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OCR A BIOLOGY > 5.2 Excretion > Flashcards

5.2 Excretion Flashcards

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1
Q

Define excretion.

A

The removal of metabolic waste from the body.

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2
Q

Define metabolic waste.

A

A substance that is produced in excess by the metabolic processes in the cells. It may become toxic.

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3
Q

what are the main excretory products.

A
  • Carbon dioxide
  • nitrogen containing compounds such as urea
  • bile pigments.
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4
Q

What are examples of excretory organs?

A
  • lungs
  • liver
  • kidney
  • skin.
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5
Q

How is the liver divided?

A

Into lobes and then into lobules.

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6
Q

What are the two interlobular vessels.

A

The hepatic artery and the hepatic portal vein.

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7
Q

What does inter mean?

A

Between.

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8
Q

What does intra mean?

A

Within.

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9
Q

What is the sinusoid?

A

The chamber where the hepatic portal vein and hepatic artery join. so that oxygenated and deoxygenated blood mix.

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10
Q

What lines the sinusoid chamber?

A

Liver cells.

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11
Q

What are kupffer cells?

A

specialised macrophages that move within the sinusoids. They break down and recycle old red blood cells and use the pigment from haemoglobin to make up bile pigments.

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12
Q

What is found at the centre of each lobule?

A

A branch of the hepatic vein.

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13
Q

What is the intralobular vessel?

A

A hepatic vein.

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14
Q

What do the bile canaliculi join together to form?

A

The bile duct which transports bile to the gall bladder where it can be stored.

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15
Q

. What are hepatocytes

A

Liver cells

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16
Q

What are the functions of liver cells?

A
  • Protein synthesis
  • the transformation and storage of carbohydrates
  • synthesis of cholesterol and bile salts
  • detoxification,
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17
Q

What’s the structure of liver cells?

A
  • Simple cuboidal shape
  • large nucleus
  • defined golgi apparatus
  • many mitochondria,
  • many microvilli
  • very dense cytoplasm.
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18
Q

How is bile formed?

A

Bile is formed by the hepatocytes and Kupffer cells. The Kupffer cells recycle the old red blood cells to produce bile pigments, which then pass into the hepatocytes so bile can be formed. The bile then passes along the bile canaliculi into the bile duct to for gall bladder where it is stored.

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19
Q

What is the difference between the hepatic portal vein and the hepatic vein?

A

The hepatic portal vein carries deoxygenated blood with waste products and toxins, as well as glucose and amino acids from digestion. Where as the hepatic vein contains deoxygenated blood but it’s cleansed from toxins.

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20
Q

What blood vessels pass into the liver?

A

The hepatic artery and the hepatic portal vein.

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21
Q

What blood vessel passes out of the liver?

A

The hepatic vein.

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22
Q

What is the function of the hepatic artery?

A

To carry oxygenated blood from the heart to the liver. The oxygen and glucose are then used in respiration for. the liver cells to complete metabolic reactions.

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23
Q

What is the function of the hepatic portal vein?

A

To carry deoxygenated blood that contains toxins from the digestive system to the liver. Where it can be sorted?

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24
Q

What is the function of the hepatic vein?

A

To carry deoxygenated blood from the liver to the heart where it can be reoxygenated at the lungs.

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25
Q

which is larger, the hepatic artery or the hepatic portal vein?

A

hepatic portal vein

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26
Q

what is the ornithine cycle?

A

a series of biochemical reactions that convert ammonia to urea

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27
Q

why are sugars stored as glycogen rather than glucose?

A
  • glycogen is insoluble so wont affect the water potential of the blood
  • glycogen is branched so it has more free ends for easy breakdown to release energy quickly
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28
Q

how is glycogen stored?

A

as granules in the cytoplasm of hepatocytes

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29
Q

what is detoxification?

A

making substances less toxic

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30
Q

what enzymes found in liver cells are used in detoxification?

