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Chapter 16- Heomeostasis > 16.6 - Role of nephron > Flashcards

16.6 - Role of nephron Flashcards

1
Q

What is one of the important function of the kidney?

A

It is to maintain the water potential of the plasma and hence tissue fluid (osmoregulation)

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2
Q

What are the role of osmoregulation in important stages:

A
  1. Formation of glomerular filtrate by ultrafiltration
  2. Reabsorbption of glucose by proximal convoluted tubule
  3. Maintenance of gradient of sodium ions in the meddulla and loop of Henle
  4. Reabsorbption of water by distal convoluted tubule and collecting duct
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3
Q

What is the function of renal artery?

A

The blood enters the kidney through the renal artery

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4
Q

What does the renal artery branch into tiny arterioles called what?

A

renal Bowman’s capulse of nephron

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5
Q

What is the afferent arteriole divide into complex capillaries known as what?

A

The glomerulus

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6
Q

What does the glomerular capillaries merge into ?

A

Efferent arteriole

sub-divides into capillaries and wind their way around various tubules of nephron before combining to form renal vein

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7
Q

What are the walls of the glomerular capillaries made up of?

A

Endothelial cells which has pores etween them

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8
Q

Process of forming glomerular filtrate

A
  1. As diameter of afferent arteriole is greater than efferent arteriole
  2. There is a build up of high hydrostatic pressure within the glomerulus
  3. As a result , water , glucose and mineral ions squeezed out of capillary to form glomerular filtrate
  4. Blood cells and lare proteins cannot pass across renal capulse as they are too large
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9
Q

The movement of filtrate out of the glomerulus is resisted by what?

(total resistance prevent the filtrate leaving glomerular capillaries)

A
  • Capillary endothelial cells
  • Connective tissue and endothelial cells of blood capillary
  • Epithlial cells of renal capulse
  • Hydrostatiic pressure of fluid in renal capsule space
  • The low water potential of blood in glomerulus
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10
Q

What are some of the modifications to reduce the barrier to the flow of filtrate?

A
  • Inner layer of renal capulse is made up of specialised cells called pdoocytes. These have spaces between them called fenstrations and allow filtrate to pass through gaps between brances , pass between cells than through them
  • Endothelium of glomerular capillaries have spaces up to 100 nm wide between cells , again fluid can therefore pass between cells than through
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11
Q

Wh does the filtrate pass from the blood into renal capulse?

A

The hydrostatic pressure of the blood in glomerulus is sufficient to vercome the resistance

The filtrate contains urea and does not contain cells or plasma proteins that are too large to pass across the connective tissue

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12
Q

How many percentage of filtrate is reabsorbed back into the blood in PCT?

A

85%

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13
Q

What does ultrafilitration operate on?

A

The basis of size of molecule

the small ones are removed

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14
Q

How is the proximal convoluted tubule adapted to reasorb subtancs into the blood by having eptihelial cells such as?

A
  1. Microvilli to provide a large surface area to reasborb substances from the filtrate
  2. Infoldings at their base to give them a larg surface area to transfer reasborbed substacnes into the blood capillaries
  3. A high density of mitochondria to provide ATP for active transport
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15
Q

How is the PCT reasorb substances into the blood by having epithelial cells?

A
  1. Sodium ions are actively transported out of the cells lining PCT into blood capillaries which carry them away. Con of NA+ of these cells lowered
  2. Na+ diffuse down the conc grad from lumen of PCT into epithlial lining cells but by special carrier proteins by facilitated diffusion
  3. Carrier proteins are specific types along with Na + and AA/Glucose - co-transport
  4. Molecules are co-transported into the cells of PCT then diffuse into blood. As a result glucose and other valueable molecules reabsorbed as well as water.
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16
Q

What amount of water enter the nephrons every day?

A

180 dm^3

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17
Q

What happens to the remainder of the of the substance rebasorbed in?

A

Collecting duct as functioning of the loop of Henle

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18
Q

What is the appearence of loop of Henle?

A

It is hair-pin shaped tubule that extends into the medulla of the kidney

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19
Q

What is the loop of Henle responsible for?

A

For water being reabsorbed from the collecting duct

therefore concentrating the urine so that it has a lower water potential than the blood

the concentration of urine is produced directly related to length of loop of Henle

20
Q

What two regions does the loop of Henle have?

A
  • Descending limb which is narrow with thin walls that are highly permeable to water
  • Ascending limb which is wider and thick walls that are impermable to water
21
Q

What does the loop of Henle acts as?

