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HCS102 Human Physiology > Renal Physiology > Flashcards

Renal Physiology Flashcards

1
Q

What is the functions of the kidney?

A

Regulate ECF volume, blood pressure, osmolarity
Maintain pH
Excrete wastes, foreign substances

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2
Q

What is the anatomy of the kidneys?

A

Outer cortex, deeper medulla, medial pelvis
Extension of pelvis (calyces) surround tips of medullary pyramids and collect urine

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3
Q

How are the arteries broken down in the kidneys?

A

Renal artery enters the kidney -> divides into segmental arteries -> several interlobar arteries -> split into arcuate arteries -> cortical radiate arteries

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4
Q

How does renal blood flow go?

A

Afferent arteriole -> glomerulus -> efferent arteriole -> peritubular capillaries

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5
Q

What are nephrons?

A

Structural and functional units of kidneys
Responsible for forming urine

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6
Q

What affects the ability to retain water?

A

Length of loop of Henle

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7
Q

What is the juxtamedullary nephron?

A

The longer loop of Henle that has the:
proximal convuluted tubule
glomerulus
distal convuluted tubule
nephron loop

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8
Q

Where do the peritubular capillaries arise from?

A

From the efferent arteriole that drains the glomerulus

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9
Q

How thick is the Glomerular Bowmans capsule?

A

One cell thick

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10
Q

Where does the blood enter and leave from the glomerulus?

A

Enters: afferent arteriole
Leaves: efferent arteriole

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11
Q

What is the efferent arteriole?

A

Receives the blood that has passed through the glomerulus (things are not filtered leave through here)

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12
Q

What is afferent arteriole?

A

Much higher blood pressure in the glomerular capillaries compared to the capillary beds (larger diameter)

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13
Q

Explain the collecting duct

A

Receive urine
Run through the medullar pyramids
Deliver the final product into calyces and renal pelvis

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14
Q

Where do the glomerular capillaries stem from? What to they do?

A

Network of capillaries that stem from afferent arteriole
Aids filtration

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15
Q

What is left that leaves through the efferent arteriole?

A

Whatever is left of plasma and blood

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16
Q

What to the pores in capillary do?

A

Allow plasma and other molecules to filter out

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17
Q

What is the glomerulus?

A

Filtration formation is role of high-pressure glomerulus -> Filtrate is essential plasma without blood proteins

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18
Q

What is found in the renal tubule?

A

Glomerular capsule
Proximal convuluted tubule
Nephron loop
Distal convuluted tubule
Second peritubular capillary bed

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19
Q

What is urine?

A

Urine is clear, yellow and acidic
Has nitrogenous wastes, water, various ions
50-120 mOsM

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20
Q

What is filtration?

A

Movement of fluid from plasma into Bowmans capsule

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21
Q

What is reabsorption?

A

Filtrate contains useful substances (glucose, amino acids, ions) which must be reabsorbed to returned to blood

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22
Q

Explain reabsorption

A

Done by tubule cells
- amino acid, glucose, water, some ions removed from filtrate and returned to blood
- movement of filtered materials from tubule to blood

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23
Q

When does tubular reabsorption begin?

A

As soon as filtrate enter the proximal convuluted tubules

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24
Q

What is secretion?

A

Movement of selected molecules from blood to tubule
- amount of a solute excreted equals the amount filtered minus the amount reabsorbed plus amount secreted

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25
Q

What happens during tubular secretion?

A

H+ K+ and creatine move from blood of peritubular capillaries through the tubule cells into filtrate to be eliminated in urine

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26
Q

Why is secretion important?

A

To rid body of drugs, excess ions
Maintain acid-base balance of blood

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27
Q

Where does the fluid filter from?

A

Bowmans capsule -> proximal tubule -> loop of Henle -> distal tubule -> collecting duct -> (drains) renal pelvis

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28
Q

What is glomerular filtration?

A

Non selective, passive process in which fluid passes from blood into glomerular capsule

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29
Q

What happens when systemic blood pressure drops too low?

A

Filtrate will be formed

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30
Q

What happens when arterial blood pressure drops too low?

A

Glomerular pressure becomes inadequate to force substances out of blood into tubules and filtrate formation stops

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31
Q

What does filtration allow?

A

Filtration allows most components of plasma to enter the tubule but excludes blood cells and almost all plasma protein

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32
Q

What happens during filtration?

