Transport in Animals Flashcards
(153 cards)
1
Q
Transport Systems: What do all living animal cells need to do to be able to survive?
A
All living animal cell need a supply of oxygen and nutrients to survive. They also need to remove waste products so that these do not build up and become toxic.
2
Q
Transport Systems: Why do very small animals not need a transport system?
A
Very small animals do not need a separate transport system, because all their cells re surrounded by (or very close to) the environment in which they live. Diffusion will supply enough oxygen and nutrients to keep the cell alive.
-Once an animal has a complex anatomy with more than two layers of cells, diffusion alone will be too slow.
3
Q
Transport Systems: What are the three main factors that influence the need for a transport system?
A
- Size
- Surface area to volume ratio
- Level of activity.
4
Q
Transport Systems: How does size influence the need for a transport system?
A
Once an animal has several layers of cells, any oxygen or nutrients diffusing in from outside will be used up by the outer layers of cells. The oxygen and nutrients will not reach the cells deeper within the body.
5
Q
Transport Systems: How does surface area to volume ration influence the need for a transport system?
A
Small animals have a large surface area compared with their volume. This is known as their surface area to volume ratio. This ratio is affected by an animal’s shape. A flatworm has a very thin, flat body, which gives it a large surface area to volume ratio. But such a body form limits the overall size that the animal can reach.
-To allow animals to grow to a large size, they need a range of tissues and structural support to give body strength. Their volume increases as their body gets thicker. But the surface area does not increase as much. So the surface area to volume ratio of a large animal is relatively small and the surface area is not large enough to supply all the oxygen and nutrients needed by the internal cells.
6
Q
Transport Systems: How does level of activity influence the need for a transport system?
A
Animals need energy from food so that they can move around. Releasing energy from food by respiration requires oxygen. If an animal is very active, its cells need good supplies of nutrients and oxygen to supply the energy for movement. Those animal, such as mammals that keep themselves warm and carry out thermoregulation need even more energy.
7
Q
Transport Systems: What are the features of an effective transport system?
A
- A fluid or medium to carry nutrients and oxygen around the body (blood)
- A pump to create pressure that will push the fluid around the body (heart)
- Exchange surfaces that enable oxygen and nutrients to enter the blood and to leave it again when they are needed.
- Tubes or vessels to carry the blood (efficient)
- Two circuits - one to pick up oxygen and another to deliver oxygen to the tissues (efficient)
8
Q
Transport Systems: What is a single circulatory system?
A
A system which passes through the heart once.
-E.g. fish
9
Q
Transport Systems: What are the advantages of a single circulatory system?
A
- Quick and takes up less space.
- Blood pressure is reduced as blood passes through the tiny capillaries so they don’t burst.
- Meets energy requirements of cold blooded animals.
10
Q
Transport Systems: What are the disadvantages of a single circulatory system?
A
- As the blood pressure is reduced as blood passes through the tiny capillaries, this means it will not flow very quickly to the rest of the body, which limits the rate at which oxygen and nutrients are delivered to respiring tissue.
- Not efficient enough if the organisms is warm blooded.
11
Q
Transport Systems: What is a double circulatory system?
A
A system which passes through the heart twice.
-E.g. mammals
12
Q
Transport Systems: What two circuits are involved in a double circulatory system?
A
- Pulmonary circuit
- Systemic circuit
13
Q
Transport Systems: What is the pulmonary circuit in a double circulatory system?
A
It carries the blood to the lungs to pick up oxygen.
14
Q
Transport Systems: What is the systemic circuit in a double circulatory system?
A
It carries the oxygen and nutrients around the body to tissues.
-It is good because it provides the high pressure needed to transport oxygen and glucose to respiring tissues to meet metabolic needs of cells.
15
Q
Transport Systems: What are the advantages of a double circulatory system?
A
- The pressure can decrease while in the pulmonary circulation, so it doesn’t damage the delicate capillaries in the lungs.
- The heart can increase the pressure of the blood after it has passed through the lungs, so blood flows more quickly to the body tissues.
- The systematic circulation can carry blood at a higher pressure than the pulmonary circulation.
- Allows for growth of cells.
16
Q
Transport Systems: What is a closed system?
A
Closed network of tubes to maintain high pressures and to bathe tissues in tissue fluid. This is due to a concentration gradient between the blood and tissues.
17
Q
Transport Systems: What is an open system?
A
Blood flows under low pressure as they have an open system which bathes the cells directly.
18
Q
What is a mammalian heart?
A
The mammalian heart is a muscular double pump. It is divided into two sides. On both sides, the heart squeezes the blood, putting it under pressure. This pressure forces the blood along the arteries.
19
Q
What is pumped on each side of the heart?
A
The right side pumps deoxygenated blood to the lungs to be oxygenated. The left side pumps oxygenated blood to the rest of the body.
20
Q
What is the difference between oxygenated and deoxygenated blood?
A
The difference between oxygenated and deoxygenated blood is that the oxygenated blood has a higher concentration of oxygen.
-Do oxygenated blood has less oxygen, but never no oxygen, otherwise a part of the body would be receiving no oxygen and the cells would die.
