Circulatory System Table

Explore the **Heart**, **Blood Vessels**, and **Blood Cells**. Anatomy & Physiology Guide.

The Heart

Right Atrium

Heart Chamber

Upper right chamber. Receives oxygen-poor blood from the body via Vena Cavae and pumps it to the right ventricle.

Flow:Body → Right Ventricle
Pacemaker (SA Node) is here.

Right Ventricle

Heart Chamber

Lower right chamber. Pumps deoxygenated blood to the lungs via Pulmonary Artery for oxygenation.

Flow:Right Atrium → Lungs
Thinner walls than Left Ventricle.

Left Atrium

Heart Chamber

Upper left chamber. Receives oxygen-rich blood from the lungs via Pulmonary Veins.

Flow:Lungs → Left Ventricle
Receives blood from 4 pulmonary veins.

Left Ventricle

Heart Chamber

Lower left chamber. Pumps oxygenated blood to the entire body via the Aorta. Has the thickest muscular wall.

Flow:Left Atrium → Body
Generates highest pressure.

Blood Vessels

Arteries

Blood Vessel

Thick-walled, elastic vessels carrying high-pressure blood AWAY from the heart. Mostly oxygenated (except Pulmonary Artery).

Flow:Heart → Body/Lungs
Pulse is felt in arteries.

Veins

Blood Vessel

Thin-walled vessels carrying low-pressure blood TOWARDS the heart. Have valves to prevent backflow. Mostly deoxygenated (except Pulmonary Vein).

Flow:Body/Lungs → Heart
Contain ~65% of body's blood.

Capillaries

Blood Vessel

Microscopic vessels (one cell thick) connecting arteries and veins. Site of gas, nutrient, and waste exchange with tissues.

Flow:Arteries → Veins
Total length ≈ 100,000 km.

Blood Components

Arteries

Blood Vessel

Thick-walled, elastic vessels carrying high-pressure blood AWAY from the heart. Mostly oxygenated (except Pulmonary Artery).

Flow:Heart → Body/Lungs
Pulse is felt in arteries.

Veins

Blood Vessel

Thin-walled vessels carrying low-pressure blood TOWARDS the heart. Have valves to prevent backflow. Mostly deoxygenated (except Pulmonary Vein).

Flow:Body/Lungs → Heart
Contain ~65% of body's blood.

Capillaries

Blood Vessel

Microscopic vessels (one cell thick) connecting arteries and veins. Site of gas, nutrient, and waste exchange with tissues.

Flow:Arteries → Veins
Total length ≈ 100,000 km.

Red Blood Cells (RBC)

Blood Cell

Erythrocytes. Biconcave discs containing Hemoglobin to carry Oxygen. No nucleus in mammals to maximize space.

Function:Oxygen Transport
Lifespan is about 120 days.

White Blood Cells (WBC)

Blood Cell

Leukocytes. Fight infections and foreign bodies. Include lymphocytes, monocytes, neutrophils, etc.

Function:Immunity & Defense
Increase during infection.

Platelets

Blood Cell

Thrombocytes. Cell fragments that clump together to stop bleeding (coagulation) at injury sites.

Function:Blood Clotting
Smallest blood cells.

Plasma

Blood Fluid

Yellowish liquid making up 55% of blood. Transports nutrients, hormones, CO₂, and waste products.

Function:Transport Medium
90% water.

Human Circulatory System: Critical Study Notes

The circulatory system (cardiovascular system) acts as a transport network. It delivers essential supplies like oxygen and glucose to cells and removes toxic waste products like carbon dioxide and urea.

Anatomy of the Heart

Right Side (Deoxygenated)

  • Right Atrium
    Receives CO₂-rich blood from Vena Cava.
  • Right Ventricle
    Pumps blood to Lungs via Pulmonary Artery.

Left Side (Oxygenated)

  • Left Atrium
    Receives O₂-rich blood from Lungs via Pulmonary Veins.
  • Left Ventricle
    Pumps blood to Body via Aorta (Highest Pressure).

Double Circulation Explained

Loop 1

Pulmonary Circulation

Transport of blood between Heart and Lungs.

RT Ventricle → Pulmonary Artery → Lungs → Pulmonary Vein → LT Atrium
Loop 2

Systemic Circulation

Transport of blood between Heart and Body Tissues.

LT Ventricle → Aorta → Body Tissues → Vena Cava → RT Atrium

Composition of Blood

55%
Plasma

Liquid matrix carrying water, salts, nutrients.

44%
RBCs

Carry Oxygen. Contains Hemoglobin.

<1%
WBCs

Immune Defense. Fight infections.

<1%
Platelets

Blood Clotting at injury sites.

Frequently Asked Questions

What is Double Circulation?

Double Circulation means blood passes through the heart twice for each complete circuit of the body. It consists of Pulmonary Circulation (Heart ↔ Lungs) and Systemic Circulation (Heart ↔ Body).

What is difference between Arteries and Veins?

Arteries carry oxygenated blood AWAY from the heart at high pressure (thick walls, no valves). Veins carry deoxygenated blood TOWARDS the heart at low pressure (thin walls, have valves).

Why is the Left Ventricle wall thicker?

The Left Ventricle pumps blood to the entire body (Systemic circulation), requiring much higher pressure than the Right Ventricle, which only pumps to the nearby lungs.

What is the function of Hemoglobin?

Hemoglobin is an iron-containing protein in Red Blood Cells that binds to oxygen in the lungs and transports it to tissues throughout the body.

What is the "Pacemaker" of the heart?

The Sinoatrial (SA) Node, located in the Right Atrium, generates electrical impulses that set the rhythm and rate of the heart beat.

What are Capillaries?

Capillaries are microscopic blood vessels where arterials and venules meet. Their walls are only one cell thick, allowing easy exchange of oxygen, nutrients, and waste with tissues.

Which blood vessel carries oxygenated blood to the heart?

The Pulmonary Vein is the only vein that carries oxygenated blood (from Lungs to Left Atrium). All other veins carry deoxygenated blood.

What is the lifespan of a Red Blood Cell?

Red Blood Cells (RBCs) live for approximately 120 days before being broken down by the spleen and liver.

What prevents backflow of blood in the heart?

Valves (Tricuspid, Bicuspid/Mitral, and Semilunar valves) ensure blood flows in only one direction, preventing it from flowing backwards.

What is the composition of Blood?

Blood is composed of Plasma (55% fluid) and Formed Elements (45%): Red Blood Cells, White Blood Cells, and Platelets.