A

Bowman’s capsule epithelium has specialised cells “podocytes”
Filtered solutes must pass through glomerular capillary endothelium (through basement membrane)

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33
Q

What are the podocytes?

A

Specialised cells that wrap around glomerular capillaries and create filtration slits

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34
Q

What are the layers of the filtration barrier?

A

Fenestrated endothelial layer
Basal lamina
Slit membrane

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35
Q

Explain the fenestrated endothelial layer

A

One cell thick
Has pores where blood cells are restricted from passing through
Large size proteins restricted from passing through to the basal lamina

36
Q

Explain the basal lamina

A

Surrounds fenestrated endothelial layer
Intermediate-sized proteins restricted from passing through

37
Q

Explain the slit membrane

A

Water, electrolytes, polypeptides, sugars, urea, amino acids filter out from here

38
Q

In renal function, how does the exchange of ions and molecules happen?

A

Between peritubular capillaries (which stem from efferent arteriole) and tubule

39
Q

What are the filtration pressures?

A

Blood pressure= 60mmHg
Capsule pressure= 18mmHg
Colloid osmotic pressure= 32mmHg

40
Q

Explain each filtration pressure

A

Blood pressure- pressure exerted by blood in capillaries
Capsule- pressure on capsule pushing back onto the glomerulus
Colloid osmotic - osmotic + oncotic (pressure exerted on system by change in plasma)

41
Q

What are they key characteristics of the cells of the proximal convuluted tubule?

A

A lot of microvili to increase surface area for absorption processes
A lot of mitochondria for extra energy to use active processes

42
Q

Why do the cells need so much mitochondria?

A

It needs a lot of energy for active process are going against concentration gradient
The energy in concentration gradient would be enough to reabsorb the filtrate

43
Q

What is on left cell membrane of proximal convuluted tubule?

A

Transporter proteins for specific molecules
- Na+ and other molecules enter cell through transporter protein (only works in presence of Na+ to reabsorb)
Sodium proton antiport
- Na+ in, H+ out
- make tubular fluid more acidic

44
Q

Why is H+ (proton) chucked out through antiport?

A

To reduce acidity of cytoplasm and make tubular fluid of cytoplasm

45
Q

What happens within the cell?

A

CO2+H2O = carbonic acid (CA)
- carbonic anhydrase catalyses reaction to alter CA which splits into HCO3- and H+ which is chucked out

46
Q

How does the alteration of carbonic acid control acid-base balance?

A

By chucking out protons and creating buffer HCO3-

47
Q

What happens on the basolateral membrane?

A

Na+/K+ ATPase which creates artificial concentration gradient
Transporter protein chucks out molecules which opens back door for passive diffusion
HCO3- buffer the ECF which diffuses into blood

48
Q

What happens when their is a deficit of Na+ in cell?

A

Na tubular fluid will be use in one of reabsorption processes

49
Q

What are the key characteristics of the cells of the descending limb of loop of Henle?

A

Facilitate movement of water (an osmotic process)
Less mitochondria only to support cell
Flat cell
Passive processes

50
Q

What are the key characteristics of the cells of ascending limb of loop of Henle?

A

Fewer mitochondria
No vili
Passive processes

51
Q

What are symporters and antiporters?

A

Symporters: transport substances in same direction
Antiporters: transport in opposite direction

52
Q

Explain transcellular pathways

A

Active process on basolateral cell membrane
Na+ gradient created by Na+ pump plays a crucial role in reabsorption and secretion
Only 20% of Na+ diffuses into capillaries

53
Q

Explain the electrochemical gradient

A

Favors the movement of Na+ from filtrate into cells
80% Na entering, exchanged by H+
Secretion of H+ plays role in HCO3- reabsorption

54
Q

What happens when Na+ HCO3- transported from tubule into peritubular interstitial cells?

A

Osmolality increases whilst osmolality in tubular fluid decrease -> proximal convuluted tubule is highly permeable to H2O

55
Q

What happens when proximal convuluted tubule is high permeable to H2O?

A

H2O reabsorption increases tubular concentration of Cl-, Ca2+, urea

56
Q

What are the key characteristics of the cells of the thick loop of Henle?

A

No vili = no massive quantity of reabsorption
Lots of mitochondria = active processes (impervious to H2O without aquaporins)

57
Q

What is on the left membrane of the thick loop cells?

A

Triport system which pumps in Na+, K+, 2Cl-
(passively against concentration gradient)
Small K+ leak channel
Na+ H+ antiport

58
Q

What is happening on the inside of cell?

