The Circulatory System and the Heart
There are 3 components to the system: Heart, Blood Vessels and Blood.
The Heart is a muscular organ that pumps blood around the body via the blood vessels. The Heart is actually two pumps held together.
The right pump forces deoxygenated blood to the lungs where it picks up oxygen and loses carbon dioxide.
The left pump forces oxygenated blood to the rest of the body, after returning to the heart.
The heart has four chambers. The upper ones are called the artia which receive blood from the vena cava on the right and the pulmonary vein on the left. The artia contract to move blood into the lower chambers, the ventricles. When the ventricles contract they force blood into the pulmonary artery from the right side and into the aorta on the left side. Valves in the heart prevent the blood backflowing (flowing in the wrong direction). The heart muscle is supplied with oxygenated blood via the coronary arteries.
The action of the two sides of the heart results in a double circulation.
- Vena Cava - deoxygenated blood back from the body to the heart
- Pulmonary Artery - deoxygenated blood from the heart to the lungs
- Pulmonary Vein - oxygenated blood back from the lungs to the heart
- Aorta - oxygenated blood from the heart to the rest of the body
- Muscular Heart Wall - thicker on the left as it has to pump blood all around the body
- Carry oxygenated blood away from the heart
- Have a thick layer of muscle
- Blood flows at high pressure due to the action of the heart, so can feel pulse
- Carry deoxygenated blood towards the heart
- Have valves to stop backflow of blood
- Thin layer of muscle
- Blood flows at a low pressure
- Connect arteries and veins
- Carry both oxygenated and deoxygenated blood
- Walls are very thin
- In close contact with cells
- Low blood pressure and slow speed to allow exchange of materials
Arteries can get blocked, weakened or narrowed due to coronary heart disease and can cause heart attacks. A stent can be placed in the artery to keep the artery open so blood can flow through it.
- The success rate is high
- They lower the risk of heart attack
- Last for a long time
- Complications like bleeding, irregular heartbeat and infection
- Arteries sometimes reclose
- Drugs needed to stop blood clotting
The valves in the heart control the direction of flow of blood. Disease can cause the valves to degenerate and stop opening and closing correctly. This make the person very tired and listless. There are two types of replacement valves:
- Mechanical Valves: made from man-made material such as metal, cloth or ceramic.
- Biological Valves: made from human or animal tissue (mostly pigs).
- The success rate is high
- They prolong life
- Expect the new valve to last up to 20 years
- May need to take blood thinners to stop clotting
- There is always a risk of serious complications with surgery
Transport in blood
Blood is a tissue. The fluid plasma contains red blood cells, white blood cells and platelets. Blood plasma transports many substances including:
- Carbon dioxide from the organs to the lungs
- Soluble products of digestion from the small intestine to other organs
- Urea from the liver to the kidneys where urine is made
Red blood cells:
- are biconcave discs which do not have a nucleus
- contain the red pigment haemoglobin
- use their haemoglobin which combines with oxygen to form oxyhaemoglobin in the lungs
- carry oxygen to all the organs where the oxyhaemoglobin splits into oxygen and haemoglobin
Transport in blood
White blood cells:
- have a nucleus
- form part of the body's defence system against microorganisms
- are small fragments of cells
- do not have a nucleus
- help blood to clot at the site of the wound
Artificial hearts have been used temporarily to keep people alive while they wait for a heart transplant. The artificial heart is not living so needs a power source, early power sources were so large that the patient had to stay in hospital. New advances mean that the patient can now use a portable owner supply and can go home.
- The artificial heart is not rejected by the body
- Keeps patient alive whilst waiting for a transplant
- Surgery can lead to bleeding and infection
- Blood does not flow as easily and can lead to clots so blood thinners (such as warfarin) need to be taken
- Parts of the heart can wear out or stop working
Artificial Blood and Blood Products
Blood transfusions are used for; replacing fluid levels, as a replacement for red blood cells(to carry oxygen) and as a replacement for blood platelets to help with clotting. Artificial blood products (like HBOCs and PFCs) are currently used, rarely, to compliment blood transfusions however there is still a lot of research to be done before they will replace blood transfusions completely. HBOCs are haemoglobin based and PFCs are completely artificial, both compounds are used to deliver oxygen around the body. Current research is concentrating on producing stem cells that can replace any blood group.
- Increased shelf life
- Does not need to be refrigerated
- More efficient at carrying oxygen
- No need to make blood group
- They effect is only short lasting
- The products are expensive
- Some concerns about safety of the products as safety testing can be problematic
Blood vs. Artificial Blood Products
Shelf life: 42 Days
Cost per Unit: £150 - £230
Duration of action: Up to 60 days
Blood group match: Match needed
Artificial Blood Products
Shelf life: 1-3 years
Storage: Room temperature
Cost per Unit: £500 - £1000
Duration of action: 2-3 days
Blood group match: No match needed
Transport Systems in Plants
Flowering plants have separate transport systems. Xylem tissue transports water and mineral ions from the roots to the stem, leaves and flowers. Phloem tissue carries dissolved sugars from the leaves to the rest of the plant, including the growing regions and the storage organs.
The movement of water from the roots through the xylem and out of the leaves is called the transpiration stream.