Heart and Lung Flashcards
The events of one heartbeat, so called cardiac cycle
- The heart releaxes and blood enters both atria from veins.
- Both atria contract to push blood into the ventricles through the atrioventricular valves
- The ventricles contract powerfully
- The atrioventricular valves shut, preventing blood from flowing back into the atria
- The semilunar valves open, allowing blood into the aorta and pulmonary artery
- The ventricles relax
- The atria begin to fill again to repeat the cycle
Why do we need a circulation?
Blood is a mass flow or a mass transport system. Large volumes of fluid are pumped rapidly around the body from organs of exchange such as the guts and lungs, to the cells that need them.
The heart is simply a pump. Mammals have a double circulation — there are two circuits that take blood on a return journey to the heart.
1 The pulmonary circulation carries blood to the lungs and back.
2 The systemic circulation carries blood to the rest of the body and back.
We need two circulations because blood goes to the lungs to collect oxygen, but in doing so it loses pressure, so it needs to return to the heart for a boost. In order to pump blood round two circulations at the same time, we need a four-chambered heart:
●Two atria. Their job is simply to fill with the right volume of blood, and pump it into the ventricles. Think of them as ‘loading chambers’.
●Two ventricles, whose job is to create pressure. They contract powerfully, forcing blood into arteries.
The right side of the heart fills with deoxygenated blood, and
pumps blood around the pulmonary circulation.
The left side of the heart fills with oxygenated blood from the lungs, which needs to be pumped around the systemic circulation. This requires more pressure, so the left ventricle has a thicker muscle wall than the right ventricle.
How many types of blood vessels are there?
There are three main types of blood vessels: arteries, veins and capillaries.
What is coronary heart disease?
It is the most common form of heart disease in which the arteries become narrower due to a build-up of fatty deposits inside them. When the coronary arteries get blocked, not enough oxygen and glucose reaches the heart muscle, part of the heart muscle dies, and a heart attack results.
When coronary arteries narrow, they can be treated by inserting a stent — a tubular wire mesh that keeps the lumen of the artery open to allow the blood to flow freely again.
How does gas exchange happened in the capillaries?
- Blood flows from the heart into arteries, then into smaller arteries, which finally branch out into capillaries. These tiny vessels take blood to within a fraction of a millimetre of all the respiring cells.
- All cells are surrounded by tissue fluid, from which cells get the oxygen and nutrients, and into which they secrete their waste and other products. Blood slows down as it flows along a capillary. The walls are one cell thick and permeable (leaky) so that exchange can happen between blood and tissue fluid. Tissue fluid is basically plasma that leaks out of the capillaries.
For each of the following blood vessels, state the pressure and the oxygen content of the blood it contains (you could do this as a table):
a) vena cava
b) pulmonary artery
c) pulmonary vein
d) aorta
a) vena cava — deoxygenated, low pressure
b) pulmonary artery — deoxygenated, high pressure
c) pulmonary vein — oxygenated, low pressure
d) aorta — oxygenated, high pressure
Blood flow is slowest in capillaries. Suggest an advantage of this slow flow.
There is more time for diffusion/exchange of materials.
Arteries carry oxygenated blood. Is this always true? Explain.
No, the pulmonary artery carries deoxygenated blood.
Most arteries lie deep under the surface of the skin, while veins run much closer to the surface. Explain the advantage of this arrangement.
There is less chance of an artery being cut. Rapid blood loss would be dangerous/fatal.
What is blood made up of?
Blood is a complex fluid containing red blood cells, white blood cells, platelets ( bits of broken cells) and plasma.
Red blood cells
Red blood cells are basically little bags of haemoglobin. They have no nucleus or any of the other normal cell contents such as mitochondria.
The function of haemoglobin is to collect oxygen where it is abundant — the lungs — and release it where it is needed — the respiring tissues.
