Cardio

Cardiovascular System Overview

Introduction to the Cardiovascular System

  • Cardiovascular system: A closed circuit consisting of heart and blood vessels (arteries, capillaries, veins).

  • Essential for supplying oxygen and nutrients to tissues, and removing waste.

  • Arteries: Transport blood away from the heart.

  • Veins: Transport blood toward the heart.

  • Capillaries: Vessels connecting arteries and veins, where gas exchange occurs.

  • Pulmonary circuit: Carries oxygen-poor blood to the lungs; picks up oxygen and releases carbon dioxide.

  • Systemic circuit: Delivers oxygen-rich blood to body cells; collects carbon dioxide in return.

Structure of the Heart

  • General features: Hollow, cone-shaped muscular pump located in the mediastinum.

  • Size: Average adult heart size - 14 cm long, 9 cm wide.

  • Location: Between the lungs, anterior to the vertebral column, behind the sternum.

  • Position: Base below the second rib, apex extends to the fifth intercostal space.

Coverings of the Heart

  • Pericardium: Membranous sac enclosing the heart.

    • Fibrous pericardium: Outer layer, tough connective tissue.

    • Serous pericardium: Inner double-layered (parietal and visceral), secretes serous fluid to reduce friction.

Heart Wall

  • Composed of three layers:

    • Epicardium: Outermost layer; decreases friction.

    • Myocardium: Thick middle layer; cardiac muscle responsible for heart contractions.

    • Endocardium: Inner layer; continuous with blood vessel endothelium, contains Purkinje fibers.

Heart Chambers and Valves

  • Four chambers:

    • Atria: Receive blood returning to the heart; thin walls.

    • Ventricles: Pump blood out; thicker walls.

  • Valves: Ensure one-way blood flow:

    • Atrioventricular (AV) valves: Tricuspid (right) and mitral (left) valves prevent backflow during contraction.

    • Semilunar valves: Prevent backflow into the ventricles.

Blood Flow Through the Heart

  • Oxygen-poor blood returns to the right atrium via venae cavae.

  • Blood flows from the right atrium → tricuspid valve → right ventricle → pulmonary semilunar valve → pulmonary trunk → lungs.

  • Oxygen-rich blood returns to the left atrium through pulmonary veins → mitral valve → left ventricle → aortic semilunar valve → aorta.

Heart Actions

  • Cardiac cycle:

    • Atrial systole (contraction) occurs while ventricles relax (diastole).

    • Ventricles contract while atria relax.

    • Brief moment of complete relaxation follows.

Cardiac Conduction System

  • Specialized heart muscle conducts impulses for contraction.

  • Key components:

    • SA Node: Pacemaker in right atrium.

    • AV Node: Delays signal, allowing atria to finish contracting.

    • AV Bundle and Purkinje fibers: Spread impulses through ventricles.

Electrocardiogram (ECG)

  • Records electrical changes during the cardiac cycle:

    • P Wave: Atrial depolarization.

    • QRS Complex: Ventricular depolarization (atria repolarization hidden).

    • T Wave: Ventricular repolarization.

Blood Vessels Overview

  • Types of blood vessels: Arteries, arterioles, capillaries, venules, veins.

  • Arteries: Carry blood under high pressure (thick walls).

  • Capillaries: Microscopic, allow exchange of gases, nutrients, and wastes.

  • Veins: Return blood to the heart, equipped with valves to prevent backflow.

Blood Pressure

  • Definition: Force of blood against vessel walls.

  • Systolic Pressure: Max pressure during heart contraction.

  • Diastolic Pressure: Min pressure during heart relaxation.

  • Measurements: Normal range is 120/80 mm Hg.

Summary of Key Components

  • The cardiovascular system consists of heart chambers, valves, and a network of blood vessels delivering oxygen and nutrients while removing waste products.

  • Proper functioning of the cardiovascular system is essential for maintaining overall health.