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Blood : Definition, Characteristics, Components, Plasma, Serum, Practice Problems and FAQs

Have you ever wondered!

How does our body manage to distribute all the nutrients to each and every cell of it?

We all know that our cells produce lots of waste everyday. How is this waste collected from different body parts and thrown out of the body?

Answer to the question is the presence of a circulatory system. It is the system that contains the heart, lymph, blood and the blood vessels which helps in the transport of nutrients and removal of waste materials.

Simple organisms like
sponges and coelenterates circulate water from their surroundings through their body cavities to facilitate the cells to exchange nutrients with waste substances. 

In the case of complex organisms they use special fluids present in their bodies normally to transport nutrients and waste materials.
Blood is the common type of body fluid in many organisms. Lymph is another fluid which helps in the transport of substances in the body.

human circulatory system

Table of Contents

Definition of Blood

Blood is the fluid connective tissue of our body, which can be considered as an ocean in which, like solid balls, cells are floating. It  is responsible for the transport of oxygen and nutrients throughout the body. It also carries carbon dioxide and waste products for removal. Blood is a thick and homogeneous liquid in which blood cells are suspended.

blood fluid connective tissue

Physical Characteristics of Blood

Blood is an opaque and mobile fluid connective tissue. It is salty in taste and bright red in colour when oxygenated and purple in colour when deoxygenated.

Components of Blood

An average person has about 4 - 6 litres of blood which forms about 6 -10% of a body’s weight. Blood consists of a watery, straw-coloured fluid called ‘plasma’ which contains all the formed elements (blood cells) floating in it. The plasma and formed elements form about 55% and 45% of total blood volume respectively.

composotion of blood

Blood Plasma

It is a yellow or straw-colored, alkaline viscous fluid constituting nearly 55% of the blood volume. 90 - 92 percent of plasma is made up of water and the rest 6 - 8% is contributed by proteins.

composition of blood

Components of Blood Plasma

The components of blood plasma are as follows: 

Proteins

Plasma contains majorly the proteins like fibrinogen, globulins and albumins.

  • Fibrinogens - They are required for coagulation or clotting of blood.
  • Globulins - They are involved mainly in the defence mechanism or immunity of the body. All antibodies are immunoglobulins. It also helps in retaining water in blood plasma.
  • Albumins - They help in osmotic balance. It is the most abundant protein found in the blood plasma.

Inorganic Salts

They are present in the plasma as ions. Sodium and chloride are the main cations and anions of the plasma respectively. Some anions like bicarbonates, phosphates and some cations like Ca++, Mg++, iron and manganese are also present in smaller amounts.

Dissolved Gases

Small amounts of carbon dioxide, oxygen and nitrogen are present in the plasma.

Waste Products

Waste products found in blood plasma are urea, uric acid, ammonia and creatinine.

Clotting Factors

Certain factors required for clotting or coagulation of blood are present in the plasma. They remain in an inactive form.

Blood Sugar

Plasma contains sugar. 80 - 100 mg per 100 ml of blood is the normal level.

Blood Cholesterol

It is the main lipid content in the plasma. 80 - 180 mg per 100 ml is the normal level.

Functions of Plasma 

The blood plasma performs the following functions:

  • Transport of nutrients throughout the body.
  • Helps in the removal of waste materials.
  • Helps in immunity.
  • Maintenance of blood pH.
  • Distribution of heat in the body uniformly.
  • Dissipation of heat by conducting it to skin.
  • Retention of fluid in the blood.
  • Helps in blood clotting. 

Serum

Serum is the liquid portion of the blood that remains after coagulation of blood. It includes inorganic salts (electrolytes), antibodies, antigens, and hormones but no clotting factors.

Practice Problems of Blood 

Question 1. Serum is different from blood because it lacks _______________.

(a) antibodies

(b) clotting factors

(c) albumins

(d) globulins

Solution : Serum is a plasma without clotting factors. It includes inorganic salts (electrolytes), antibodies, antigens, and hormones but no clotting factors.

Question 2. Which plasma protein is responsible for blood clotting

(a) Fibrinogen

(b) Globulin

(c) Serum amylase

(d) Albumin

Solution : Plasma contains  majorly the proteins like fibrinogen, globulins and albumins. Fibrinogens are required for coagulation or clotting of blood. Globulins are involved mainly in the defence mechanisms or immunity of the body. Albumins help in osmotic balance.

Question 3. Lymph differs from blood because it contains

(a) no plasma

(b) more RBCs and less WBCs

(c) more WBCs and no RBCs

(d) plasma without proteins

Solution : Lymph is the fluid which helps in the transport of substances in the body. It contains WBCs which help provide immunity. 

Question 4. Normal blood pH is 

(a) 7.3 

(b) 7.2 

(c) 7.4 

(d) 8.4

Solution : Blood has a slightly alkaline pH which is around 7.4. 

FAQs of Blood 

Question 1. Write down the functions of blood plasma?

Solution : Blood plasma plays a vital role in many bodily activities as follows:

  • Transport of nutrients throughout the body.
  • Helps in the removal of waste materials.
  • Helps in immunity.
  • Maintenance of blood pH.
  • Distribution of heat in the body uniformly.
  • Dissipation of heat by conducting it to skin.
  • Retention of fluid in the blood.
  • Helps in blood clotting. 

Question 2. Write down the composition of blood plasma?

Solution : The components present in the blood plasma are proteins, inorganic salts, dissolved gases, waste products, clotting factors etc.

Question 3. How is plasma different from serum?

Solution : Serum is the liquid portion of the blood that remains after coagulation of blood. It includes inorganic salts (electrolytes), antibodies, antigens, and hormones but no clotting factors.

Question 4 What are plasma proteins?

Solution : Plasma contains  majorly the proteins like fibrinogen, globulins and albumins. Fibrinogens are required for coagulation or clotting of blood. Globulins are involved mainly in the defence mechanisms or immunity of the body. Albumins help in osmotic balance. It is the most abundant protein found in the blood plasma.

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Structural Organization in Animals Cells: The Unit of Life Biomolecules
Cell Cycle and Division Transport in Plants Mineral Nutrition
Photosynthesis in Higher Plants Respiration in Plants Plant Growth and Development
Digestion and Absorption Breathing and Exchange of Gases Body Fluids and Circulation
Excretory Products and their Elimination Locomotion and Movement Neural Control and Coordination
Chemical Coordination and Integration

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