B5f: Waste disposal Flashcards Preview

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Flashcards in B5f: Waste disposal Deck (12):
1

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

2

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

3

How do kidneys work? (2)

filter blood at high pressure, removing glucose, salts, water, urea

reabsorb useful substances (all glucose, some salts, some water)

4

Where is urea produced and removed? (2)

produced in liver from excess amino acids

removed from blood by kidneys

5

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

6

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

7

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

8

Describe how blood is filtered in the nephron(5+3+2)

1. 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

2. selective reabsorption
-all sugar and sufficient are reabsorbed through active transport
-sufficient water is reabsorbed according to the level of the hormone ADH

3. 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

9

What regulates the amount of salt and water in the body

loop of Henle, rest of tubule and collecting duct

10

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)

11

Why must CO2 be removed from the body?

toxic effect at high levels

12

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