Blood- An Overview: Properties, Composition & Functions

Blood Properties Composition & Functions
Blood- An Overview: Properties, Composition & Functions

What is blood?

Blood is a body fluid in animals including humans. It is a fluid form of connective tissue which mainly transports oxygen and carbon dioxide between cells and lungs.

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What are the properties of blood?

The properties of blood are enlisted below:

  1. Color: Red in color. Arterial blood is scarlet red and venous blood is purple-red.
  2. Volume: In the adult- 4.5-5 L. In newborn baby- about 450 ml
  3. pH: Blood is slightly alkaline. pH range- 7.35-7.45
  4. Osmotic pressure: It is equal to 0.945% NaCl.
  5. Viscosity: viscosity of blood = 5x viscosity of water
  6. Specific gravity: 1.052-1.061

What is the composition of blood?

The composition of blood are enlisted below:

Roughly blood is divided into blood cells and plasma.

Blood cells: Blood cells are also known as formed elements. Three types of blood cells are found in the blood.

  1. Red blood cell (RBC)/ Erythrocyte
  2. White blood cell (WBC)/ Leukocyte
  3. Platelet/ Thrombocyte

Plasma: The liquid portion of the blood is called plasma. It is about 55% of the total blood. Plasma is subdivided into solids, water, and gases.

  1. Solids: There are two types of plasma solids. Organic and inorganic. Organic solids are like plasma proteins, carbohydrates, fats, antibody, amino acids, enzymes, hormones, etc. Different ions from the inorganic portion.
  2. Water: (92-93)% of total plasma is water.
  3. Gases: Plasma contains gases like oxygen, nitrogen, carbon dioxide, etc.

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What are the functions of blood?

The functions of blood are described below in a list:

  1. Blood transports oxygen from lungs to cells (including lungs cells) and carbon dioxide from cells (including lungs cells) to the lungs.
  2. Blood helps to transport nutritive substances absorbed from the gastrointestinal tract to different parts of the body for proper growth and production of energy.
  3. Blood removes the waste products produced in different tissues and carries them to excretory organs like the kidney, skin, lungs, etc.
  4. Blood helps to maintain the water balance of the body.
  5. Blood also contributes to regulating the acid-base balance of the body.
  6. Hormones are directly released and carried by the blood.
  7. Body temperature is maintained by the flow of blood.
  8. WBC of blood acts as a defense force during the body attacked by foreign organisms.
  9. Platelet in the blood plays the main role in coagulation.
  10. Blood serves the body as a source of proteins, glucose, sodium, and potassium in conditions like starvation, fluid loss, and electrolyte loss.

This is the gross anatomy of blood. Hope this will help you to enrich your knowledge. We will discuss specific parts of blood in detail someday. Stay with us.


Essentials of Medical Physiology, 6th Edition: Sembulingam K, Sembulingam Prema

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