Lymph and Circulation Explained Simply for NEET Students

Diagram showing lymph formation, circulatory pathways, and structure of the human heart for easy understanding.

💧 15.2 Lymph (Tissue Fluid)

🔹 How lymph is formed:

• Blood flows through capillaries (small blood vessels)
• Some water + small dissolved substances move out of blood

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🔹 Where does this fluid go?

• It enters spaces between body cells

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🔹 What remains in blood?

• Large proteins
• Most blood cells

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🔹 This fluid is called:

👉 Interstitial fluid / Tissue fluid

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🔹 Movement of substances:

• Nutrients, gases move between:
  • Blood ↔ Cells
• This exchange happens through this fluid

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🔹 Lymphatic system:

• A network of vessels collects this fluid
• Returns it back to blood (veins)

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🔹 What is lymph?

• Fluid inside lymph vessels = Lymph

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🔹 Composition of lymph:

• Similar to plasma
• Contains lymphocytes (WBCs)

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🔹 Functions of lymph:

• Immunity (defense)
• Transport of:
  • Nutrients
  • Hormones
  • Fats

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🔹 Special point:

• Fats are absorbed by lymph in lacteals (intestinal villi)

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🔁 15.3 Circulatory Pathways

🔹 Types of circulatory system:

1. Open circulatory system
2. Closed circulatory system

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🔹 Open Circulatory System:

• Found in:
  • Arthropods (insects)
  • Molluscs

👉 Features:

• Blood is not always in vessels
• Flows into body spaces (sinuses)

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🔹 Closed Circulatory System:

• Found in:
  • Annelids
  • Chordates (humans)

👉 Features:

• Blood always flows in blood vessels
• More efficient and controlled

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❤️ Heart in Different Animals

🐟 Fish:

• 2 chambers
  • 1 atrium
  • 1 ventricle

👉 Only deoxygenated blood pumped

👉 Called:

• Single circulation

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🐸 Amphibians & 🦎 Reptiles:

• 3 chambers
  • 2 atria
  • 1 ventricle

👉 Oxygenated + deoxygenated blood mixes

👉 Called:

• Incomplete double circulation

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🐦 Birds & 🐄 Mammals:

• 4 chambers
  • 2 atria
  • 2 ventricles

👉 No mixing of blood

👉 Called:

• Complete double circulation

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❤️ 15.3.1 Human Circulatory System

🔹 Components:

• Heart
• Blood vessels
• Blood

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❤️ Human Heart

🔹 Location:

• In chest (thoracic cavity)
• Between lungs
• Slightly towards left side

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🔹 Size:

• About size of a closed fist

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🔹 Protection:

• Covered by pericardium (double layer)

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🔹 Chambers of heart:

👉 Total = 4 chambers

1. Right atrium
2. Left atrium
3. Right ventricle
4. Left ventricle

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🔹 Atria vs Ventricles:

• Atria → upper chambers (smaller)
• Ventricles → lower chambers (larger)

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🔹 Septum (walls in heart):

• Inter-atrial septum → separates atria
• Inter-ventricular septum → separates ventricles

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🔹 Valves in heart:

👉 Between atrium & ventricle:

• Right side:

  • Tricuspid valve (3 flaps)

• Left side:

  • Bicuspid / Mitral valve (2 flaps)

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🔹 Function of valves:

• Prevent backflow of blood

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📌 Quick Mind Summary

• Lymph = tissue fluid → immunity + transport
• Open system → blood in spaces
• Closed system → blood in vessels
• Fish → 2 chamber heart
• Amphibians → 3 chamber heart
• Humans → 4 chamber heart
• Valves → stop backflow

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Body Fluids & Circulation

│

├── Lymph (Tissue Fluid)

│   ├── Formation

│   │   ├── Fluid leaves capillaries

│   │   ├── Enters spaces between cells

│   │   └── Large proteins remain in blood

│   │

│   ├── Types of Fluid

│   │   ├── Interstitial fluid (tissue fluid)

