The Heart

The heart consists of a specialised cardiac muscle with its blood supply and nerve supply, bound by a sheet of connective tissue.

The cardiac muscles surrounds four chambers, two atriums and two larger ventircles. On each side of the heart there is a upper atria and lower ventricle. Tendons bring blood to the atria and veins carry blood away from the ventricles.

The muscluar wall of the atria is thinner than the walls of the ventricles. The wall of the left ventricle is thicker than the wall of the right ventricle.

Deoxygenated blood returns to the body in two main veins, the superior and inferior vena cava. These veins carry blood to the right atrium, from where it flows into the right venticle to be pumped into the lungs via arteries.

Once oxygenated in the lungs, the blood returns to the heart through the pulmonary vein. The blood enters the left atrium, flows into the left ventricle and is pumped out of the heart via the aorta.

Atrial and ventricular diastole

• Blood flows into the atria- elastic recole of the the atrial walls generates low pressure in the atria, helping to draw blood into the heart.
• As the venticles begin to relax, blood tends to fall back from the aorta and pulomary artery causing the semi lunar valves to close.

Atrial systole

• As the atria fills with blood, the pressure in the atria increases. The atrio-ventricular valves are pushed open and blood flows into the relaxing ventricles. The two atria contract, forcing the remaing blood into the ventricles.

Ventricular systole

• The ventricles contract. This increases the pressute in the ventricles, so the atrio-ventricular close.
• The semi-lunar valves are open, and blood begins to flow into the relaxing atria.

Atherosclerosis is the hardening a narrowing of the arteries.

• When endothelium is damaged, a inflammatory response is caused
• LDL Cholesterol gets deposited on artery wall
• Calcium and fibrous tissue also build up at site, forming a atheroma
• This build up gets bigger and harder overtime due to CA2+ deposites
• Plaque bulges into lumen

Blood clotting is a cascade of chemical change caused by clotting factord

•  
  • Platelets stick to the damaged blood vessel
  • Thromboplastin is released from damaged tissue and forms platelets
  • Platelets stick to each other forming a platelet plug
  • Active thromboplastin leads to prothrombin
  • Then converted into an active enzyme thrombin
  • Which catalyses to fibrinigin (soluble)
  • Into fibrin which (insoluble) forming a mesh that traps red blood cells to form the clot

Stroke
Causes - The blockage of artery in the brain, the longer the brain lacks oxygen the worse damaged the brain will be- atheroclerosis is the underlying cause of stroke
Symptoms - Mini Stroke -> Transient ischaemic attacks

Coronary Heart Disease

Angina
Causes - Blood flow to an area of heart decreases due to the fact it is restricted- blood can still flow through but less due to the artery lumen narrowing as plaque has formed. Limited oxygen and thus anerobically respiring, called anerobic respiration.
Symptoms - Breathlessness, dizziness

Myocardial Infarction
Causes - the conary ateries are blocked, as the arteries that pump blood to the heart they can no longer pump oxygen into the heart. The blood clot forms rapidly & the lack of oxygen from the blockage results in no respiration and the cells die within the heart.
Symptoms - Nausea, Sharp pain

A labelling the heart game

http://www.sciencelearn.org.nz/Contexts/See-through-Body/Sci-Media/Animations-and-Interactives/Label-the-heart