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Biology > Chapter 8: Transport In Mammals > Flashcards

Chapter 8: Transport In Mammals Flashcards

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1
Q

What is systemic circulation?

A

Blood is pumped out from the left ventricle into the aorta and travels from there to other parts of the body, except the lungs. It returns to the right side of the heart in the vena cava. This is known as systemic circulation.

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2
Q

What is pulmonary circulation?

A

Blood is pumped out of the right ventricle into the pulmonary arteries which carry it to the lungs. After passing through the lungs, the blood is transported in the pulmonary veins to the left side of the heart. This is called the pulmonary circulation.

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3
Q

What can be described as a double circulatory system?

A

The combination of pulmonary circulation and systemic circulation makes a closed double circulatory system.

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4
Q

What are the layers that make up the walls of arteries and veins?

A
  1. Tunica intima
  2. Tunica media
  3. Tunica externa
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5
Q

What is the function of arteries?

A

These blood vessels transport blood swiftly to the tissues at high pressures.

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6
Q

What is the tunica intima made up of?

A

It is an inner endothelium(lining tissue) made up of a layer of flat cells(squamous epithelium). It is an inner endothelium(lining tissue) made up of a layer of flat cells(squamous epithelium).

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7
Q

What is the tunica media and what is it made of?

A

It is the middle layer of the walls making up the arteries and veins. It contains smooth muscle, elastic and collagen fibres.

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8
Q

What is the tunica externa and what is it made of?

A

It is the outer layer of arteries and veins. It contains elastic and collagen fibres.

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9
Q

What is the function of the tunica intima in relation to its structure?

A

The tunica intima contains squamous epithelium/ flat cells allowing this layer to be smooth and hence minimising friction with the moving blood.

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10
Q

What is the usual blood pressure in the aorta?

A

120 mm Hg or 16 kPa

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11
Q

Which blood vessel has the thickest walls?

A

Arteries

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12
Q

What is the largest artery?

A

Aorta

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13
Q

Why does the tunica media in arteries contain elastic fibres?

A

The elastic fibres allow the wall to stretch as the high pressure blood surges into them, and then recoils inwards as the pressure drops.

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14
Q

What is the difference between arteries close to the heart and those further away?

A

Arteries further away from the heart have fewer elastic fibres in the tunica media, but have more muscle fibres.

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15
Q

What are arterioles?

A

As arteries reach the tissue to which they are transporting blood, they branch into smaller and smaller vessels called arterioles.

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16
Q

What does the smooth muscle in the walls of arteries help with? Give an example (exercise)

A

Arteries further away from the heart and arterioles have a greater proportion of smooth muscle present in the tunica media, than those closer to the heart. This muscle can contract, narrowing the diameter of the arteriole and so reducing blood flow. This helps to control the volume of blood flowing into a tissue at different times. For example, during exercise, arterioles that supply the muscles with blood would be wide as their walls relax, while those carrying blood to certain other organs would be narrow, constricting blood flow.

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17
Q

What is the smallest blood vessel?

A

Capillary

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18
Q

What is the diameter of a typical human capillary?

A

7um

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19
Q

What is the function of a capillary?

A

The function of capillaries is to bring the blood as close as possible to all cells, allowing the rapid transfer of substances between the cell and blood.

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20
Q

What are capillary beds?

A

Capillaries form a network throughout every tissue in the body except the cornea and cartilage. Such networks are sometimes known as capillary beds.

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21
Q

Describe the structure of the walls of capillaries.

A

The walls of capillaries are extremely thin and are made up of a single layer of endothelial cells. There are many tiny gaps between the individual cells that make up the endothelium.

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22
Q

How does the structure of a capillary relate to its function? (3)

A

Due to its small size, capillaries can bring blood as close as possible to all the cells of the body.
Also, due to the very small diameter of capillaries, blood travels very slowly, that is blood is at a lower pressure than in the arteries. This lower pressure increases the opportunity for diffusion to occur.
Due to the gaps between the individual cells that form the endothelium, it also allows for the formation of tissue fluid.

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23
Q

How are veins formed from capillaries?

A

As blood leaves the capillary bed, capillaries join up to form larger vessels known as venules. These venules join to form veins.

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24
Q

What is a typical venous blood pressure?

A

5mm Hg or less. It is a very low value.

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25
Q

What is the function of veins?

A

It is to return blood to the heart.

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26
Q

What is the difference between the walls of an artery and that of a vein?

A

The walls of veins have fewer elastic fibres and muscle fibres in their tunica media. The tunica media is therefore much thinner.