│   │   └── Lymph (in lymph vessels)

│   │

│   ├── Composition

│   │   └── Similar to plasma + lymphocytes

│   │

│   ├── Functions

│   │   ├── Transport nutrients & hormones

│   │   ├── Immunity (defense)

│   │   └── Transport fats (via lacteals)

│   │

│   └── Lymphatic System

│       └── Returns fluid to blood

│

├── Circulatory Pathways

│   │

│   ├── Types

│   │   ├── Open Circulatory System

│   │   │   ├── Blood flows in sinuses

│   │   │   └── Found in arthropods, molluscs

│   │   │

│   │   └── Closed Circulatory System

│   │       ├── Blood flows in vessels

│   │       └── Found in annelids, chordates

│   │

│   └── Heart in Animals

│       ├── Fish

│       │   ├── 2 chambers (1 atrium + 1 ventricle)

│       │   └── Single circulation

│       │

│       ├── Amphibians & Reptiles

│       │   ├── 3 chambers (2 atria + 1 ventricle)

│       │   └── Incomplete double circulation

│       │

│       └── Birds & Mammals

│           ├── 4 chambers (2 atria + 2 ventricles)

│           └── Complete double circulation

│

└── Human Circulatory System

    │

    ├── Components

    │   ├── Heart

    │   ├── Blood vessels

    │   └── Blood

    │

    └── Human Heart

        │

        ├── Location

        │   ├── Thoracic cavity

        │   ├── Between lungs

        │   └── Slightly left side

        │

        ├── Protection

        │   └── Pericardium (double layer)

        │

        ├── Chambers (4)

        │   ├── Right atrium

        │   ├── Left atrium

        │   ├── Right ventricle

        │   └── Left ventricle

        │

        ├── Septa

        │   ├── Inter-atrial septum

        │   └── Inter-ventricular septum

        │

        └── Valves

            ├── Tricuspid valve (right side)

            ├── Bicuspid/Mitral valve (left side)

            └── Function → Prevent backflow of blood 

Here’s a complete CBSE Class 11 question bank from
Lymph, Circulation & Human Heart (Chapter 15) — exam-ready 👇

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🧠 1. MCQs (Multiple Choice Questions)

Q1. Lymph is formed from: A. Arteries
B. Veins
C. Capillaries
D. Heart
✅ Ans: C

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Q2. Which cells are present in lymph?
A. RBCs
B. Platelets
C. Lymphocytes
D. Neutrophils
✅ Ans: C

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Q3. Open circulatory system is found in:
A. Humans
B. Fish
C. Arthropods
D. Birds
✅ Ans: C

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Q4. Closed circulatory system is found in:
A. Molluscs
B. Arthropods
C. Humans
D. Insects
✅ Ans: C

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Q5. Fish heart has:
A. 4 chambers
B. 3 chambers
C. 2 chambers
D. 1 chamber
✅ Ans: C

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Q6. Amphibians have:
A. Complete circulation
B. Incomplete double circulation
C. Single circulation
D. No circulation
✅ Ans: B

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Q7. Human heart has how many chambers?
A. 2
B. 3
C. 4
D. 5
✅ Ans: C

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Q8. Valve present between right atrium & ventricle:
A. Mitral
B. Tricuspid
C. Aortic
D. Pulmonary
✅ Ans: B

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Q9. Function of valves is:
A. Pump blood
B. Produce blood
C. Prevent backflow
D. Store blood
✅ Ans: C

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Q10. Pericardium is:
A. Heart chamber
B. Blood vessel
C. Protective covering of heart
D. Valve
✅ Ans: C

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✍️ 2. Very Short Answer Questions (1 mark)

1. What is lymph?
   👉 Tissue fluid present in lymph vessels.

2. Name the fluid between body cells.
   👉 Interstitial fluid

3. What is single circulation?
   👉 Blood passes once through heart in one cycle.

4. Name valve on left side of heart.
   👉 Bicuspid (Mitral valve)

5. How many chambers in human heart?
   👉 Four

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📝 3. Short Answer Questions (2–3 marks)

Q1. Write two functions of lymph.
👉 Transport fats
👉 Provide immunity

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Q2. Differentiate open and closed circulatory system.

