Blood is a vital fluid in the human body that performs a variety of essential functions necessary
for maintaining life. It is a specialized bodily fluid that delivers necessary substances to the
body’s cells and transports waste products away from those same cells. Blood is composed of
four main components: plasma, red blood cells, white blood cells, and platelets.
Components of Blood
1. Plasma:
o Description: Plasma is the liquid portion of blood,
comprising about 55% of its total volume.
o Composition: It is mainly water (about 90-92%), but it
also contains proteins, electrolytes, nutrients, hormones,
gases, and waste products.
o Functions:
▪ Transport: Plasma transports nutrients, hormones, and
proteins to the parts of the body that need it. Cells also
deposit their waste products into the plasma.
▪ Clotting: It contains clotting factors and proteins like
fibrinogen which help in blood clotting.
▪ Immune Defense: Plasma carries antibodies and other proteins that are part of the immune
system.
▪ Maintenance: It helps maintain blood pressure and volume.
2. Red Blood Cells (Erythrocytes):
o Description: Red blood cells are the most abundant cells in the blood, making up about 40-45%
of its volume.
o Composition: These cells contain the protein hemoglobin, which is responsible for their red
color.
o Functions:
▪ Oxygen Transport: Hemoglobin binds to oxygen in the lungs and carries it to tissues throughout
the body.
▪ Carbon Dioxide Removal: They help transport carbon dioxide, a waste product of metabolism,
from the tissues back to the lungs for exhalation.
3. White Blood Cells (Leukocytes):
o Description: White blood cells are a critical part of the immune system, making up about 1% of
the blood.
o Types:
▪ Neutrophils: The most common type, which fights bacteria and fungi.
▪ Lymphocytes: Include T cells (which attack infected or cancerous cells) and B cells (which
produce antibodies).
▪ Monocytes: They differentiate into macrophages and dendritic cells to help in phagocytosis
(engulfing and digesting cellular debris and pathogens).
▪ Eosinophils: They fight parasites and are involved in allergic reactions.
▪ Basophils: They release histamine and other chemicals during allergic reactions.
o Functions:
▪ Immune Response: White blood cells protect the body against both infectious disease and
foreign invaders.
▪ Inflammatory Response: They are involved in the inflammation process, responding to
infections and injuries.
4. Platelets (Thrombocytes):
o Description: Platelets are small cell fragments that are crucial for blood clotting, making up
about 1% of the blood.
o Functions:
▪ Clot Formation: They aggregate at the site of a blood vessel injury, adhere to the vessel wall,
and form a platform for blood clotting to stop bleeding.
▪ Healing: Platelets release growth factors that aid in the repair of damaged tissues.
Functions of
Blood
1. Transportation:
o Blood transports oxygen
from the lungs to the cells of
the body and carbon dioxide
from the cells to the lungs.
o It carries nutrients from the
digestive system and delivers
them to cells.
o Hormones and other
signaling molecules are
transported to their target
organs.
o Metabolic waste products are
carried to the kidneys, liver,
and lungs for excretion.
2. Regulation:
o Blood helps regulate body
temperature by absorbing
and distributing heat
throughout the body.
o It maintains pH balance by using buffers.
o Blood helps maintain fluid balance within the body.
3. Protection:
o White blood cells and antibodies in the blood are part of the immune system, defending the body
against pathogens.
o Blood clotting mechanisms prevent excessive blood loss after injuries.
Youtube link: https://www.youtube.com/watch?v=81w0BXg7QJA
Answer following question based on above given description:
1. Describe the composition and main functions of plasma in the blood.
2. Explain the importance of clotting factors in plasma and their role in the blood clotting process.
3. What is the primary function of red blood cells, and how do they accomplish this task?
4. Discuss the role of hemoglobin in red blood cells.
5. How do red blood cells contribute to the transport of carbon dioxide in the body?
6. Explain the role of neutrophils in fighting infections.
7. How do monocytes aid in the body's defense against pathogens?
8. What is the primary function of platelets in the blood?
9. Explain the consequences of having a low platelet count in the blood.
10. Discuss the role of blood in maintaining pH balance within the body.
