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Understanding How the Heart Works

Apr 23, 2025

How the Normal Heart Works

Overview

  • The heart is a vital muscular organ responsible for circulating blood throughout the body.
  • Located in the center of the chest, it functions continuously, even during sleep.
  • The heart and blood vessels constitute the cardiovascular system, essential for delivering oxygen and nutrients.
  • Blood picks up oxygen in the lungs, then circulates through the body via the heart.

Structure of the Heart

  • Two-sided Pump:
    • Consists of the right and left sides.
    • Contains four chambers: two atria (upper) and two ventricles (lower).
  • Chambers:
    • Right atrium and ventricle pump oxygen-poor blood to lungs.
    • Left atrium and ventricle pump oxygen-rich blood through the body.
  • Septa (Septa/Septum):
    • Divide the heart into two sides, preventing blood mix.

Heart Valves

  • Tricuspid Valve: Between right atrium and right ventricle.
  • Pulmonary Valve: Between right ventricle and pulmonary artery.
  • Mitral Valve: Between left atrium and left ventricle.
  • Aortic Valve: Between left ventricle and aorta.

Blood Circulation Process

  • Major Veins & Arteries:
    • Superior and Inferior Vena Cava: Carry oxygen-poor blood to right atrium.
    • Blood flows through tricuspid valve to right ventricle.
    • Right ventricle pumps blood to lungs via pulmonary valve and artery.
    • Pulmonary Veins: Bring oxygen-rich blood to left atrium.
    • Blood flows through mitral valve to left ventricle.
    • Left ventricle pumps blood into aorta via aortic valve.
    • Blood distributed throughout the body, delivering oxygen.

Heart's Control System

  • Heartbeat initiated by electrical impulse from sinus node, the heart's pacemaker.
  • Sinus node located in the top right atrium.
  • Electrical signals cause atria and ventricles to contract, pumping blood.

Transition after Birth

  • Ductus Venosus: Stops carrying blood post-birth, begins constricting in hours/days.
  • First breath expands lungs, reduces pressure, promotes blood flow to lungs.
  • Ductus Arteriosus: Constricts, fully closes within 24-48 hours, blood directed to lungs.
  • Foramen Ovale: Closes as left atrium pressure increases after birth.

Contact Information

  • For more details, contact the Cardiac Center at Children's Hospital of Philadelphia.
  • Outpatient appointments and inquiries: 215-590-4040.
  • Second opinions and referrals: 267-426-9600.
  • Visit Cardiac Center for more information.