A
  • catalase
  • cytochrome p450
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31
Q

what does catalase catalyse?

A

the breakdown of hydrogen peroxide into oxygen and water

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32
Q

describe the detoxification of alcohol

A

ethanol is broken down into ethanal by the enzyme ethanol dehydrogenase. The ethanal is then broken down into ethanoic acid by ethanal dehydrogenase. The ethanoic acid then becomes acetyl coenzyme A which is used in respiration

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33
Q

what do the hydrogen ions combine with during the detoxification of alcohol?

A

oxidized NAD to make reduced NAD

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34
Q

What is NAD?

A

a coenzyme used to oxidize fatty acids in the live

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35
Q

what to processes are involved in forming urea?

A
  1. deamination
  2. ornithine cycle
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36
Q

outline the process of forming urea

A

amino acid -> ammonia -> urea

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37
Q

why are amino acids broken down and not excreted as a whole?

A

They contain lots of energy so they are broken down into carbohydrates and ammonia.

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38
Q

what is deamination?

A

removing the amino group to produce ammonia and an organic keto acid.

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39
Q

outline deamination

A

2 amino acids + oxygen —> keto acid + ammonia

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40
Q

why must ammonia be converted to urea?

A

it is very soluble and highly toxic

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41
Q

what are the keto acids used for?

A

they are either:
- stored as lipids or cholesterol
- used in respiration

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42
Q

where does the ornithine cycle occur?

A

in the mitochondria of hepatocytes

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43
Q

outline the ornithine cycle

A
  1. ammonia is combine with carbon dioxide to produce ornithine
  2. water is added to produce urea and ornithine.
  3. urea is excreted and ornithine is reused
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44
Q

what is ornithine?

A

an amino acid

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45
Q

what happens to the urea when it leaves the ornithine cycle?

A

it enters the blood and leaves the liver via the hepatic artery, it is then transported to the kidneys.

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46
Q

What are the two main functions of the kidney in the body

A
  1. osmoregulation
  2. excretion
47
Q

What the 3 main areas of the kidney?

A
  • Cortex
  • Medulla
  • renal pelvis.
48
Q

How is hydrostatic pressure increased in the glomerulus?

A

The afferent arteriole has a larger lumen than the efferent Arteriole, which creates pressure.

49
Q

What is a nephron?

A

The functional unit of the kidney responsible for forming urine.

50
Q

What are the two stages of forming urine.

A
  • Ultrafiltration
  • selective reabsorption.
51
Q

Where does ultrafiltration occur?

A

Bowman’s capsule.

52
Q

Outline the process of ultrafiltration.

A

Small molecules have felt out the capillaries of the Glomerulus into the Bowman’s capsule to form the glomerular filtrate.

53
Q

What small molecules are filtered out of the blood?

A
  • Amino acids
  • water
  • glucose
  • urea
  • inorganic ions such as Na+, K + CL -.
54
Q

What are the three layers that make up the filter

A
  1. Capillary endothelium
  2. basement membrane
  3. Bowman’s capsule epithelium.
55
Q

Where does selective reabsorption occur?

A

Proximal convoluted tubule.

56
Q

Outline selective reabsorption.

A

Useful molecules are reabsorbed from the filtrate and returned to the blood.

57
Q

What factors affect water potential in the glomerulus and the Bowman’s capsule?

A

Pressure and solute concentration.

58
Q

Where does the ureta join the kidney?

A

At the renal pelvis.

59
Q

What is present in the cortex of the kidney?

A
  • glomerulus
  • bowmans capsule
  • proximal convoluted tubule
  • distal convoluted tubule
60
Q

What is present in the medulla of the kidney?

A
  • loop of henle
  • collecting duct
61
Q

Which arteriole leads into the glomerulus?

A

afferent

62
Q

Which arteriole leads out of the glomerulus?

A

efferent

63
Q

What forces the substance out of the blood into the Bowman’s capsule to be filtered.

