May 12, 2021

Composition of Blood | Human Blood Notes for SSC and UPSC exams

Share and Enjoy !


Human Blood | Composition of Blood Notes PDF – Hello Aspirants, welcome to our site Today, we are providing you Human Blood | Composition of Blood Short notes PDF which helps you to understand about composition of blood in brief for competitive exams.

Human Blood:

Blood is a fluid connective tissue. The pH value of blood is 7.4. It is basic in nature. There is an average of 5-6 liters of blood in the human body. It also fights infection and regulates temperature. The study of blood is known as Hematology.

Composition of Blood:

Plasma is the largest component comprising of 55%. And blood cells make up the remaining 45% of the blood.


Blood Plasma is liquid portion of Blood (55% of blood). it contain 90% water, and the remaining 10% is a mix of protein, minerals, carbohydrates, and other essential minerals.

The proteins present in plasma play an important role in the human body:

  • Fibrinogen – helps in blood coagulation.
  • Albumin – maintains osmotic pressure of plasma, transports lipids, and steroid hormones.
  • Globulin – Participates in the Immune System

Functions of Plasma:

Plasma helps in maintaining satisfactory blood pressure. It also helps in volume to supplying critical proteins for blood clotting and immunity in the body. Medium for the exchange of vital minerals such as sodium and potassium. It also helps to maintain a proper pH (acid-base) balance in the body, which is necessary for cell function.


The serum is similar to plasma but without blood cells or a clotting factor. it will contain a lot of proteins, but not fibrinogen. It is often used to identify blood groups, and for diagnosis of different types of diseases. Serology is the branch of medical science that is involved in study of blood serum.

Human Blood Cell:

  • Red Blood Cell (RBC)
  • White Blood Cell (WBC)
  • Platelets

Human RBCs (Red Blood Cells):

From Greek erythros for “red” and kytos for “hollow vessel”, with -cyte translated as “cell” in modern usage. The most important function of red blood cells is the transport of oxygen to the tissues. Nearly half of the blood’s volume (40% to 45%) is red blood cells. RBCs contain haemoglobin, an important pigment that absorbs oxygen in the lungs, and delivers it to tissues. It collects oxygen from the lungs, travels via the heart to deliver oxygen to all the cells in the body. RBCs are doughnut-shaped but without the hole. This shape is called a biconcave disc. The RBCs in mammalian vertebrates like humans do not have a nucleus when they mature.

Human Red Blood Cells (RBCs) – Production & Life Cycle:

RBCs are produced in the liver of the fetus during its embryonic life but then is succeeded by the bone marrow for adults. The RBCs develop in the bone marrow and circulate for about 100–120 days in the body before their components are recycled by macrophages. Death:  The RBCs & platelets die in the spleen which is why it is called the “Graveyard of RBCs”


Haemoglobin is a protein which contains iron. Red blood cells get their red colour because of the presence of haemoglobin Haemoglobin abbreviated Hb or Hgb. The standard amount of Hb: 14.5mg of haemoglobin in every 100 ml of blood. If the amount of Hb is lesser than this standard, it is considered anaemic.


The Bilirubin is the by-product you get when red blood cells are broken down. It is excreted from the body in urine & faecal matter. It is brownish yellow in colour. The yellow colour of bruises and brown colour in faeces is due to Bilirubin. The liver secretes bilirubin, which then goes into the bile, gallbladder, and finally into the intestines to be excreted. Bilirubin is excreted from the body in urine & faecal matter. The levels of Bilirubin are usually monitored to check for diseases. High levels of bilirubin in the body indicate Jaundice, which is caused when red blood cell levels are high. It causes yellow skin & eyes.

Packed RBCs, also known as red cell concentrate and packed cells, are RBCs that have been separated for blood transfusion.

Human WBCs (White Blood Cells):

WBCs are also called leukocytes. They are very important as they are cells of the immune system, which is responsible for fighting infections & foreign bodies. WBC are nucleated, meaning their cells have a nucleus. They have a short lifespan of 2 – 5 days. WBC are irregular in shape and thus distinguished based on their structure and function.

They are broadly classified in 5 types, namely:

  • Neutrophils
  • Eosinophils
  • Basophils
  • Lymphocytes
  • Monocytes
Types of White Blood Cells

The above five can be further classified based on their structure:

  Granulocytes – Granules in their cell cytoplasm     Agranulocytes – No granules in their cell cytoplasm  


These cells are vital for producing antibodies that help the body to defend itself against bacteria, viruses, and other threats come inside our body.


These cells are powerful WBCs that destroy bacteria and fungi.