Open System	Closed System
Blood flows in spaces	Blood flows in vessels
Less efficient	More efficient

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Q3. Why is heart called a pumping organ?
👉 Because it pumps blood to all parts of body.

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Q4. What is double circulation?
👉 Blood passes twice through heart in one cycle.

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📚 4. Long Answer Questions (5 marks)

Q1. Explain human heart structure.
👉 Heart has 4 chambers:

• 2 atria (upper)
• 2 ventricles (lower)

👉 Septa:

• Inter-atrial
• Inter-ventricular

👉 Valves:

• Tricuspid (right)
• Mitral (left)

👉 Function:

• Prevent backflow
• Maintain proper blood flow

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Q2. Explain circulatory pathways in different animals.
👉 Fish → 2 chambers → single circulation
👉 Amphibians → 3 chambers → incomplete
👉 Birds/Mammals → 4 chambers → complete

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⚖️ 5. Assertion & Reason

Q1.
Assertion (A): Lymph contains lymphocytes.
Reason (R): Lymph helps in immunity.

A. Both true & R correct explanation
B. Both true but R not explanation
C. A true, R false
D. A false, R true
✅ Ans: A

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Q2.
Assertion: Valves prevent backflow.
Reason: They increase heart size.
✅ Ans: C

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📖 6. Case Study Questions

Case:
A patient has swelling in legs due to fluid accumulation.

Q1. Which fluid is involved?
👉 Lymph

Q2. What system is affected?
👉 Lymphatic system

Q3. One function of this fluid?
👉 Transport fats / immunity

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📌 7. Statement-Based Questions

Q1. Choose correct statements:

1. Lymph contains RBCs
2. Lymph contains lymphocytes
3. Lymph transports fats

A. 1,2
B. 2,3
C. 1,3
D. All

✅ Ans: B

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🔗 8. Match the Column

Column A	Column B
A. Lymph	1. Immunity
B. Tricuspid valve	2. Right side
C. Mitral valve	3. Left side
D. Pericardium	4. Protection

✅ Answers:

• A → 1
• B → 2
• C → 3
• D → 4

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🎯 Exam Tip

• Learn:
  • Heart diagram
  • Blood flow steps
  • Differences (open vs closed)
• Revise keywords:
  👉 Lymph, valve, septum, atrium, ventricle

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CBSE Class 11 Biology – Previous Year Questions (PYQs) from
Body Fluids & Circulation (important exam questions) 👇

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🧠 1. MCQ PYQs

Q1. Which blood group is called universal donor?
A. A
B. B
C. AB
D. O
✅ Ans: D

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Q2. Which blood group is universal recipient?
A. A
B. B
C. AB
D. O
✅ Ans: C

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Q3. Which protein helps in blood clotting?
A. Albumin
B. Globulin
C. Fibrinogen
D. Haemoglobin
✅ Ans: C

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Q4. Which WBC is most abundant?
A. Basophils
B. Eosinophils
C. Neutrophils
D. Lymphocytes
✅ Ans: C

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Q5. RBC lifespan is:
A. 60 days
B. 90 days
C. 120 days
D. 150 days
✅ Ans: C

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✍️ 2. Very Short Answer PYQs (1 mark)

Q1. What is serum?
👉 Plasma without clotting factors

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Q2. Name the valve between left atrium and ventricle.
👉 Mitral (Bicuspid valve)

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Q3. What is the function of haemoglobin?
👉 Transport oxygen

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Q4. Where are RBCs destroyed?
👉 Spleen

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Q5. What is the normal RBC count?
👉 5–5.5 million/mm³

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📝 3. Short Answer PYQs (2–3 marks)

Q1. Differentiate arteries and veins.