21
Q
Externally, what does the heart look like?
A
The heart sits slightly off centre to the left of the chest cavity. The main part of the heart consists of dark red muscle which feels very firm. This is the muscle, surrounding the two main pumping chambers, the ventricles. Above the ventricles are two thin-walled chambers - the atria. These are much smaller than the ventricles and easy to overlook. The coronary arteries lie on the surface of the heart.
22
Q
What are the coronary arteries?
A
The coronary arteries lie over the surface of the heart. They carry oxygenated blood to the heart muscle itself. As the heart is a hard-working organ, these arteries are very important. If they become constricted, it can have severe consequences for the health of the heart and of the animal. Restricted blood flow to the heart muscle reduces the delivery of oxygen and nutrients such as fatty acids. This may cause angina or a heart attack.
23
Q
Why is there a layer of fat around the heart?
A
- To protect the heart
- For insulation
24
Q
What are the different parts of the heart?
A
- Right atrium
- Tricuspid valves (atrioventrivular valves)
- Right ventricle
- Septum
- Semilunar valves
- Chordae tendineae (tendinous cords)
- Left Atrium
- Bicuspid valves (atrioventricular valves)
- Left Ventricle
25
What are the blood vessels in the heart?
- Vena Cava (superior and inferior)
- Pulmonary artery
- Pulmonary veins
- Aorta
26
What is the vena cava?
- Great veins, superior and inferior
| - Transport deoxygenated blood from the body, to the right atrium.
27
What is the right atrium?
- Thin muscular walls as blood is under low pressure.
| - One way valves at entrance to prevent backflow of blood into the vena cava.
28
What are the tricuspid valves?
- The right atrioventricular valves
| - Prevent back flow of blood into the atrium
29
What is the right ventricle?
-As the lungs are quite close to the heart, muscular walls are not too thick but able to build sufficient pressure to move the blood onto the lung capillaries from the pulmonary artery.
30
What is the septum?
- Inner dividing wall of the heart.
- Is not complete until after birth, and so mixture of blood occurs in the foetus. It does not need to be separate because blood comes from its mother's placenta, through the umbilical cord. The gap closes after birth.
31
What is the pulmonary artery?
-Carries deoxygenated blood from the heart to the lungs to be oxygenated.
32
What are the semilunar valves?
- Inside both the aorta and pulmonary artery.
| - Prevents backflow of blood into ventricles.
33
What are the pulmonary veins?
-Carried oxygenated blood from the lungs to the heart to be pumped to the rest of the body.
34
What is the left atrium?
- Thin walled chamber
| - Same function as the right atrium
35
What is the left ventricle?
- Very thick muscular wall
- Thicker than the right ventricle wall because it gas to produce sufficient force to move the blood to all the extremities.
36
What are chordae tendineae?
- String like structures
- Attached to the papillary muscles and the edges of the valve cusps, thus preventing the valve flaps turning inside out.
37
What is the aorta?
- The aorta is the biggest artery in the body
| - It carries the oxygenated blood to the rest of the body to oxygenate the cells.
38
What is the pathway of blood around the body?
- Enters through the vena cava into the right atrium.
- Passes through the tricuspid valves and into the right ventricle.
- Passes through the semilunar valves, and exits the heart through the pulmonary artery, where it travels to the lungs to pick up oxygen. It becomes oxygenated.
- Re-enters the heart, through the two pulmonary veins into the left atrium.
- Passes through the bicuspid valves and into the left ventricle.
- Pass through the semilunar valves and exits the heart through the aorta, travelling around the body, providing respiring cells with oxygen. It eventually becomes deoxygenated and the process repeats.
39
Why does the heart receive the most oxygen?
The heart receives the most oxygen as it is the first place oxygen is delivered because it is closest to the aorta. As the blood travels around the body, more and more oxygen in used up so oxygen concentration decreases.
40
What is heart disease?
When coronary arteries become narrower and blocked meaning oxygen and nutrients can't get to the heart, resulting in a heart attack as the heart is unable to function.
41
What is myocardial infarction?
A heart attack
42
What is the apex?
The point, made up of the left ventricle.
43
What does anterior, posterior and lateral mean?
The front, back and side of the heart
44
Why is pressure in the heart important?
The muscle of each chamber contracts to create increased pressure in the blood. The higher the pressure created in the heart, the further it will push the blood.
45
Why are the walls of the atria quite thin?
The muscle of the atria is very thin. This is because these chambers do not need to create much pressure. Their function is to push the blood into the ventricles.
46
Why are the walls of the ventricles thicker than the walls of the atria?
It enables the ventricles to pump blood out of the heart, either to the lungs or the rest of the body.
47
Why are the walls of the right ventricle much thinner than those of the left ventricle?
The right ventricle pumps deoxygenated blood to the lungs. The lungs are in the chest cavity, so the blood does not need to travel very far. Also, the lungs contain a lot of very fine capillaries that are in close contact with the walls of the alveoli. The alveoli walls are very thin and there is little or no tissue fluid. So the capillaries are not supported and could easily burst. The pressure of the blood must be kept down to prevent the capillaries in the lungs bursting.
