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Biology A1 & A2 > 3B: Mass transport > Flashcards

3B: Mass transport Flashcards

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1
Q

Describe 3 adaptations of red blood cells

A
  • Biconcave shape = maximises SA for gas exchange
  • Small + flexible = to pass through narrow capillaries (pressed to the sides to maximise gas exchange)
  • No nucleus = more room to carry respiratory gases
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2
Q

What is the function of red blood cells?

A

To transport O₂ around the body

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3
Q

How does haemoglobin allow RBCs to carry respiratory gases (especially oxygen)

A
  • It has an affinity for oxygen (can carry up to 4 O2 molecules)
  • Oxygen binds to the ‘haem’ Fe2 + group of haemoglobin
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4
Q

What is haemoglobin called when it becomes oxygenated?

A

Oxyhaemoglobin

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5
Q

What are the haemoglobins?

A
  • The haemoglobins are a group of chemically similar molecules found in many different organisms.
  • They are protein molecules with quaternary structures
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6
Q

Describe the primary structure of a haemoglobin molecule.

A

Sequence of amino acids in the 4 polypeptide chains

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7
Q

Describe the secondary structure of a haemoglobin molecule.

A

Each of the 4 polypeptide chains is coiled into a helix

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8
Q

Describe the tertiary structure of a haemoglobin molecule.

A

Each polypeptide chain is folded into a precise shape

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9
Q

Why is the tertiary structure of a haemoglobin molecule so important?

A
  • The tertiary structure of a protein determines the 3D shape of the protein
  • For haemoglobin this is an important factor in its ability to carry oxygen
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10
Q

Describe the quaternary structure of a haemoglobin molecule.

A
  • All 4 polypeptides are linked together to form an almost spherical molecule
  • Each polypeptide is associated with a haem group
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11
Q

What does each haem group, in haemoglobin, contain?

A

Each haem group contains a ferrous group (Fe2+) ion
- Each iron ion can combine with a single oxygen molecule
= a total of 4 O2 molecules can be carried

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12
Q

In humans, where does the loading/ associating of haemoglobin & oxygen take place?

A

In the lungs

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13
Q

In humans, where does the unloading/ dissociating of haemoglobin & oxygen take place?

A

In the tissues

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14
Q

What is the process by which haemoglobin binds with oxygen called?

A

Loading/ associating

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15
Q

What is the process by which haemoglobin releases its oxygen called?

A

Unloading/ dissociating

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16
Q

What is the role of haemoglobin?

A

To transport oxygen from gas exchange surafces to respiring tissues

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17
Q

To be efficient at transporting oxygen, haemoglobin must:

A
  • Readily associate with oxygen at the surface where gas exchange takes place
  • Readily dissociate from oxygen at those tissues requiring it
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18
Q

What adaptation allows haemoglobin to readily associate + dissociate from oxygen in different environments?

A

The fact that haemoglobin can change its affinity for oxygen under different conditions.

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19
Q

How does haemoglobin change its affinity for oxygen in different environments?

A

Because its shape changes in the presence of certain substances, e.g carbon dioxide

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20
Q

Describe what happens to haemoglobin in respiring tissue.

A
  • In respiring tissue there’s a high CO₂ conc. and a low O₂ conc.
  • In the presence of carbon dioxide, the new shape of the haemoglobin molecule binds more loosely to oxygen
  • It has a low affinity for O₂
    = resulting in the haemoglobin unloading its oxygen
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21
Q

Describe what happens to haemoglobin at the gas exchange surface.

A
  • At the exchange surface there’s a high O2 conc. and a low CO2 conc.
  • This means that the haemoglobin will have a high affinity for O2
    = resulting in the haemoglobin loading its oxygen
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22
Q

Why do different hemoglobins have different affinities for oxygen?

A

Due to the shape of the molecule

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23
Q

Why do different organisms have haemoglobins with different shapes - and therefore oxygen affinities?

