The adult human heart has four cavities inside it and these are called 'chambers'. They are divided into two at the top the atria or atrium for singular, and two at the bottom the ventricles. The heart is divided into two down the middle.
- Blood enters and fills the atria, the bicuspid and tricuspid valves are closed.
- The atria contract gently and push the blood into the ventricles.
- The ventricles then contract which closes the bicuspid and tricuspid valves and pushes the blood out to the semi lunar valves into the pulmonary artery and the aorta.
The blood the heart pumps goes into different locations, the left ventricle pumps blood all over the body whereas the right ventricle just pumps blood into the lungs which in turn goes back into the left side of the heart. The first beat (lub) is the sound of two atrial vavles closing while the second beat (dub) is the sound of two semi-lunar valves closing.
The Circulatory System
The heart and blood vessels transport food molecules, water and oxygen to cells around the body and remove waste products like carbon dioxide. There is a double circulation which is in two inter-connecting loops.
- Blood returns from the body to the right atrium. The blood has lost most of the oxygen it has carried and becomes deoxygenated.
- The right ventricle pumps the blood along the pulmonary artery to the lungs where it picks up fresh oxygen. It is now oxygenated.
- The oxygenated blood enters the left side of the heart and is pumped out through the aorta to the body.
- Once it reaches the capillaires around the body, oxygen diffuses out to the surrounding cells.
- The deoxygenated blood is carried back towards the heart in the veins. These join up to form the vena cava which is the largest vein.
Useful tip: Veins only carry deoxygenated blood except for the pulmonary vein. This is the only one that carries oxygenated blood because it takes blood from the lungs to the left heart ready to get pumped round the body.
Normally circulation takes blood straight back to the capillaries in each organ or tissue. However hepatic circulation is a special type of circulation, because blood from the digestive system carries all sorts of molecules it takes a special detour which stops the rest of the circulatory system getting clogged up. This special detour is calles the Hepatic Portal System.
Hepatic means to do with the liver. The liver is the factory organ of the body. It deals with all sorts of chemicals, breaking them down and rearranging them.
The hepatic portal vein carries blood to the liver. Then the blood can leave the liver for the heart.
Plasma is the main ingredient in your blood, plasma contains:
- Dissolved carbon dioxide: This is the waste gas produced by respiration in cells
- Dissolved glucose and amino acids: Food molecules for respiration, building and repairing cells
- Urea: Waste product of digestion, this is lost from the kidney
- Antibodies and antitoxins: Chemicals that protect us from disease and poisons
- Hormones: Chemicals that control some of our body functions
Red Blood Cell
Red Blood Cells contain the oxygen carrying molecules of haemoglobin. Iron is needed for the production of haemoglobin if your diet lacks this mineral you are likily to develop the disease of aenamia.
Red Blood Cells are different to other blood cells because they don't have a nucleus. They are just a cell containing haemoglobin, the cells are a dougnut shape. When blood picks up oxygen we call it oxygenated. This happens because haemoglobin creates weak bonds with oxygen to create a complex molecule called oxyhaemoglobin.
Platelets are fragments of larger cells
Their job is to clot blood and plug it to stop the body loosing to much blood. Without the clotting mechanism a simple cut would make us bleed to death!