A

A counter-current multipler

22
Q

First stage of counter current multipler

A

Sodium ions are actively transported out of the ascenind limb of the loop of Henle using ATP provided by many mitochondria in cells of walls

23
Q

Second stage of counter current multipler

A
  • This will create a lower water potential (high ion concentration) in the region of the medulla between the two limbs (called interstial region)
  • In normal circumstances water would pass out of the ascending limb by osmosis. Howeber thick walls are almost impermable to water and very little if any escapes
24
Q

Third step of counter current system

A
  • Walls of the descending limb are however, very permable to water and pass out of filtrate by osmosis into intersital space.
  • This water enters the blood capillaries in this region of osmosis is carried away
25
Q

Fourth step of counter-current system

A
  • Filtrate will progressively lose water in this way as it moves down from the descending limb lowering its water potential
  • It reaches its lowest water potential at the tip of the hairpin
26
Q

Fifth step of counter current system

A
  • At the base of the ascending limb , Na+ diffuses out of filtrate as it moves up the ascending limb these ions are also actively pumped out
  • Therefore filtrate develops a progressively higher water potential
27
Q

Sixth step of counter-current multipler

A
  • In intersitial space between the ascending limb and the collecting duct there is greater water potential with the highest water potential (lowest concentration of ions) in cortex and increasingly lower water poetnail (hgihest concentration of ions) the further the medulla one goes
28
Q

Seventh step of counter-current system

A

The collecting duct is more permeable to water so the filtrate moves down it

The water passes out of it by osmosis

This water passes by osmosis into the blood vessls that occupy this space and is carried away

29
Q

Eigth step of the counter-current system

A
  • As water moves out of the filtrate
  • Its water potential is lowered
  • However, the water potential is also lowered in the intersitial space
  • So water continoues to move out by osmosis down the whole length of the collecting duct
  • The counter-current multiplier ensures there is always a water potential drawing water out of tubule
30
Q

Diagram of counter-current system

A
31
Q

What happens to the water that passes out of the collecting duct by ososis?

A

Does through channel proteins that are specific to water (aquaporins)

32
Q

What can ADH do?

A

Antidiuretic hormone can alter the number oc channels and control water loss

By the time the filtrate now called urine leaves the collecting duct on way to bladder , it has lost most of its water and has lowest water potential (is more concentrated than blood)

33
Q

What are the cells that make up of distal convulted tubule?

A

It has many micorvilli and many mitochondria to reabsorb material rapidly from the filtrate by active transport

34
Q

What is the main role of the distal convulted tubule?

A
  • To make final adjustments to the water and salts that are reasborbed to control the pH of the blood by selecting what ions to reabsorb
  • To achieve this its permeability of walls become altered due to the influence of various hormoned
35
Q

Explain counter-current multipler

A
  • Filtrate in the collecting duct with a lower water potential meetsintersitial flulid with even lower water potentisl
  • This means although water potential gradient between collecting duct and intersitial fluid is small , it exists for the whole length of the duct
  • There is a steady flow of water in the intersitial fluid so around 80% of water enters the intersilital fluid and hence the blood
  • If two flows were in the same direction less water would enter the blood
36
Q

Why does concentration of glomuerulus fall in PCT?

A

Glucose is actively transported out of tubule so concentration falls

37
Q

Why does concentration of glomerulus peak in loop of Henle, drops then increases in DCT and collecting duct?

A

Na+

Na+ will increase as they enter descending limb and leave ascending limb

Water is absorbed from the tubule , increasing the concentration of Na+ also K+ is actively transported into the tubule to be removed in urine

38
Q

Why does line 3 increase in DCT?

A

Urea

Concentration rises as water is removed from tubule

39
Q

Describe how urea is removed from blood

A
  • Hydrostatic pressure
  • Causes ultrafiltration at Bowman’s capsule
40
Q

Describe how urea is concentrated in the urine

A

Reabsorption of water by osmosis

  • At the PCT
  • Active transport of ions / glucose creates gradient
41
Q

The glomeruluar filtrate is the total volume of filtrate formed per minute

Explain the effect on glomerular filtration rate of a large loss of blood from the body

A

It will decrease blood pressure

So less filtrate is formed

42
Q

A diabetic person and a non-diabetic person ate the same amount of glucose

One hour later , the glucose concentration in the blood of a diabetic person was higher than the non-diabetic person.

Explain why?

A

Doesn’t produce enough insulin/lack of

So will devrease the uptake of glucose in blood

Won’t convert glucose to glycogen

43
Q

The urine of a non-diabetic person will not contain glucose

Explain why

A

As glucose is reabsorbed by active transport in blood by PCT

44
Q

A high blood glucose concentration could cause glucose to be present in the urine of a diabetic petson

Suggest how

A

Glucose not reasborbed at all

PCT is hort

High concentration in filtrate

45
Q

IIf the glomerular filtrate of a diabetic person contains a high concentration of glucose produce large amount of urine

A
  • Glucose in filtrate lowers water potential;
  • Lower Ψ gradient
  • Less water reabsorbed by osmosis;
46
Q

In some forms of kidney disease, proteins from the blood plasma are found in the urine. Which part of the nephron would have been damaged by the disease to cause proteins from blood plasma to be present in the urine? Explain your answer (3)

A
  • Glomerulus / Bowman’s capsule / renal capsule;
  • Basement membrane;
  • proteins can only pass through if filter damaged;
47
Q

Some desert mammals have long loops of Henle and secrete large amounts of antidiuretic hormone (ADH). Explain how these two features are adaptations to living in desert conditions (6)

A
  • More water (from filtrate) reabsorbed
  • By osmosis;
  • From collecting duct
  • Due to longer loop of Henle
  • Large amounts of ADH means they act on collecting duct
  • Makes cells more permeable

Chapter 16- Heomeostasis (7 decks)

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