A
  • Because each species produces a haemoglobin with a slightly different amino acid sequence
  • Therefore the haemoglobin of each species will have a different tertiary + quaternary structure
    = and hence different oxygen binding properties
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24
Q

What is the partial pressure of oxygen (PO2) referring to?

A

The amount of oxygen in the tissue

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25
Q

What is PO2 measured in?

A

kPa

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26
Q

What is the graph that shows the relationship between the saturation of haemoglobin + O2 and the PO2 known as?

A

The oxygen dissociation curve

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27
Q

What shape is the graph that shows the relationship between the saturation of Hb + O2 and the PO2 known as?

A

An S-shape

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28
Q

Why is the oxygen dissociation curve shallow initially?

A
  • The shape of the Hb molecule makes it difficult for the first O2 molecule to bind to 1 of the sites on its 4 polypeptide subunits because they are closely united
  • Therefore in low O₂ conc.s little O₂ binds to Hb
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29
Q

What does Hb refer to?

A

Haemoglobin

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30
Q

How does the binding of the 1st O2 change the hemoglobins structure?

A
  • The binding of the first O₂ changes the quaternary structure of the Hb molecules
  • Which causes it to change shape
  • This change makes it easier for the other subunits to bind to an O₂ molecule
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31
Q

Why does the gradient of the oxygen dissociation curve then steepen?

Hint: positive cooperativity

A
  • After the 1st O2 binds, it takes a smaller increase in the PO2 to bind the 2nd oxygen molecule than it did to bind the 1st one.
  • This is known as positive cooperativity because the binding of the first molecule makes it easier for the next one and so on.
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32
Q

Why does the gradient of the oxygen dissociation curve reduce and flatten off?

A
  • After the binding of the 3rd oxygen, the probability of the last binding site being filled is lower
  • This is because with the majority of the binding sites occupied, it is less likely that a single oxygen molecule will find an empty site to bind to
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33
Q

The further to the left the curve, the _______ is the affinity of Hb for oxygen.

A

The further to the left the curve, the greater is the affinity of Hb for oxygen.

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34
Q

What does it mean for the haemoglobin molecule if it has a high affinity for oxygen?

A

It means it will load oxygen readily but will unload it less easily

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35
Q

What does it mean for the haemoglobin molecule if it has a low affinity for oxygen?

A

It means it will load oxygen less readily but will unload it more easily

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36
Q

The further to the right the curve, the _____ is the affinity of Hb for oxygen.

A

The further to the right the curve, the lower is the affinity of Hb for oxygen.

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37
Q

What is carbon dioxides effect on haemoglobin’s affinity for oxygen?

A

In the presence of CO2, Hb has a reduced affinity for O2

- The greater the conc. of CO2 the more readily the Hb releases its oxygen (The Bohr effect)

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38
Q

Describe the behaviour of haemoglobin at the gas exchange surface (e.g lungs)

A
  • Low conc. of CO2
  • High conc. of O2
  • The affinity of Hb for O2 is increased
    = O2 is readily loaded by haemoglobin
  • The reduced CO2 conc. has shifted the oxygen dissociation curve to the left
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39
Q

Why is the conc. of carbon dioxide low at the gas- exchange surface (e.g lungs)

A

The conc. of CO2 is low because it diffuses across the exchange surface and is excreted from the organism

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40
Q

Describe the behaviour of haemoglobin in rapidly respiring tissues

A
  • High conc. of CO2
  • Low conc. of O2
  • The affinity of Hb for O2 is reduced
    = O2 is readily unloaded from the Hb into the muscle cells
  • The increased CO2 conc. has shifted the oxygen dissociation curve to the right
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41
Q

Why does the greater the CO2 conc. mean the more readily Hb will unload O2?

A

This is because dissolved carbon dioxide is acidic and the low pH causes Hb to change shape

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42
Q

What is the pH like at the gas exchange surface? What does this mean for Hb and oxygen loading?