A

CO2+H20=CA
H+ out from antiport
HCO3- leaks out on basolateral

59
Q

What is on the basolateral membrane?

A

Cl- K+ leak channels
Na+/K+ ATPase
- during against concentration gradient
- reason for mitochondria
HCO3- leaks out

60
Q

What molecules are diffused by paracellular diffusion in thick loop cells?
What bounces off membrane?

A

Na+, K+, Ca2+, Mg+
H2O

61
Q

What are the key characteristics of distal convuluted tubule?

A

A bit of vili for more surface area to absorb more sodium chloride
A lot of mitochondria
Impervious to water, needs aquaporins
Artificial concentration gradient to facilitate transporters to work

62
Q

What is on the left membrane?

A

Na+ and Cl- enter cell through transporter proteins
H2O bounce off membrane

63
Q

What is on the basolateral membrane?

A

Na+/K+ ATPase
Cl- leak channel

64
Q

What is on both membranes of the principal cell of distal convuluted tubule?

A

Na+ leak channel enters
K+ leak channel leaves
————————————-
Na+/K+ ATPase
K+ leaves through leak channels

65
Q

What is on both membranes and in cell of the intercalated cell of distal convuluted tubule?

A

Maintain pH through proton ATPase
In the cell: CO2+H2O=CA
HCO3- leaks out which is engaged in buffering process

66
Q

What is the difference between the cortical and inner medullary collecting duct?

A

Cortical: more mitochondria
Inner: only to collect and act as a barrier

67
Q

What happens in the loop of Henle?

A

Increased interstitial osmolality causes water to diffuse out of descending limb and some Na+, Cl- to diffuse in

68
Q

How does fluid travel through loop of Henle?

A

Concentration fluid descends, travel in opposite direction to fluid returning from higher osmolality region of deep medulla

69
Q

How is blood supply prevented to medulla?

A

Prevented from dissipating the osmotic pressure between cortex and medulla

70
Q

What reabsorbs H2O in loop of Henle?

A

Vasa recta capillaries H2O reabsorbed from loop of Henle and medullary collecting ducts

71
Q

Explain step 1 start of the counter current multiplier

A

Start:
Filtrate coming in
Move around and up
320 mOsM
Dynamically equilibrate with interstitial fluid
Movement of H2O

72
Q

Explain step 2 transport of counter current multiplier

A

Transport:
Fluid moves and osmotic equilibration
More water from descending limb into interstitium into ascending limb
Dilutes fluid in ascending limb and concentrates fluid in descending limb

73
Q

Explain step 3 move and step 4 transport of counter current multiplier

A

Move: Moves down again and get equilibration
More fluid which goes up to re-equilibrate
Transport: Dilutes urine in ascending limb and concentrates urine in descending limb

74
Q

What is volume control?

A

Changes in major osmotic component of ECF will result in changes in ECF volume

75
Q

What is the main regulator of body fluid volume?

A

Control of Na+ by kidneys through atrial and stretch receptors

76
Q

What does the renal afferent arteriole stimulate?

A

ADH release, water reabsorption and release of renin

77
Q

What occurs when more dilation and more flood filters?

A

More dilation, more blood filtered the greater the volume that is produced

78
Q

What happens when more constriction occurs?

A

More constricted, less blood filtered, less filtrate, less urine produced

79
Q

Explain the angiotensin system

A

Kidney releases Renin which acts on angiotensinogen released by liver to create angiotensin I
The lungs then release angiotensin-converting enzyme to create angiotensin II

80
Q

What does angiotensin II cause through vasopressin?

A

Increase H2O reabsorption by kidney tubules which conserves H2O which helps correct ECF volume and arterial blood pressure

81
Q

What does angiotensin II cause through thirst?

A

Thirst increases fluid intake which helps correct ECF volume and arterial blood pressure

82
Q

What does angiotensin II cause through arteriolar vasoconstriction?

A

Helps correct ECF volume and arterial blood pressure

83
Q

What secrets aldosterone and what does it do to the kidneys?

A

Adrenal cortex secrets aldosterone which increases Na+ reabsorption by renal tubules which conserves H2O which helps correct ECF volume and arterial blood pressure

84
Q

What promotes to ADH release and water retension?

A

Large falls in blood volume or pressure

85
Q

Why is the renin-angiotensin mechanism important?

A

For regulating blood pressure

HCS102 Human Physiology (8 decks)

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