48
Why are the walls of the left ventricle much thicker than those of the right ventricle?
The walls of the left ventricle can be two or three times thicker than those of the right ventricle. The blood from the left ventricle is pumped out through the aorta and needs sufficient pressure to overcome the resistance of the systemic circulation.
49
Cardiac Cycle: What is the cardiac cycle?
The sequence of events involved in one heartbeat.
| -The events happen continuously and simultaneously (in and out at the same time).
50
Cardiac Cycle: On average how many times does the heart beat per minute?
60-80 times per minute
51
Cardiac Cycle: What is diastole?
Both the atria and ventricles are relaxed. Blood enters the heart through the Vena Cava (R) and the Pulmonary Veins (L). It flows through the atria and into the ventricles. At this point, the atrial ventricular valves are open and the semilunar valves are closed.
52
Cardiac Cycle: How long does the diastole phase last?
0.4 seconds
53
Cardiac Cycle: What are the pressure changes involved in diastole?
- The ventricle walls are relaxed (and recoiling). The ventricular pressure is decreasing and the atrial pressure is higher than the ventricular pressure, as the atrial ventricular valves are open, this causes blood to flow through the atria and into the ventricles.
- As blood enters the atria and then the ventricles, ventricular pressure and atrial pressure slowly increases. The valves remain open as atria begin to contract.
54
Cardiac Cycle: What is atrial systole?
Atrial Systole is the contraction of the atria. The atria squeeze out the last little bit of blood into the ventricles. At this point, the atrial ventricular valves are open and the semilunar valves are closed.
55
Cardiac Cycle: How long does the atrial systole phase last?
0.1 seconds
56
Cardiac Cycle: What are the pressure changes involved in atrial systole?
As the atria contract, the atrial ventricular valves stay open to allow the blood to flow into the ventricles. This is caused by a small increase in pressure in the atria.
57
Cardiac Cycle: What is ventricular systole?
Ventricular Systole is the contraction of the ventricles and starts when the ventricular pressure is higher than the atrial pressure. At this point, the atrial ventricular valves snap shut and the semilunar valves open.
58
Cardiac Cycle: How long does the ventricular systole phase last?
0.3 seconds
59
Cardiac Cycle: What are the pressure changes involved in ventricular systole?
- As the ventricles contract, ventricular pressure becomes a lot higher than atrial pressure. Blood fills the atrioventricular valve flaps causing them to snap shut. This is to prevent backflow because as the pressure becomes higher, the blood tries to return to the atria but can’t as the valves have snapped shut.
- All four valves remain shut for a very short period of time, before the ventricular pressure causes the semilunar valves to open and then the blood exits the heart through the aorta (L) or the Pulmonary Artery (R). The semilunar valves open because the ventricular pressure is higher than the aortic and pulmonary artery pressure. As blood exits the heart through the aorta and pulmonary artery, ventricular pressure decreases, lower than the aortic and pulmonary artery pressure. The semilunar valves close to prevent blood trying to flow back into the ventricles as they are not relaxed again.
60
Cardiac Cycle: How do the atrioventricular valves work?
- When the ventricular walls relax and recoil after contracting, the pressure in the ventricles drops below the pressure in the atria. This causes the atrioventricular valves to open. Blood entering the heart flows straight through the atria and into the ventricles. The pressure in the atria and the ventricles slowly rises as they fill with blood. The valves remain open while the atria contract.
- As the ventricles begin to contract, the pressure of the blood in the ventricles rises. When the pressure rises above that in the atria, the blood starts to move upwards. This movement fills the valve pockets and keeps them closed. This prevents the blood flowing back into the atria.
61
Cardiac Cycle: How do the semilunar valves work?
- When the ventricles start to contract, the pressure in the major arteries is higher than the pressure in the ventricles. This means that the semilunar valves are closed. As the ventricles contract, the pressure inside rises above the pressure in the aorta and pulmonary arteries, the semilunar valves are pushed open. The blood is under very high pressure, so it is forced out of the ventricles in a powerful spurt.
- Once the ventricle walls have finished contracting, the heart muscle starts to relax. Elastic tissue in the walls of the ventricles recoils to stretch the muscle out again and return the ventricles to its original size. This causes the pressure in the ventricles to drop quickly. As it drops below the pressure in the major arteries, the semilunar valves are pushed closed by blood starting to flow back towards the ventricles and collecting in the pockets of the valves. This prevents blood returning to the ventricles.
62
Cardiac Cycle: What are the sounds of the heart made by?
The valves closing
| -lub sounds, dup sound
63
Cardiac Cycle: What is the first sound of the heart made by?
The first sound, lub, is made by the atrioventricular valves closing as the ventricles start to contract.
64
Cardiac Cycle: What is the second sound of the heart made by?
The second sound, dub, is made by the semilunar valves closing as the ventricles start to relax.
65
Cardiac Cycle: Why is the first sound of the heart louder than the second?
The atrioventricular valves snap shut, so this noise is louder than the closing of the semilunar valves, which shut because blood is accumulating in their pockets.