A
  • The pH is slightly raised due to the low conc. of carbon dioxide
  • The higher pH changes the shape of Hb into one that enables it to load oxygen readily
  • This shape also increases the affinity of Hb for oxygen, so it’s not released while being transported in the blood to the tissues
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43
Q

What is the pH of carbon dioxide in solution like?

A

It is acidic (low pH)

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44
Q

What is the pH of the blood within the respiring tissues like?

A
  • CO₂ is acidic in solutions

- So the pH of the blood within the tissues is lowered

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45
Q

How does a lower pH (in respiring tissues) effect haemoglobin?

A

Lower pH changes the shape of Hb = lowers affinity for O₂

- Therefore Hb unloads O₂ into the respiring tissues

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46
Q

Explain how: the more active a tissue, the more oxygen is unloaded.

A

The higher the rate of respiration –> the more CO2 the tissues produce –> the lower the pH –> the greater the Hb shape change –> the more readily the O2 is unloaded –> the more O2 is available for respiration

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47
Q

In humans, where does haemoglobin become saturated with oxygen?

A

When it passes through the lungs

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48
Q

What is the overall saturation of haemoglobin at atmospheric pressure? Why?

A

97%

- Not all Hb molecules are loaded with their maximum 4 oxygen molecules

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49
Q

When haemoglobin reaches a tissue with a low respiratory rate, how many oxygen molecules will be released?

A

Only 1 oxygen will normally be released

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50
Q

After reaching a tissue with a low respiratory rate, what will the oxygen % of the blood (containing haemoglobin) returning to the lungs be like?

A

The blood returning to the lungs will therefore contain Hb that is still 75% saturated with oxygen

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51
Q

If tissue is very active, how many oxygen molecules are normally unloaded?

A

3 oxygen molecules will usually be unloaded from each Hb molecules

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52
Q

How have some organism’s haemoglobin molecules evolved to live in an environment with a low PO2?

A
  • Animals that live in an environment with a lower PO2 have evolved haemoglobin that has a higher affinity for oxygen
  • Compared to the haemoglobin of animals that live where the PO2 is higher
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53
Q

What is the oxygen dissociation curve of a lugworms haemoglobin like? What does this mean?

A
  • The dissociation curve is shifted far to the left of that of a human
  • This means that the haemoglobin of the lugworm is fully loaded with oxygen even when there if little available in its environment
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54
Q

How are llamas adapted to their environment?

Answer in relation to its haemoglobin

A
  • Llamas live at high altitudes = the atmospheric pressure is lower and so is the PO2
  • It is therefore difficult to load haemoglobin with oxygen
  • Llamas have a type of haemoglobin that has a higher affinity for oxygen than human haemoglobin
  • The oxygen dissociation curve will shift to the left of human Hb
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55
Q

What happens to the SA:V when the size of the organism increases?

A

The SA:V decreases

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56
Q

Why are specialised exchange surfaces required for larger organisms?

A
  • Because as the size of an organism increases it’s SA:V decreases
  • SA:V decreases to a point where the needs of the organism cannot be met by the body surface/ diffusion alone
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57
Q

The lower the SA:V the _____ active the organism, the _____ is the need for a more __________ transport system with a ____.

A

The lower the SA:V the More active the organism, the Greater is the need for a more Specialised transport system with a Pump.

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58
Q

Give an example of a suitable medium used in many organisms transport systems to carry materials.

A

Blood

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59
Q

Why is the suitable transport medium in may organisms transport systems water based?

A
  • Suitable mediums are normally a liquid based on water
  • This is because water readily dissolves substances
  • Also water can be moved around easily, as it can also be a gas (e.g air breathed out of the lungs)
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60
Q

What is a common feature of transport systems, relating to it being a closed and tubular?

A

Commonly transport systems are:

  • Closed
  • Consisting of tubular vessels that contain the transport medium and forms a branching network to distribute it to all parts of the organism
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61
Q

What type of circulatory system do mammals have?

A

A closed, double circulatory system

62
Q

Why does blood pass through the heart twice for each complete circuit of the body?