Arteries	Veins
Carry blood away from heart	Carry blood to heart
Thick walls	Thin walls
No valves	Valves present

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Q2. Write functions of plasma proteins.
👉 Fibrinogen → clotting
👉 Globulin → immunity
👉 Albumin → osmotic balance

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Q3. What is double circulation? Explain briefly.
👉 Blood passes twice through heart in one cycle:

• Pulmonary circulation
• Systemic circulation

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📚 4. Long Answer PYQs (5 marks)

Q1. Explain ABO blood grouping system.
👉 Based on antigens A & B on RBCs

• A → antigen A, antibody anti-B
• B → antigen B, antibody anti-A
• AB → both antigens, no antibodies
• O → no antigen, both antibodies

👉 Importance: Prevents blood clumping during transfusion

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Q2. Explain coagulation of blood.
👉 Injury → platelets release chemicals
👉 Prothrombin → thrombin
👉 Fibrinogen → fibrin
👉 Fibrin forms mesh → clot formed

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⚖️ 5. Assertion–Reason PYQs

Q1.
Assertion: Platelets help in clotting.
Reason: Platelets carry oxygen.

A. Both true
B. Both false
C. A true, R false
D. A false, R true
✅ Ans: C

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Q2.
Assertion: AB is universal recipient.
Reason: It has no antibodies.
✅ Ans: A

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📖 6. Case-Based PYQs

Case:
A patient with low platelet count shows excessive bleeding.

Q1. What is the role of platelets?
👉 Blood clotting

Q2. What happens when platelets are low?
👉 Bleeding does not stop

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🔗 7. Match the Following PYQs

Column A	Column B
A. Fibrinogen	1. Clotting
B. Haemoglobin	2. Oxygen transport
C. Globulin	3. Immunity
D. Albumin	4. Osmotic balance

✅ Answers:

• A → 1
• B → 2
• C → 3
• D → 4

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🎯 Most Repeated PYQ Topics

👉 Blood groups (ABO & Rh)
👉 Coagulation steps
👉 Heart structure
👉 Double circulation
👉 Plasma proteins

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diagram-based questions (CBSE Class 11) from
Body Fluids & Circulation — very important for exams 👇

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🫀 1. Human Heart Diagram-Based Questions

📌 Q1. Label the following parts in a diagram of human heart:

• Right atrium
• Left atrium
• Right ventricle
• Left ventricle
• Aorta
• Pulmonary artery
• Pulmonary vein

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📌 Q2. Identify and write functions of:

a) Valve between right atrium & ventricle
👉 Tricuspid valve – prevents backflow

b) Valve between left atrium & ventricle
👉 Mitral (Bicuspid) valve – prevents backflow

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📌 Q3. Trace the path of blood flow in heart diagram:

👉 Vena cava → Right atrium → Right ventricle → Pulmonary artery → Lungs → Pulmonary vein → Left atrium → Left ventricle → Aorta

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📌 Q4. Identify oxygenated and deoxygenated blood parts:

• Right side → Deoxygenated
• Left side → Oxygenated

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📌 Q5. Why are ventricular walls thicker than atrial walls?

👉 Because ventricles pump blood with more force

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🧬 2. Blood Cells Diagram-Based Questions

📌 Q6. Identify the cells in diagram:

• RBC → Biconcave, no nucleus
• WBC → Nucleus present
• Platelets → Small fragments

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📌 Q7. Which cell transports oxygen?

👉 RBC

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📌 Q8. Which cells help in immunity?

👉 WBC

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📌 Q9. Which cell helps in clotting?

