Cardiovascular System: Heart//STUDIED

The Organization of the Cardiovascular System

• Pulmonary Circuit: Carries blood to and from the lungs for gas exchange.
• Systemic Circuit: Carries blood to and from the rest of the body.
• Blood Vessels:
  • Arteries: Carry blood away from the heart.
  • Veins: Carry blood to the heart.
  • Capillaries: Small, thin-walled vessels between arteries and veins.
• Chambers of the Heart:
  • Right atrium: Collects blood from the systemic circuit.
  • Right ventricle: Pumps blood to the pulmonary circuit.
  • Left atrium: Collects blood from the pulmonary circuit.
  • Left ventricle: Pumps blood to the systemic circuit.

Anatomy of the Heart

• Located in the mediastinum, posterior to the sternum.
• Base: Flatter top where large vessels attach.
• Apex: Pointed tip.
• Pericardium:
  • Pericardial cavity lined with pericardium (pericardial sac).
  • Visceral pericardium: Inner layer, adherent to the heart.
  • Parietal pericardium: Outer layer.
  • Pericardial fluid: Lubricates layers.
  • Pericarditis: Inflammation of the pericardium.
  • Cardiac tamponade: Excess fluid compresses the heart.

Superficial Anatomy of the Heart

• Atria: Thin-walled chambers with auricles.
• Ventricles: Thick-walled chambers.
• Coronary sulcus: Divides atria and ventricles.
• Interventricular sulci: Separate right and left ventricles.

The Heart Wall

• Epicardium: Outer layer (same as visceral pericardium).
• Myocardium: Middle, muscular layer.
• Endocardium: Inner epithelial lining.
• Cardiac Muscle Tissue:
  • Striated, single nucleus, involuntary.
  • Intercalated discs: Allow rapid action potential travel.

Internal Anatomy and Organization

• Interatrial septum: Divides atria.
• Interventricular septum: Divides ventricles.
• Atrioventricular (AV) valves: One-way flow from atria to ventricles.
• Right Atrium:
  • Receives blood from the superior and inferior vena cava.
  • Auricle: Expandable portion.
• Right Ventricle:
  • Papillary muscles and chordae tendineae prevent valve inversion.
  • Thinner wall than left ventricle.
  • Blood exits through the pulmonary trunk to pulmonary arteries.
• Left Atrium:
  • Receives blood from pulmonary veins.
• Left Ventricle:
  • Papillary muscles and chordae tendineae.
  • Thicker wall than right ventricle.
  • Blood exits through the aorta to the systemic circuit.
• Atrioventricular Valves:
  • Right AV valve (tricuspid): Three flaps.
  • Left AV valve (bicuspid/mitral): Two flaps.
• Semilunar Valves:
  • Pulmonary semilunar valve: Base of pulmonary trunk.
  • Aortic semilunar valve: Base of aorta.

Abnormalities of Blood Flow through the Heart

• Murmurs: Indicate turbulent blood flow.
• Regurgitation/Insufficiency: Backflow due to incomplete valve closure.
• Stenosis: Narrowed valve opening.

The Fetal Heart

• Foramen ovale: Bypasses pulmonary circuit, shunting blood from right atrium to left atrium.
• Ductus arteriosus: Connects pulmonary trunk and aorta, bypassing fetal lungs.

Blood Supply to the Heart

• Coronary circulation supplies blood to heart muscle.
• Coronary Arteries:
  • Right coronary artery: Supplies right atrium, parts of both ventricles, SA and AV nodes.
  • Left coronary artery: Supplies left atrium, left ventricle, interventricular septum.
• Cardiac Veins: Return blood from heart muscle to right atrium.

The Heartbeat

• Cardiac Physiology
  • Atria contract then ventricles.
• Cardiac Cycle: Electrical event recorded on ECG.
• Conducting System:
  • SA node (pacemaker) → AV node → AV Bundle → bundle branches → Purkinje fibers
• Electrocardiogram (ECG):
  • P-wave: Atrial contraction.
  • QRS complex: Ventricular contraction.
  • T-wave: Ventricular repolarization.
• Abnormalities of the Heartbeat:
  • Bradycardia: Less than 60 BPM.
  • Tachycardia: Greater than 100 BPM.

Cardiodynamics

• Stroke Volume: Volume of blood ejected per beat.
• Cardiac Output: CO (ml/min) = heart rate (beats/min) X stroke volume (ml/beat)

Factors Affecting Heart Rate

• Parasympathetic stimulation: Slows heart (acetylcholine).
• Sympathetic stimulation: Speeds heart (epinephrine and norepinephrine).

Overview of Cardiovascular Pressures

• Arterial Blood Pressure:
  • Systolic pressure: Peak pressure during ventricular systole.
  • Diastolic pressure: Lowest pressure during ventricular diastole.
  • Pulse pressure: Difference between systolic and diastolic pressure.
  • Hypertension: Abnormally high blood pressure ( > 140/90).
  • Hypotension: Abnormally low blood pressure.

Cardiovascular Regulation

• Tissue Perfusion is affected by:
  • Cardiac output
  • Peripheral resistance
  • Blood pressure
• Regulatory Mechanisms:
  • Autoregulation: Localized adjustments (vasodilators, vasoconstrictors).
  • Neural Mechanisms: Medulla oblongata (cardiovascular centers), baroreceptors.
  • Hormonal Regulation: ADH, angiotensin II, erythropoietin, natriuretic peptides (ANP, BNP).