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bioregulatory systems 🦠 > the genitourinary system > Flashcards

the genitourinary system Flashcards

1
Q

what are 5 functions of the kidney

A

1) excretion of metabolic products eg urea, uric acid and creatinine
2) excretion of foreign substances eg drugs
3) homeostasis of body fluids, electrolytes and acid-base balance
4) regulates blood pressure
5) secreted hormones eg erythropoietin and renin

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2
Q

what does erythropoietin do

A

protects RBCs against destruction

stimulates stem cells of the bone marrow to increase production of RBCs

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3
Q

what does renin do

A

it is released in response to low blood pressure or Na+ depletion
converts angiotensinogen to angiotensin 1

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4
Q

where does renal blood supply to the kidneys come from

A 
peritubular capillaries (reabsorption - max SA, secretion and oxygen and nutrients for nephron function)
tiny blood vessels in the kidney that filter and reabsorb
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5
Q

what is the pathway for blood travelling in the kidney

A 
renal artery 
segmental artery
interlobar artery
arcuate artery
interlobular artery
afferent arteriole
glomerular capillaries
efferent arteriole
peritubular capillaries
interlobular vein
arcuate vein
interlobar vein
renal vein
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6
Q

what is the function of detrusor muscle

A

contracts to build pressure in the urinary bladder to support urination
during urination this contracts

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7
Q

what is the function of the trigone

A

stretching of this triangular region to its limit signals the brain about need for urination

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8
Q

what is the function of the internal sphincter

A

Internal sphincter = Involuntary control

involuntary control to prevent urination - smooth muscle contracts

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9
Q

what is the function of the external sphincter

A

voluntary control to prevent urination (surrounds urethra - striated muscle)

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10
Q

what is the function of the bubourethral gland

A

produces thick lubricant which is added to watery semen to promote sperm survival

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11
Q

what is a nephron

A

a functional unit of the kidney

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12
Q

what is the structure for a nephron (chronological)

A

afferent arteriole
glomerulus - has capillaries
bowmans capsule
efferent arteriole
proximal convoluted tubule (epithelial rich in mitochondria - transport happens here)
thin descending loop of Henle
thin ascending loop of Henle (epithelial = low density of mitochondria - passive)
thick ascending loop of Henle (epithelial = rich in mitochondria - active reabsorption salt)
distal convoluted tubule (epithelial rich in mitochondia - active)
collecting duct (principal cells = low density mitochondria and intercalated cells = rich AT)

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13
Q

what is the ratio for superficial to juxtamedullary nephrons

A

~10:1

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14
Q

what is the juxtaglomerular apparatus

A

specialised structure formed by distal convoluted tubule and glomerular afferent arteriole

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15
Q

what are the constituents of the juxtaglomerular apparatus

A 
macula densa (specialised cells lining the wall of the DCT)
extraglomerular mesangial cells 
juxtaglomerular cells (afferent arteriole) - produce renin (conversion of angiotensinogen to angiotensin 1 - controls aldosterone production)
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16
Q

what is the function of the juxtaglomerular apparatus

A

GFR regulation through tubuloglomerular feedback mechanism

renin secretion for regulating blood pressure

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17
Q

what arteriole branches out to form peritubular capillaries surrounding the nephron

A

efferent arteriole

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18
Q

pathway for bringing in blood

A

afferent arteriole > glomerular capillaries > efferent arteriole > peritubular capillaries surrounding nephron

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19
Q

what are the 4 main processes that happen in the nephron

A

1) glomerular filtration (into bowmans capsule)
2) reabsorption (substances are reabsorbed - move from tubular filtrate into blood)
3) secretion (substances move from blood into filtrate)
4) excretion (through urine)

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20
Q

how is urine produced

A

different substances undergo a different combination of renal processes to produce urine

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21
Q

what is the passive process of glomerular filtration

A

fluid is “driven” through the semipermeable glomerular capillaries into the Bowmans capsule space by the hydrostatic pressure of the heart
hydrostatic = pushing

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22
Q

describe the filtration barrier

A

size and charge dependent
highly permeable to fluids and small solutes
impermeable to cells and proteins (blood cells and proteins)

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23
Q

what is the direction of filtration

A

glomerulus to bowmans capsule

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24
Q

what are the spaces between podocytes called

A

slits
made up of finger like projections creating very small spaces between them - only water and small solutes can pass through

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25
Q

what is the charge of the molecules the blood is mostly composed of

A

negatively charged molecules

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26
Q

what is hydrostatic pressure

A

pushing force
fluid exerts this pressure (outward pressure)
solute and fluid molecules are shoved out

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27
Q

what is oncotic pressure

A

pulling force
solute (eg proteins) exerts this pressure (inwards pressure)
fluid molecules drawn in across a semipermeable membrane

