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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
What happens during tubular secretion?
H+ K+ and creatine move from blood of peritubular capillaries through the tubule cells into filtrate to be eliminated in urine
26
Why is secretion important?
To rid body of drugs, excess ions Maintain acid-base balance of blood
27
Where does the fluid filter from?
Bowmans capsule -> proximal tubule -> loop of Henle -> distal tubule -> collecting duct -> (drains) renal pelvis
28
What is glomerular filtration?
Non selective, passive process in which fluid passes from blood into glomerular capsule
29
What happens when systemic blood pressure drops too low?
Filtrate will be formed
30
What happens when arterial blood pressure drops too low?
Glomerular pressure becomes inadequate to force substances out of blood into tubules and filtrate formation stops
31
What does filtration allow?
Filtration allows most components of plasma to enter the tubule but excludes blood cells and almost all plasma protein
32
What happens during filtration?
Bowman's capsule epithelium has specialised cells "podocytes" Filtered solutes must pass through glomerular capillary endothelium (through basement membrane)
33
What are the podocytes?
Specialised cells that wrap around glomerular capillaries and create filtration slits
34
What are the layers of the filtration barrier?
Fenestrated endothelial layer Basal lamina Slit membrane
35
Explain the fenestrated endothelial layer
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
Explain the basal lamina
Surrounds fenestrated endothelial layer Intermediate-sized proteins restricted from passing through
37
Explain the slit membrane
Water, electrolytes, polypeptides, sugars, urea, amino acids filter out from here
38
In renal function, how does the exchange of ions and molecules happen?
Between peritubular capillaries (which stem from efferent arteriole) and tubule
39
What are the filtration pressures?
Blood pressure= 60mmHg Capsule pressure= 18mmHg Colloid osmotic pressure= 32mmHg
40
Explain each filtration pressure
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
What are they key characteristics of the cells of the proximal convuluted tubule?
A lot of microvili to increase surface area for absorption processes A lot of mitochondria for extra energy to use active processes
42
Why do the cells need so much mitochondria?
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
What is on left cell membrane of proximal convuluted tubule?
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
Why is H+ (proton) chucked out through antiport?
To reduce acidity of cytoplasm and make tubular fluid of cytoplasm
45
What happens within the cell?
CO2+H2O = carbonic acid (CA) - carbonic anhydrase catalyses reaction to alter CA which splits into HCO3- and H+ which is chucked out
46
How does the alteration of carbonic acid control acid-base balance?
By chucking out protons and creating buffer HCO3-
47
What happens on the basolateral membrane?
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
What happens when their is a deficit of Na+ in cell?
Na tubular fluid will be use in one of reabsorption processes
49
What are the key characteristics of the cells of the descending limb of loop of Henle?
Facilitate movement of water (an osmotic process) Less mitochondria only to support cell Flat cell Passive processes
50
What are the key characteristics of the cells of ascending limb of loop of Henle?
Fewer mitochondria No vili Passive processes
51
What are symporters and antiporters?
Symporters: transport substances in same direction Antiporters: transport in opposite direction
52
Explain transcellular pathways
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
Explain the electrochemical gradient
Favors the movement of Na+ from filtrate into cells 80% Na entering, exchanged by H+ Secretion of H+ plays role in HCO3- reabsorption
54
What happens when Na+ HCO3- transported from tubule into peritubular interstitial cells?
Osmolality increases whilst osmolality in tubular fluid decrease -> proximal convuluted tubule is highly permeable to H2O
55
What happens when proximal convuluted tubule is high permeable to H2O?
H2O reabsorption increases tubular concentration of Cl-, Ca2+, urea
56
What are the key characteristics of the cells of the thick loop of Henle?
No vili = no massive quantity of reabsorption Lots of mitochondria = active processes (impervious to H2O without aquaporins)
57
What is on the left membrane of the thick loop cells?
Triport system which pumps in Na+, K+, 2Cl- (passively against concentration gradient) Small K+ leak channel Na+ H+ antiport
58
What is happening on the inside of cell?
CO2+H20=CA H+ out from antiport HCO3- leaks out on basolateral
59
What is on the basolateral membrane?
Cl- K+ leak channels Na+/K+ ATPase - during against concentration gradient - reason for mitochondria HCO3- leaks out
60
What molecules are diffused by paracellular diffusion in thick loop cells? What bounces off membrane?
Na+, K+, Ca2+, Mg+ H2O
61
What are the key characteristics of distal convuluted tubule?
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
What is on the left membrane?
Na+ and Cl- enter cell through transporter proteins H2O bounce off membrane
63
What is on the basolateral membrane?
Na+/K+ ATPase Cl- leak channel
64
What is on both membranes of the principal cell of distal convuluted tubule?
Na+ leak channel enters K+ leak channel leaves ------------------------------------- Na+/K+ ATPase K+ leaves through leak channels
65
What is on both membranes and in cell of the intercalated cell of distal convuluted tubule?
Maintain pH through proton ATPase In the cell: CO2+H2O=CA HCO3- leaks out which is engaged in buffering process
66
What is the difference between the cortical and inner medullary collecting duct?
Cortical: more mitochondria Inner: only to collect and act as a barrier
67
What happens in the loop of Henle?
Increased interstitial osmolality causes water to diffuse out of descending limb and some Na+, Cl- to diffuse in
68
How does fluid travel through loop of Henle?
Concentration fluid descends, travel in opposite direction to fluid returning from higher osmolality region of deep medulla
69
How is blood supply prevented to medulla?
Prevented from dissipating the osmotic pressure between cortex and medulla
70
What reabsorbs H2O in loop of Henle?
Vasa recta capillaries H2O reabsorbed from loop of Henle and medullary collecting ducts
71
Explain step 1 start of the counter current multiplier
Start: Filtrate coming in Move around and up 320 mOsM Dynamically equilibrate with interstitial fluid Movement of H2O
72
Explain step 2 transport of counter current multiplier
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
Explain step 3 move and step 4 transport of counter current multiplier
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
What is volume control?
Changes in major osmotic component of ECF will result in changes in ECF volume
75
What is the main regulator of body fluid volume?
Control of Na+ by kidneys through atrial and stretch receptors
76
What does the renal afferent arteriole stimulate?
ADH release, water reabsorption and release of renin
77
What occurs when more dilation and more flood filters?
More dilation, more blood filtered the greater the volume that is produced
78
What happens when more constriction occurs?
More constricted, less blood filtered, less filtrate, less urine produced
79
Explain the angiotensin system
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
What does angiotensin II cause through vasopressin?
Increase H2O reabsorption by kidney tubules which conserves H2O which helps correct ECF volume and arterial blood pressure
81
What does angiotensin II cause through thirst?
Thirst increases fluid intake which helps correct ECF volume and arterial blood pressure
82
What does angiotensin II cause through arteriolar vasoconstriction?
Helps correct ECF volume and arterial blood pressure
83
What secrets aldosterone and what does it do to the kidneys?
Adrenal cortex secrets aldosterone which increases Na+ reabsorption by renal tubules which conserves H2O which helps correct ECF volume and arterial blood pressure
84
What promotes to ADH release and water retension?
Large falls in blood volume or pressure
85
Why is the renin-angiotensin mechanism important?
For regulating blood pressure

HCS102 Human Physiology (8 decks)

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