A

High hydrostatic pressure created by the narrowing of the lumen.

64
Q

What is the glomerulus?

A

A knot of capillaries.

65
Q

What is the main filter?

A

The basement membrane, as it is a fine mesh layer, so only small substances can pass through.

66
Q

what substances stay in the blood after ultrafiltration.

A
  • Water
  • blood plasma
  • red blood cells
  • platelets
  • large plasma proteins.
67
Q

During ultrafiltration, where is the region of high water potential?

A

The capillary of the glomerulus.

68
Q

During ultrafiltration, where is the region of low water potential?

A

Bowman’s capsule

69
Q

Why is there a region of high water potential in the capillary of the glomerulus?

A

Because the blood plasma creates higher pressure and higher solute concentration.

70
Q

Why is there a region of low water potential in Bowman’s capsule?

A

Because for glomerulonefiltrate creates lower pressure and has a lower solute concentration. Due to the large volume of water.

71
Q

What cells make up the bowmans capsule endothelium.

A

podocyte cells

72
Q

How does pressure affect water potential in the glomerulus and Bowman’s capsule?

A

Blood pressure is relatively high in the glomerular capillaries, which raises the water potential above that of the filtrate in Bowman’s capsule. This means that water moves from the capillaries into the Bowman’s capsule.

73
Q

How does solute concentration affect water potential in the glomerulus and Bowman’s capsule.

A

large plasma proteins stay in the blood so solute concentration in the capillaries is higher than in the filtrate. This means the water potential of the blood is lower than that of the filtrate. So water moves from bowman’s capsule into the capillaries.

74
Q

What is reabsorbed in the loop of Henle and collecting duct

A

Water and salts.

75
Q

What molecules are reabsorbed during selective reabsorption?

A
  • All glucose and amino acids
  • vitamins
  • inorganic ions
  • some urea.
76
Q

Describe selective reabsorption.

A

Sodium ions are pumped out of the epithelial cell into the blood, by active transport, where they are then carried away, which lowers the concentration of sodium ions in the epithelial cells. This means sodium ions move into the epithelial cells from the glomerular filtrate alongside glucose or amino acids by secondary active transport via a co-transporter protein. The glucose/amino acids diffuse out of the epithelial cells into the capillary.

77
Q

What process pumps the sodium ions out of the epithelial cell and into the capillary?

A

Active transport.

78
Q

Where is secondary active transport seen in selective reabsorption?

A

When the sodium and glucose into the epithelial cell via the co-transporter protein as a result of actively pumping the sodium ions out into the capillary.

79
Q

Where does the descending limb of a loop of Henley descend into.

A

The medulla

80
Q

Where does the ascending limb of loop of Henley ascend into?

A

the cortex

81
Q

What lowers the mineral ion concentration in the proximal convoluted tubule?

A

The sodium potassium pump moving sodium ions out of the epithelial cell into the blood where they are then carried away.

82
Q

Where does selective reabsorption occur?

A

The proximal convoluted tubule.

83
Q

What molecules are reabsorbed?

A
  • all glucose
  • amino acids
  • vitamins
  • inorganic ions
  • some urea
84
Q

What happens to water potential when molecules are reabsorbed?

A
  • water potential of the filtrate increases
  • water potential of the blood decreases.
85
Q

What causes water to move back into the blood by osmosis?

A

This steep water potential gradient created from the reabsorption of mineral ions.

86
Q

Where are salts reabsorbed back into the blood?

A

Where the Filtrate drips through the loop of Henle

87
Q

How are salts reabsorbed back into the blood?

A

Diffusion

88
Q

Where can water be reabsorbed?

A

The loop of Henle and the collecting duct

89
Q

Where’s the main function of the loop of henle?

A

To ensure the recovery of water and sodium chloride ions from the urine, limiting the amount of water intake needed for survival.

90
Q

How does the structure of the loop of Henle benefit its function?