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28
Q

in the IF, in which direction does the hydrostatic and oncotic pressure go

A

IF hydrostatic goes into blood vessel

IF oncotic goes out of vessel

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29
Q

what is the equation for net ultrafiltration pressure (Puf)

A

Puf = HPgc - HPbw - 3.14159265359gc

HPgc = hydrostatic pressure in glomerular capillaries (pushing out)
HPbw = hydrostatic pressure in bowmans capsule
3.14159265359gc = oncotic pressure of plasma proteins in glomerular capillaries
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30
Q

what is the definition for GFR

A

the amount of fluid filtered from the glomeruli into the bowmans capsule per unit time (mL/min)
sum of the filtration rate of all functioning nephrons - both kidneys

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31
Q

what is the equation for GFR

A

GFR = Puf x Kf

where Kf is an ultrafiltration coefficient (membrane permeability and SA available for filtration) - any changes in filtration forces or Kf = GFR imbalances

32
Q

what is the GFR range for healthy males and females

A 
males = 90-140 mL/min
females = 80-125 mL/min
33
Q

what does a fall in GFR suggest

A

it is a cardinal feature of a renal disease - with a build up of excretory products in the plasma

34
Q

describe myogenic regulation of GFR if arterial pressure increases

A

arterial pressure increases > afferent arteriole stretches > smooth muscles lining the arteriole contracts > afferent arteriole contracts > vessel resistance rises > blood flow reduces > filtration decreases to stabilise GFR

35
Q

how does tubulo-glomerular feedback mechanism regulate an increase in GFR

A 
increase in GFR
increased NaCl in loop of Henle
change detected by macula densa cells
increased ATP and adenosine discharged to afferent arteriole
afferent arteriole constricts
GFR stabilises
36
Q

how does tubulo-glomerular feedback mechanism regulate an decrease in GFR

A 
decrease in GFR
decreased NaCl in loop of Henle
change detected by macula densa cells
decreased ATP and adenosine discharged to afferent arteriole
afferent arteriole dilates
GFR stabilises
37
Q

what is renal clearance

A

the number of litres of plasma that are completely cleared of the substance per unit time
(only concerned with excretory roles played in the kidneys ie rate of removal of a substance X from the blood and excretion through urine)
each substance goes through a unique filtration

38
Q

what is the equation for renal clearance

A

C = U x V/P

U = conc of substance in urine
V = rate of urine production
P = conc of substance in plasma

for eg if C = 50 mL/min this means that 50 mL of plasma has been cleared of that substance per minute

39
Q

how can we practically determine GFR

A

if a molecule is freely filtered (and neither reabsorbed nor secreted in the nephron then the amount filtered = excreted - thus GFR can be measured by measuring renal clearance of this molecule

40
Q

what is the ideal molecule and its properties

A

inulin

a plant polysaccharide
freely filtered 
neither reabsorbed nor secreted
not toxic
measurable in urine and plasma
however not found in mammals and needs to be transfused
41
Q

what molecule is most commonly used as a measure of GFR

A

creatinine
waste product from creatin in muscle metabolism
amount released is fairly constant
if renal function is stable, then creatinine amount in urine is stable
low creatinine clearance or high plasma creatinine may indicate renal failure

42
Q

what does freely filtered mean

A

conc of x in plasma = conc of x in glomerular filtrate
a freely filtered substance may be absorbed or secreted later on
freely filtered refers to the glomerulus - capillaries

43
Q

what is renal plasma flow

A

volume of blood arriving at the kidney per unit time

44
Q

how do you work out renal plasma flow

A

if the total amount of a molecule entering the kidney equals the amount excreted, then the renal clearance of this molecule equals the renal plasma flow (RPF)

45
Q

what is PAH

A

para aminohippurate

all PAH is removed from the plasma passing through the kidney through filtration and secretion

46
Q

what is the filtration fraction and the range

A

the ratio of the amount of plasma which is filtered, and which arrives via the afferent arteriole
range = 0.15-0.2
a value of 0.15 suggests that 15% of the plasma has been filtered

47
Q

what does renal clearance equal to if the total amount of that substance entering the kidney is the total amount excreted

A

renal clearance = renal plasma flow

48
Q

what is the equation for filtration fraction

A

FF = GFR/RPF

49
Q

what happens when there is an electrical gradient difference

A

charged ions are able to travel to the side of the membrane which is of the opposite charge

50
Q

what are the 3 types of active transport

A

primary active
endocytosis
secondary active

51
Q

what is primary active transport

A

there is use of ATP straight away - eg sodium potassium pump found in nephron - uses 1 ATP to transport ions