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27
Q

How is the structure of veins related to its function? (3)``

A
  1. Due to the low pressure blood flowing through the veins, when the leg muscles contract, blood is squeezed upwards through the semilunar valves formed from the endothelium of veins. This prevents blood flowing back down.
  2. Veins have a larger lumen than arteries due to the low pressure. This therefore decreases vessel resistance allowing more blood to go past the half-moon valves.
  3. The tunica media of veins contain fewer muscle and elastic fibres as the blood present in veins is already at a lower pressure.
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28
Q

What type of valves do veins have?

A

Veins have semilunar valves which are formed from their endothelium.

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29
Q

What is blood plasma? What does it contain? (7)

A

This is the liquid part of blood. It is a dilute solution of salts, glucose, amino acids, vitamins, waste products such as urea, plasma proteins and fats.

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30
Q

What is tissue fluid?

A

As blood flows through capillaries within tissues, some of the plasma leaks out through the gaps between the endothelial cells of the capillary wall and seeps into the spaces between the cells of the tissues. The leaked plasma that fills these spaces is known as tissue fluid.

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31
Q

What is the role of tissue fluid in the human body?

A

Tissue fluid forms the immediate environment of each individual body cell. It is through the tissue fluid that exchanges of materials between cells and the blood occur.

32
Q

Explain the two pressures resulting in the formation of tissue fluid.

A

The fluid is affected by two pressures. At the arterial end of the capillary bed, the blood pressure inside the capillary is enough to push fluid out of the tissue.
Also, since tissue fluid lacks the high concentration of proteins that are too large to enter the tissue fluid, the fluid tends to flow back into capillaries from the tissue fluid near the venous end of the capillary bed. However, more fluid flows out of capillaries than into them, so that there is a net loss of fluid from the blood in the capillaries as it flows through a capillary bed.

33
Q

What is the normal flow rate of blood?

A

80 cm^3/s

34
Q

What is an oedema and what causes it?

A

If blood pressure is too high, too much fluid is forced out of capillaries and may accumulate in the tissues. This build up of fluid is called oedema. One of the roles of an arteriole is to reduce the pressure of the blood before it enters capillaries.

35
Q

Describe the lymphatic system

A

The remaining fluid that has not seeped back into the capillaries, is collected and returned to the blood system by means of lymph vessels or lymphatics. Lymphatics are tiny vessels found in almost all tissues of the body. Lymphatics contain tiny valves, which allow the tissue fluid to flow in but stop it from leaking out. The valves in the lymph vessels are large enough to allow protein molecules from entering. This is important as protein molecules are too large to enter the capillaries, hence preventing an oedema due to the high concentration in the tissue fluid. The fluid inside the lymphatics is known as lymph. Lymphatics join up to form larger lymph vessels which transport the lymph back to the large veins that run beneath the collarbone, the subclavian veins. As in veins, the movement of fluid along the lymphatics is largely caused by the contraction of muscles around the vessels and is kept going in one direction by the valves. Lymph vessels also have smooth muscle in their walls, which can contract to push the lymph along. At intervals along the lymph vessels, there are lymph nodes which are involved in the protection against disease and contain WBCs which remove bacteria and unwanted particles as well as secrete antibodies.

36
Q

How does the structure of the lymphatics relate to its roles? (2)

A
  1. The valves present in lymphatics are large enough to allow protein molecules from the tissue fluid to enter, preventing the possibility of an oedema. This is important because proteins are too big to fit into capillaries. The valves also help with moving the low pressure blood in one direction, towards the subclavian vein.
  2. The smooth muscles present in the walls of lymphatics can contract to move the lymph along. This contraction along with the contraction of muscle around the vessels.
37
Q

How much blood is present in the body?

A

5 dm^3

38
Q

What are red blood cells also called?

A

Erythrocytes

39
Q

Where are red blood cells produced as a fetus and after birth?

A

As a fetus, the red blood cells are produced by the liver. By the time a baby is born, the liver has stopped manufacturing red blood cells and instead the bone marrow produced them.

40
Q

What is the average diameter of a red blood cell?

A

7um

41
Q

Describe how the structure of red blood cells relate with its function. (5)

A
  1. Red blood cells are shaped as a biconcave disc: The dent in each side of the red blood cell increases the surface area:volume ratio. This large surface area means that oxygen can diffuse easily in and out of the cell.
  2. They are very small: The diameter is about 7nm. This means that capillaries can carry red blood cells in them, bringing the haemoglobin as close to the cells as possible to allow for quick diffusion.
  3. They are very flexible: The cells are able to deform to enter capillaries that are smaller than the diameter of a red blood cell. This is due to their specialised cytoskeleton with protein fibres allowing them to be squashed into different shapes.
  4. They have no nucleus, no mitochondria and no endoplasmic reticulum: The lack of these organelles means that there is more room for haemoglobin, so maximising the amount of oxygen that can be carried by each red blood cell.
  5. They have a thin outer membrane: This allows oxygen to diffuse easily.
42
Q

What are white blood cells also known as?