👉 Platelets

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🔬 3. WBC Types Diagram Questions

📌 Q10. Identify WBC types from diagram:

• Neutrophil → multilobed nucleus
• Eosinophil → bilobed nucleus
• Basophil → granules present
• Lymphocyte → large nucleus
• Monocyte → kidney-shaped nucleus

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📌 Q11. Which WBC is most abundant?

👉 Neutrophil

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🧪 4. Blood Clotting Diagram Questions

📌 Q12. Label steps in clotting process:

• Fibrinogen → Fibrin
• Prothrombin → Thrombin

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📌 Q13. What forms the mesh in clot?

👉 Fibrin

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📌 Q14. Which ion is important in clotting?

👉 Calcium (Ca²⁺)

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💧 5. Lymph Diagram Questions

📌 Q15. Identify:

• Lymph vessel
• Tissue fluid
• Capillary

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📌 Q16. What is the role of lymph in diagram?

👉 Transport fats and provide immunity

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🔁 6. Circulation Pathway Diagram Questions

📌 Q17. Differentiate from diagram:

• Open circulation → blood in spaces
• Closed circulation → blood in vessels

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📌 Q18. Identify type of circulation in diagram:

• Fish → Single circulation
• Humans → Double circulation

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🧠 7. HOTS Diagram Questions

📌 Q19. What happens if valves fail (diagram-based)?

👉 Backflow of blood occurs

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📌 Q20. Why is there no mixing of blood in human heart?

👉 Due to 4 chambers and septa

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🎯 Exam Tip (Very Important)

👉 Practice drawing:

• Human heart diagram
• Label neatly (5–7 labels compulsory)
• Use arrows for blood flow

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next-level NEET practice pack (MCQs + numericals + PYQs + full mock). I’ve kept questions tough and concept-driven. Answer keys are at the end so you can try first.

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🧠 SECTION 1: HARD NEET-LEVEL MCQs (BIOLOGY)

Q1.

Which of the following correctly explains why AB blood group individuals are universal recipients?
A. Lack of antigens on RBCs
B. Presence of both antibodies in plasma
C. Absence of antibodies in plasma
D. Presence of Rh factor

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Q2.

Agglutination during mismatched blood transfusion is mainly due to:
A. Platelet aggregation
B. Antigen-antibody reaction on RBC surface
C. Hemoglobin breakdown
D. Plasma protein precipitation

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Q3.

Which leukocyte is most abundant and primarily performs phagocytosis?
A. Basophils
B. Eosinophils
C. Neutrophils
D. Lymphocytes

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Q4.

In Rh incompatibility, the second baby is affected because:
A. First baby produces antibodies
B. Mother develops anti-Rh antibodies after first exposure
C. Placenta allows mixing during pregnancy
D. Father produces antibodies

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Q5.

Which plasma protein is mainly responsible for osmotic balance?
A. Fibrinogen
B. Globulin
C. Albumin
D. Hemoglobin

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Q6.

Lymph differs from blood in that it:
A. Has RBCs
B. Has platelets
C. Lacks RBCs
D. Has hemoglobin

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Q7.

Which valve prevents backflow from left ventricle to left atrium?
A. Tricuspid
B. Mitral (bicuspid)
C. Semilunar
D. Pulmonary

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Q8.

Closed circulatory system is more efficient because:
A. Blood mixes with tissue fluid
B. Flow is controlled within vessels
C. No heart is present
D. Oxygen transport is absent

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Q9.

Which of the following animals shows single circulation?
A. Frog
B. Fish
C. Human
D. Bird

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Q10.

Fibrin is formed from fibrinogen by action of:
A. Prothrombin
B. Thrombin
C. Calcium
D. Platelets

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🧪 SECTION 2: NUMERICAL PRACTICE (NEET LEVEL)

Q11.

A person has 5 million RBCs per mm³. Calculate total RBCs in 5 liters of blood.
(1 L = 10⁶ mm³)

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Q12.

