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Biology > The kidney > Flashcards

The kidney Flashcards

1
Q

What is the anatomy of the kidneys?

A
  • kidneys receive oxygenated blood through renal artery
  • the b-blood is filtered in the kidneys forming urine
  • the urine passes into the ureters then is transport to the bladder
  • urine is stored in the bladder and eventually removed from the body via the urethra
  • renal vein returns the filtered blood to the heart via the vena cava
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2
Q

What are the internal structures of the kidney?

A

Fibrous capsule = outer membrane surrounding and protecting the kidney

Renal cortex = outer region containing Bowman’s capsules, DCT, PCT and blood vessels

Renal medulla = inner region containing pyramids, loops of Henle, collecting ducts. and blood vessels

Renal pelvis = funnel shaped cavity that collects urine into the ureters

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3
Q

What is a nephron?

A

basic structural and functional kidney unit

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4
Q

What are nephrons responsible for?

A
  • filtering blood
  • reabsorbing useful substances back into the blood
  • removing waste from the blood
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5
Q

What is the pathway of the filtrate through a nephron?

A

1) bowman’s capsule
2) proximal convoluted tubule
3) loop of henle
4) distal convoluted tubule
5) collecting duct

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6
Q

What is the function of the bowman’s capsule and glomerulus?

A

Bowman’s capsule = surrounds and protects a capillary ball (glomerulus)

Glomerulus = forms filtrate and contains podocyte cells in its inner layer

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7
Q

What is the structure and function of the proximal convoluted tubule?

A
  • epithelial cells in its wall have microvilli to increase their SA
  • reabsorbs useful substances (e.g water, glucose, and salt) into surrounding capillaries
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8
Q

What is the structure and function of the loop of henle?

A
  • long hairpin loop extends from cortex into the medulla and back into the cortex
  • creates a high solute gradient in the medulla helping with selective reabsorption
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9
Q

What is the structure and function of the distal convoluted tubule?

A
  • surrounded by fewer capillaries than the PCT
  • fine-tunes the water balance by reabsorbing water into surrounding capillaries (due to ADH)
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10
Q

What is the structure and function of the collecting duct?

A
  • attaches to nephrons
  • collects filtrate from nephrons and further fine-tunes the water balance before urine formed is passed to bladder
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11
Q

What are the 4 blood vessels associated with nephrons?

A

Afferent arteriole = this supplies glomerulus with blood

Glomerulus = fluid forced out of the blood within the capillary mass into the Bowman’s capsule through ultrafiltration

Efferent arteriole = this carries blood away from the glomerulus

Capillaries around PCT, DCT loop of Henle = these absorb salts glucose, and water

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12
Q

What is ultrafiltration?

A
  • small molecules (e.g water, glucose, mineral ions and urea) filter out the blood and into the Bowman’s capsule forming glomerular filtrate
  • larger molecules remain in the bloodstream.
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13
Q

Why is ultrafiltration important?

A

selective movement is essential for filtering blood and maintaining a balance of substances in the body

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14
Q

What is the process of ultrafiltration?

A

1) blood enters glomerulus through afferent arteriole

2) blood leaves glomerulus via the smaller efferent arteriole, maintaining a high hydrostatic pressure

3) this high pressure forces molecules out of the blood through pores in the capillary endothelium.

4) the molecules move through the basement membrane with collagen fibres acting as a selective filter preventing large molecules and blood cells passing into the Bowman’s capsule

5) the molecules move through the Bowman’s capsule epithelium (specialised podocyte cells with extensions wrap around capillaries helping to filter the blood

6) filtered fluid collects in Bowman’s capsule

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15
Q

What substances filter into the glomerular filtrate?

A
  • water
  • salt
  • glucose
  • urea
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16
Q

What substances remain in the blood during ultrafiltration?

A
  • blood cells
  • platelets
  • proteins
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17
Q

What is GFR?

A

glomerular filtrate rate

volume of glomerular filtrate formed per minute, the volume of blood that is filtered through the kidneys in a given time

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18
Q

What are the adaptations of the PCT for selective reabsorption?

A

Microvilli = increase SA for reabsorption

Basal infoldings = further increase SA for moving substances into surrounding capillaries

Numerous mitochondria = organelle provide ATP for active transport involved in reabsorption

Co-transporter proteins in plasma membrane = allow co-transport of substances from filtrate into epithelial cells

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19
Q

What is the reabsorption process in the PCT?