These cells alert the body to infections by secreting chemicals into the bloodstream of our blood, mostly to combat allergies.


These cells are responsible for destroying parasites and cancer cells and they are part of an allergic response.


These cells are responsible for attacking and breaking down germs or bacteria that enter the body.


  • Platelets are irregular in shape.
  • Nucleus is absent.
  • They are produced in the bone marrow.
  • The average lifespan of platelets is 3-5 days.
  • Functions: Platelets are also known as thrombocytes are a component of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping, thereby initiating a blood clot to prevent too much blood from the body.

Human Blood Types:

  • Landsteiner discovered the common blood types A, B, and O in 1901.
  • Alfred von Decastello has discovered the AB blood group in the year 1902.
  • The term “Rh” was a short form of “Rhesus factor.”
  • In 1937, It was discovered by Karl Landsteiner and Alexander S. Wiener who, at the time, believed it to be a similar antigen found in rhesus monkey red blood cells.
  • Rh factor is present then blood will be positive and absent then it will be negative.
  • When the Rh factor is present in the blood, then it indicates a positive blood type and a negative blood type when the Rh factor is absent.
Classification of human blood
Classification of Human Blood

Erythroblastosis Fetalis:

  • Haemolytic disease of the Foetus and Newborn (HDFN) is called, “Erythroblastosis Fetalis.” It is a blood disorder that occurs when the blood types of a mother and baby are incompatible.
  • When two people whose blood groups have different Rh Factors, viz the father has a positive blood group, and the mother has a negative blood group.
  • If the conceived baby has a positive blood group, this baby is born safely. However, the mother’s body develops antibodies against the Rh factor (positive blood group)
  • When this happens, if the mother becomes pregnant again and the baby has a positive blood group, her WBCs perceive the baby’s RBCs as a foreign body, and attacks them. This baby is at serious risk of dying.

Blood Compatibility Chart for Donation:

Blood TypeDonate Blood ToReceive Blood From
A+A+, AB+A+, A-, O+, O-
A-A+, A-, AB+, AB-A-, O-
B+B+, AB+B+, B-, O+, O-
B-B+, B-, AB+, AB-B-, O-
O+O+, A+, B+, AB+O+, O-
AB- AB+, AB-AB-, A-, B-, O-  

Blood Clotting:

  • A blood clot is a clump of blood that has changed from a liquid to a gel-like or semisolid state after the clotting.
  • Clotting is a necessary process that can prevent you from losing too much blood from the body in certain instances, such as when you’re injured or cut.
  • The average time for blood clotting is about 2-5 minutes.
  • Thromboplastin is a plasma protein that aids in blood coagulation by catalyzing the conversion of prothrombin to thrombin.
  • Thrombin is a serine protease that converts fibrinogen into fibrin in blood coagulation.
  • Heparin is a protein produced in the liver. It is an anti-blood-clotting agent.
  • It keeps blood in liquid form.
  • Heparin becomes deactivated when thrombin is formed Thrombin + Fibrinogen in presence of Vitamin K makes Fibrin.
  • It is an insoluble protein formed from fibrinogen during the clotting of blood.
  • It forms a fibrous mesh structure that aids in impedes the flow of blood.

In short, we will say that this topic is very interesting and important for the exams because in this topic you learn about the composition of blood, Blood Plasma and various types of blood cells like RBCs, WBCs, Platelets in our body. Therefore, we will be providing you short notes PDF for Composition of Blood | Human Blood by which you can easily understand this topic.

Interested Candidates can download Composition of Blood | Human Blood Short Notes PDF from the below available link.

Other Biology Topics Notes

Friends, on our site we provide you complete study material for Competitive Exam. Here, on this site, we daily post new free study materials that help you score good marks in your competitive exam. So, please daily visit our site, for free study material and other updates regarding exams.

Join us on “Telegram Channel”

For daily current affairs, latest govt. vacancies details, more free study materials, E-Book PDFs, Handwritten Notes, and Latest updates of all competitive exams.

Join us on “Telegram Group”

Friends, for any assistant, queries, and questions related to exams ask in our Telegram Group and follow us on Facebook & Instagram, and also comment on this post. We will help you as soon as possible.

Follow and Like our “Facebook Page”

Follow us on “Instagram”

And please don’t forget to join the telegram channel for the updates and share this post with your friends on social media platforms.

Thank you!

Comments for any Query or Feedback

Share and Enjoy !


One thought on “Composition of Blood | Human Blood Notes for SSC and UPSC exams

Leave a Reply

Your email address will not be published. Required fields are marked *