Teas- The heart pg 103-106

Structure of the heart

The heart wall consist of three distinct layer-

• Epicardium- outer protective layer, secretes lubricating fluid.

• Myocardium- Middle muscular layer, responsible for pumping blood.

• Endocardium- inner lining of the chambers and valves.

Chambers and valves- the heart has four chambers and four primary valves

• Receiving chambers- right atrium (from body) and left atrium (from lungs).

• Discharging Chambers- right ventricle (to lungs) and left ventricle (to body).

• Atrioventricular (AV) Valves- tricuspid (right) and Mitral/Bicuspid (left). They prevent backflow into the atria.

• Semilunar valves- pulmonary (right) and aortic (left). They prevent backflow into the ventricles.

Blood pressure and circulation

Blood pressure (BP) is the force exerted on vessel walls, measured in mmHg (e.g., 120/80).

• Systole- maximum pressure when ventricles contract.

• Diastole- minimum pressure when ventricles relax.

The two circuits

1. systemic circuit- carries oxygenated blood from the left ventricle to the body and returns deoxygenated blood to the left atrium.

2. Pulmonary circuit- carries deoxygenated blood from the right ventricle to the lungs and returns oxygenated blood to the left atrium.

Endothelial cells

The endothelium is the thin inner lining of all blood vessels.

• Function- Acts as a barrier, reduces friction, and regulates blood flow.

• Regulation- releases peptides (endothelins) for vasoconstriction and chemicals for blood clotting.

Electrical conduction system

The heart generates its own rhythmic electrical impulses in a specific sequence-

1. SA Node (pacemaker)- starts the impulse, triggers atria to contract (P wave on ECG)

2. AV Node- slows the impulse to allow ventricles to fill (PR segment).

3. Bundle of his and Purkinje fibers- carry the impulse to the ventricles, causing them to contract (QRS complex).