Cardiac Muscle and Blood

Systole: Chambers are contracting; Diastole: Chambers are at rest. Blood pressure reflects the pressure during both phases.

Heart Sounds:

• "lub" (S1): Mitral and Tricuspid valves close.

• "dub" (S2): Aortic and Pulmonic valves close.

• S3: Early diastole filling; S4: Late diastole atrial contraction.

Heart Murmurs: Result from incomplete valve closure, causing abnormal blood flow.

Fetal Heart Development: Begins as tubes, developing into a heart. Lungs are not used; oxygen is supplied by the mother.

• Foramen Ovale: Opens between atria, closes after birth, redirecting blood from lungs to body.

• Ductus Arteriosus: Shunt between pulmonary artery and aorta, closes after birth, functioning as a ligament.

Coronary Vessels: Heart receives blood first, followed by the brain and the rest of the body.

Major Vessels: Subclavian a., common carotid. Arteries have thicker walls of smooth muscle for maintaining flow.

Blood Circulation: Leaves heart via arteries, progresses to arterioles and capillaries, returns via venules and veins to vena cava.

Capillaries: Smallest vessels for gas and nutrient exchange; RBCs must deform to pass through.

Blood Composition: Plasma (92% water, 7% proteins), erythrocytes (oxygen transport), leukocytes (defense), and thrombocytes (clotting).

Sickle Cell Anemia: Genetic condition causing pain, anemia, and infections.

ECG Waves:

• P-Wave: Atrial depolarization.

• QRS Complex: Ventricular depolarization.

• T-Wave: Ventricular repolarization.

Cardiac Conduction: Sinoatrial (SA) Node (heart pacemaker); Atrioventricular (AV) Node; Purkinje fibers for ventricular contraction.

Cardiac Muscle: Contains actin and myosin, has a branched structure, with intercalated discs for communication between cells.