A
  • Increases efficiency of mineral ion transfer between limbs.
  • Create a decreasing water potential deeper into the medulla.
91
Q

What part of the loop of Henle is permeable to water?

A

The descending limb.

92
Q

Where is the filtrate water potential at its lowest?

A

At the bottom of the loop.

93
Q

What part of the leap of Henle is impermeable to water, but allows the movement of sodium and chloride ions out of the filtrate?

A

The ascending limb

94
Q

Describe what happens in the loop of Henle

A
  1. Sodium and chloride ions are actively transported out of the upper ascending limb of the loop of Henle into the medulla, which lowers the water potential of the medulla
  2. Water then leaves the ascending limb by osmosis as the water potential is higher than in the medulla. 3. This creates a very low water potential in the loop of Henle, so sodium and chloride ions diffuse out from high to low concentration until it is isotonic.
  3. Then only water will be left in the loop of Henle, so it can be removed in the collecting doctrine.
95
Q

What happens in the distal convoluted tubule?

A

The fine tuning of ions. So if the body lacks salt sodium ions are actively pumped out into the blood.

96
Q

What words can describe the loop of henle?

A

Multiplier and countercurrent system.

97
Q

What is ADH stand for?

A

Antidiuretic hormone.

98
Q

When is ADH released?

A

When more water needs to be reabsorbed.

99
Q

What detects the water levels in the blood?

A

osmoreceptors

100
Q

What are osmoreceptors?

A

Receptors were detected for water levels in the blood and then stimulate the release of ADH if water levels are too low

101
Q

Where is ADH produced?

A

In a neurosecretory cell in the hypothalamus.

102
Q

Why is ADH released from?

A

from the posterior pituitary gland into the blood.

103
Q

What does ADH do?

A

ADH causes aquaporin storage vesicles to fuse with the membrane of the collecting tubeule cell. This means there are more aquaporins along the membrane, so more water can travel from the lumen of the collecting duct into the bloodstream.

104
Q

What is needed for the aquaporins to stay fused to the membrane?

A

A constant supply of ADH

105
Q

What happens when there is no longer any ADH stimulation?

A

The vesicles will reform.

106
Q

What are two causes of kidney failure?

A
  • kidney infection
    -raised blood pressure
107
Q

How can a kidney infection cause kidney failure?

A

The podocyte and tubule cells become damaged so can no longer act as a filter, meaning large proteins and blood can enter the filtrate.

108
Q

How can raise blood pressure cause kidney failure?

A

This could increase hydrostatic pressure, resulting in the damage of epithelial cells in the basement membrane, which means it can no longer act as a filter, so large plasma proteins and blood can pass into the filtrate.

109
Q

What is measured when detecting kidney failure?

A

The glomerular filtrate rate. This is where the creatinine levels are measured, as they are a waste product formed from muscle cells.

110
Q

What are the two methods for treating kidney failure?

A
  • haemodialysis
  • kidney transplant
111
Q

Why are kidney transplants harder to come by?

A

There could be fewer donor kidneys which need to be a match as they could be rejected. when you have a kidney transplant, you are put on immunosuppressant drugs, which makes you more susceptible to disease.

112
Q

When may urine be sampled.

A

When testing for pregnancy, anabolic steroids or drugs.

113
Q

What hormone is tested for during a pregnancy test?

A

HCG

114
Q

Outline hemodialysis.

A

Blood is removed for cleansing by dialysis, a heparin pump prevents the blood from clotting whilst outside the body. The blood enters the dialyser which contains fine capillary tubes of dialysis membrane. There is dialysis fluid flowing in a counter current system to the blood. The dialysis fluid has the ideal concentration of substances in the blood. This means:
- glucose remains in the blood as the concentration gradient is equal.
- Urea will diffuse out of the blood as there is none in the dialysis fluid.
- Red blood cells and plasma are too large to pass through so they stay in the blood.

OCR A BIOLOGY (21 decks)

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