B5f: Waste disposal Flashcards
What is important to maintain in the blood plasma and why? (1+2)
constant concentration of water molecules in blood plasma
prevents too much water moving into/out of tissues by osmosis
keeps blood pressure constant
Describe the gross structure of a kidney and associated blood vessels (5)
cortex(outside of medula)
medulla(surrounded by cortex)
waste urine, containing water, salts and urea, passes down ureter to bladder
blood flows in through renal artery
filtered blood leaves kidney in renal vein
How do kidneys work? (2)
filter blood at high pressure, removing glucose, salts, water, urea
reabsorb useful substances (all glucose, some salts, some water)
Where is urea produced and removed? (2)
produced in liver from excess amino acids
removed from blood by kidneys
What controls the concentration of urine and how? (1+2)
antidiuretic hormone (ADH), released by pituitary gland
ADH in blood +permeability of kidney tubules so +water reabsorbed back into blood
ADH production controlled by negative feedback mechanism; as blood passes through brain, hypothalamus detects how watery it is; if watery, less ADH released, less water reabsorbed in kidneys, more water lost in urine, making the blood less watery
Factors affecting the amount and concentration of urine produced (3)
water intake; lower water intake, less excess water to dilute other wastes, produce concentrated urine
heat; +hot, +sweat, +water evaporates to cool skin, increasing water loss, more ADH released into blood for kidneys to reabsorb more water, less excess water to be removed, only small amount of quite concentrated urine produced
exercise; +exercise, +hot, +sweat, +water evaporates to cool skin, increasing water loss, more ADH released into blood for kidneys to reabsorb more water, less excess water to be removed, only small amount of quite concentrated urine produced
Describe the structure of the kidney tubule (nephron) (3)
a filter unit of glomerulus (knot of capillaries) inside a capsule, where high pressure filtration occurs
a region for selective reabsorption, where useful substances eg glucose pass into blood
a region for salt and water regulation
Describe how blood is filtered in the nephron(5+3+2)
- Ultrafiltration
- blood enters kidney under +pressure in renal artery; blood goes from afferent arteriole into glomerulus, and leaves in efferent arteriole
- afferent wider than efferent, creating a bottleneck, blood can’t leave glomerulus as fast as it enters, so under high pressure
- results in high pressure filtration; substances w/ small molecules (water, salts, urea, glucose) filtered out of blood into capsule
- membranes between capillaries in glomerulus and the capsule act as filters, so big molecules (proteins) not filtered out and stay in blood - selective reabsorption
- all sugar and sufficient are reabsorbed through active transport
- sufficient water is reabsorbed according to the level of the hormone ADH - release of wastes
- the wastes that are not reabsorbed(e.g. urea, excess salt and water) continue out of the nephron, into the ureter and down to the bladder as urine
What regulates the amount of salt and water in the body
loop of Henle, rest of tubule and collecting duct
Describe the principles of a dialysis machine (4)
used if kidney failure, can’t filter blood
dialysis fluid has same conc of sodium + glucose as blood plasma (so they are not removed from blood)
semipermeable membrane between blood and dialysis fluid lets small ions and waste substances in but not big molecules (protein)
waste (urea) + excess water from blood diffuse across the membrane into dialysis fluid (osmosis)
Why must CO2 be removed from the body?
toxic effect at high levels
How does the body respond to increased CO2 levels in the blood? (2)
detected by brain
responds by +rate of breathing, excess CO2 diffuses out of blood at alveoli, CO2 in blood
