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Biology A-level OCR Yr13 > Excretion- the kidney > Flashcards

Excretion- the kidney Flashcards

1
Q

what occurs in the kidneys?

A

-made of many nephrons which act as filtering units
-urine is produced in kidney tubules which passes out through ureter

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2
Q

Where does urine flow after leaving the ureter?

A

flows into bladder. When bladder is full, the sphincter opens and urine passes out the body through the urethra

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3
Q

what is the cortex?

A

-dark, outer layer
-where filtering of blood takes place
-very dense capillary network carrying blood from the renal artery to nephrons

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4
Q

what is the medulla?

A

-lighter colour
-contains tubules of nephrons that form the pyramids of the kidney and collecting duct

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5
Q

what is the pelvis?

A

-central chamber where urine collects before passing down the ureter

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6
Q

Function of the nephrons? (overview)

A

-filtering of blood
-majority of filtered blood is returned, removing the nitrogenous wastes and balancing mineral ions and water

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7
Q

what are the main structures found in the nephron?

A

-bowman’s capsule
-proximal convoluted tubule
-loop of Henle
-Distal convoluted tubule
-collecting duct

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8
Q

Describe the bowmans capsule

A

-cup shaped structure that contains the glomerulus, a triangle of capillaries
-more blood goes into the glomerulus than leaves it due to the ultrafiltration process that takes place

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9
Q

Describe the proximal convoluted tubule

A

-first coiled region ofter the bowmans capsule, found in cortex
-where many substances needed are reabsorbed

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10
Q

Describe the loop of henle

A

-long hoop of tubule that creates a region with a very high solute concentration in the tissue fluid deep in the kidney medulla.
-descending limb runs down from cortex to medulla
-ascending limb travels from medulla to cortex

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11
Q

Describe distal convoluted tubule

A

-second twisted tubule where the fine-tuning of the water balance occurs
-the permeability of the walls depends on levels of ADH (antidiuretic hormone)
-further regulation of the ion balance and pH of blood also takes place in this tubule

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12
Q

Describe the collecting duct

A

-urine passes down the collecting duct through the medulla to the pelvis.
-more fine tuning of water balance takes place
-walls are sensitive to ADH

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13
Q

Describe the network of capillaries around the nephron

A

capillaries lead to venule which lead to renal vein. The blood that leaves has reduced levels of urea and levels of glucose and amino acids stays almost the same as when blood entered- glucose is slightly less due to being used for selective reabsorption
-mineral ion concentration is restored

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14
Q

how is tissue fluid formed in the ultrafiltration process?

A

-the glomerulus is supplied with blood by wide afferent arteriole from the renal artery. The blood then leaves through the narrower efferent arteriole.
-this increases the pressure in the capillaries of the glomerulus, forcing blood out the capillary wall.
-fluid passes through the basement membrane (1st filter with gaps in endothelium)

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15
Q

what substances consist in the filtrate?

A

-glucose
-water
-salts (Na+, Cl-)
-amino acids
-vitamins
-hormones

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16
Q

what substances are not filtrated?

A

white blood cells, red blood cells, plasma proteins

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17
Q

Describe the additional filter in the wall of the bowmans capsule?

A

wall involves padocyte cells which have extentions called pedicels that wrap around capillaries- makes sure no additional large substances pass through.

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18
Q

what is the function of reabsorption?

A

-ultrafiltration removes urea, glucose, water, salts etc and many of these substances are needed in the body.
-ultrafiltrate is hypotonic (less concentrated than blood plasma)
-main function of nephron is to return most filtered substances

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19
Q

what occurs in the proximal convoluted tubule?

A

-glucose, amino acids, vitamins and hormones are moved back into blood by active transport
-as sodium ions (Na+) move out by active transport, the water potential in the tubule to increase. Water moves out the tubule by osmosis. Therefore chloride ions (Cl-) follow by diffusion.

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20
Q

adaptions of the convoluted tubule?

A

-covered with microvilli (increasing surface area over which substances can be reabsorbed)
-many mitochondria providing ATP for active transport

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21
Q

what occurs in the loop of henle?

