Important Notes on Body Fluids and Circulation for NEET

NEET Preparation: Important Notes of Biology for NEET Body Fluids and Circulation

During the last-minute preparation for NEET, revision is the most important activity. It not only help memorise the topic but also increases your accuracy. However, during this time, revising entire chapters may not seem feasible due to the vastness of NEET syllabus. Thus, a chapter-wise note, like important notes of biology for NEET body fluids and circulation, can be helpful for your final revisions.

This post includes important notes on body fluids and circulation. It covers all the necessary body fluids and circulation class 11 notes that are vital for NEET 2020 exam.

Body Fluids and Circulation Notes


  • Body fluids are a type of fluid within an organism that help the cells to transport substances via body cavities. They can be blood, lymph, urine, tissue fluid, etc. 

  • Two types of fluid circulation can be observed – intracellular circulation and extracellular circulation.

  • Single-celled organisms like amoeba perform intracellular circulation inside their cell via cyclosis.

  • In extracellular circulation process, body fluids circulate across the cells.

  • Through the circulatory system, body fluids distribute different substances like hormones, gasses, nutrients, etc. throughout the body and eliminate waste materials like urine from the body. 

  • The circulatory system has two types – open and closed.

Body Fluids

While revising the body fluids and circulation notes, you should start from the body fluids and its components and then go to its circulation.


Blood, a connective tissue that consists of plasma, formed elements and fluid matrix.


  • Constituting 55% of the entire blood volume, this viscose fluid contains 90%-92% of water and 6%-8% proteins, glucose, amino acids, and electrolytes.

  • The major protein elements are albumins, fibrinogens, and globulins.

  • The electrolytes like Ca++, Na+, Cl-, etc. are found in small amounts.

Formed Elements

These formed elements are composed of thrombocytes, erythrocytes, and leukocytes.

  • Thrombocytes

  1. Thrombocytes or blood platelets help in the process of blood clotting.

  2. A specific cell in the bone marrow called megakaryocyte produces blood platelets.

  3. Count – 1.5-3.5 lakh per mm-3 blood.

  • Erythrocytes

  1. They are commonly known as red blood cells or RBC. 

  2. Colour – Red due to haemoglobin.

  3. Count – 50-55 lakh per mm-3 blood in adult human.

  4. Created in - Bone marrow.

  5. Shape – Biconcave.

  6. Nucleus – mostly absent.

  7. Lifespan - 120 days on average. 

  8. Wrecked in – spleen that is known as the RBC graveyard.

  9. The primary function of RBC, the most abundantly available cell in blood, is to transport the respiratory gasses in cells.

  • Leucocytes

  1. Commonly known as white blood cell.

  2. Colour – Colourless.

  3. Count – 6-8 thousand per mm-3 blood in adult human.

  4. Nucleus – Present.

  5. Lifespan – 3-4 days on average. 

  6. Majorly two types – agranulocytes and granulocytes.

  7. Granulocytes consist of basophils, eosinophils, and neutrophils.

  8. Agranulocytes consist of lymphocytes and monocytes.

  9. Both neutrophils and monocytes have the phagocytic ability.

  10. Basophils secret serotonin, histamine, etc. and thus, present in inflammatory reactions.

  11. Eosinophils help in resisting infections and also, present in allergic reactions.

  12. Lymphocytes help to build up the immune response of organisms.

Blood Groups

  • ABO Grouping

Depending on the availability of antigen on the surface of RBCs, there are four blood groups.

Blood Group

Antigen presents on RBCs

Antibodies present in plasma

Donor group




A, O




B, O


A, B


A, B, AB, O



Anti-A, Anti-B


  • RH Grouping

Usually, 80% of individuals’ RBCs contain Rh antigen on their surface. These individuals are known as Rh+ and who do not have Rh antigen known as Rh-.


Lymph is another connective tissue that helps to drain the interstitial or tissue fluid to major veins. 

  • It is composed of lymphocyte cell and develops the immunity system of the organisms. 

  • Exchange of substances from the blood to cell occurs via lymph.

Circulation System

Another most important topic from body fluids and circulation NEET notes is the difference between open and closed circulatory system.

Open Circulatory System

Closed Circulatory System

The blood flow in an open circulatory system happens via large open channels and spaces known as sinuses and lacunae in tissues.

The blood flow in a closed circulatory system happens via closed chambers known as blood vessels and heart.

In this system, the blood is directly connected with the tissue.

Here, blood is not directly connected with tissues.

Blood flows slowly with low pressure.

Blood flows rapidly with high pressure.

Exchange of substances occurs directly from blood to tissues.

Exchange of substances occurs via the capillary wall and tissue fluid.

In this system, the volume of blood cannot be regulated as it flows via open channels. Thus, it is less efficient.

Here, as the blood flows within vessels, it can be controlled by relaxation and contraction of different muscles.

It mostly observed in invertebrates and molluscs.

It is mostly observed in echinoderms and all vertebrates.

The presence of respiratory pigment is not mandatory. 

The presence of respiratory pigment like haemoglobin is compulsory. 

The above mentioned content is mostly in bullet format so you can quickly look through these points. These important notes of biology for NEET body fluids and circulation can help you answer the model tests and analyse your weak points easily. Once you are aware of your weak points, you can work on those by learning body fluids and circulation NEET notes and overcome your problems. 

FAQ (Frequently Asked Questions)

1. How Many Types of Blood Circulations Are There in The Human Body?

In humans, there are majorly three types of blood circulation systems found – coronary, pulmonary, and systemic circulation. Coronary circulation happens through coronary arteries and coronary veins.

2. What Are The Fractions of Cardiac Output?

The amount of pure blood that passes into organs per minute is known as the fraction of that organ. Cardiac fraction is 200 ml/min, renal fraction is 1300 ml/min, hepatic fraction is 1500 ml/min, cephalic fraction is 700 to 800 ml/min.

3. What is The Main Difference Between Neurogenic Heart And Myogenic Heart?

A ganglion near heart initiates the heartbeat in the neurogenic heart. But a modified patch of heart muscle begins the heartbeat in the myogenic heart.