kidney function 1

Question 1

what is the function of the kidneys ?

Answer 1

to excrete metabolites or ingested substances

Question 2

what are some examples of the substances that kidneys excrete ?
where do these substances come from ?

Answer 2

• urea from protein
• uric acid from nucleic acids
• creatinine from creatine
• hormone metabolites
• end products of haemoglobin breakdown
• foreign chemicals

Question 3

what are the 3 ways the kidneys control plasma ?

Answer 3

• volume regulation
• osmoregulation
• pH regulation

Question 4

what are some examples of hormones that act on the kidney ?

Answer 4

• anti-diuretic hormone (ADH)
• aldosterone
• natriuretic peptides
• parathyroid
• fibroblast growth factor 23

Question 5

what are some hormones produced by the kidney ?

Answer 5

renin
vitamin D3
erythropoietin
prostaglandins

Question 6

where are the kidneys found ?

Answer 6

• found behind the peritoneum
• one kidney on either side of vertabarl coloumn
• between T12 and L3 vertbrea

Question 7

what is each nephron made up of ?

Answer 7

• renal corpuscle

- tubule

Question 8

what arteriole supplies the kidneys ?

Answer 8

afferent arteriole

Question 9

where is the ultrafiltration found ?

Answer 9

in bowmans capsule

Question 10

where is the filtration barrier ?

Answer 10

between bowmans spaces + glomerulus

Question 11

what make up the 3 layers of the filtration barrier ?

Answer 11

• fenestrated capillary endothelium
• basement membrane
• tubular epithelium ( podocytes )

Question 12

what is a feature of the fenestrated capillary endothelium ?

Answer 12

has large pore sizes

up to 15 nm

Question 13

what is a feature of the basement membrane ?

Answer 13

has fixed polyanions ( negative charges )

Question 14

what is a feature of the tubular epithelium ?

Answer 14

has filtration silts

8nm

Question 15

what are the podocyte foot process?

Answer 15

refers to large extensions of the podocyte

Question 16

how are podocytes connected ?

Answer 16

they digilate with each other

do not touch

Question 17

what are the 2 types of nephrons ?

where are the types found ?

Answer 17

• cortical (85%)
  outer 2/3 of cortex
• juxtamedullary (15%)
  inner 1/3 of cortex

Question 18

what is a feature of the cortical nephron ?

Answer 18

has short loop of Henle

doesn’t penetrate into medullla

Question 19

what is a feature of juxtamedullary nephrons ?

Answer 19

has a long loop of Henle

plunges deep into medulla

Question 20

what is the juxtaglomerular apparatus ?

Answer 20

macula densa + juxtaglomerular cells

can sometimes include extraglomerular mesangial cells

Question 21

what is interesting about the nephron blood supply ?

Answer 21

has 2 sets of arteiroles ( afferent + efferent )
has 2 sets of capillary beds (glomeruli + peritubular )
work in series

Question 22

what are the 3 basic renal processes ?

Answer 22

1. glomerular filtration
2. tubular reabsorption
3. tubular secretion

Question 23

what is glomerular filtration ?

what does it rely on ?

Answer 23

refers to the 20% of plasma that enters the Bowman’s capsule
relies on hydrostatic + osmotic gradients

Question 24

what is the tubular secretion ?

Answer 24

secretion of solutes from peritubular capillaries into the tubules
also refers to movement of solute from tubule epithelium to tubule lumen

Question 25

what is tubular reabsorption ? | where is it greatest ?

Answer 25

movement of materials from the filtrate in the tubules into the peritubular capillaries greatest in proximal tubules

Question 26

what does the amount of substance excreted into urine depend on ?

Answer 26

amount excreted = amount filtered + amount secreted - amount reabsorbed

Question 27

what is another renal process ?

Answer 27

metabolism - removes substances from blood / glomeular filtrate + metabolise them

Question 28

what does glomerular filtration depend on ?