A
  • Because when blood is passed through the lungs, its pressure is reduced
  • If the blood passed straight to the rest of the body, circulation would be very slow (due to the low pressure)
  • Blood is returned to the heart to boost its pressure before it is sent to the rest of the body
63
Q

If mammals have a high body temp, what does this mean for their metabolism?

A

High body temp = high metabolism

64
Q

Which side of the heart deals with oxygenated blood? Where does this come from?

A
  • The left

- It comes from the lungs (via the pulmonary vein)

65
Q

Which side of the heart deals with deoxygenated blood? Where does this come from?

A
  • The right

- It comes from the body

66
Q

Describe the atrium

A
  • Thin- walled
  • Elastic
  • Stretches as it collects blood
  • Above the ventricle
67
Q

Describe the ventricle

A
  • Much thicker muscular wall than the atrium

- Below the atrium

68
Q

Why does the ventricle have a thicker, more muscular wall than the atrium?

A

Because it has to contract strongly to pump blood some distance, either to the lungs or the rest of the body

69
Q

Why does the left ventricle have a thicker muscular wall than the right ventricle?

A
  • The right ventricle pumps blood only to the lungs so it can be at a lower pressure
  • The left ventricle pumps blood to the rest of the body, the thick muscular wall enables it to contract to create a high pressure
70
Q

What are the valves between the atrium and ventricle called?

A

The atrioventricular valves

71
Q

What are the two types of atrioventricular valve?

A

The right & the left atrioventricular valves

72
Q

What type of valve is the right atrioventricular valve?

A

The right atrioventricular valve is tricuspid

73
Q

What type of valve is the left atrioventricular valve?

A

The left atrioventricular valve is bicuspid

74
Q

In what direction do the ventricles pump blood?

A

The ventricles pump blood away from the heart and into the arteries

75
Q

What do the atria receive blood from?

A

The atria receive blood from the veins

76
Q

What are the vessels that connect the heart to the lungs called?

A

Pulmonary vessels

77
Q

Describe the role of the aorta

A
  • Connected to the left ventricle

- Carries oxygenated blood to all parts of the body except the lungs

78
Q

Describe the role of the vena cava

A
  • Connected to the right atrium

- Brings deoxygenated blood back from the tissues of the body (except the lungs)

79
Q

Describe the role of the pulmonary artery

A
  • Connected to the right ventricle
  • Carries deoxygenated blood to the lungs
  • Where the it is replenished and its CO2 is removed
  • Unusually for an artery it carries deoxygenated blood
80
Q

Describe the role of the pulmonary vein

A
  • Connected to the left atrium
  • Brings oxygenated blood back from the lungs
  • Unusually for a vein it carrys oxygenated blood
81
Q

How is oxygen supplied to the heart?

A
  • Although oxygenated blood passes through the left side of the heart, the heart does not use this oxygen to meet its own requirements
  • The coronary arteries supply the heart with oxygenated blood
82
Q

Describe the coronary arteries

A
  • Supply the heart muscle with oxygen

- They branch off the aorta shortly after it leaves the heart

83
Q

What can the blockage of the coronary arteries lead to?

A

Blockages of these arteries, e.g by a blood clot, lead to myocardial infarction

84
Q

What is myocardial infarction also known as?

A

A heart attack

85
Q

Describe what happens during myocardial infarction.

A
  • Because an area of the heart muscle is deprived of blood and therefore oxygen
  • The muscle cells in this region are unable to respire (aerobically) and so die
86
Q

What are 4 risk factors that increase the risk of the individual suffering from cardiovascular disease?

A
  1. Smoking
  2. High blood pressure
  3. Blood Cholesterol
  4. Diet
87
Q

Why does the carbon monoxide in tobacco cause heart diseases?

A

Carbon monoxide:

  • It combines easily + irreversibly with haemoglobin (=carboxyhemoglobin) which reduces its oxygen-carrying capacity.
  • To supply the same quantity of oxygenated blood the heart must work harder
  • This can lead to raised blood pressure which increases the risk of coronary heart disease + strokes
88
Q

How does the carbon monoxide in tobacco cause chest pain/ heart attack?