66
Cardiac Cycle: What is stroke volume?
Stroke volume is the amount of blood pumped out of the heart during each contraction.
67
Cardiac Cycle: What is cardiac output?
The volume of blood pumped per minute by each ventricle of the heart.
68
Cardiac Cycle: How is cardiac output calculated?
Cardiac output (dm^3/min) = stroke volume x heart rate.
69
Cardiac Cycle: Why is the heart described as myogenic?
'Generates rhythmic impulses in absence of stimulation from the autonomic centre in the brain'.
The cardiac muscle is unusual in that it can initiate its own contraction. It is able to beat without the brain, as it can create its own impulses and so is described as myogenic.
The muscle will contract and relax rhythmically even if it is not connected to the body.
Despite not needed the heart to create its own rhythm, the brain is still connected to the heart as it tells the heart when to raise or lower the rate.
70
Cardiac Cycle: What do the atria and ventricles both have in relation to the beat of the heart?
The muscles from the atria and the ventricles each have their own natural frequency of contraction.
-The atria muscles tends to contract at a higher frequency than the ventricular muscle.
71
Cardiac Cycle: What is the problem with the heart being myogenic?
The fact that the heart is myogenic could cause inefficient pumping (a condition known as fibrillation) if the contractions of the chambers are not synchronised. So the heart needs a mechanism that can coordinate the contractions of all four chambers.
72
Cardiac Cycle: What is the pathway followed by the wave of excitation?
- Sinoatrial node initiates the wave of excitation, setting the rhythm of the heart.
- The wave then quickly spreads over the atria, causing atrial systole.
- The wave then passes through the antrioventricular node, which delays the wave until atrial systole has finished.
- The wave then travels down the bundle of his and then across the Purkyne fibres whuch spread the excitation over the ventricle walls, causing ventricular systole to begin.
73
Cardiac Cycle: How is the heart beat initiated?
In the wall, at the top of the right atrium, near the point where the vena cave empties blood into the atrium, is the sinoatrial node (SAN). This is a small patch of tissue that generates electrical activity. Then SAN initiates a wave of excitation at regular intervals, setting the rhythm of the heart. In a human, this occurs approximately 55-80 times a minute. The SAN is also known as the pacemaker.
74
Cardiac Cycle: When might a pacemaker need to be fitted?
Pacemakers need to be fitted when all the impulse nodes fail and the heart has no rhythm to beat to.
75
Cardiac Cycle: How does the wave of excitation initiate atrial systole?
The wave of excitation quickly spreads over the walls of both atria. It travels along the membranes of the muscle tissue. As the wave of excitation passes, it causes the cardiac muscle cells to contract. This is atrial systole.
76
Cardiac Cycle: How does the wave of excitation pass over into the ventricles?
At the base of the atria is a disc of tissue than cannot conduct the wave of excitation. So the excitation cannot spread directly to the ventricle walls. At the top of the interventricular septum, is another node - the atrioventricular node (AVN). This is the only route through the disc of non-conducting tissue. The wave of excitation is delayed in this node. This allows time fro the atria to finish contracting and for the blood to flow down into the ventricles before they begin to contract.
77
Cardiac Cycle: How does the wave of excitation initiate ventricular systole?
After the delay in the AVN, the wave of excitation is carried away from the AVN and down specialised conducting tissue. This is the Purkyne tissue and it runs down Bundle of His, in the interventricular septum. At the base of the septum, the wave of excitation soreads out over the wall of the ventricles. As the excitation spreads upwards from the base (apex) of the ventricles, it causes the muscles to contract. This means that the ventricles contract from the base upwards, pushing blood up to the major arteries at the top of the heart.
78
Cardiac Cycle: How can the electrical activity of the heart be measured?
We can monitor the electrical activity of the heart using an electrocardiogram (ECG). This involves attaching a number of sensors to the skin. Some of the electrical activity generated by the heart spreads through the tissues next to the heart and onwards to the skin. The sensors on the skin pick up the electrical excitation created by the heart and convert this into a trace.
-If the ECG is not regular it can show arrhythmia. It can also show if the heart has enlarged or if the Purkyne system is not conduction electrical activity properly.
79
Cardiac Cycle: What does each part of an ECG show?
P wave = excitation of atria
QRS complex = excitation of ventricles
T wave = ventricular diastole
80
Cardiac Cycle: Why is atrial diastole not show on an ECG?
Atrial diastole is overshadowed by ventricular systole as they happen at the same time. Atrial diastole would happen at the QRS complex.
81
Cardiac Cycle: What does it mean if the ST section of the ECG is elevated?
A heart attack (myocardial infarction)
82
Cardiac Cycle: What does it mean if a small and unclear P wave is shown on an ECG?
Atrial fibrillation (the beat is not coordinated, or the heart is contracting very quickly.
83
Cardiac Cycle: What does It mean if a deep S wave is shown on an ECG?
Abnormal ventricular hyperthrophy (increase in muscle thickness).
84
Blood Vessels: How is blood circulated in an open circulatory system?
Blood circulates directly through the body cavity, so the tissues and cells of the animal are bathed directly in blood.