A
  • sodium ions are actively transported to capillaries reducing the Na+ concentration in epithelial cells lining the PCT
  • Na+ moves from the PCT lumen into the epithelial cells down its concentration gradient
  • Na+ is co-transported with substances like glucose and amino acids into the epithelial cells
  • these reabsorbed molecules can then diffuse into capillaries
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20
Q

What is the role of the DCT?

A

makes final adjustments to the filtrate’s content by reabsorbing water and salts

21
Q

What does the reabsorption process in the DCt involve?

A
  • reabsorption of any remaining useful substances mainly through active transport
  • alteration of DCT membrane permeability to regulate further reabsorption of water and solutes
  • regulation of blood pH by selectively reabsorbing certain ions
22
Q

Describe the structure of the loop of henle?

A

U-shaped tubule within the kidney nephron, starting in the cortex, descending into the medulla

23
Q

Describe the descending limb of the loop of henle?

A
  • 1st section
  • narrow
  • impermeable to ions
  • highly permeable to water
24
Q

Describe the ascending limb of the loop of henle?

A
  • 2nd section
  • wider
  • permeable to ions
  • impermeable to water
25
Q

How does the loop of henle concentrate urine?

A
  • decreases water potential in the medulla via active transport of ions out of filtrate
  • these ions transport into the tissues of the medulla that surround the loop of Henle (interstitial space)
  • this establishes a water potential gradient that allows water to be reabsorbed into the blood from filtrate in the collecting duct
26
Q

How is water reabsorbed in the loop of henle?

A

1) descending limb walls are permeable to water so water leaves the filtrate via osmosis into the interstitial space

2) filtrate loses water as it moves down descending limb reaching its lowest water potential at the tip in the medulla

3) water that is lost is reabsorbed into blood in the surrounding capillaries by osmosis and is carried away

4) the ascending limb is impermeable to water but permeable to sodium and chloride ions

5) Na+ and Cl- diffuse out of the filtrate into the interstitial space at the bottom of the ascending limb due to the low water potential of the filtrate

6) This concentrates ions in the interstitial space in the medulla making its water potential very low

7) Na+ and Cl- need to be actively transported out of the top of the ascending limb because their concentration in filtrate decreases as it ascends (the water potential increases)

8) creates a water potential gradient in the interstitial space with the highest water potential in the cortex and an increasingly lower water potential deeper into the medulla

27
Q

What happens when filtrate enters the collecting duct?

A

1) water moves from the filtrate in the collecting duct into the interstitial space

2) water then moves into surrounding capillaries, by osmosis to be carried away

3) water continues to exit the filtrate as it moves through collecting duct, even in the medulla when most water has already been lost because of the low water potential established by the loop of Henle in the surrounding interstitial space

4) urine leaving the collecting duct has a very low water potential as most water has been reabsorbed into the blood

28
Q

What is the countercurrent multiplyer?

A

concentrates urine and ensures there is always a water potential gradient drawing water out of the collecting duct

29
Q

How does the countercurrent multiplier work?

A
  • as filtrate moves down the collecting duct it loses water decreasing its water potential
  • due to the pumping of ions out of the ascending limb of the loop of Henle the water potential of the surrounding tissues in the medulla is lower than in the collecting duct
  • this allows water to continue to move out of filtrate down the whole length of the collecting duct
30
Q

What is osmoregulation?

A

control of the water potential of the blood keeping the water potential of bodily fluids within a narrow range

31
Q

What are the key features of ADH?

A
  • produced in the hypothalamus
  • stored in posterior pituitary gland after production
  • target cells are those lining the DCTs and collecting ducts in the kidneys
32
Q

What are the mechanisms of ADH action?

A

1) ADH attaches to receptors on cell surface in the DCT and collecting duct

2) this triggers the activation of cAMP a second messenger initiating a series of reactions that lead to phosphorylation of water channel proteins called aquaporins

3) aquaporin vesicles merge with the cell-surface membrane

4) water moves through aquaporins by osmosis from the DCT and collecting duct into the surrounding interstitial space

5) water is then reabsorbed into the surrounding blood vessels

33
Q

How is the release of ADH controlled?

