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ICSE Class 8 Biology Question 9 of 16

The Circulatory System — Question 3

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Question 1(c)

Karl Landsteiner classified human blood into four categories on the basis of proteins (antigens) found on the surface of the RBCs. Compatibility of blood groups must be checked during blood transfusion. Which of the following statements are incorrect ?

P. Blood group 'AB' is the universal donor as it does not contain any antibodies.

Q. Blood group 'AB' is the universal recipient as it contains both the antigens 'A' and 'B'.

R. Blood group 'O' is the universal recipient as it does not contain any antigens.

  1. Only R
  2. Only P and R
  3. Only P and Q
  4. Only Q and R
Answer

Only P and R

Reason — Blood group 'AB' has antigens A and B so people with AB blood group can receive blood from all types, while Blood group 'O' has neither antigen A nor B, so people with blood group O can give their blood to all the groups but can only receive blood from O blood types. Hence, a person with AB blood group is called a universal recipient, and a person with O blood group is called a universal donor.

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Biology | Chapter 8: Circulatory SystemWeb Content

Circulatory System – Interactive Study Guide

Quick Overview

The circulatory system transports blood, oxygen, nutrients, and hormones throughout the body. It consists of the heart (pump), blood (transport medium), and blood vessels (pipelines).

Blood Components

ComponentFunctionKey Fact
Plasma (55%)Transports dissolved substances90% water, carries nutrients, hormones, waste
RBCCarry oxygenBiconcave disc, no nucleus, contain haemoglobin
WBCFight infectionsHave nucleus, larger than RBC, immune defence
PlateletsBlood clottingCell fragments, no nucleus

Blood Group Quick Reference

ABO System

O = Universal Donor (no antigens) | AB = Universal Recipient (no antibodies)

GroupAntigenAntibody
AAanti-B
BBanti-A
ABA & BNone
ONoneanti-A & anti-B

Heart – Quick Facts

  • 4 chambers: RA, RV, LA, LV
  • 4 valves: Tricuspid (R), Bicuspid (L), 2 Semilunar
  • Septum divides right (deoxy) from left (oxy)
  • Left ventricle = thickest wall

Double Circulation

Two Circuits

Pulmonary: RV → Pulmonary artery → Lungs → Pulmonary veins → LA

Systemic: LV → Aorta → Body → Vena cava → RA

Blood Vessels Comparison

ArteriesVeinsCapillaries
DirectionAway from heartTo heartConnect A to V
WallsThickThin1 cell thick
ValvesNoYesNo

Self-Test Questions

Test Yourself
  1. Why is the left ventricle wall thicker than the right?
  2. Draw and label the human heart.
  3. What is double circulation? Describe both circuits.
  4. Why is blood group O called universal donor?
  5. What is the function of valves in veins?

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