Blood Cells, ABO Blood Groups, Heart Conditions and the Lymphatic System (ICSE Class 8 Biology)
Updated 17 October 2026 · Fact-checked
RBCs carry oxygen; WBCs fight germs. In the ABO system O is the universal donor and AB the universal acceptor. Palpitations are a rapid or irregular heartbeat, cardiac arrest is the sudden stopping of the pumping, and hypertension is persistently high blood pressure. Lymph, a plasma-like fluid with white cells, forms a parallel circulation that returns tissue fluid to the blood.
Follow the arrows: O can give to every group (universal donor), and AB can receive from every group (universal acceptor).
Illustration drawn for QuestionBuddy.
Understand Blood Cells, Blood Groups, Heart Conditions and the Lymphatic System
Blood is plasma carrying RBCs, WBCs and platelets.
| RBCs | WBCs | |
|---|---|---|
| Shape | small biconcave discs | larger, irregular |
| Nucleus | none in mature human RBCs | present |
| Pigment | haemoglobin (red, iron) | none |
| Function | carry O₂ from lungs to tissues | fight infection: engulf germs or make antibodies |
| Number | very many | far fewer |
Blood groups (ABO). Four groups, A, B, AB and O, decided by markers on RBCs. A wrong transfusion makes RBCs clump, which can be fatal, so blood is matched first.
| Group | Can give to | Can receive from |
|---|---|---|
| A | A, AB | A, O |
| B | B, AB | B, O |
| AB | AB | all (universal acceptor) |
| O | all (universal donor) | O |
O RBCs carry neither A nor B marker; AB plasma has no antibodies against A or B.
Heart conditions.
- Palpitations: awareness of a fast, strong or irregular heartbeat; follows exercise, fear, too much tea or coffee or fever and is often harmless; see a doctor if frequent or with chest pain, dizziness or breathlessness.
- Cardiac arrest: the heart suddenly stops pumping effectively; the person collapses with no pulse. Help: call for medical help, give CPR (chest compressions) and use a defibrillator if available.
- Hypertension: blood pressure stays higher than normal for a long time (normal adult about 120/80 mm Hg). Risks include salt, obesity, smoking, alcohol, stress and lack of exercise; strains the heart and can cause heart attack, stroke and kidney damage. Prevention: less salt, exercise, no smoking, stress control, check-ups.
Lymphatic system (parallel circulation).
- Some plasma leaks from capillaries and bathes cells as tissue fluid.
- Extra fluid enters thin lymph vessels and is called lymph: pale yellow, with lymphocytes (WBCs) but no RBCs.
- Lymph flows slowly through lymph nodes (neck, armpits, groin) that filter germs, and drains into large veins near the neck.
- Functions: returns tissue fluid to the blood; fights infection; carries digested fats from the intestine.
Functions to remember. Heart: pumps blood. RBC: carry oxygen. WBC: defence. Lymph: drains fluid, defends, carries fat.
Flow chart. Capillary → tissue fluid → lymph vessels → lymph nodes → large vein near the neck → blood.
Blood Cells, Blood Groups, Heart Conditions and the Lymphatic System: key facts
- RBC and WBC
- RBC: no nucleus, haemoglobin, carries oxygen | WBC: nucleus, no haemoglobin, defence
- RBCs far outnumber WBCs.
- ABO donor chart
- O gives to all
- AB takes from all
- A gives to A, AB
- B gives to B, AB
- O universal donor; AB universal acceptor.
- Conditions and lymph
Palpitations fast heartbeat Cardiac arrest pumping stops, CPR Hypertension high BP 120/80 normal Lymph WBCs, no RBCs - Lymph returns to veins.
How to answer Blood Cells, Blood Groups, Heart Conditions and the Lymphatic System questions
Expect a table of donors and recipients, a transfusion judgement, definitions of the three heart conditions, and the comparison of blood and lymph.
- 1For transfusion, check the donor group against what the recipient can receive.
- 2Use O as donor to all and AB as acceptor from all.