Answer 28

- molecular size - charge - shape of substance

Question 29

what is not found in ultrafiltrate ?

Answer 29

- cells + large proteins | - drugs + certain ions because they bind to proteins

Question 30

what can effect the glomerulus ?

Answer 30

- infection - damage - high blood pressure

Question 31

what is the result of a damaged glomerulus ?

Answer 31

- protein in urine ( proteinuria) - haemoglobin in urine ( haemoglobinuria) - red cells in urine (haematuria)

Question 32

what is the glomerular filtration rate (GFR)?

Answer 32

volume of fluid filtered from the glomeruli per minute ml/min

Question 33

what does GFR depend on ?

Answer 33

1. net filtration pressure 2. permeability characterisitc 3. surface area also regulated by hormonal + neural control

Question 34

what is GFR a good determinate of ? | what does a high GFR mean ?

Answer 34

- renal functiton | - higher GFR = greater excretion of salt + water

Question 35

what are the 2 starling forces involved in filtrations ?

Answer 35

hydrostatic pressure difference | colloid osmotic pressure difference

Question 36

what determines the hydrostatic pressure difference ?

Answer 36

pressure of fluid against glomeularus wall

Question 37

what determins colloid osmotic pressure ?

Answer 37

pressure exerted by large molecules

Question 38

how does plasma flow across the capillary wall with reference to pressure ?

Answer 38

- high to low hydrostatic pressure | - low to high colloid osmotic pressure

Question 39

what is the net glomerular filtration pressure ?

Answer 39

16 mmHG

Question 40

how can you decrease GFR ?

Answer 40

- constriction of afferent arteriole = decreased glomerular capillary hydrostatic pressure = decreased GFR - dilation of efferent arteriole = decreased glomerular capillary hydrostatic pressure = decreased GFR

Question 41

how to increase GFR ?

Answer 41

- dilation of afferent arteriole = increased glomerular capillary hydrostatic pressure = increased GFR - constriction of efferent arteriole = increased glomerular capillary hydrostatic pressure = increased GFR

Question 42

how does sympathetic influence effect the SA of filtration ?

Answer 42

increase sympathetic activity = contraction of mesangial cells = decreased SA for filtration = decreased GFR

Question 43

why is urine output much less than GFR ?

Answer 43

because reabsorption occurs

Question 44

describe the structure of the cells found in the proximal tubule :

Answer 44

- walls are a single layer of columnar cells - have lots of microvilli - lots of mitochondria

Question 45

how are organic nutrients reabsorbed ?

Answer 45

Na coupled co-transporter in the luminal membrane a tubular maximum system specific transporters for specific molecules

Question 46

how is glucose reabsorbed ?

Answer 46

SGLT-Na dependent glucose co-transporter on the luminal membrane glucose enters the proximal tubules + leaves via a GLUT faciliated transporter on the basolateral membrane

Question 47

how are amino acids reabsorbed ?

Answer 47

- reabsorbed in proximal tubule | - different transporters for different groups of amino acids e.g ones for neutral AA, basic AA + acidic AA

Question 48

how is protein reabsorbed ?

Answer 48

- mostly reabsorbed in the proximal convulated tubule - absorbed by endocytosis + degraded into amino acids - amino acids are later reabsorbed by transporters on basolateral membrane

Question 49

how does secretion take place in the proximal tubule ?

Answer 49

- 2 stage process | - involves basolateral + luminal membrane transporters

Question 50

what are examples of some organic acids secreted in the proximal tubules ?

Answer 50

- bile salts - fatty acids - drugs e.g penicillin - para-aminohippuric acid ( PAH)

Question 51

how are organic anions secreted ?

Answer 51

- anion enters epithelial cells via transporters | - enters tubule lumen via ATP dependent transporter

Question 52

what are some examples of organic cations

Answer 52

- choline - creatinine - morphine - atropine

Question 53

how are cation secreted ?

Answer 53

enter cell via transporters | enter tubule via countertransporters