A

Leucocytes

43
Q

How do white blood cells differ from red blood cells?

A
  1. They have a nucleus unlike RBCs which lack one
  2. Most white blood cells are larger than red blood cells
  3. They are either spherical or irregular in shape. RBCs have a biconcave shape.
44
Q

What is the red colour of red blood cells caused by?

A

The pigment, haemoglobin

45
Q

What is the rate of lymph flow in the largest lymph vessel?

A

100 cm^3/h

46
Q

What two groups can white blood cells be categorised into?

A
  1. Phagocytes: Cells that destroy invading microorganisms by phagocytosis.
  2. Lymphocytes: They destroy microorganisms, not by phagocytosis. Some of them secrete antibodies which attach to and destroy invading cells.
47
Q

What is a haemoglobin dissociation curve?

A

This is where the partial pressure of oxygen is plotted against the percentage saturation of haemoglobin with oxygen.

48
Q

Why does the dissociation curve have an S shape?

A

This is because when an oxygen molecule combines with one haem group, the whole haemoglobin molecule becomes slightly distorted. The distortion makes it easier for a second oxygen molecule to combine with the second haem group. This in turn makes it easier for a third and even easier for the final oxygen molecule to combine. At a certaain part of the curve, a small change in the partial pressures of oxygen causes a very large change in the amount of oxygen carried by the haemoglobin.

49
Q

What does the shape of the haemoglobin dissociation curve reflet?

A

It reflects the way oxygen atoms combine with haemoglobin molecules.

50
Q

What is the Bohr effect?

A

The presence of a high partial pressure of CO2 causes haemoglobin to release oxygen. This is called the Bohr effect.

51
Q

What happens when carbon dioxide diffuses into red blood cells?

A

In the cytoplasm of red blood cells there is an enzyme, carbonic anhydrase that catalyses the reaction between carbon dioxide and water producing carbonic acid. The carbonic acid then dissociates producing hydrogen ions and hydrogencarbonate ions. Haemoglobin readily combines with the hydrogen ions, forming haemoglobinic acid(HHb). In so doing, it releases the oxygen which it is carrying.

52
Q

What are the results of the formation of HHb?

A
  1. The reaction in which haemoglobin reacts with the hydrogen ions results in a prevention of a potential high concentration of hydrogen ions which would have resulted in a low pH, making the blood very acidic. In doing so, haemoglobin acts as a buffer, helping in maintaining the pH of the blood close to neutral.
  2. The Bohr effect would occur wherein the high partial pressure of carbon dioxide causes the haemoglobin to release oxygen.
53
Q

What happens to the products produced in the process of diffusion of carbon dioxide into a red blood cell?

A

Most (85% of CO2) of the hydrogencarbonate ions will diffuse out of the RBC into the blood plasma where they are carried in solution.
Some carbon dioxide does not dissociate and remains as carbon dioxide molecules. Some of these molecules dissolve in the blood plasma (5% of CO2)
Other carbon dioxide molecules diffuse into RBCs and combine directly with amine groups of some of the haemoglobin molecules. The compound formed is carbaminohaemoglobin. This makes up 10% of all CO2 molecules.

54
Q

What happens to the carbon dioxide in the blood once it reached the lungs?

A

Carbon dioxide moves down the concentration gradient from the blood to the air in the alveoli. This stimulates the carbon dioxide in the carbaminohaemoglobin to leave the RBC, and the hydrogencarbonate and hydrogen ions to recombine to form carbon cioxide molecules. this leaves the haemoglobin molecules free to combine with oxygen and ready to begin another circuit.

55
Q

What is the reaction of carbon monoxide with haemoglobin? What does treatment involve? Describe why.

A

The CO will combine readily with the haem groups in the haemoglobin molecules forming carboxyhaemoglobin. Haemoglobin combines with CO 250 times more readily than it does with oxygen. Treatment involves administration of pure oxygen and carbon dioxide.

56
Q

Is air pressure higher or lower at higher altitudes?

A

It is lower.

57
Q

What may happen due to altitude sickness?

A

Due to a reduction in oxygen at higher altitudes, the arterioles in brains may dilate, increasing the amount of blood flowing into the capillaries, so that fluid begins to leak into the brain tissues, causing disorientation.