- In some animals, the action of the body muscles during movement may help to circulate the blood.
- In others such as insects, there is a muscular pumping organ. This is a long, muscular tube that lies just under the dorsal (upper) surface of the insect. Blood from the body enters the heart through pores called Ostia. The heart then pumps the blood towards the head by peristalsis. At the forward end of the heart, nearest the head, the blood simply pours out into the body cavity.
- Some larger and more active insects, such as locusts, have open-ended tubes attached to the heart. These direct the blood towards active parts of the body, such as the leg and wing muscles.
85
Blood Vessels: Why don't all animals have an open system?
An open system work for insects because they are small. The blood does not have to travel far. Also, the do not rely on blood to transport oxygen and carbon dioxide. They use a separate transport system for this.
-Larger organisms rely on the blood to transport oxygen and carbon dioxide. In an open circulatory system the blood remains at a low pressure and the flow is very slow. This would not be sufficient to supply the needs of the muscles in a large, active animal. It would also mean that many other parts of the body do not receive sufficient oxygen or nutrients.
86
Blood Vessels: What happens in closed circulatory systems?
In larger animals the blood always stays entirely in the vessels. A separate fluid called tissue fluid bathes the tissues and cells. This enables the heart to pump the blood at a higher pressure so it flows more quickly. This means it can deliver oxygen and nutrients more quickly, and remove carbon dioxide and other wastes more quickly.
87
Blood Vessels: What are the three types of blood vessel?
- Arteries
- Veins
- Capillaries
88
Blood Vessels: What is a lumen?
The inside space of a tubular structure
89
Blood Vessels: What is the tunica intima?
Innermost layer
| -Arteries and veins have one
90
Blood Vessels: What is the tunica media?
Middle layer
| -Arteries and veins have one
91
Blood Vessels: What is the tunica adventitia?
Outermost layers
| -Arteries and veins have one
92
Blood Vessels: What are arteries and veins made up of?
- Collagen fibres
- Smooth muscle
- Elastic fibres
- Endothelium
- Lumen
93
Blood Vessels: What are the features of collagen fibres?
Collagen has high tensile strength with some flexibility.
94
Blood Vessels: What are the features of smooth muscle?
Contracts (shorten) and constrict (narrows) the arteries.
95
Blood Vessels: What are the features of the elastic fibres?
Provides organs and tissues with the ability to stretch and recoil. They are thin and interwoven with collagen fibres to stop them from tearing, and allowing them to maintain their strength and shape.
96
Blood Vessels: What are the features of the endothelium?
Inner layer of cells, made from a single layer of cells. It can fold or unfold.
It is also very smooth to reduce friction and so preventing damage.
97
Blood Vessels: What is the function of an artery?
Arteries carry blood away from the heart. The blood is at a high pressure, so the artery wall must be able to withstand the pressure.
98
Blood Vessels: What are the features of an artery?
- The lumen is relatively small to maintain high pressure.
- The wall is relatively thick and contains collagen to give it strength to withstand high pressure.
- The wall has elastic tissue that allows the wall to stretch and then recoil when the heart pumps. This is felt as a pulse in the areas where the arteries lie close to the skin. The recoil maintains the high pressure while the heart relaxes. The fibres stretch outwards during systole and shorten during diastole.
- The wall also contain smooth muscle that can contract and constrict the artery. The constriction narrows the lumen of the artery. (In arterioles this is used to limit blood flow to certain organs and tissues so that it can be directed to other tissues.)
- The endothelium is folded and can unfold when the artery stretches.
99
Blood Vessels: What are arterioles?
- Arise from an arterial branch.
- Lined with smooth muscles which allows their diameter to be controlled by nerves or hormones.
- They are the only cells that regulate blood pressure.
- Can constrict or dilate.
100
Blood Vessels: What is the function of a vein?
Veins carry blood back to the heart. The blood is at low pressure and the walls do not need to be thick.
101
Blood Vessels: What are the features of a vein?
- The lumen is relatively large (larger than arteries) to ease the flow of blood.
- The walls have thinner layers of collagen, smooth muscles and elastic tissue than arteries. They do not need to recoil, and are not actively constricted to reduce blood flow.
- The main feature of the veins Is that they contain valves to help the blood flow back to the heart and to prevent it flowing in the opposite direction. As the walls are thin, the vein can be flattened by the action of the surrounding skeletal muscle. Pressure is applied to the blood, forcing the blood to move along in a direction dictated by the valves.
102
Blood Vessels: How do veins carry blood back to the heart?
As blood needs to travel against gravity, there is a vacuum around the heart which has intrathoratic pressure which allows the blood to act against gravity and travel back to the heart.
Muscle contraction also helps push the blood back up to the heart as it compresses veins which pushes the blood back up.
103
Blood Vessels: What are venules?
A ring of muscle around capillaries that regulates blood pressure.
104
Blood Vessels: What is the function of a capillary?
Capillaries have very thin walls. They allow exchange of materials between the blood and cells of tissues via the tissue fluid.
105
Blood Vessels: What are the features of a capillary?
