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Excretion Flashcards

1
Q

What is excretion

A

The removal of waste products from the body

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2
Q

What is metabolism

A

All the chemical reactions that happen in your cells. It produces waste products such as CO2 and nitrogenous waste.

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3
Q

Why does excretion happen

A

The waste products of metabolism are often toxic and so if they built up they would cause damage. So it removes the waste products.

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4
Q

What are the functions of the liver

A

Excess amino acids are broken down

Removal of harmful substances from the blood

Storage of glycogen

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5
Q

How does the liver carry out it’s function of breaking down amino acids

A

1) The amine groups are removed from any excess amino acids forming ammonia and organic acids (deamination)
2) The organic acids can be respired to give ATP or converted to carbohydrate and stored as glycogen.
3) Ammonia is too toxic to be excreted directly so it is combined with CO2 in the ornithine cycle to create urea
4) Urea is released from the liver into the blood, the kidneys then filter the blood and remove the urea as urine

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6
Q

Why does the liver carry out it’s function of breaking down amino acids

A

Amino acids contain nitrogen which can’t usually be stored in the body so excess amino acids can be damaging.

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7
Q

Why does the liver carry out it’s function of removing harmful substances from the blood

A

They are broken down into less harmful compounds to be excreted called detoxification.

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8
Q

What are some of the harmful products broken down in the liver

A

Alcohol (ethanol)

Paracetamol

Insulin

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9
Q

How does the liver remove alcohol from the blood

A

It is broken down into ethanal which is broken into a less harmful substance called acetic acid. Excess alcohol can lead to cirrhosis of the liver and it’s cells die and scar tissue blocks blood flow.

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10
Q

What does the live do with excess glucose

A

Converts it to glycogen and stores it as granules in its cells until needed

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11
Q

What does the hepatic artery do

A

Supplies the liver with oxygenated blood from the heart, so the liver has a good supply of oxygen for respiration providing plenty of energy

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12
Q

What does the hepatic vein do

A

Take deoxygenated blood away from the liver

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13
Q

What does the hepatic portal vein do

A

Brings blood from the duodenum and ileum so it’s rich in the products of digestion. Any ingested harmful substances are filtered out and broken down straight away

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14
Q

What does the bile duct do

A

Takes bile to the gall bladder to be stored

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15
Q

What is the liver made up of

A

Liver lobules - cylindrical structures made of cells called hepatocytes that are arranged in rows radiating out from the centre

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16
Q

What does each liver lobule contain

A

A central vein that connects to the hepatic vein. Many branches of the hepatic artery, hepatic portal vein and bile duct are also found connected to each lobule

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17
Q

What are the hepatic artery and portal vein connected to

A

The central vein by capillaries called sinusoids

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18
Q

How does blood run through the lobule

A

Through the sinusoids past the hepatocytes that remove harmful substances and oxygen from the blood. The harmful substances are broken down by the hepatocytes into less harmful substances that then re-enter the blood. The blood then runs to the central vein and the central veins from the lobules to form hepatic vein. Kupffer cells attached to the walls of the sinusoids remove bacteria and break down old red blood cells.

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19
Q

What do hepatocytes produce

A

Bile and secrete it into tubes called bile canaliculi. These tubes drain into bile ducts from all the lobules eventually connect up and leave the liver.