A
  • The reduction in the oxygen-carrying capacity of blood means it may be insufficient to supply the heart muscle during exercise
  • Leads to angina (chest pain) or, in severe cases a myocardial infarction (heart attack)
89
Q

What are the two main components of tobacco that cause heart diseases?

A

Nicotine and carbon monoxide

90
Q

How does the nicotine in tobacco cause heart diseases?

A

Nicotine:
- Stimulates the production of the hormone adrenaline, which increases the heart rate and raises blood pressure
= There is a greater risk of smokers suffering coronary heart disease/ stroke
- ALSO: makes the platelets in the blood ‘sticky’
= Leads to a higher risk of thrombosis and hence strokes/ myocardial infarction

91
Q

What lifestyle factors increase blood pressure?

A
  • Excessive prolonged stress
  • Certain diets
  • Lack of exercise
92
Q

Why does high blood pressure increase the risk of heart disease?
(How hard the heart works…)

A
  • Higher pressure in the arteries means the heart must work harder to pump blood into them –> more prone to failure
93
Q

What is an aneurysm?

A

The weakening of the wall of an artery

94
Q

Why does high blood pressure make it more likely to develop a haemorrhage?

A

The high pressure in the arteries means that they are more likely to develop an aneurysm and burst causing haemorrhage

95
Q

What do the walls of arteries do to try and combat high blood pressure, and why can this be an issue?

A

The walls of the arteries tend to become thickened and may harden
- Which restricts the flow of blood

96
Q

What is cholesterol and how is it transported?

A
  • Cholesterol is a lipid that is an essential component of membranes
  • It is transported in the blood plasma as tiny spheres of lipoproteins
97
Q

What are the two types of lipoproteins?

A
  • High density lipoproteins (HDLs)

- Low density lipoproteins (LDLs)

98
Q

Describe high-density lipoproteins

A

HDLs:

  • Remove cholesterol from tissues + transport it to the liver for excretion
  • they protect arteries against heart disease
99
Q

Describe low- density lipoproteins

A

LDLs:
- Transport cholesterol from the liver to the tissues including the artery walls which they infiltrate
= leading to the development of atheroma which may lead to heart disease

100
Q

How does diet increase the risk of heart diseases?

A
  • High levels of salt increases blood pressure

- High levels of saturated fat increase low density lipoprotein levels and hence blood cholesterol conc.

101
Q

What types of foods reduce the risk of heart disease?

A
  • Foods that act as antioxidants e.g vitamin C

- Non-starch polysaccharide (dietary fibre)

102
Q

What are the two phases of the cardiac cycle?

A
  • Contraction (systole)

- Relaxation (Diastole)

103
Q

What is diastole?

A

The relaxation of the heart

104
Q

During diastole, how does the blood return to the atria of the heart?

A

Blood returns to the atria of the heart through the pulmonary vein (from lungs) and the vena cava (from body)

105
Q

During diastole, what happens to the pressure of the atria and what does this cause to happen?

A
  • They fill up with blood so the pressure in them rises
  • This pressure exceeds that in the ventricles so the atrioventricular valves open allowing blood to pass into the ventricles
106
Q

During diastole, what force is the passage of blood aided by?

A

The passage of blood is aided by gravity

107
Q

During diastole, what are the ventricle + atria walls like?

A

The muscular wall of both the atria and ventricle are relaxed

108
Q

During diastole, what does the relaxation of the ventricle walls cause them to do?
- What is a result of this?

A
  • It causes them to recoil and this reduces the pressure within the ventricle
  • This causes the pressure to be lower than in the aorta and the pulmonary artery
    = the semi-lunar valves in the aorta + pulmonary artery CLOSE
109
Q

What makes the ‘dub’ sound of the heart beat?

A

The semi-lunar valves in the aorta + pulmonary artery closing makes a ‘dub’ sound
- During diastole

110
Q

Describe what happens in atrial systole.