- The walls consist of a single layer of flattened endothelial cells that reduces the diffusion distance for the materials being exchanged.
- The lumen is very narrow - its diameter is the same as that of a red blood cell (7µm). This ensures that the red blood cells are squeezed as they pass along the capillaries. This helps them give up their oxygen because it presses them close to the capillary wall, reducing the diffusion path to the tissues.
- There are tiny gaps in the endothelium cells to allow some substances out.
106
What is an intracellular compartment?
Inside the cell (cytoplasm)
107
What is an extracellular compartment?
Outside the cell
108
What are the different types of body fluid?
- Plasma
- Tissue Fluid
- Lymph
- Serum
109
What are the cellular parts of the blood?
- Erythrocytes (RBC)
- Leucocytes (WBC)
- Platelets
110
Plasma: What is plasma?
Plasma is the liquid part of the blood. (Blood minus RBC, WBC, Platelets).
111
Plasma: What is the function of plasma?
Plasma's function is to carry components of the blood, red blood cells, white blood cells and platelets through the body.
-It also carries hormones, nutrients and proteins to different parts of the body.
112
Plasma: What does plasma contain?
- Oxygen
- Glucose
- Amino acids
- Hormones
- Urea
- Antibodies
- Ions
- Plasma proteins
- Fatty acids
113
Plasma: What are the types of plasma proteins?
- Albumin
- Globulin
- Fibrinogen
114
Plasma: How is plasma formed?
Plasma is created by centrifuging the blood which happens outside of the body. It separates the liquid from the cellular part of the blood.
115
Tissue Fluid: What is tissue fluid?
Tissue fluid is similar to blood but it doesn't contain most of the cells found in the blood, or plasma proteins.
116
Tissue Fluid: What is the function of tissue fluid?
The role of tissue fluid is to transport oxygen and nutrients from the blood to the cells, and to carry carbon dioxide and other wastes back to the blood. It bathes the cells in nutrients and other substances to allow them to carry out different processes, for example oxygen and glucose for respiration.
117
Tissue Fluid: What does tissue fluid contain?
- Oxygen
- Carbon dioxide
- Nutrients
- wastes
- Amino acids
- Sugars
- Hormones
- Salts
118
Tissue Fluid: How is tissue fluid formed?
- Blood flowing into an organ or tissue is contained in the capillaries. At the atrial end of a capillary, the blood is under high pressure due to the contraction of the heart muscle, this is known as hydrostatic pressure. It will push the blood plasma out of the capillaries. The fluid can leave through the tiny gaps in the endothelium of the capillaries.
- The fluid that leaves the blood consists of plasma with dissolved nutrients and oxygen. All the red blood cells, platelets and most of the white blood cells remain in the blood, as do the plasma proteins. These are too large to be pushed out through the gaps.
- The fluid that leaves the capillary is known as the tissue fluid. This fluid surrounds the body cells so exchange of gases and nutrients can occur across the cell surface membranes. This exchange occurs by diffusion and facilitated diffusion. Oxygen and nutrients enter the cells; carbon dioxide and other wastes leave the cells.
119
Tissue Fluid: How does tissue fluid return to the blood?
As well as the hydrostatic pressure of the blood, the tissue fluid itself also has some hydrostatic pressure which will tend to push the fluid back into the capillaries. Both the blood and the tissue fluid also contain solutes, giving them a negative water potential. The water potential of the tissue fluid is less negative than that of the blood. This means that water tends to move back into the blood from the tissue fluid by osmosis, down the water potential gradient.
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Tissue Fluid: What pressures are acting while tissue fluid is returning to the blood?
At the venous end of the capillary, the blood has lost the hydrostatic pressure. The combined effect of the hydrostatic pressure in the tissue fluid and the osmotic force of the plasma proteins is sufficient to move fluid back into the capillary. It carried with it any dissolved waste substances, such as carbon dioxide, that have left the cells.
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Tissue Fluid: What is Oedema?
- Accumulation of fluid in the tissues or cavities.
- Occurs due to decreased plasma protein concentration.
- Seen in kidney failure as proteins are lost in urine or in liver failure as less proteins are made so lower solute potential.
- It also happens after starvation as lack of food means no protein is being provided or made.
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Tissue Fluid: Why does oedema cause swelling?
-As there are less plasma protein in the blood there is a higher water potential. This means there is more fluid lost to tissue fluid at atrial end, and very little re-enters at the venous end, meaning tissue swells as it is full of fluid.
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Lymph Fluid: What is the lymphatic system?
Not all tissue fluid returns to the blood capillaries. Some is drained away into the lymphatic system. The lymphatic system consists of a number of vessels that are similar to capillaries. They start in the tissues and drain the excess fluid into larger vessels, which eventually re-join the blood system in the chest cavity.
-Lymph fluid eventually becomes plasma, and lymph vessels also absorb fats from the small intestine, where they form lacteals inside each villus.
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Lymph Fluid: What is the function of lymph fluid?
The function of lymph is to carry fluid through the lymphatic system to remove toxins, waste and other unwanted material.
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Lymph Fluid: What does lymph fluid contain?
