Circulatory System and Blood

5 min

Study of Heart, Vessels, and Blood Components

The Core Concept

The heart pumps blood through arteries to the body and returns it via veins. Blood carries oxygen using RBCs, protects via WBCs, and stops bleeding using Platelets.

Exam Importance

High weightage in SSC CGL, Railway NTPC, and State Police exams.
Direct questions on Blood Groups (ABO) and Rh factor are very common.
Must-know topic for understanding human physiology and diseases.

Memory Shortcuts

A for Arteries = 'Away' from the heart (carry pure blood).
WBC = 'Warriors' (Fight infections and provide immunity).
O- (O Negative) = 'Original' Universal Donor.

Arteries vs. Veins

Feature	Arteries	Veins
Direction	Heart to Body	Body to Heart
Blood Type	Oxygenated	Deoxygenated
Wall	Thick & Elastic	Thin
Valves	Absent	Present

Blood Components

RBC

(Oxygen Transport)

Oxygen Transport

Contains Hemoglobin for oxygen.

WBC

(Immunity Guard)

Immunity Guard

Fights germs and viruses.

Platelets

(Clotting Factor)

Clotting Factor

Prevents excessive blood loss.

Plasma

(Liquid Matrix)

Liquid Matrix

Makes up 55% of blood.

Common Exam Traps

Universal donor is O PositiveUniversal donor is O Negative

O Negative lacks all antigens, making it truly universal.

All arteries carry oxygenated bloodPulmonary artery carries CO2 blood

The only artery carrying deoxygenated blood is the Pulmonary artery.

AB Negative is the universal recipientAB Positive is the universal recipient

AB Positive can receive any blood type safely.

Quick Check

Q1.Which blood component is responsible for carrying oxygen?

Q2.Which blood group is known as the Universal Recipient?

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