Important definitions and examples
Closed circulatory system: The blood is maintained/enclosed in vessles. An example of this would be any vertibrates
Open circulatory system: The blood is not constantly contained in vessles, it can flow into the body cavity, haemocyoel (blood space). An example of this would be an insect.
Single circulatory system: The blood goes to the lungs/ gills to be oxygenated but doesn't return to the heart like in a double circulatory system it flows directly to the rest of the body.
Double circulatory system: This system has two curcits: Pulmonary circulatation(to and from the lungs) and systemic circulation(to and from the rest of the body).
Structure of the heart
The left ventrical is much thicker than the right this is because the blood is at higher pressure, this is oxygenated blood travelling to the body.
There are two semilunar values stopping back flow of blood in the aorta and pulmonary artery. There is also two antroventricular valves: Buicuspid and Tricuspid both of these prevent backflow of blood in the ventricles back to the atria.
The pulmonary vein has oxygenated blood from the lungs and the pulmonary artery takes deoxygenated blood back to the lungs at a higher pressure.
There is also the septum that is the muscle separting the right and left venticles.
The rhythmic system of the heart
In the heart you have the S.A.N (sino-atrial node) that sets the natural rhythm of the heart and send a wave of excitation through the atrial walls. The response from the artial walls is contraction and the muscle in both atria contract simultanously. The muscles of the ventricals do not contract at the same time as the atria. This is due to the fact between the atria and the ventriacals there is a band of non conducting fibers so the electrical impulses can only travel through one pathway: the A.V.N (atriaventricular node) This change of pathway created a 0.1s delay and then the electrical signals are passed from the a.v.n to the purkyine tissue that branches through the ventricals and to the septum. The electrical impulses travel up the septum and cause the ventricals to contract, thus increasing the pressure and pushing the blood into the arteies.
The cardiac cycle
The heart fills with blood, this is called the atrial systole, this happens due to the muscles in the atrial walls contracting.
After around 0.1s the ventricals contract, this is ventricular sysole. The muscluar walls of the ventricals increases the pressure and pushes the blood out of the heart.
There is then Ventricular distole this is where the atria and ventricals relax.