A

-reabsorption of water and salt ions
-water is moved out by osmosis
-as water moves out, the filtrate becomes more concentrated (Na+, Cl-) in the descending limb of the medulla. At the end of the loop, a hypertonic point is reached
-up the ascending limb, the concentration of salt decreases as ions diffuse out the filtrate. This produces a high salt conc in medulla tissue- an isotonic point is reached
-Salts can be moved out the filtrate further by active transport
-the ascending limb of the loop of henle is impermeable to water, so filtrate becomes increasingly dilute
-at the top of the ascending limb, a hypotonic point is reached.

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22
Q

Describe what occurs in the distal convoluted tubule?

A

-permeability of walls varies with levels of ADH
-If the body lacks salt, Na+ ions will be pumped out the DCT by active transport with Cl- ions following the electrochemical gradient (diffusion).
-water can also leave the tubule by osmosis if the walls are permeable in response to ADH
-DCT balances water, salt and pH of blood

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23
Q

Describe what occurs in the collecting duct?

A

-collecting duct passes through the concentrated tissue fluid in the renal medulla
-water moves out by osmosis as levels of Na+ ions increase in surrounding fluid
-reabsorption of water is controlled by ADH

24
Q

how does ADH control water levels in the blood?

A

ADH increases the permeability of the distal convoluted tubule and most importantly the collecting duct to water. Negative feedback mechanism

25
Q

Where is ADH produced and secreted?

A

produced in the hypothalamus and secreted and stored in the pituitary gland

26
Q

describe the mechanism for the action of ADH in the tubule cells?

A

-hormone does not cross the membrane of the tubule cells
-hormone binds to receptors on cell membrane triggering formation of cyclic AMP (cAMP) as a secondary messenger inside the cell.

27
Q

what is a secondary messenger?

A

molecule which relays signals received in the cell surface receptors to the molecules inside the cell

28
Q

What cascade of events does cAMP cause in the action of ADH?

A

-vesicles in cells lining collecting duct fuse with cell surface membranes on the side of the cell in contact with the tissue fluid of the medulla
-membranes of vesicles contain protein based water channels (aquaporins) and they are inserted into cell surface membrane, they make it permeable to water
-this provides route for water to move out of the tubule cells into tissue fluid of medulla and the blood capillaries by osmosis

29
Q

when more ADH is released?

A

-more water channels inserted into tubule cell membranes
-more water leave tubules by osmosis
-small amount of urine
-concentrated urine
-water is returned to the capillaries maintaining the water potential of blood and therefore the tissue fluid

30
Q

when less ADH is released?

A

-levels of cAMP fall
-water channels are removed from tubule cell membranes and enclosed in vesicles.
-collecting duct becomes impermeable to water once more, so no water can leave.
-large amounts of urine
-dilute urine
-maintains water potential of blood and tissue fluid

31
Q

how are changes in water level of blood determined?

A

by osmoreceptors in the hypothalamus. Osmoreceptors are sensitive to the inorganic ions in the blood and linked to the release of ADH.

32
Q

What occurs for more ADH to be secreted by the pituitary gland?

A

-concentration of inorganic ions in the blood rises and water potential of the blood and tissue fluid is store negative.
-detected by osmoreceptors in the hypothalamus
-they send nerve impulses to the posterior pituitary gland which releases stored ADH in the blood

33
Q

what occurs for less ADH to be secreted by the pituitary gland?

A

-water potential becomes less negative
-change detected by osmoreceptors of the hypothalamus.
-nerve impulses to the posterior pituitary are reduced or stopped so release of ADH is inhibited.
-very little reabsorption of water takes place as wall of collecting duct is impermeable.

34
Q

why are urine samples used in diagnostic tests? give examples

A

-urine contains water, urea, mineral salts, hormones toxins
-presence of glucose in urine can indicate diabetes

35
Q

how is hCG produced in pregnant women?

A

a developing placenta forms human chorionic gonatrophin

36
Q

how do modern pregnancy tests work? (broad)

A

test for hCG by relying on monoclonal antibodies

37
Q

what are monoclonal antibodies?

A

antibodies from a single clone of cells that are produced to target particular cells or chemicals in the body.

38
Q

how are monoclonal antibodies made from hCG?