A

negative feedback system

involves osmoreceptors in the hypothalamus that responds to changes in blood water and ion levels

34
Q

What can trigger the release of ADH?

A
  • lack of water
  • excessive salt intake
  • sweating
35
Q

What happens in the body when there is a lack of water?

A

1) Water moves from osmoreceptors into the blood by osmosis

2) osmoreceptors shrink detecting the decrease in the water potential of the blood and produce ADH

3) Nerve signals prompt the release of ADH from the posterior pituitary gland and ADH is transported via the blood to the kidneys

4) increase in aquaporins in DCT and collecting duct cell membranes makes them more permeable to water

5) more water is reabsorbed back into the blood

6) urine becomes more concentrated and is produced in smaller volumes

36
Q

What happens in the body when there is an excess of water?

A

1) water moves into osmoreceptors from the blood by osmosis

2) osmoreceptors detect an increase in the water potential of the blood

3) nerve signals to the posterior pituitary gland decrease reducing ADH release

4) DCT and collecting duct cell membranes become less permeable to water

5) less water is reabsorbed back into the blood

6) urine becomes more dilute and is produced in larger volumes

37
Q

Why is urine often used to sample for medical conditions?

A

contains water, urea, mineral salts, hormones, toxins, and various breakdown products

the composition of these substances can give us crucial evidence

38
Q

What are some key indicators for medical conditions found in the urine?

A
  • presence of glucose in often indicates diabetes
  • elevated creatine levels may suggest muscle or kidney damage
  • presence of blood or proteins in urine may signal kidney disorders
39
Q

What are the 2 main causes of kidney failure?

A

Kidney infections = lead to inflammation and swelling of kidneys damaging the cells responsible for filtering and reabsorption

High BP = can damage the glomeruli capillaries so proteins and blood leak into the urine

40
Q

What are indicators of kidney failure?

A
  • low GFR indicates less effective blood filtration
  • blood test can measure the level of creatinine in the blood which estimates the GFR
  • high creatinine level indicates that the kidneys are not working properly
41
Q

What are the effects of kidney failure?

A
  • mineral ion build up in blood causing loss of osmotic balance
  • buildup of toxic urea in blood can damage cells
  • high BP may cause heart problems and strokes
  • loss of calcium weakening bones
  • buildup of proteins in the blood causing joint pain and stiffness
  • anemia causing tiredness and lethargy
42
Q

How does renal dialysis filter the blood?

A

1) patient’s blood passes along one side of a semi-permeable membrane while dialysis fluid flows on the other

2) dialysis fluid contains normal plasma levels of mineral ions so ions diffuse through the semi-permeable dialysis tubing membrane into blood

3) dialysis fluid contains normal plasma levels of glucose so glucose also diffuses from dialysis fluid into blood

4) dialysis fluid contains no urea so urea is removed from the blood into the dialysis fluid by diffusion

5) larger molecules like blood cells and proteins remain in the blood as they are too large to pass through the membrane

43
Q

What is haemodialysis?

A
  • blood leaves patients body and flows into a dialysis machine
  • blood is filtered in the dialysis machine and returned to the body
44
Q

What is peritoneal dialysis?

A
  • peritoneum is a membrane lining the abdominal cavity
  • it acts as a surface which substances are exchanged between blood and dialysis fluid
  • dialysis fluid is injected into and then drained from the abdominal cavity so blood can be filtered within the body
45
Q

What are the pros and cons of peritoneal dialysis?

A

pros
- no need for specialist equipment
- can be done at home
- patient can be mobile during treatment

cons
- risk of infection
- required more frequently

46
Q

What are the pros and cons of haemodialysis dialysis?

A

pros
- lower infection risk
- required less frequently

cons
- requires specialist equipment
- must be done in hospital
- patient must be immobile during treatment

47
Q

What are advantages of kidney transplants?

A
  • no need for regular dialysis
  • no need for diet monitoring
  • prevents build up of waste products between dialysis
  • improves life quality
  • one of cost
48
Q

What are disadvantages of kidney transplants?

A
  • risk of rejection if the immune system recognises antigens on donor organ as foreign and attacks it
  • shortage of donor kidneys
  • need of medication to suppress immune system
  • involves major surgery
49
Q
A

Biology (22 decks)

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