Circulatory System Overview

Double Circulation

• Double circulation is a process involving two circuits: pulmonary and systemic.
• Pulmonary (minor) circulation: This circuit carries deoxygenated blood from the right ventricle to the lungs via the pulmonary artery. Oxygenation occurs in the alveoli, and the oxygenated blood returns to the left atrium via pulmonary veins.
• Systemic (major) circulation: Oxygenated blood leaves the left ventricle via the aorta, distributing oxygen throughout the body through capillaries. Deoxygenated blood returns to the right atrium via the vena cavae.

The Heart and Cardiac Cycle

• Heart Structure: The heart's right atrium receives deoxygenated blood from the vena cavae. The right ventricle pumps this blood to the lungs. Oxygenated blood from the lungs enters the left atrium and is pumped to the body through the aorta. A septum separates the right and left sides of the heart. The heart wall is composed of myocardium.
• Cardiac Cycle: The heart's rhythmic pumping involves systole (contraction) and diastole (relaxation).
  • Atrial systole: Atria contract, pushing blood into the ventricles.
  • Ventricular systole: Ventricles contract, forcing blood into the pulmonary arteries and aorta.
  • Diastole: Atria and ventricles relax, allowing blood to fill the heart for the next cycle.
• Heart Rate Abnormalities: Problems with valve function can cause murmurs or arrhythmias (irregular heartbeats). Bradycardia (slow heart rate) is less than 60 beats per minute (bpm), and tachycardia (fast heart rate) exceeds 100 bpm. Normal heart rate is 60-100 bpm. Measure heart rate by counting for 30 seconds and multiplying by 2.

Blood and Blood Vessels

• Blood Composition: Blood is a viscous, red fluid consisting of:
  • Plasma (65%): Yellowish liquid (water, salts, proteins, waste)
  • Erythrocytes (44%): Red blood cells; carry oxygen via hemoglobin.
  • Leukocytes (1%): White blood cells; fight infection.
  • Platelets (1%): Cell fragments; involved in blood clotting.
• Blood Vessels: Three types of blood vessels transport blood:
  • Arteries: Carry blood away from the heart. Strong, thick walls to handle pressure.
  • Veins: Carry blood toward the heart. Thinner walls, contain valves to prevent back flow.
  • Capillaries: Microscopic vessels connecting arterioles and venules. Very thin walls for gas and nutrient exchange with cells.

Function of the Heart

• The heart pumps blood to the lungs for oxygenation and to the body for delivering oxygen and nutrients to cells.

This quiz covers the double circulation process involving pulmonary and systemic circuits. You'll explore how blood flows through the heart, including the structure of the heart and the cardiac cycle. Test your knowledge on the pathways of oxygenated and deoxygenated blood.