58
Q

What are some adaptations of people at high altitudes? (4)`

A
  1. The number of red blood cells increase from presenting 40-50% to 50-70%. The exposure to lower partial pressures of oxygen results in broad chests, providing larger lung capacities than normal. the heart is often larger, especially on the right side which pumps blood to the lungs. They also have more haemoglobin in their blood than usual.
59
Q

What is the name of the muscle of which your heart is made?

A

Cardiac muscle

60
Q

What is the name of the arteries that are present on the heart and what is their function?

A

The coronary arteries deliver oxygenated blood to the walls of the heart.

61
Q

By what muscle is the left and right sides of the heart separated?

A

Septum

62
Q

What is the upper chamber of the heart on either side called and what does it do?

A

They are known as atria and they receive blood from the veins.

63
Q

What are the valves between the atria and ventricles called? (3)`

A

Atrioventricular valves
The valve on the left side of the heart is known as the bicuspid valve. The valve on the right side is known as the tricuspid valve.

64
Q

What is the typical number of beats per minute?

A

70

65
Q

What is the cardiac cycle?

A

It is the sequence of events that makes up one heart beat.

66
Q

What are the three stages of a cardiac cycle?

A

Atrial systole
Ventricular systole
Ventricular diastole.

67
Q

What happens during atrial systole?

A

During this stage, the heart is filled with blood and the muscle in the atrial wall contracts. The pressure developed by this contraction is not great, because the muscular walls of the atria are only thin, but is enough to force the blood in the atria down through the atrioventricular valves into the ventricles which prevent backflow.

68
Q

What happens during ventricular systole?

A

About 0.1 seconds after atrial systole, the ventricles contract. The thick, muscular walls of the ventricles squeeze inwards on the blood, increasing its pressure and pushing it out of the heart. This creates a pressure difference between that of the atria and ventricles with more pressure generated in the ventricles causing the atrioventricular valves to close, preventing backflow. The high pressure created in the ventricles pushes open the semilunar valves in the arteries to allow blood to pass through.

69
Q

How long does ventricular systole last?

A

0.3 seconds

70
Q

What happens during ventricular diastole?

A

The whole of the heart muscle then relaxes and the pressure in the ventricles drops. The blood from the veins flows into the atria at a very low pressure, but due to the thin walls of the atria, it provides very little resistance to the flow of blood. Some of the blood trickles down into the ventricles through the atrioventricular valves.

71
Q

Why doesn’t high blood pressure which passed out of the heart in ventricular systole flow back in?

A

this is due to the semilunar valves of the arteries preventing backflow.

72
Q

Which walls are thicker: atria or ventricles? Why?

A

The walls of the ventricles are thicker due to the contraction of their muscles having to push blood out of the heart and around the body.

73
Q

Which ventricle has thicker muscles and why?

A

The left ventricle has thicker muscles. If the right ventricle which supplies the lungs with blood had a high pressure as that of the blood in the aorta, tissue fluid would accumulate in the lungs.`

74
Q

What is myogenic in the heart and why?

A

The cardiac muscle is myogenic as it naturally contracts and relaxes and does not need to receive impulses from a nerve to make it contract.

75
Q

How does the cardiac cycle work? ref. SAN

A

Each cardiac cycle is initiated in a specialised patch of muscle in the wall of the right atrium called the sinoatrial node/SAN/pacemaker, which is said to be myogenic. Their natural rhythm of contraction is slightly faster than the rest of the heart muscle. Each time the SAN contract, it sets up a wave of electrical activity which spread out rapidly across the atrial walls. The cardiac muscle in the atrial walls responds to this excitation wave by contracting, at the same rhythm as the SAN. Thus, all the muscle in both the atria contracts almost simultaneously.
A feature of the heart is that it briefly delays the excitation wave in its passage from the atria to the ventricles. There is a band of fibres between the atria and ventricles which does not conduct the excitation wave, not allowing it to pass into the ventricle walls. The only route is through a patch of conducting fibres in the septum, known as the atrioventricular node/AVN. The AVN picks up the excitation wave as it spreads across the atria and, after a delay of about 0.1 seconds, passes it on to a bunch of conducting fibres known as the Purkyne tissue, which runs down the septum between the two ventricles. This transmits the excitation wave very rapidly down to the base of the septum, from where it spreads outwards and upwards through the ventricle walls. This causes the cardiac muscle to contract from the bottom up, so squeezing the blood upwards and into the arteries.

76
Q

What is fibrillation?

A

It is where the heart wall simply flutters rather than contracting due to the excitation wave becoming chaotic.

77
Q

What is an ECG?

A

An electrocardiogram is a graph of voltage against time.

Biology (19 decks)

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