Kidney and ultrafiltration COPY Flashcards Preview

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Flashcards in Kidney and ultrafiltration COPY Deck (41):
1

What are the two main function of the kidney?

Excretion
Osmoregulation

2

Define excretion

Removal of nitrogenous metabolic waste from the body

3

Define osmoregulation

the control of the water potential of the bodies fluids (plasma tissue fluid and lymph) by regulating the water content, and therefore the solute concentration

4

What occurs to excess amino acids that are not assimilated into proteins?

The excess amino acids are deaminated in the lier and the amino group is converted to urea.

5

Define Deaminated

The removal of an amine group from a molecule.
Excess amino acids are deaminated in the liver and the amine group is converted into urea.

6

How is urea formed

Excess amino acids in the liver are deaminated(an amine group is removed from a molecule then that amine group is converted into urea.

Other nitrogen-containing waste products can also be converted to urea
although a low concentration of creatinine is released in both sweat and urine.

7

Where is urea transported to

it is transported in the plasma to the kidneys so it can be excreted in the urine.

8

How many kidneys do humans have

two kidneys

9

where are the two kidneys located?

Located either side of the vertebral column.

10

General facts about the kidney

Both are covered with a tough renal capsule

Each kidney recieves blood from a renal artery and returns blood to the general circulation in a renal vein

The blood from the renal artery is filtered in the outer layer known as the cortex

11

Ultra filtration in the bowmans capsule

Blood arrives in the capillaries of the glomerulus from the affferent arteriole

it has high hydrostatic pressure due to

the hearts contraction increase the pressure of arterial blood
the afferent arteriole has a wider diameter than the efferent arteriole

12

What are the 3 layers of the bowmans capsule

JAMIE WE NEED TO CHANGE THIS CARD - THE BOWMANS CAPSULE DOES NOT HAVE 3 LAYERS the wall made up of 80nm diameter endotheilium cells
called fenestrae

the basement membrane is an extra cellular layer of proteins,mainly collagen and glycoproteins.
acts as a molecular filter and is the selective barrier acting like a sieve between the blood and the nephron

the wall of the bowmans capsule is made of squamous epithelial cells called podocytes

13

What are the 5 substances that make up glomerular filtrate

water
glucose
salts
urea
amino acids

14

why do only those 5 substances make it into glomerular filtrate

some molecules are to large to pass through such as platelets large proteins such as antibodies and albumin
therefore remain in the blood.

15

what is the difference betweeen plasma and glomerular filtrate

Glomerular filtrate doesnt contain proteins whereas plasma does

16

define selective reabsorbtion

the uptake of specific molecules and ions from the blomerular filtrate in the nephron back into the bloodstream

17

What is the Proximal convoluted tubule

longest and widest part of the nephron it carries the filtrate away from the Bowmans capsule
the blood vessels around the PCT reabsorbs the glucose.

18

what is ultrafiltration

is the filtration in the capillaries of the glomerulus that forces the solutes and water through the fenestrae of the capillaries,

through the basement membrane and through the filtration slits between the pedicels into the cavity of the Bowman's capsule,

in short
Filtration under high pressure is ultrafiltration

19

What does the sieve action of the capillary walls and basement membrane do?

allows smaller molecules to pass through but retains the blood proteins and cells in the capillaries

20

Define selective reabsorption

the uptake of specific molecules and ions from the glomerular filtrate in the nephron back into the bloodstream

21

What are the 4 characteristics of the PCT (Proximal Convoluted Tubule)

It has:

Large surface area because it is long and there are a million nephrons in the kidney

Cuboidal epithelial cells in its walls. their surface area is increased by microvilli,
(each about 1 UM facing the lumen and invaginations called basal channels in the surface facing the basement membrane and capillary)

Many mitochondria which provide ATP for active transport

Tight junctions between the cells for the PCT epithelium.
These are multiprotein complexes that encircle a cell.
They prevent molecules from diffusing between the adjacent cells or from the cell back into the glomerular filtrate

22

Why does the PCT have a large surface area

Large surface area because it is long and there are a million nephrons in the kidney

23

Why does the PCT have Cuboidal epithelial cells and why is the surface area increased as a result of microvilli

Cuboidal epithelial cells in its walls. their surface area is increased by microvilli,
(each about 1 UM facing the lumen and invaginations called basal channels in the surface facing the basement membrane and capillary)

24

Why does the PCT have mitochondria

Provides ATP for active transport

25

Why does the PCT have tight junctions between the cells for the PCT epithelium

These are multiprotein complexes that encircle a cell.
They prevent molecules from diffusing between the adjacent cells or from the cell back into the glomerular filtrate

26

How does the PCT regulate The PH of the filtrate

Exchange hydrogen carbonate ions which increase the pH with Hydrogen ions which decrease the pH

27

What percentage of salts in the filtrate is reabsorbed into the blood

70%

28

what is the main type of transport that occurs during reabsorbtion of salts

mainly active transport

29

How are glucose and amino acids reabsorbed into the blood

All of the glucose and amino acids are reabsorbed into the blood via co transport with sodium ions

30

Explain how glucose and amino acids are reabsorbed via cotransport with sodium ions

A glucose molecule and two sodium ions bind to a transport protein in the cuboidal epithelium cell membrane.

they enter the cell by facillitated diffusion

dissociate from the transporter and diffuse across

sodium ions are pumped in the capillary

Glucose move in by facilitated diffusion

Co transport (also known as secondary active transport)
keeps the sodium ion concentration in the epithelial cell low, enhancing its diffusion into the cell.