52
Q

what is endocytosis

A

small proteins are reabsorbed this way in the proximal convoluted tubule

53
Q

what is secondary active transport

A

2 or more ions are coupled, one ion is moving downhill (high to low electrochemical gradient) providing energy for uphill movement (low to high) of another molecule

54
Q

when both molecules travel in the same direction

A

symport

55
Q

when molecules travel in opposite directions

A

antiport

56
Q

what cells line the nephron tube

A

epithelial cells

57
Q

what is the basolateral cell membrane

A

side facing the blood

58
Q

what is the apical cell membrane

A

facing tubular filtrate

59
Q

what is a tight junction

A

some substances are able to be transported from filtrate into blood from paracellular (between cells) pathways

60
Q

what is a transcellular pathway

A

transport through a cell

eg water through aquaporins

61
Q

how is sodium reabsorbed

A

Na/K ATPase pump - using 1 ATP to transport sodium out from cell into blood

62
Q

is there a low conc of Na+ inside the cell? and if there is, what does it mean :)

A

yea lmao
sodium from tubular fluid travels downhill > low conc created from pump created the downhill gradient for Na+ travelling from tubular fluid into cell
when this is coupled with other transporters it provides energy for other molecules to move uphill

63
Q

what happens in the early proximal convoluted tubule

A

region of high activity
sodium and bicarbonate reabsorption
- Na/K ATPase pump - pumps out Na+ of the cell - low conc in cell
- CO2 from tubular fluids enter by diffusion - by carbonic anhydrase converts CO2 and H2O > H+ and HCO3-
- H+ is pumped out through sodium hydrogen antiporter - sodium moving downhill and proton uphill (secondary AT) into tubular fluid
- bicarbonate is transported into blood by symporter - body wants to keep bicarbonate for acid balance
- angiotensin 2 regulates Na+ reabsorption by increasing Na+H+ antiporters

64
Q

how is glucose reabsorbed in the early proximal convoluted tubule

A

wants to keep 100% glucose
ATPase pump - low conc of sodium inside cell - travels downhill gradient out of cell
providing energy for uphill transport of glucose by symptorter (SGLT2) - glucose is reabsorbed by glucose transporter

65
Q

what are the substances reabsorbed in the early proximal convoluted tubule and their %

A 
67% Na+
67% Cl- 
80% HCO3- 
100% glucose
667% water
100% amino acids
66
Q

what are the substances secreted from the early proximal convoluted tubule

A 
drugs
ammonia
bile salts
prostaglandins 
vitamins (folate and ascorbate)
67
Q

what reabsorption happens at the Loop of Henle

A

fluid enters at ascending region - no water reabsorbed but a lot of salt is reabsorbed - passively in the thin region and actively in the thick region
- when a lot of salt = reabsorbed in the medullary region > increases osmolarity of medulla > helps passive reabsorption of water by simple osmosis
- high osmolarity surrounding the loop of henle
water = reabsorbed in the descending side - when filtrate reaches middle loop region = hyperosmotic and because of high salt being reabsorbed in ascending side - by the time it exits the loop - fluid becomes hypoosmotic

68
Q

how does salt reabsorption actively occur in the thick ascending region

A

Na+/K+/Cl- symporter transports K+/Cl-/Na+ into the cell and Cl- and K+ are reabsorbed by K+/Cl- symporter

69
Q

what are the substances reabsorbed and their %

A

25% Na+
25% Cl-
15% water

70
Q

how does reabsorption occur in the early distal convoluted tubule

A

sodium and chloride reabsorption
Na+/K+ ATPase pump has created a sparsity of Na inside cell > allowing NA+/Cl- to be transported into the cell via symporter
- reabsorbed using K+/Cl- symporter
water channels are absent in the early region

71
Q

how does active Ca2+ reabsorption happen in the early distal convoluted tubule

A

CA enters cell through calcium channels and are reabsorbed by
Na+/Ca2+ antiporter and Ca2+ ATPase pump

72
Q

how does reabsorption happen in the late? DCT and collecting duct

A

in principal cells - Na+ reabsorption and K+ secretion through channels
important during hyperkalemia
aldosterone regulates Na+ absorption by increasing apical Na+ channels and basolateral Na+/K+ ATPase pumps
ADH regulates water reabsorption by increasing apical aquaporins - basolateral aquaporins almost always present - apical aquaporins are inserted as needed

73
Q

what do intercalated cells do

A

maintaining acid base balance

74
Q

how many intercalated cell types are there and what are they

A

there are 2 types

alpha and beta intercalated cells

75
Q

what do alpha intercalated cells do

A

H+ secretion and HCO3- reabsorption

76
Q

what do beta intercalated cells do

A

H+ reabsorption and HCO3- secretion

77
Q

what happens in case of alkalosis

A

beta cells become more active to bring back homeostatic conditions

bioregulatory systems 🦠 (54 decks)

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