Blood is the life line of the human body. The functions that it performs are extremely critical to the well-being of the body. This essential fluid transports oxygen and various nutrients to every cell in the human body. It also carries carbon dioxide, ammonia, uric acid and other waste products, from the cells to the excretory organs in order to be thrown out of the body. Other than these vital functions, blood works to regulate our body temperature, maintaining it at a comfortably constant value. It is also fundamental to keeping our immune system in clock-work functioning order.
So then, what is this vital fluid actually made of?
Human blood is a highly sophisticated tissue, made up of more than 4,000 different kinds of components. These components of blood work at transporting essential nutrients, shuttling waste products out of the body, clotting bleeds, fighting off invaders and so much more. The average human being has about 5 litres of blood circulating inside his body. A new-born baby hardly has a cup of blood in his body! By the time a child is 5 to 6 years old, he has about the same amount of blood as an adult.
While there are around 4000 components of blood, four of these are the most important- they are the red blood cells, white blood cells, platelets, and plasma.
Red Blood Cells–
Also called erythrocytes, red blood cells (RBC’s) are quite large microscopic cells sans a nucleus. Almost half the total blood volume is made up of RBC’s. These cells perform the crucial function of transportation of oxygen from the lungs to every living tissue of the body and shuttling carbon dioxide from the cells to the lungs. RBC’s are continuously produced in the bone marrow from stem cells at a rate of about 2-3 million cells per second. 95% of an RBC is made up of Haemoglobin, a protein that transports oxygen to individual cells. Thus each RBC has about 270,000,000 haemoglobin molecules! Blood gets its typical red colour due to oxygenated red blood cells.
White Blood Cells-
White blood cells (WBC’s), also called leukocytes, are the soldiers of the human body. Their main function is to seek out, identify, and destroy alien invaders such as bacteria, viruses and fungi, thereby protecting our body from infections, diseases and related damage.
WBCs are of five types-
- Basophil- These cells release histamines in response to allergens that may have come into contact with
the body. These histamines trigger remedial reactions such as sneezing, watering of eyes, itching, etc. in order to flush out the offending allergen from the human body.
- Eosinophil- These cells destroy the invading germs, bacteria, virus etc.
- Lymphocytes- These cells scan the human body for viruses, seek out cells that the virus has invaded and kill them.
- Monocytes- These cells digest bacteria and viruses.
- Neutrophils- These are the most plentiful white blood cells in the blood. These cells eat up bacteria, thus keeping our system safe from all kinds of germs that it comes into contact with.
Blood platelets are also called thrombocytes. These cells carry out the vital function of clotting of blood, without which you would bleed to death due to the smallest injury. Thirteen different blood clotting factors work alongside platelets to cause clotting of blood. One factor triggers another and so on, till the vascular rupture at the sight of a wound is plugged completely, preventing further bleeding.
The clear, yellow watery fluid which carries the red cells, white cells, and platelets is called the Plasma. It makes up almost 55% of the blood’s volume. Besides these, it also carries blood clotting factors, lipids, hormones, electrolytes, enzymes, sugars, vitamins, antibodies and other proteins. About 500 proteins have been recognized in human plasma until now.