IB MYP Integrated Science- Biology - Structure of the heart & Blood vessels-Study Notes - New Syllabus

Structure of the Heart & Blood Vessels

🌟 Introduction

The heart and blood vessels together form the circulatory system.
The heart pumps blood, and the vessels distribute it throughout the body.
Goal: supply oxygen + nutrients and remove wastes.

Structure of the Heart

The heart is a muscular, cone-shaped organ located slightly left of the chest.
Made of cardiac muscle (does not fatigue easily).

A. External Structure

• Protected by pericardium (double-layered membrane).
• Filled with pericardial fluid to reduce friction.
• Has 4 chambers:
  • Upper: Right atrium, Left atrium
  • Lower: Right ventricle, Left ventricle
• Left ventricle is the thickest because it pumps blood to the whole body.

B. Internal Structure

1. Right Atrium

• Receives deoxygenated blood from the body through:
  • Superior vena cava
  • Inferior vena cava

2. Right Ventricle

• Pumps deoxygenated blood to the lungs through the pulmonary artery.
• Has the tricuspid valve between right atrium and right ventricle.

3. Left Atrium

• Receives oxygenated blood from the lungs through pulmonary veins (only veins carrying oxygen rich blood).

4. Left Ventricle

• Pumps oxygenated blood to the whole body through the aorta.
• Has the bicuspid (mitral) valve between left atrium and left ventricle.

C. Valves in the Heart

Valves ensure one-way flow and prevent backflow.

Atrioventricular (AV) Valves:

• Tricuspid (right side)
• Bicuspid/Mitral (left side)

Semilunar Valves:

• Pulmonary valve
• Aortic valve

D. Double Circulation

Pulmonary circulation:
Heart → Lungs → Heart
(Blood becomes oxygenated)

Systemic circulation:
Heart → Body → Heart
(Delivers oxygen, picks up wastes)

– Ensures efficient oxygen supply.
– Maintains high pressure.

Blood Vessels

Three major types: arteries, veins, capillaries.

Arteries

• Carry blood away from the heart.
• Usually carry oxygenated blood (except pulmonary artery).
• Thick, elastic walls to handle high pressure.
• Narrow lumen.

Function: Transport blood under high pressure.

Veins

• Carry blood toward the heart.
• Usually carry deoxygenated blood (except pulmonary vein).
• Thin walls, large lumen.
• Have valves to prevent backflow (pressure is low).

Function: Return blood to the heart at low pressure.

Capillaries

• Smallest, one-cell-thick vessels.
• Connect arteries and veins.
• Allow exchange of gases, nutrients, wastes.

Function: Diffusion between blood and tissues.

📋 Summary Table

🧠 Quick Recap
Heart has 4 chambers: RA, RV, LA, LV.
Left ventricle = strongest (thickest wall).
Valves: tricuspid (right), bicuspid (left), plus 2 semilunar.
Pulmonary artery is the only artery with deoxygenated blood.
Pulmonary vein is the only vein with oxygenated blood.
Arteries = thick walls, no valves.
Veins = thin walls, have valves.
Capillaries = one-cell thick, exchange happens here.