- 3Define each heart condition with one cause or action.
- 4For lymph, say it has WBCs but no RBCs and drains to veins.
- 5Give two points when comparing RBCs and WBCs.
Blood Cells, Blood Groups, Heart Conditions and the Lymphatic System in real life
The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.
Camp of donors
Suppose a hospital needs blood for four patients of groups A, B, AB and O, and a donor camp brings in a donor of group O.
Which patients can receive the O blood and why?
Try it first, then show the solutionSolution
- Group O RBCs carry neither A nor B marker.
- So they are not clumped by the antibodies in any recipient.
- All four patients can receive it.
Answer: All four, because O is the universal donor.
Memory hook: O gives to all.
Swollen gland in the neck
Suppose a child with a sore throat develops tender lumps on both sides of the neck, which settle when the infection ends.
What are the lumps and why did they swell?
Try it first, then show the solutionSolution
- They are lymph nodes, found in the neck, armpits and groin.
- Lymph nodes filter germs from lymph and contain lymphocytes.
- During infection they work harder and swell, then settle.
Answer: Lymph nodes swell as they filter germs from lymph during an infection.
Memory hook: Nodes are the body's germ filters.
Tricks to remember Blood Cells, Blood Groups, Heart Conditions and the Lymphatic System
Short memory aids. Say each one aloud once, then use it on a question the same day.
O is zero markers
Group O has no A or B marker, so it can be given to all.
Use it when: Universal donor.
AB takes all
AB accepts from every group.
Use it when: Universal acceptor.
Lymph has no red
Lymph is pale because it lacks RBCs.
Use it when: Blood versus lymph.
Blood Cells, Blood Groups, Heart Conditions and the Lymphatic System: solved examples
Ordered from board level to HOTS. Try each one before you open the solution.
Example 1: Universal acceptor · 1 mark · MCQBoard level
The group that can receive blood from all four groups is:
(a) A (b) B (c) AB (d) O
Try it first, then show the solutionSolution
- AB plasma has no antibodies against A or B.
Answer: (c).
Example 2: Expand and define · 2 marks · Short answerBoard level
Define hypertension and give two ways of preventing it.
Try it first, then show the solutionSolution
- Blood pressure that stays higher than normal for a long time (1 mark).
- Less salt and oily food, exercise, no smoking, stress control (any two) (1 mark).
Answer: Persistently high BP; less salt and regular exercise.
Example 3: Who can give to whom · 3 marks · Short answerHarder board level
Use the chart to answer: (a) To which groups can group A blood be given? (b) From which groups can a group O person receive blood? (c) Why can a group O person not receive group A blood?
Try it first, then show the solutionSolution
- (a) A and AB (1 mark).
- (b) O only (1 mark).
- (c) Group O plasma has antibodies against the A marker, which would clump the donor's RBCs (1 mark).
Answer: (a) A, AB. (b) O only. (c) Antibodies in O plasma clump A cells.
Example 4: Compare · 4 marks · Long answerHarder board level
Give four differences between RBCs and WBCs.
Try it first, then show the solutionSolution
- RBCs are small biconcave discs; WBCs are larger and irregular (1 mark).
- Mature human RBCs have no nucleus; WBCs have a nucleus (1 mark).
- RBCs have haemoglobin; WBCs do not (1 mark).
- RBCs carry oxygen; WBCs fight infection; RBCs are far more numerous (1 mark).
Answer: Shape, nucleus, haemoglobin, function and number.
Example 5: Lymph or blood · 4 marks · Case-basedHOTS / competency
A fluid sample is pale yellow, contains many lymphocytes, no RBCs, and flows slowly in thin vessels through nodes. (a) Name it. (b) Give two functions. (c) Why is it called a parallel circulation?
Try it first, then show the solutionSolution
- (a) Lymph (1 mark).
- (b) Returns tissue fluid to the blood; fights infection; carries digested fats (any two) (1 mark).
- (c) It forms a second system of vessels alongside the blood vessels (1 mark).
