Cardiovascular Disease

Diapositiva 1

• 
• Blood vessels
• Arteries:
• Thick walls
• Narrow lumen
• No valves
• Elastic fibres
• Veins:
• Wide lumen
• Thinner walls
• Valves
• Fewer elastic fibres
• Capillaries:
• Narrow vessels
• Thin walls

Diapositiva 2

• 
• Pie de imagen: The heart
• The heart contracts(systole), blood is forced into arteries and their elastic walls stretch to accommodate the blood. The thick artery walls can withstand the high pressure generated from the heart.
• Eventually the blood reaches the smaller arteries and capillaries where the blood flows more slowly due to their narrow lumens. This allow exchange between the blood and the surrounding cells through the one cell thick capillary walls. This involves a rapid diffusion.
• Blood travels into pulmonary vein, left atrium through the mitral valve into the left ventricle, through the aortic valve and into the aorta.
• Blood comes back from the superior/inferior vena cava, right atrium through the tricuspid valve, into right ventricle and through pulmonary valve and into the pulmonary artery.

Diapositiva 3

• The cardiac cycle
• -Each double beat is called a cardiac cycle.
• -The thickness of the muscle walls of the chambers of the heart determines the pressure that can be generated.
• -The cardiac cycle is simple into 3 phases:
• Atrial Systole - Blood flows into the left and right atria. As it fills, the pressure opens the valves and blood begins to leak into the ventricles. The atria walls contracts to force more blood.
• Ventricular Systole - The ventricles contracts to increase the pressure upwards, this forces the semilunar valves to open to go through the pulmonary arteries and aorta. The atrioventricular valves closes to prevent blood flowing back into the atria.
• Cardiac Diastole - The atria and ventricles relax during this phase. Elastic recoil of the relaxing heart walls lowers pressure. The semilunar valves closes to prevent further back flow into the ventricles. Low pressure in the atria helps draw blood from the pulmonary veins.
• The cardiac cycle consists of:
• -electrical activity
• -muscle contractions
• -pressure changes
• -movements of valves

Diapositiva 4

• Atherosclerosis - is a narrowing of an artery due to deposits of cholesterol and formation of plaques. This process occurs:
• The endothelium which lines the artery becomes damaged(may cause by high blood pressure or toxins from cigarettes)
• White blood cells move into the damaged artery walls and cause cholesterol to be deposited in the wall to form an atheroma.
• A plaque is formed from deposited calcium salts and fibrous tissue.
• Atheroma and plaques partially block arteries, increasing blood pressure which leads to risks of heart disease and strokes as it is causing further damage. This process is called positive feedback.

Diapositiva 5

• 
• Blood Clot - the direct contact of blood with collagen within the damaged blood vessel wall also triggers a complex series of chemical changes in the blood. A cascade of changes results in the formation of blood clot.
• Platelets and damaged tissue release a protein called Thromboplastin.
• Thromboplastin activates an enzyme that catalyses the conversion of the protein prothrombin into an enzyme called thrombin. A number of other protein factors, Vitamin K and Ca2+ must be present for this to happen.
• Thrombin then catalyses the conversion of the soluble fibrinogen into insoluble protein fibrin.
• A mesh of fibrin forms that traps more platelets and red blood cells to form a clot.