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Biology Year 2 > C12 Kidney and ultrafiltration > Flashcards

C12 Kidney and ultrafiltration Flashcards

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1
Q

What are the two main function of the kidney?

A

Excretion

Osmoregulation

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2
Q

Define excretion

A

Removal of metabolic waste made by the body

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3
Q

Define osmoregulation

A

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

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4
Q

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

A

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

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5
Q

Define Deaminated

A

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.

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6
Q

How is urea formed

A

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.

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7
Q

Where is urea transported to

A

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

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8
Q

How many kidneys do humans have

A

two kidneys

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9
Q

where are the two kidneys located?

A

Located either side of the vertebral column.

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10
Q

General facts about the kidney

What is a NEPHRON ?

A

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 ,the cortex contains the bowman capsule and glomerulus and the proximal and distal

The middle region of the kidney is known as the MEDULLA and contains the loops of Henle and the collecting ducts

A NEPHRON IS THE FUNCTIONAL UNIT OF THE KIDNEY, A NEPHRON IS AN INDIVIDUAL BLOOD FILTERING UNIT

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11
Q

Ultra filtration in the bowmans capsule

A

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

it has high hydrostatic pressure due to

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

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12
Q

WHAT ARE THE 3 LAYERS WHICH SEPARATE BLOOD IN THE GLOMERULUS FROM THE SPACE INSIDE THE BOWMAN’S CAPSULE ( THIS IS CALLED THE BOWMAN’S SPACE).

WHAT ARE THE PROCESSES ON THE PODOCYTES CALLED ?

A

1 ) the capillary walls in the glomerulus are made up of a single layer of ENDOTHELIAL CELLS with PORES called FENESTRAE, about 80nm in diameter.

2 ) the BASEMENT MEMBRANE is an extra cellular layer of proteins,mainly collagen and glycoproteins.
It acts as a MOLECULAR FILTER and is the selective barrier acting like a sieve between the blood and the nephron

3) the wall of the bowmans capsule is made of SQUAMOUS EPITHELIAL CELLS called PODOCYTES

The processes on the podocytes are called PEDICELS, their function is to wrap around the capillary and pull it closer to the basement membrane. SEE DIAGRAM PGE 235 IN TEXT BOOK.
The gaps in between the PEDICELS are called FILTRATION SLITS- SEE DIAGRAM PGE 235

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13
Q

What are the 5 substances that make up glomerular filtrate, IE SOLUTES (4) and WATER (1 )

A 
water
glucose                       SOLUTE
salts, ( Na+, K+, Cl - )   SOLUTE
urea                             SOLUTE
amino acids                 SOLUTE
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14
Q

why do only those 5 substances make it into glomerular filtrate

A

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

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15
Q

what is the difference betweeen plasma and glomerular filtrate

A

Glomerular filtrate doesnt contain proteins whereas plasma does

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16
Q

define selective reabsorbtion

A

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

SELCTIVE REABSORPTION IS THE PROCESS BY WHICH USEFUL PRODUCTS ARE REABSORBED BACK INTO THE BLOOD AS THE FILTRATE FLOWS THROUGH THE NEPHRON.

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17
Q

What is the Proximal convoluted tubule

A

longest and widest part of the nephron it carries the filtrate away from the Bowmans capsule.

The blood in the capillaries around the PCT reabsorb all the glucose and amino acids, some of the urea and most of the water and sodium and chloride ions from the filtrate in the proximal convoluted tubule.

18
Q

what is ultrafiltration

A

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
Q

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

A

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

20
Q

Define selective reabsorption

A

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

21
Q

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

A

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
Q

Why does the PCT have a large surface area

A

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

23
Q

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

A

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
Q

Why does the PCT have mitochondria

A

Provides ATP for active transport

25
Q

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

A

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
Q

How does the PCT regulate The PH of the filtrate

A

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

27
Q

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

A

70%

28
Q

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

A

mainly active transport

29
Q

How are glucose and amino acids reabsorbed into the blood

A

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

30
Q

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

A

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
Q

How much water of the glomerular filtrate is reabsorbed

A

90%

32
Q

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

A

50%

33
Q

What does secondary active transport mean

A

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

34
Q

What are the reasons why you find glucose in urine

A

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
Q

What is the major challenge of terrestrial organisms

A

preventing dehydration

36
Q

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

A

Proximal convoluted tubule

Distal convoluted tubule

37
Q

What is the mechanism of water reabsorption

A

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

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
Q

The first step of the reabsorbtion of water

A

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
Q

2nd step of the reabsorption of water

A

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
Q

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

A

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
Q

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

A

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

42
Q

WHAT IS THE VASA RECTA ?

A

THE VASA RECTA IS THE CAPILLARY NETWORK SURROUNDING THE LOOP OF HENLE

Biology Year 2 (37 decks)

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