Body Fluids and Circulation NEET Notes 2026 – Important Points, Tricks, Mnemonics & MCQs

1. Most Important Points to Remember (HighYield for NEET)

 1️⃣ Blood Composition

Blood = Plasma (55%) + Formed elements (45%) 

Plasma

•  90–92% water
•  6–8% proteins
•  Major plasma proteins:
•  Fibrinogen → clotting
•  Globulin → immunity
•  Albumin → osmotic balance

⚠ Trick to remember:

FGA = Fight, Guard, Adjust

•  Fibrinogen → Forms clot
•  Globulin → Guards body
•  Albumin → Adjusts osmotic pressure

 2️⃣ Formed Elements

 RBC (Erythrocytes)

Key facts for NEET:

Features	Value
Count	5-5.5 million/mm3
Life Span	120 Days
Formation	Red Bone Marrow
Destruction	Spleen (Graveyard of RCBs)

Function: Transport O₂ and CO₂ via haemoglobin.

WBC (Leucocytes)

Count: 6000–8000/mm³

Types:

Granulocytes

•  Neutrophils (60–65%)
•  Eosinophils (2–3%)
•  Basophils (0.5–1%)

Agranulocytes

•  Lymphocytes (20–25%)
•  Monocytes (6–8%)

Mnemonic:

Never Eat Bad Lunch Monday

• N – Neutrophils
• E – Eosinophils
• B – Basophils
• L – Lymphocytes
• M – Monocytes

 Platelets

•  Count: 1.5–3.5 lakh/mm³
•  Function: Blood clotting

Produced from megakaryocytes.

3️⃣ Blood Groups (Very Frequently Asked)

 ABO Blood Group System

Blood Group	Antigen	Antibody
A	A	Anti-B
B	B	Anti-A
AB	A+B	none
O	none	Anti-A and Anti-B

Important NEET Facts:

•  O → Universal Donor
•  AB → Universal Recipient 

Mnemonic:

• O Gives All
• AB Takes All

 Rh Factor

•  Rh antigen present → Rh+
•  Rh antigen absent → Rh−

 Rh Incompatibility

Disease:

Erythroblastosis Fetalis

Occurs when:

Rh mother + Rh+ fetus

4️⃣ Blood Clotting Mechanism

Sequence (NEET favourite):

Prothrombin → Thrombin

Fibrinogen → Fibrin

Key factor:

Calcium ions essential

Simple trick:

PTF Rule

• P → Prothrombin
• T → Thrombin
• F → Fibrin

5️⃣ Lymph

Features:

•  Colourless fluid
•  Contains lymphocytes
•  Transports fats

Important NEET point:

Lacteals absorb fats

6️⃣ Types of Circulatory System

Type	Example
Open	Arthropods
Closed	Vertebrates

 7️⃣ Heart Evolution (Very Important)

Organism	Chambers
Fish	2
Amphibians	3
Reptiles	3
Crocodile	4
Birds	4
Mammals	4

Mnemonic:

• Fish → 2
• Amphibian → 3
• Reptile → 3
• Bird & Mammal → 4

8️⃣ Human Heart (Very Important)

Heart chambers:

•  Right Atrium
•  Right Ventricle
•  Left Atrium
•  Left Ventricle

Valves:

Valve	Position
Tricuspid	RA-RV
Bicuspid	LA-LV
Semilunar	Aorta and Pulmanory artery

 9️⃣ Pacemaker of the Heart

Pacemaker = Sinoatrial Node (SAN)

Reason:

Highest rate of impulse generation 70–75/min. 

10️⃣ Cardiac Cycle (VERY IMPORTANT)

Duration:

0.8 seconds

Heart rate:

72 beats/min

Stroke Volume:

70 ml

Cardiac Output Formula:

\text{Cardiac Output} = \text{Stroke Volume} \times \text{Heart Rate}

Normal cardiac output:

≈ 5 litres/min

11️⃣ Heart Sounds

Sound	Cause
Lub	Closure of AV Valves
Dub	Closure of Semilunar Valves

 12️⃣ ECG Waves

Wave	Meaning
P Wave	Atrial Depolarization
QRS	Ventricular Depolarization
T Wave	Ventricular Repolarization

Major Mistakes Students Make in This Chapter

Mistake 1

Confusing plasma and serum

Correct:

Serum = Plasma − Clotting factors

Mistake 2

Wrong RBC count

Correct:

5–5.5 million/mm³

Mistake 3

Confusing universal donor

Correct:

O group

Mistake 4

Thinking pacemaker = AV node

Correct:

SAN

Mistake 5

Misunderstanding cardiac cycle duration

Correct:

0.8 seconds

Quick Revision Tricks for NEET

 Trick for WBC functions

NEBLM

• Neutrophil → phagocytosis
• Eosinophil → allergy
• Basophil → histamine
• Lymphocyte → immunity
• Monocyte → macrophage

Heart Valve Trick

Try Pulling My Aorta

T → Tricuspid

P → Pulmonary

M → Mitral

A → Aortic

Analytical NEET Level Questions

Question 1: Which blood group can donate blood to all groups?

1. A
2. B
3. O
4. AB

Answer: C

Question 2: The pacemaker of heart is:

1. AV node
2. SA node
3. Purkinje fibers
4. Bundle of His

Answer: B

Question 3: Correct sequence of blood clotting:

1. Prothrombin → Thrombin → Fibrinogen
2. Fibrinogen → Fibrin → Prothrombin
3. Prothrombin → Thrombin → Fibrin
4. Thrombin → Prothrombin → Fibrin

Answer: C

Question 4: Which WBC is most abundant?

1. Basophil
2. Neutrophil
3. Monocyte
4. Lymphocyte

Answer: B

Expected NEET Questions From This Chapter (2026)

Most probable topics:

1️⃣ Blood groups

2️⃣ Cardiac cycle

3️⃣ ECG waves

4️⃣ SAN pacemaker

5️⃣ Double circulation

6️⃣ WBC functions