Circulatory System Overview

Lecture Introduction

• Presenter: Andy from Med School EU
• Focus: Anatomy and physiology of the circulatory system
• Breakdown: Two-part video series
  • Video 1: Blood vessels, blood circulation, and blood components
  • Video 2: Heart anatomy and functions

Circulatory System Pathway

1. Right Ventricle

   • Pumps deoxygenated blood into pulmonary arteries
   • Pulmonary arteries carry blood to the lungs

2. Pulmonary Circulation

   • Blood becomes oxygenated in the lungs via capillaries
   • Oxygenated blood returns to the heart via pulmonary veins

3. Left Atrium and Ventricle

   • Blood enters left atrium from pulmonary veins
   • Left ventricle pumps oxygenated blood into the aorta

4. Systemic Circulation

   • Aorta distributes oxygenated blood to the body
   • Blood returns deoxygenated via superior and inferior vena cava

5. Right Atrium

   • Cycle repeats as blood flows back into the right atrium

Blood Vessel Anatomy

Arteries and Veins

• Outer Layer: Connective tissue
• Middle Layer: Tunica media (smooth muscle and elastic fibers)
  • Thicker in arteries to handle high pressure
• Inner Layer: Endothelium
• Veins: Contain one-way valves to prevent backflow

Capillaries

• Composed solely of endothelium
• Site of gas exchange

Arterioles and Venules

• Arterioles: Control blood flow into capillaries by dilating or constricting
• Venules: Gather blood from capillaries to veins

Blood Volume and Components

Blood Volume

• Males: 5-6 liters
• Females: 4-5 liters
• Comprises 6-8% of body mass
• 20% of extracellular fluid

Blood Composition

• Plasma:

  • Yellowish liquid
  • Makes up 55% of blood
  • Functions as volume filler and clotting factor

• Formed Elements: 45%

  • Buffy Coat: 1%
    • Platelets (thrombocytes) and white blood cells (leukocytes)
  • Red Blood Cells (Erythrocytes): 99% of formed elements

Conclusion

• Next video will focus on heart anatomy and physiology