The Circulatory System and The Heart

Overview

• The circulatory system is an organ system that transports oxygen and nutrients to the body's tissues.
• It relies on three main components:
  • Blood: Carries oxygen and nutrients.
  • Blood vessels: Hold and transport the blood.
  • Heart: Pumps the blood through the vessels.

Double Circulatory System

• The circulatory system is a double loop system:
  • One loop carries deoxygenated blood from the heart to the lungs, gets oxygen, then returns to the heart.
  • The other loop carries oxygenated blood from the heart to the body, delivers oxygen, becomes deoxygenated, and returns to the heart.

Structure of the Heart

• The heart has four chambers with thick muscular walls: two atria (top chambers) and two ventricles (bottom chambers).
• It has veins and arteries coming in and out.
• Key points about heart diagrams:
  • Left side of the heart is on our right in diagrams.
  • Right side of the heart is on our left in diagrams.

Chambers and Valves

• Atria: Top chambers (singular: atrium).
• Ventricles: Bottom chambers.
• Valves: Located between chambers and vessels, prevent backward flow of blood.

Blood Flow Through the Heart

1. Blood enters the heart via the vena cava (deoxygenated) and pulmonary vein (oxygenated).
2. Flows into the right atrium and left atrium, respectively.
3. Atria contract, pushing blood into the ventricles.
4. Ventricles contract, pushing blood into the pulmonary artery (to lungs) and aorta (to body).
5. Atria refill with new blood, and the cycle repeats ~70 times per minute (~100,000 times daily).

Pacemaker Function

• Pacemaker cells: Located in the right atrium, produce electrical impulses causing heart contractions.
• Artificial pacemakers: Implanted device to regulate heartbeats when natural pacemakers fail.

Arteries vs. Veins

• Artery: Carries blood away from the heart.
• Vein: Carries blood to the heart.
• Pulmonary artery carries deoxygenated blood (still an artery).
• Pulmonary vein carries oxygenated blood (still a vein).

Coronary Arteries

• Supply the heart muscle with oxygenated blood.
• Branch off from the aorta and encircle the heart.

Summary

• Heart structure, function, and circulatory system mechanisms.
• Importance of valves, pacemaker cells, and coronary arteries.