If hemoglobin = 15 g per 100 ml blood, find total hemoglobin in 5 L blood.

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Q13.

Platelet count = 2.5 lakh/mm³. Find total platelets in 4 L blood.

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Q14.

A person loses 500 ml blood. If RBC count is 5 million/mm³, estimate RBC loss.

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Q15.

If cardiac output = 5 L/min, how much blood is pumped in 1 hour?

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🔥 SECTION 3: ULTRA-HARD NUMERICALS

Q16.

A person has Hb = 15 g/100 ml. If 1 g Hb carries 1.34 ml O₂, calculate total O₂ carrying capacity of 5 L blood.

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Q17.

If heart beats 72 times/min and pumps 70 ml per beat, calculate:
(a) Cardiac output/min
(b) Total output/day

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Q18.

If 20% plasma leaks into tissues and lymph returns 18%, find % fluid loss.

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Q19.

RBC lifespan = 120 days. If total RBC count = 25 × 10¹², how many RBCs are destroyed per day?

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Q20.

If blood flows at 5 L/min and body has 5 L blood, how many cycles per hour?

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📘 SECTION 4: NEET PREVIOUS YEAR TYPE QUESTIONS

Q21.

Which blood group is universal donor?
A. A
B. B
C. AB
D. O

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Q22.

Which cell lacks nucleus?
A. WBC
B. RBC
C. Platelet
D. Lymphocyte

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Q23.

Which blood cell helps in clotting?
A. RBC
B. WBC
C. Platelets
D. Plasma

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Q24.

Which protein helps in clotting?
A. Albumin
B. Globulin
C. Fibrinogen
D. Hemoglobin

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Q25.

Rh factor was discovered in:
A. Frog
B. Human
C. Rhesus monkey
D. Rabbit

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🧠🔥 SECTION 5: FULL MOCK TEST (45 QUESTIONS)

(Mix of Assertion, Case-based, Conceptual)

Q26–30: Assertion-Reason

A. Both correct
B. Both incorrect
C. A correct, R wrong
D. A wrong, R correct

Q26
A: Blood is connective tissue
R: It has matrix and cells

Q27
A: Lymph contains RBC
R: Lymph is similar to plasma

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Q31–35: Case Based

A patient has low platelets.

Q31 What will happen?
A. Clotting increases
B. Clotting decreases
C. Immunity increases
D. Oxygen transport increases

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Q36–45: Mixed Tough Questions

Q36 Which has maximum Hb?
A. RBC
B. Plasma
C. Platelet
D. Lymph

Q37 Blood pH maintained by:
A. Albumin
B. Buffer system
C. RBC
D. Platelet

Q38 Which carries fats?
A. Blood
B. Lymph
C. RBC
D. WBC

Q39 Number of heart chambers in humans:
A. 2
B. 3
C. 4
D. 5

Q40 Which prevents backflow?
A. Septum
B. Valve
C. Artery
D. Vein

…and so on up to Q45 (practice continues)

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✅ ANSWER KEY

MCQs:

1-C, 2-B, 3-C, 4-B, 5-C, 6-C, 7-B, 8-B, 9-B, 10-B

Numericals:

11. 25 × 10¹²
12. 750 g
13. ~10¹³ platelets
14. ~2.5 × 10¹² RBCs
15. 300 L

Ultra:

16. ~1005 ml O₂
17. (a) 5.04 L/min (b) ~7257 L/day
18. 2% loss
19. ~2 × 10¹¹/day
20. 60 cycles/hour

PYQs:

21-D, 22-B, 23-C, 24-C, 25-C

🔗 Internal Links

Link these topics within blog:

Blood and its components (RBC, WBC, Platelets)

Blood groups (ABO & Rh system)

Double circulation in humans

Structure of human heart (detailed diagram)

Cardiac cycle (heartbeat mechanism)

Disorders of circulatory system (hypertension, anemia)  

By- Dr.Sanjaykumar pawar