The Cardiovascular System: The Heart – Structure, Function, and Pathology

The Cardiovascular System: The Heart

Introduction

The heart is the central organ of the cardiovascular system, responsible for pumping blood throughout the body. It ensures the delivery of oxygen and nutrients to tissues and the removal of waste products. Understanding the heart's anatomy, physiology, and associated pathologies is essential for students of anatomy and physiology.

Latin and Medical Terminology

• Angio-: Vessel

• Ather-: Fatty deposit

• Brady-: Slow

• Diastol-: Stand apart (relaxation phase)

• Edem-: Swelling

• -gram: Record

• Lun-: Moon (often refers to the lungs)

• Myo-: Muscle

• Papill-: Nipple

• Phleb-: Vein

• Scler-: Hard

• Syn-: Together

• Systol-: Contraction

• Tachy-: Fast

Cardiovascular Organization

Circuits

• Pulmonary Circuit: Carries oxygen-poor blood from the right side of the heart to the lungs and returns oxygen-rich blood to the left side of the heart.

• Systemic Circuit: Delivers oxygen-rich blood from the left side of the heart to the body and returns oxygen-poor blood to the right side.

Structures

• Heart

• Blood vessels (arteries, veins, capillaries)

• Blood

• Associated membranes and connective tissues

Heart - Superficial Anatomy and Membranes

Pericardium

• Parietal Pericardium: Outer layer, lines the pericardial cavity.

• Visceral Pericardium (Epicardium): Inner layer, covers the heart surface.

• Pericardial Cavity: Space between parietal and visceral layers, contains pericardial fluid.

• Pericardial Fluid: Reduces friction between heart and pericardial sac during contractions.

Wall of the Heart

• Epicardium (Visceral pericardium)

  • Function: Reduces friction.

  • Composed of: Connective tissue, capillaries, nerve fibers, and adipose tissue in deeper layers.

• Myocardium

  • Function: Pumps blood out of the heart chambers.

  • Composed of: Cardiac muscle tissue.

• Endocardium

  • Function: Inner lining of all heart chambers, continuous with inner lining of blood vessels.

  • Composed of: Epithelium, connective tissue, elastic and collagen fibers, covers Purkinje fibers.

Heart - Superficial Anatomy

• Auricles (L & R): Flap-like extensions of the atria.

• Coronary Sulcus: Groove separating atria from ventricles.

• Anterior and Posterior Interventricular Sulci: Grooves marking the position of the septum between the ventricles.

Heart - Chamber Anatomy

• Atria: Upper chambers receiving blood returning to the heart.

• Ventricles: Lower chambers pumping blood out of the heart.

• Atrioventricular (AV) Valves:

  • Tricuspid (Right AV): Between right atrium and right ventricle.

  • Mitral/Bicuspid (Left AV): Between left atrium and left ventricle.

• Semilunar Valves:

  • Pulmonary: Entrance to pulmonary trunk.

  • Aortic: Entrance to aorta.

• Chordae Tendineae: Tendinous cords attaching AV valve cusps to papillary muscles, preventing valve prolapse.

Heart - Vessel Anatomy

• Superior Vena Cava: Returns deoxygenated blood from upper body to right atrium.

• Inferior Vena Cava: Returns deoxygenated blood from lower body to right atrium.

• Pulmonary Arteries: Carry deoxygenated blood from right ventricle to lungs.

• Pulmonary Veins: Carry oxygenated blood from lungs to left atrium.

• Aorta: Main artery carrying oxygenated blood from left ventricle to body.

Heart - Blood Flow

1. Deoxygenated blood enters right atrium via superior and inferior vena cava.

2. Passes through tricuspid valve into right ventricle.

3. Pumped through pulmonary valve into pulmonary arteries to lungs.

4. Oxygenated blood returns via pulmonary veins to left atrium.

5. Passes through mitral valve into left ventricle.

6. Pumped through aortic valve into aorta and systemic circulation.

Cardiac Muscle

• Cardiac muscle cells have a single, centrally located nucleus.

• Cells are connected by intercalated discs, allowing rapid transmission of electrical impulses.

• Cardiac muscle functions as a functional syncytium (acts as a single coordinated unit).

The Conducting System

• Autorhythmicity: The heart generates its own electrical impulses.

• Pacemaker Cells:

  • Sinoatrial (SA) Node: Initiates heartbeat, located in right atrium.

  • Atrioventricular (AV) Node: Delays impulse, allowing atria to contract before ventricles.

• Conducting Cells:

  • Internodal Pathways: Connect SA and AV nodes.

  • Atrioventricular Bundle (Bundle of His): Conducts impulse from AV node to ventricles.

  • Bundle Branches: Carry impulses through interventricular septum.

  • Purkinje Fibers: Distribute impulse through ventricular myocardium.

Electrocardiogram (ECG) Waves

• P wave: Atrial depolarization (contraction).

• QRS complex: Ventricular depolarization (contraction).

• T wave: Ventricular repolarization (recovery).

Additional Cardiovascular Vocabulary

• Heart Sounds:

  • S1 (lubb): Closure of AV valves during ventricular systole.

  • S2 (dubb): Closure of semilunar valves during ventricular diastole.

• Cardiac Output: Volume of blood pumped by each ventricle per minute.

  • Formula: $\text{Cardiac Output} = \text{Heart Rate} \times \text{Stroke Volume}$

• Cardioacceleratory Center: Increases heart rate via sympathetic stimulation.

• Cardioinhibitory Center: Decreases heart rate via parasympathetic stimulation.

Pathologies

Pericarditis

• Causes: Viral/bacterial infection, myocardial infarction, trauma, advanced lung cancer, dissecting aortic aneurysm.

• Symptoms: Sharp, stabbing pain posterior to sternum, worsened by breathing or lying down.

• Results: Pericardial layers rub together, causing friction and pressure on the heart (may lead to cardiac tamponade).

• Treatment: Antibiotics (if bacterial), anti-inflammatory drugs.

Cardiac Tamponade

• Symptoms: Increased pressure in right atrium, visible neck vein engorgement, anxiety, difficulty breathing, palpitations, pallor, chest pain.

• Treatment: Pericardiocentesis (removal of excess pericardial fluid with a syringe).

Mitral Valve Prolapse

• Definition: One or both cusps of the mitral valve bulge into the left atrium during ventricular contraction.

• Symptoms: Chest pain, palpitations, fatigue, anxiety; increased risk of endocarditis.

• Treatment: Beta blockers, surgery (mitral valve repair).

Summary Table: Heart Wall Layers

Layer	Location	Function	Main Components
Epicardium	Outer	Reduces friction	Connective tissue, capillaries, nerves, adipose
Myocardium	Middle	Pumps blood	Cardiac muscle tissue
Endocardium	Inner	Lines chambers, covers valves	Epithelium, connective tissue, Purkinje fibers

Example: Cardiac Output Calculation

If the heart rate is 75 beats per minute and the stroke volume is 70 mL per beat:

$\text{Cardiac Output} = 75 \times 70 = 5250$ mL/min or 5.25 L/min

Additional info:

• Some slide content was inferred and expanded for clarity and completeness.

• Images referenced in the slides were described and their academic context provided.