31

How much water of the glomerular filtrate is reabsorbed

90%

32

How much urea and small proteins of the glmerular filtrate is reabsorbed

50%

33

What does secondary active transport mean

the coupling of diffusion, down an electrochemical gradient providing energy for the transport, e.g. of glucose up its concentration gradient

34

What are the reasons why you find glucose in urine

if the concentration of glucose in the filtrate is too high there may be too few transport molecules in the membranes of the proximal convoluted tubule cells to absorb it all
meaning that the glucose passes through the loop of Henle

The pancreas secretes too little insulin

The response of liver cells to insulin is reduced because insulin receptors in surface membranes are dammaged.)

35

What is the major challenge of terrestrial organisms

preventing dehydration

36

where are the two locations that water is reabsorbed from the glomerular filtrate to the blood

Proximal convoluted tubule
Distal convoluted tubule

37

What is the mechanism of water reabsorption

Filtrate enters the descending limb of the loop of Henle

moves down into a hairpin bend and up into the ascending limb

The walls of the ascending limb are impermeable to water.

Actively transport sodium and chloride ions out of the filtrate in the tubule into the tissue fluid in the medulla

A longer loop of Henle means that more ions can be exported into the medulla

the loops of Henle collectively concentrate salts in the tissue fluid, which therefore has a low water potential

As the filtrate climbs from the bottom of the hairpin,

it contains progressively fewer ions.

it becomes increasingly dilute and its water potential increase.

----------------------------------------------
The walls of the descending limb are permeable to water and slightly permeable to sodium and chloride ions

As filtrate flows down the descending limb,

Water diffuses out by osmosis

into the tissue fluid of the medulla

which has a low water potential

it then moves into the vasa recta
i.e. the capillaries surrounding the loop of Henle

at the same time, sodium and chloride ions diffuse into the descending limb

As the filtrate flows down the descending limb, it contains progressively less water and more ions and so

at the bottom of the hairpin bend

the filtrate is at its most concentrated with the lowest water potential

--------------------------------------------------
Having two limbs of the loop running side by side,

with the fluid flowing down in one and up in another, enables the maximum concentration to be built up at the apex of the loop

this mechanism is a counter-current multiplier

bc

flow in the two limbs is in opposite directions and the concentration of solutes is increased, the solute concentration is even higher in the medulla.
------------------------------------------------------
The collecting duct runs back down into the medulla

passing through the region of low water potential.

water, therefore, diffuses out of the collecting duct via osmosis

down a water potential gradient

the longer the loop of Henle,

the lower the water potential in the medulla and the more water leaves the collecting duct by osmosis

the filtrate becomes more concentrated than the blood

the water is reabsorbed into the vasa recta

38

The first step of the reabsorbtion of water

Filtrate enters the descending limb of the loop of Henle

moves down into a hairpin bend and up into the ascending limb

The walls of the ascending limb are impermeable to water.

Actively transport sodium and chloride ions out of the filtrate in the tubule into the tissue fluid in the medulla

A longer loop of Henle means that more ions can be exported into the medulla

the loops of Henle collectively concentrate salts in the tissue fluid, which therefore has a low water potential

As the filtrate climbs from the bottom of the hairpin,

it contains progressively fewer ions.

it becomes increasingly dilute and its water potential increase.

39

2nd step of the reabsorption of water

The walls of the descending limb are permeable to water and slightly permeable to sodium and chloride ions

As filtrate flows down the descending limb,

Water diffuses out by osmosis

into the tissue fluid of the medulla

which has a low water potential

it then moves into the vasa recta
i.e. the capillaries surrounding the loop of Henle

at the same time, sodium and chloride ions diffuse into the descending limb

As the filtrate flows down the descending limb, it contains progressively less water and more ions and so

at the bottom of the hairpin bend

the filtrate is at its most concentrated with the lowest water potential

40

Explanation of the involvement of a countercurrent multiplier in the reabsorption of water

Having two limbs of the loop running side by side,

with the fluid flowing down in one and up in another, enables the maximum concentration to be built up at the apex of the loop

this mechanism is a counter-current multiplier

bc

flow in the two limbs is in opposite directions and the concentration of solutes is increased, the solute concentration is even higher in the medulla.

41

What is the final stage (collecting duct) of the reabsorption of water

The collecting duct runs back down into the medulla

passing through the region of low water potential.

water, therefore, diffuses out of the collecting duct via osmosis

down a water potential gradient

the longer the loop of Henle,

the lower the water potential in the medulla and the more water leaves the collecting duct by osmosis

the filtrate becomes more concentrated than the blood

the water is reabsorbed into the vasa recta