A

-mouse injected with hCG
-B cells that make required antibodies are removed from spleen and fused with myeloma, a type of cancer cell which divides rapidly
-new fused cell is called hybridoma
-hybridoma reproduce rapidly forming desired antibodies
-antibodies are collected and purified

39
Q

how does a pregnancy test work? (depth)

A

-wick soaked in morning (highest level of hCG)
-If pregnant, mobile antibodies in test will bind to hCG forming hCG antibody complex forming coloured line
-urine carries along the test to first window
-at the first window, there are immobilised monoclonal antibodies that only bind to the hCG/antibody complex. If pregnant, line appears on first window
-urine flows to second window
-at second window, immobilised monoclonal antibodies only bind to mobile antibodies, regardless if they are bound to hCG or not. This line forms weather woman is pregnant or not, to test the pregnancy test is working

40
Q

what is an anabolic steroid?

A

drugs that mimc action of testosterone and stimulate growth of muscles.

41
Q

how can anabolic steroids be checked for in athletes?

A

anabolic steroids are excreted in the urine and urine can be tested through gas chromatography

42
Q

what is an immunoassay?

A

using monoclonal antibodies to bind to a drug or its breakdown product to test drug

43
Q

what ways can you test drugs?

A

-immunoassay
-gas chromatography
-mass spectrometer

44
Q

If the kidneys are infected or affected by high blood pressure, this may cause?

A

-protein in the urine if basement membrane or podocytes of bowman capsular damaged, plasma proteins can release in the urine
-blood in the urine

45
Q

when kidneys fail completely, the concentrations of urea and mineral ions build up in the body? what are the effects?

A

-loss of electrolyte balance: excess ions causing osmotic imbalances in tissues
-build up of toxic urea in blood (urea is toxic)
-high blood pressure: by maintaining water balance of blood (heart problems/ strokes)
-weakened bones (calcium/phosphorus balance in blood lost)
-pain and stiffness in joints as abnormal proteins build up in the blood
-anaemia: kidneys are involved in the production of hormone erythropoietin that stimulates formation of red blood cells.

46
Q

what measure is widely used to indicate kidney disease?

A

glomerular filtration rate

47
Q

how is GFR measured?

A

measures level of creatinine in the blood. It is the breakdown product of muscles. If levels of creatinine go up, indicates kidneys not working

48
Q

what are the two types of renal dialysis?

A

haemodialysis and peritoneal dialysis

49
Q

Describe haemodialysis? cons and pros

A

cons:
-involves dialysis machine
-usually carried out in hospital
-dialysis takes eight hours and has to be repeated regularly
-diets need to be managed (little salt and protein)
-can only drink at the start of the dialysis process
-blood thinning drugs
pros:
-blood can be cleansed
-could be done at home

50
Q

How does haemodialysis work?

A

-blood flows from patients artery into dialysis machine, where it flows through partially permeable dialysis membranes
-membranes mimic basement membrane of bowmans capsule. Other side of membrane is dialysis fluid.

51
Q

how does the dialysis fluid prevent loss of useful substances?

A

-contains normal plasma levels of glucose to ensure there is no net movement od glucose out the blood
-contains normal plasma levels of mineral ions so excess mineral ions diffuse out the blood, thus restoring electrolyte balance of blood.
-dialysis fluid contains no urea to maintain a steep concentration gradient for urea to leave the blood into the dialysis fluid
-blood and dialysis fluid flow in opposite directions to maintain a counter current exchange system and maximise exchange

52
Q

is there active transport in haemodialysis?

A

no, only diffusion down concentration gradients

53
Q

Describe peritoneal dialysis?

A

-done inside the body and makes use of the natural dialysis membranes, peritoneum.
-dialysis fluid introduced to abdomen using a catheter
-after dialysis, dialysis fluid is drained off and discarded, leaving blood balanced and excess minerals and urea is removed.

54
Q

advantages and disadvantages of peritoneal dialysis?

A

pros:
-can be done at home
cons:
-takes several hours for dialysis to take place, so that urea and excess mineral ions pass out the blood capillaries, into tissue fluid and out across the peritoneal membrane into dialysis fluid.

55
Q

how does a kidney transplant take place?

A

-blood vessels are joined and the ureter of the new kidney is inserted into the bladder
-kidney can be made from stem cells

56
Q

advantages and disadvantages of kidney transplants?

A

disadvantage:
-risk of rejection
-immunosuppressant drugs needed to prevent rejection however this makes patient vulnerable to secondary infections
-transplanted organs don’t last forever
-donor is not readily available

57
Q

how does rejection work?

A

antigens of donor organ differ from antigens on the cells of the recipient and the immune system is likely to recongnise.

Biology A-level OCR Yr13 (15 decks)

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