- It finally drains into large veins near the neck, joining the blood circulation (1 mark).
Answer: Lymph; returns fluid and fights infection; runs parallel to blood and joins it.
Where students lose marks in Blood Cells, Blood Groups, Heart Conditions and the Lymphatic System
The slips examiners see most often, and what to write instead.
Mistake: Calling AB the universal donor
Universal is read as all, giving and taking confused.
Do this: O gives; AB takes.
Usually costs: 1 mark.
Mistake: Writing that lymph contains RBCs
Lymph and blood are treated alike.
Do this: Lymph has plasma-like fluid and WBCs, but no RBCs.
Usually costs: 1 mark.
Mistake: Cardiac arrest and heart attack as the same
Both are heart emergencies.
Do this: Cardiac arrest is stopped pumping; heart attack is a blocked supply to the muscle.
Usually costs: 1 mark.
Mistake: Only one point in RBC and WBC differences
Answers give only function.
Do this: Write shape, nucleus, pigment, function and number.
Usually costs: 1 mark.
Exam tips
- O gives to all; AB takes from all.
- Normal adult blood pressure about 120/80 mm Hg.
- Lymph: WBCs, no RBCs, returns to veins near the neck.
- Name CPR and defibrillator for cardiac arrest.
Practice questions on Blood Cells, Blood Groups, Heart Conditions and the Lymphatic System
Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.
Q1 · 1 mark · Very short answerBoard level
What is cardiac arrest?
Hint
Pumping stops.
Answer
The sudden stopping of the heart's effective pumping, so that the person collapses with no pulse.
Q2 · 1 mark · Assertion-reasonHarder board level
Assertion (A): A person of blood group AB can receive blood from any group.
Reason (R): The plasma of group AB has no antibodies against the A or B marker.
(a) (A) is true and (R) is false.
(b) (A) is false and (R) is true.
(c) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(d) Both (A) and (R) are true, but (R) is not the correct explanation of (A).Hint
Antibodies.
Answer
(c).
Q3 · 3 marks · Short answerHarder board level
A person suddenly collapses, has no pulse and is not breathing normally. State the condition and three steps a bystander should take.
Hint
Call, compress, shock.
Answer
Cardiac arrest. Call for medical help, begin CPR with chest compressions, and use a defibrillator if one is available.
Q4 · 4 marks · Long answerHarder board level
Explain why blood must be matched before a transfusion, and why O is called the universal donor. Mention what happens in a wrong match.
Hint
Clumping.
Answer
In a wrong match the recipient's antibodies clump the donor's RBCs, which can block vessels and be fatal. Group O RBCs carry neither A nor B marker, so they are not clumped by anyone's antibodies, which makes O the universal donor.
Q5 · 3 marks · Case-basedHOTS / competency
Read and answer.
Suppose a 55-year-old man has blood pressure 160/100 mm Hg on three visits and often eats very salty food.
(a) Name the condition. (1)
(b) Compare his pressure with the normal value. (1)
(c) Name two organs at risk. (1)Hint
Normal is 120/80.
Answer
(a) Hypertension. (b) It is 40 mm Hg higher in the first figure and 20 mm Hg higher in the second than 120/80. (c) Heart and kidneys (or brain, through stroke).
Test your recall
Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.
1.Which pigment gives RBCs their colour?Show answer
Haemoglobin.
2.Which group is the universal donor?Show answer
O.
3.What do lymph nodes do?Show answer
Filter germs from lymph.
4.What is the normal adult blood pressure?Show answer
About 120/80 mm Hg.
5.What machine can restart a heart rhythm?Show answer
A defibrillator.
Blood Cells, Blood Groups, Heart Conditions and the Lymphatic System: frequently asked questions
Is the Rh factor needed in Class 8?
The syllabus names only the A, B, AB and O groups.
Are palpitations always serious?
No, but frequent ones or those with chest pain need a doctor.
Is the lymphatic system detailed?
Only an introduction is required.
Where is the heart structure covered?
In the previous topic.