Lymph fluid is very similar to tissue fluid and contains the same solutes.
- There will be less oxygen and fewer nutrients as these have been absorbed by body cells. There will also be more carbon dioxide and wastes that have been released from the body cells. Lymph also has more fatty material that has been absorbed from the intestines.
- It also contain many lymphocytes.
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Lymph Fluid: What are lymph nodes?
Lymphocytes are produced in the lymph nodes. The lymph nodes are swelling found at intervals along the lymphatic system. They filter any bacteria and foreign material from the lymph fluid. The lymphocytes can then engulf and destroy these bacteria and foreign particles. This is part of the immune system that protects the body from infection.
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Serum: What is serum?
Serum is the liquid part of the blood with the fibrinogen removed, which is what helps the blood to clot.
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Serum: What if the function of serum?
Plasma is used to treat patients with severe burns and to help determine blood groups.
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Carriage of oxygen: How is oxygen transported around the body?
Oxygen is transported in the erythrocytes (RBC). These cells contain the protein haemoglobin, in which oxygen binds, causing it to become oxyhaemoglobin.
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Carriage of oxygen: What is haemoglobin?
- Quaternary structure, as it has four chains
- Two alpha chains, two beta chains of polypeptides.
- In each of the chains has a haem group attached.
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Carriage of oxygen: What is a haem group?
The haem group is a non-protein, and contains a single iron atom in the form of Fe2+.
- This iron atom can attract and hold an oxygen molecule and the haem group is said to have an affinity for oxygen.
- As each haem group can hold one oxygen molecule, each haemoglobin molecule can carry four oxygen molecules.
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Carriage of oxygen: How is oxygen taken up by haemoglobin?
Oxygen molecules are loaded one O2 molecule at a time, and so very slowly.
- The first molecule of O2 combines with an Hb and slightly distorts it (conformational change), meaning the loading of the first molecule is slow.
- For the second molecule it becomes easier, and for the third easier still.
- Joining the fourth molecule is harder because there is less space for it to fit.
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Carriage of oxygen: How is oxyhaemoglobin formed?
The binding of oxygen to haemoglobin is a reversible reaction and the oxygen and haemoglobin are bonded together loosely.
-Hb + 4O2 HbO8
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Carriage of oxygen: How is oxygen released?
Because oxygen in needed in the body tissues for aerobic respiration, oxyhaemoglobin must be able to release oxygen. This is called dissociation.
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Carriage of oxygen: What does partial pressure mean?
The pressure exerted by one gas in a mixture of gases.
| -In relation to oxygen, it is also called oxygen tension.
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Carriage of oxygen: What is the atmospheric partial pressure of oxygen?
Atmospheric pressure is about 100kPa, and oxygen makes up about one fifth of this.
-Partial pressure of oxygen is about 20kPa.
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Carriage of oxygen: What is the partial pressure of oxygen as it travels through the body?
- Inhaled air (inside alveoli) has a PO2 of 14kPa (6kPa is lost as it has to travel through structures in the body)
- PO2 of resting tissue is 5.3kPa, as the oxygen is being utilised which tissue is respiring.
- PO2 of active tissue is 2.7kPa.
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Carriage of oxygen: What is % saturation?
Refers to the overall degree of loading of Hb with oxygen.
| -Blood near lungs almost has 100% saturation because lungs is where blood is oxygenated.
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Carriage of oxygen: What is the oxyhaemoglobin dissociation curve?
Shows the relationship between the partial pressure of oxygen and the degree of saturation of haemoglobin. It is S (sigmoid) shaped.
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Carriage of oxygen: Why is the oxyhaemoglobin dissociation curve sigmoid shaped?
- At a low oxygen tension, the haemoglobin does not readily take up oxygen molecules. This is because the haem groups that attract the oxygen are in the centre of the haemoglobin molecule. This makes it difficult for the oxygen to reach the haem group. The difficulty in combining with the first molecule accounts for the low saturation level of haemoglobin at low oxygen tensions.
- As the oxygen tension rises, the diffusion gradient into the haemoglobin molecule increases. Eventually one oxygen molecule diffuses into the haemoglobin molecule and associates with one of the haem groups. This causes a slight chance in the shape of then haemoglobin molecule known as a conformational change. It allows more oxygen molecules to diffuse into the haemoglobin molecule and associate with the other haem groups relatively easily. This accounts for the steepness of the curve as the oxygen tension rises.
- Once the haemoglobin molecule contains three oxygen molecules, it becomes more difficult for the fourth molecule to diffuse in and associate with the last available haem group. This means it is difficult to achieve 100% saturation, despite an increase in oxygen tension.
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Carriage of oxygen: Why is mammalian haemoglobin well adapted to transporting oxygen?
Mammalian haemoglobin is well adapted to transporting oxygen to the tissues of a mammal.
- The oxygen tension found in the lungs is sufficient to produce almost 100% saturation.
- The oxygen tension in respiring body tissues is sufficiently low to cause oxygen to dissociate readily from the oxyhaemoglobin.
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Carriage of oxygen: What is fetal haemoglobin?