A
  • The contraction of the atrial walls + the recoil of the relaxed ventricle walls
    = forces the remaining blood into the ventricles from the atria
111
Q

What is atrial systole?

A

The contraction of the atria

112
Q

During atrial systole, what is the muscle of the ventricle walls like?

A

The muscle of the ventricle walls remains relaxed

113
Q

What is ventricular systole?

A

The contraction of the ventricles

114
Q

Describe what first happens in ventricular systole.

A
  • After a short delay to allow the ventricles to fill with blood, their walls contract simultaneously
115
Q

During ventricular systole, what does the contraction of the ventricle walls result in?

A
  • Increases the blood pressure in the ventricles

- Which forces the atrioventricular valves shut (preventing the backflow of blood into the atria)

116
Q

What makes the ‘lub’ sound of the heart beat?

A

The ‘lub’ sound is made by the closing of the atrioventricular valves during ventricular systole

117
Q

During ventricular systole, what happens to the pressure in the ventricles after the atrioventricular valves close?

A

With the atrioventricular valves closed, the pressure in the ventricles rises further
- Once the pressure exceeds that in the aorta + pulmonary artery blood is forced into them

118
Q

During ventricular systole, the ventricular walls contract forcefully.

What feature of the ventricles makes this possible, and what does this create?

A

Thick muscular walls

- This creates the high pressure necessary to pump blood around the body

119
Q

Blood will always move from an area of ______ pressure to one of _____ pressure.

A

Blood will always move from an area of higher pressure to one of lower pressure.

120
Q

What is the role of valves?

A

To prevent the backflow of blood

121
Q

Describe the atrioventricular valves & their role

A
  • Between the left atrium and left ventricle & the right atrium and right ventricle
  • Prevent backflow when contraction of the ventricles means that ventricular pressure exceeds atrial pressure
  • When the ventricles contract = these are closed, so:
    Blood moves to the aorta + pulmonary artery rather than back to the atria
122
Q

Describe the semi-lunar valves & their role

A
  • In the aorta and the pulmonary artery

- Prevent backflow into ventricles when the pressure of these vessels exceed that in the ventricles

123
Q

What has happened to make the pressure of the aorta and pulmonary artery exceed that in the ventricles?

A
  • This happens when the elastic walls of the aorta + pulmonary artery recoil increasing the pressure in them & when the ventricle walls relax reducing the pressure in them
124
Q

What has happened to make the ventricular pressure exceed the atrial pressure?

A

The contraction of the ventricles (ventricular systole)

125
Q

What is cardiac output?

A

The volume of blood pumped by one ventricle of the heart in 1 min `

126
Q

What 2 factors do the cardiac output depend on?

A
  • The heart rate

- The stroke volume

127
Q

What is the stroke volume?

A

The volume of blood pumped out at each beat

128
Q

What are the 4 different types of blood vessel?

A
  • Arteries
  • Arterioles
  • Capillaries
  • Veins
129
Q

What is the outer layer that arteries, arterioles and capillaries all have?

A

Tough fibrous outer layer

- resists pressure changes from both within and outside

130
Q

What is the function of arteries?

A

To carry blood away from the heart and into arterioles at high pressure

131
Q

What is the function of arterioles?

A

Smaller arteries that control blood flow from arteries to capillaries, blood is at a lower pressure than arteries

132
Q

What is the function of capillaries?

A

Tiny vessels that link arteries to veins, they exchange metabolic materials e.g O2, CO2 between the blood and body cells

133
Q

What is the function of veins?

A

Carry blood from capillaries in tissues back to the heart, under low pressure

134
Q

What is the function of the muscle layer in arteries, arterioles and veins?

A

The muscle layer can contract and so control the flow of blood

135
Q

Describe the function of the elastic layer that arteries, arterioles and veins all have.

A

Helps to maintain blood pressure by stretching and springing back (recoiling)

136
Q

Describe the thin inner lining (endothelium) that arteries, arterioles and veins all have.

A

Smooth to reduce friction and thin to allow diffusion

137
Q

Describe the lumen that arteries, arterioles and veins all have.

