowman’s capsule, as part of the filtrate. It is not reabsorbed in the tubules, thus it passes in solution to the collecting duct. The fluid then passes through ureters into the bladder where it is temporarily stored, then out of the body through the urethra.
How are glucose, amino acids and salts reabsorbed?
Glucose, amino acids and salts diffuse into the CELLS lining the proximal convoluted tubule. They are then actively transported into the interstitial fluid, where they enter the blood capillaries via diffusion.
What is the function of a fistula?
Blood pressure in artery is higher than in the vein. Since blood can flow from artery to vein, more blood at higher pressure flows into the vein. The vein becomes larger and stronger over time, allowing a greater amount of blood to pass through the dialysis machine. It increases the pace of filtration, allowing all the blood to be filtered in a shorter period of time.
What is the renal corpuscle/malpighian corpuscle?
The glomerulus and the Bowman’s capsule
Is egestion part of excretion?
No. Egestion is the removal of undigested material from the alimentary canal. Undigested material is not formed from substances within the cell and has never been absorbed to into the cells. Hence, egested material is not a product of metabolic processes.
