Blood: Type, Definition,Composition, Functions, Components
Blood is a vital fluid that circulates throughout the body, delivering oxygen and nutrients to cells and removing waste products. It plays a key role in maintaining bodily functions, including immune defence and regulation of temperature. In this article, blood, components of blood, types of blood cells, blood vessels, functions of blood, regulation, Blood Formation, and Importance of Blood are discussed. Blood is a topic of the chapter Body Fluids and Circulation in Biology
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- What Is Blood?
- Composition of Blood
- Types of Blood Cells
- Blood Vessels
- Functions of Blood
- Regulation
- Blood Formation
- Importance of Blood
What Is Blood?
Blood is a fluid, very special, that courses in the arteries and veins throughout the body, carrying along every cell and tissue's requirements, from oxygen and nutrients to metabolic wastes. Its part in homeostasis assists in carrying on all functions in the body.
Composition of Blood
About 55% of the blood consists of plasma with different types of cells. They perform particular roles, and these roles help in running the human body.
Plasma makes up roughly 55% of the volume of blood. It is a fluid medium through which substances circulate. It comprises water, electrolytes, proteins, including albumin, globulins, and fibrinogen, hormones, and waste products.
Types of Blood Cells
The types of blood cells are listed below-
Red Blood Cells (Erythrocytes)
They are disc-shaped cells, nucleated, and have haemoglobin, which enables them to carry oxygen from the lungs to various tissues in the body. They also help transport carbon dioxide back to the lungs for exhalation.
White Blood Cells (Leukocytes)
WBCs represent one of the most important components of immunity and carry out host defence against various attacking infections. Major types of WBCs include neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Each subset performs different functions related to the immune response.
Platelets (Thrombocytes)
Platelets are described as small, irregular cell fragments playing a crucial role in hemostasis. When a blood vessel is injured, platelets are first to adhere to the damaged site. Various substances, known as clotting factors are released which activate other platelets. This whole activation mechanism results in platelet plugs, for sealing small breaks in the walls of the blood vessels, hence decreasing outliers of bleeding.
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Blood Vessels
Blood vessels are the channels or conduits, through which blood is distributed to all the parts of the body from the heart, and back to the heart.
Arteries
Arteries distribute blood from the heart to various regions in the body, and they are thick and muscular to withstand high pressure as blood is being pumped from the heart.
Veins
Veins return blood from different body organs back to the heart; they have thinner walls compared to arteries and have valves that prevent backflow of the blood, thus returning blood.
Capillaries
Capillaries are microscopic, thin-containing vessels in which gas exchange and nutrient exchange occur between blood and tissues; they connect arteries to veins and allow the exchange of oxygen, carbon dioxide, nutrients, and waste materials.
Functions of Blood
Blood performs several critical functions necessary to maintain health and homeostasis.
Transport
Oxygen and Carbon Dioxide: Red blood cells take up oxygen from the lungs to the tissues and in an exchange manner get out with carbon dioxide from the tissues and back to the lungs to be exhaled.
Nutrients And Waste Products
Nutrient absorptions by the digestive system are transported by the blood into the different cells of the body, while metabolic waste from cell activities is carried to places such as the kidneys for excretion.
Hormones
The blood distributes hormones that are secreted from endocrine glands to target organs/tissues, which regulate many of the body's physiological processes.
Regulation
Blood regulation is explained below-
Temperature:
By transport and re-distribution of heat generated from metabolically active tissues to the skin surface blood aids in the elimination of body heat.
pH Balance:
Blood behaves as a buffer regulating the hydrogen ion concentration, thus stabilizing pH to very narrow limits, optimal for the functioning of enzymes and other cellular actions.
Fluid Balance:
Blood maintains the fluid balance in the body through the exchange of water and electrolytes between the blood and tissues.
Immune Response:
The white blood cells and antibodies contained in blood protect the body from infections; it identifies the pathogen and kills it.
Blood Clotting:
Platelets and clotting factors in blood form clots, which seal off the vessel, if injured, preventing a profuse loss of blood from the body.
Blood Formation
The process through which the blood's formed components are created is known as hemopoiesis (hematopoiesis). The epiphyses of flat bones (such as the ribs and cranial bones), long bones (such as the humerus and femur), vertebrae, and the pelvis are where hemopoiesis occurs. Hemocytoblasts, which are hemopoietic stem cells, divide in the red bone marrow to create several types of "blast" cells. Each of these cells develops into a distinct developed element.
The production of erythrocytes, or erythropoiesis, starts with the development of proerythroblasts from hemopoietic stem cells. Several phases of development occur for three to five days as ribosomes multiply and haemoglobin is produced.
Colony-stimulating factors (CSFs), which are hormones made by mature white blood cells, encourage leukopoiesis, the process of creating leukocytes. The division of the hemopoietic stem cells initiates the creation of each kind of white blood cell.
Megakaryoblasts, which are the precursors of thrombopoiesis, the production of platelets, are created from hematopoietic stem cells. Megakaryocytes, which are enormous cells with a massive, multilobed nucleus, are created when megakaryoblasts divide without cytokinesis. The plasma membrane then infolds into the cytoplasm, causing the megakaryocytes to split into pieces.
Importance of Blood
All of the body's components can continue to function by receiving oxygen and nutrition through the blood. The lungs, kidneys, and digestive system use the blood to transport carbon dioxide and other waste products for elimination from the body. Additionally, blood distributes hormones throughout the body and fights infections.
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| Facts about Blood | Facts about Blood Group |
| Types of Blood Cells | Blood coagulation |
| ABO Blood Group | Circulatory System |
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Frequently Asked Questions (FAQs)
Blood is made up of plasma, red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).
Arteries take oxygenated blood away from the heart to the body at very high pressure, while veins return oxygen-depleted blood to the heart at very low pressure with the help of valves that do not let blood flow again in the same direction.
Red blood cells transfer oxygen from the lungs to tissues and carbon dioxide from tissues back to the lungs, which will eventually be exhaled out.
Blood redistributes the transferred accumulative heat from active respiring tissue towards the skin surface and then transfers it out through radiation or sweat.
Blood clotting, or hemostasis, becomes crucial so that after injury no one over-bleeds. Both platelets and clotting factors work together to form a clot to seal off the injured blood vessel.
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