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20
Q

What does the central vein look like under a light microscope

A

Large white circular shape

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21
Q

What does the sinusoids look like under a light microscope

A

White spaces

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22
Q

What does the hepatocytes look like under a light microscope

A

Cells that radiate from the hepatocytes with red dots as nuclei

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23
Q

What are the functions of the kidney

A

To excrete waste products

Regulate water potential of the blood

24
Q

How does the kidney excrete waste products

A
  • Blood enters through the renal artery and passes through capillaries in the cortex
  • As blood passes through substances are filtered out of the blood and into long tubules (ultrafiltration)
  • Useful substances (glucose) are reabsorbed back into the blood from the tubules in the medulla and cortex (selective reabsorption)
  • The remaining unwanted substances such as urea pass along the tubules, along the ureter to the bladder where they’re expelled as urine
  • Filtered blood passes out through the renal vein
25
What are nephrons
Long tubules along with the bundles of capillaries where blood filtered are called nephrons. There are around 1 million in each kidney
26
What is the pathway of structures in a nephron
Glomerulus Bowman's capsule Proximal convoluted tubule Loop of Henle Distal convoluted tubule Collecting duct
27
Where does blood come from before entering the glomerulus
Comes from the renal artery in the afferent arteriole
28
What happens in the glomerulus and bowman's capsule during blood filtrations
Ultrafiltration - the high pressure forces liquid and small molecules out of the capillary into the Bowman's capsule
29
What takes the filtered blood away from the glomerulus
The efferent arteriole
30
What three layers make up the Bowman's capsule
The capillary wall Basement membrane Epithelium
31
Where does selective reabsorption occur
Proximal convoluted tubule Loop of Henle Distal convoluted tubule
32
Where do useful substance go after leaving the tubules in the nephron
Enter the capillary network that is wrapped around them
33
What does the epithelium of the wall of the PCT have and why
Microvilli to provide a large surface area for reabsorption of useful materials from the filtrate into the blood
34
What is reabsorbed and by what processes in the PCT
Useful solutes like glucose, amino acids, vitamins and some salts by active transport and facilitated diffusion Also some urea is reabsorbed by diffusion
35
What enters the blood from the loop of Henle, DCT and collecting duct and why
Water enters by osmosis due to the lower water potential in the blood than the filtrate
36
What equipment in needed for a kidney dissection
A mammals kidney, a dissecting tray, a scalpel, an apron, lab gloves
37
What are the two limbs of the loop of Henle
Ascending and descending
38
What do the two limbs of the loop of Henle help to set up
The countercurrent multiplier mechanism which helps to reabsorb water back into the blood
39
What happens in the top of the ascending limb in the countercurrent multiplier
At the top, Na+ and Cl- ions are actively pumped out into the medulla. This limb is impermeable to water and so the water will stay inside the tubule, creating a low water potential due to the high concentration of ions.
40
What happens in the descending limb in the countercurrent multiplier
Because there is lower water potential in the medulla, water moves out by osmosis. This makes the filtrate more concentrated. The water in the medulla is then reabsorbed into the blood through capillary's
41
What happens at the bottom of the ascending limb in the countercurrent multiplier
Na+ and Cl- ions diffuse out into the medulla lowering the water potential in the medulla. As this limb is impermeable to water it stays in the tubule.
42
What happens in the collecting duct in the countercurrent multiplier
Water moves out of the collecting duct by osmosis and is then reabsorbed into the blood capillaries.
43
What does an animal with a longer loop of Henle mean
They can reabsorb more water. The larger the ascending limb, the more ions can be pumped out creating a very low water potential. Meaning more water moves out of the nephron and collecting duct giving very concentrated urine
44
How are animals living in dry conditions loop of Henle's adapted
They will often have a longer one to save as much water as possible
45
What is the water potential of the blood monitored by
Cells called osmoreceptors in the hypothalamus
46
When are osmoreceptors stimulated and what happens
Stimulated by low water potential in the blood causing the hypothalamus to send nerve impulses to the posterior pituitary gland which releases ADH (anti diuretic hormone)
47
What does the release of ADH do
It makes the walls of the DCT and collecting duct more permeable to water so more water is reabsorbed from these tubules into the medulla and then into the blood by osmosis. This then produces a small amount of concentrated urine which reduces water lost from the body.
48
What happens to ADH levels when you are dehydrated
They rise to increase the water content of the blood
49
What happens to ADH levels when you are hydrated
They fall as you have taken in lots of water and the water content of the blood needs to be reduced
50
What happens as a result of a rise in ADH levels
1) The water content of blood drops, so water potential drops which is detected by osmoreceptors in the hypothalamus 2) The posterior pituitary gland then is stimulated to release more ADH into the blood. 3) This means the DCT and collecting duct are more permeable so water is reabsorbed into the blood by osmosis 4) A small amount of highly concentrated urine is produced and less water is lost
51
What happens as a result of a fall in ADH levels
1) The water content of the blood rises increasing its water potential which is detected by osmoreceptors in the hypothalamus 2) The posterior pituitary gland will release less ADH into the blood 3) This means the DCT and collecting duct are less permeable so less water is reabsorbed into the blood by osmosis 4) A large amount of dilute urine is produced and more water is lost
52
What is kidney failure
Is when kidneys can't carry out their normal functions because they do not work properly.
53
How can kidney failure be detected
By measuring the glomerular filtration rate (GFR) - the rate at which blood is filtered from the glomerulus into the Bowman's capsules
54
What does a lower rate of GFR mean
The kidneys aren't working properly which could be caused by kidney infections or high blood pressure
55
How do kidney infections cause kidney failure
Caused by inflammation of kidneys, which can damage the cells therefore interfering with filtering in the Bowman's capsules, or with reabsorption in the other parts of the nephrons
56
How does high blood pressure cause kidney failure
It can damage the glomeruli as the blood there is already under high blood pressure but the capillaries can be damaged if the blood pressure gets too high. This means that larger molecules such as proteins are able to get through the capillary walls and into the urine.

Biology (23 decks)

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