A

Not actually a layer but the central cavity of the blood vessel through which blood flows

138
Q

What differs between each type of blood vessel?

A

The relative proportions of each layer

139
Q

Describe the structure of the artery related to function (4 features)

A
  • Thick muscle layer compared to veins
  • Thick elastic layer compared to veins (stretching & recall happens = important that high blood pressure is kept high to reach everywhere in the body)
  • Overall very thick walls (resists the vessel bursting under pressure)
  • No valves (except in arteries leaving heart) because blood is under constant high pressure so it tends not to flow backwards
140
Q

Describe the structure of the arteriole related to function (2 features)

A
  • Muscle layer relatively thicker than arteries (contraction allows for constriction of the lumen = restricts blood flow & controls its movement into the capillaries)
  • Elastic layer relatively thinner than in arteries because blood pressure is lower
141
Q

Describe the structure of the vein related to function (4 features)

A
  • Muscle layer relatively thin compared to arteries (bc veins carry blood away from tissues so their constriction/ dilatation can’t control the flow)
  • Elastic layer relatively thin compared to arteries (low blood pressure = no bursting and too low to create recoil reaction)
  • Overall thin walls (low pressure, allows them to be flattened easily)
  • Valves throughout (no back flow - low pressure) When muscles contract, the veins are compressed (inc. pressure) so the valves ensure the blood flows in 1 direction only (towards the heart)
142
Q

Describe the structure of capillaries related to function (5 features)

A
  1. Walls consist of mostly the lining layer (very thin so diffusion pathway is short = faster diffusion between cells blood)
  2. Numerous + highly branched (large SA)
  3. Narrow diameter (can permeate tissues = no cell is far from a capillary so short diffusion pathway)
  4. Very narrow lumen (RBCs flattened against the side of the capillary = bringing them closer to the cells they are supplying O2 to = again reducing diffusion pathway)
  5. Spaces between lining cells (allow white blood cells to escape to deal with infections)
143
Q

What is tissue fluid & what is it’s function?

A
  • It is a watery liquid that contains glucose, amino acids, fatty acids, ions in solution and oxygen
  • It supplies all of these substances to the tissues and in return it receives carbon dioxide & other waste materials from tissues
144
Q

What is tissue fluid formed from?

A

Blood plasma

145
Q

The formation of tissue fluid: What type of pressure does the heart pumping create?

A

When the heart pumps blood it creates hydrostatic pressure at the arterial end of the capillaries

146
Q

The formation of tissue fluid: What does the hydrostatic pressure cause to happen?

A

The hydrostatic pressure causes tissue fluid to be forced out of the blood plasma

147
Q

The formation of tissue fluid: What 2 forces oppose the outward pressure?

A

The outward pressure is however, opposed by 2 other forces:

  • The hydrostatic pressure of the tissue fluid outside the capillaries, which resists outward movement of liquid
  • The lower water potential of the blood, due to the plasma proteins, that causes water to move back into the blood within the capillaries
148
Q

The formation of tissue fluid: The combined effect of all the forces causes what to happen?

A

The combined effect of all these forces creates an overall pressure that pushes tissue fluid out of the capillaries at the arterial end

149
Q

The formation of tissue fluid: The pressure is only enough for what to happen? what is this called?

A

This pressure is only enough to force small molecules out of the capillaries, leaving all cells & proteins in the blood because these are too large to cross the membranes
- this filtration under pressure is called ultrafiltration

150
Q

When does tissue fluid return to the circulatory system?

A

Once it has exchanged metabolic materials with the cells it bathes its returns to the circulatory system

151
Q

Describe tissue fluids return to the circulatory system

A
  • The loss of tissue fluid from the capillaries reduces the hydrostatic pressure inside them = by the time blood reaches the end of the capillary network its hydrostatic pressure is usually lower than that of the tissue outside it
  • Therefore the tissue fluid is forced back into the capillaries

Biology A1 & A2 (19 decks)

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