As red blood cells pass through the lungs, haemoglobin combines with oxygen to form bright red oxyhaemoglobin. As it passes through the respiring tissues in the rest of the body, the haemoglobin gives up its oxygen, becoming a darker red as it does so.
White blood cells
White blood cells defend the body against attack by microbes/pahtogens.
Lymphocytes produce antibodies to destroy microorganisms and memory lympohocytes give us immunity to specific diseases. Phagocytes engulf and digest microorganisms.
About 70% of white blood cells are phagocytes.
Platelets
Platelets are cell fragments which help clot the blood.
Plasma
Plasma is the yellow liquid which transports dissolved food molecules, carbondioxide, and urea as well as all the blood cells. It’s mainly water.
Plasma also contains other important substances such as hormones, blood clotting factors and heat.
Red blood cells do not live very long. Use your knowledge of their structure to suggest why.
They have no nucleus, so are not able to repair themselves and therefore have a short life.
The higher the altitude at which people live, the greater the volume of red blood cells in their blood. Suggest an advantage of this adaptation.
At higher altitude, each red cell carries less oxygen. So having more red blood cells compensate for this/allows more oxygen to be carried.
Why exchange gas?
● All living things must respire — this is the release of energy from
organic molecules such as glucose.
● Respiration uses oxygen, and produces carbon dioxide.
● So all living things must exchange these gases.
● Large organisms — and especially those with high energy demands, such as mammals — need to exchange lots of gas.
● That is why special gas exchange organs such as lungs and gills have evolved.
Explain why we cannot drink seawater to cure dehydration.
Seawater has a high salt concentration, which will draw water out of the blood by osmosis and make dehydration worse.
Blood clotting is a relatively fast reaction. Give two advantages of
this fact.
Less blood loss; less chance of infection.
The lungs contain no muscle. Explain how they inflate.
The lungs are attached to the ribcage and diaphragm (1 mark). The intercostal muscles and diaphragm contract (1 mark), increasing the volume in the thorax (1 mark) and lowering the pressure (to below atmospheric) (1 mark). So air flows in (1 mark).
a) Describe how our breathing pattern changes when we exercise.
b) Explain the need for this change.
a) We breathe more deeply, and more frequently.
b) Any three from:
- Muscles respire.
- So they need more oxygen.
- And they make more CO2
- l So gas exchange must be faster.
The young of frogs and toads are called tadpoles and they have gills. Predict what features these gills will have in order to maximise gas exchange.
large surface area, thin membranes, good blood supply
Smoking effects and health
- Nicotine in smoke makes your heart beat faster and increases your blood pressure. Your heart then need to work faster.
- Carbon monoxide in smoke lowers the amount of oxygen blood can carry as it binds easily to haemoglobin. In pregnant smoker, the developing foetus gets less oxygen and so grows more slowly.
- Substances in smoke, tar and particulates, damages the cilia (ciliated epithelial cells), that line the airways (trachea, bronchi and bronchioles). And increase the risks that arteries will become narrowed by fatty material (atheroma). This can cause heart attacks and strokes.
- Increases cholesterol which causes coronary artery to narrow and less oxygen gets to heart muscles, more anaerobic respiration. Can increase risk of heart attack.
Smoking damage to the lungs
Tobacco smoke has the following effects:
- Cilia are destroyed so dirt and bacteria are not removed.
- Emphysema – the walls of the alveoli are damaged and break down to form large irregular air spaces which do not exchange gases efficiently. These all act to decrease the rate of diffusion of O2 through the alveoli into the blood, and the rate of diffusion of O2 from the blood into the respiring tissues. The same is true for CO2 but in the opposite direction. This makes smokers breathless.
- Lung cancer- tar and other chemicals cause cells to mutate and form cancers in the lungs and throat.
- Carbon monoxide binds to haemoglobin, lowering the oxygen levels in the blood. In pregnant women, this deprives the fetus of oxygen and can lead to smaller babies and stillbriths.
- Smoking also affects the circulatory system and causes an increased risk of heart attacks and strokes.