-The haemoglobin of a mammalian fetus has a higher affinity for oxygen than that of adult haemoglobin. Fetal haemoglobin must be able to 'pick up' oxygen from an environment that makes adult haemoglobin release oxygen. In the placenta, the fetal haemoglobin must absorb oxygen from the fluid in the mothers blood. This reduces the oxygen tension within the blood fluid, which in turn makes the maternal haemoglobin release oxygen. So the oxyhaemoglobin dissociation curve for fetal haemoglobin is to the left of the curve for adult haemoglobin.
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Carriage of oxygen: Why does fetal haemoglobin need to have a higher affinity for oxygen than adult haemoglobin?
Fetal haemoglobin has a higher affinity because it gets oxygen from its mother's blood across the placenta.
- By the time the mother's blood reaches the placenta its oxygen saturation has decreased because some has been used up by the mother's body. The placenta has a low pO2, so adult oxyhaemoglobin will unload its oxygen (adult oxyhaemoglobin will dissociate).
- For the fetus to get enough oxygen to survive, its haemoglobin has to have a higher affinity for oxygen than adult haemoglobin. This means fetal haemoglobin takes up oxygen(becomes more saturated) in lower pO2 than adult haemoglobin. If its haemoglobin have the same affinity for oxygen as adult haemoglobin, its blood wouldn't be saturated enough.
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Carriage of oxygen: How is carbon dioxide transported in the blood?
Carbon dioxide is released from respiring tissues. It must be removed from these tissues and transported to the lungs. Carbon dioxide in the blood is transported in three ways:
- 5% is dissolved directly in plasma
- 10% is combined directly with haemoglobin to form a compound called carbaminohaemoglobin.
- 85% is transported in the form of hydrogencarbonate ions (HCO3-)
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Carriage of oxygen: What is partial pressure of carbon dioxide?
The partial pressure of carbon dioxide (pCO2), is a measure of the concentration of CO2 in the cell. pCO2 also affects oxygen unloading. Haemoglobin gives up its oxygen more readily at a higher pCO2, allowing the cells to get more O2 during respiration.
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Carriage of oxygen: What is the Bohr Effect?
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Where tissues (such as contracting muscles) are respiring more, there will be more carbon dioxide. As a result there will be more hydrogen ions produced in the red blood cells. This makes the oxyhaemoglobin release more oxygen. This is the Bohr Effect. At any particular oxygen tension, the oxyhaemoglobin releases more oxygen when more carbon dioxide is present. So when more carbon dioxide is present, haemoglobin is less saturated with oxygen. This makes the oxyhaemoglobin dissociation curve shift downwards and to the right (the Bohr shift).
-The Bohr effect results in oxygen being more readily released where more carbon dioxide is produced from respiration. This is what the muscles need for aerobic respiration to continue.
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Carriage of oxygen: How are hydrogencarbonate ions formed?
As carbon dioxide diffuses into the blood, some of it enters the red blood cells. It combines with water to form a weak acid called carbonic acid. This is catalysed by the enzyme carbonic anhydrase.
-CO2 +H2O -carbonic anhydrase-> H2CO3
This carbonic acid dissociates to release hydrogen ions (H+) and hydrogencarbonate ions (HCO3-).
-H2CO3 --> HCO3- + H+
The hydrogencarbonate ions then diffuse out of the red blood cell into the plasma.
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Carriage of oxygen: What is the chloride shift?
The hydrogencarbonate ions diffuse out of the red blood cell into the plasma. The charge inside the red blood cell is maintained by the movement of chloride ions (Cl-) rom the plasma into the red blood cell. This is called the chloride shift. If charge is not maintained, membranes could be disrupted and enzymes could be effected, reducing efficiency.
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Carriage of oxygen: What is a buffer?
- Has the ability to maintain the body's pH.
- The intracellular and extracellular pH has to be maintained at constant level 7.4. It is maintained by the buffering ability of body fluids.
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Carriage of oxygen: How does haemoglobin act as a buffer?
The hydrogen ions released from H2CO3 cause the contents of the red blood cell to become very acidic. The increase in acidity causes oxyhaemoglobin to unload its oxygen so that haemoglobin can take up the hydrogen ions. This forms haemoglobinic acid (reduced haemoglobin), maintaining the pH.
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Carriage of oxygen: How is carbon dioxide removed from the body?
When the blood reaches the lungs, the low pCO2 causes the hydrogencarbonate and hydrogen ions to recombine into CO2 (and water). The CO2 then diffuses into the alveoli and is breathed out.
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Carriage of oxygen: What is the benefit of the oxyhaemoglobin curve shifting to the left?
-Caused by increase in pH, or decrease in CO2.
Unloads less O2, which is good for high or low altitudes with little oxygen, e.g. birds or fish. Also good when on mountains. (Athletes train in high altitudes to produce more red blood cells to hold more oxygen and provide more when competing).
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Carriage of oxygen: What is the benefit of oxyhaemoglobin curve shifting to the right?
-Caused by decrease in pH, or decrease in CO2.
| Unloads more O2, which is good when exercises as cells need to respire more to provide more energy.
