Second Lecture on Heart Anatomy and Physiology

Learning Objectives

• Understanding of heart anatomy including chambers, pericardial sac, myocardium, valves, innervation, and blood supply
• Familiarity with cardiovascular physiology including cardiac cycle, heart sounds, heart waves, and ECG
• Knowledge of common heart pathologies
• Clinical examination techniques related to the heart

Anatomy of the Heart

• The heart is a muscular organ encased in a fibrous pericardial sac containing lubricating fluid.
• Myocardium is the heart muscle, lined internally by endothelium.
• Divided into two pumps: right heart (pumps to lungs) and left heart (funnels blood to body).
• Each side consists of an atrium and a ventricle, with blood flow governed by valves.

Heart Chambers and Septa

• Four chambers are divided by septa:
  • Interatrial septum (right and left atria)
  • Interventricular septum (right and left ventricles)
• Surface grooves mark the heart’s septal divisions.

Pericardium

• Tough, cone-shaped sac surrounding the heart and great vessels, firmly attached to the diaphragm.
• Contains no gap junctions like skeletal muscle; adjacent myocardial cells connect through intercalated discs facilitating synchronized contraction.

Heart Innervation

• Rich supply of sympathetic and parasympathetic nerves.
• Parasympathetic fibers (vagus nerve) release acetylcholine; sympathetic fibers release norepinephrine.

Heart Valves

• Atrioventricular (AV) valves:
  • Tricuspid valve (right) with three cusps, preventing backflow during ventricular contraction.
  • Mitral valve (left) with two cusps, assisted by papillary muscles.
• Semilunar valves (aortic and pulmonary): three cusps each, preventing regurgitation during diastole.

Heart Sounds

• S1: First heart sound marking ventricular contraction.
• S2: Closure of aortic and pulmonary valves.
• S3: Rapid ventricular filling sound, normal in children and active adults.
• S4: Atrial contraction sound, occurring just before S1.

ECG (Electrocardiogram)

• Records electrical activity during heartbeats, producing a waveform strip.
• Normal adult heart rates range from 60 to 100 bpm; tachycardia exceeds 100 bpm, bradycardia falls below 60 bpm.
• Key waveforms:
  • P wave: Atrial contraction indicator, duration of 0.06 - 0.12 seconds.
  • QRS complex: Ventricular depolarization and contraction, duration of 0.06 - 0.10 seconds.
  • T wave: Ventricular repolarization, duration of 0.1 - 0.25 seconds.

Pathology of the Heart

• Heart Failure: Heart's inability to pump adequately; results in fluid buildup and organ dysfunction.
• Congenital Heart Disease: Present at birth, including left-to-right and right-to-left shunts.
• Ischemic Heart Disease: Inadequate blood flow to myocardium, leading to angina and myocardial infarction (MI).
• Hypertensive Heart Disease: Complications due to continuous high blood pressure.

Additional Conditions

• Valvular Heart Disease: Malfunctioning heart valves affecting blood flow.
• Cardiomyopathies: Diseases affecting heart muscle function.
• Pericardial Disease: Inflammation or infection of the pericardial sac.
• Tumors: Rare heart tumors.

Atherosclerosis

• Leading cause of death due to plaque buildup in vital arteries, can cause myocardial infarction, cerebral infarction, and aortic aneurysm.

Blood Pressure

• Hypertension affects about 25% of the population.
• Normal adult blood pressure: <140/90 mm Hg; borderline: 140-160/90-95 mm Hg; definite: >160/95 mm Hg.
• Controlled blood pressure reduces atherosclerosis-related diseases and events like strokes.

Clinical Signs of Cardiovascular Issues

• Cyanosis: Bluish skin indicative of reduced oxygen levels.
• Xanthelasma: Yellowish cholesterol deposits around the eyes.
• Leg edema: Swelling in the legs due to fluid retention associated with heart dysfunction.