Blood and it's Components | General Awareness for SSC CGL PDF Download

Blood Definition

Blood is the body fluid in humans and other animals that delivers essential materials for life to the body’s cells. It is sometimes referred to as a fluid "tissue" because, like solid tissues, it contains various types of cells that perform complex functions.

Blood components are primarily produced in the bone marrow, where special cells generate red cells, white cells, and platelets. "Blood cancers" like leukemia are actually cancers of the bone marrow. As cancerous tissue replaces healthy bone marrow tissue, the production of healthy red blood cells, white blood cells, and platelets is hindered.

Despite appearing as a simple red fluid, blood is as complex as any tissue in the body. Here we will discuss its functions, components, and some clinically important characteristics.

Functions of Blood

Bringing Vital Substances to Cells Complex multicellular organisms need sophisticated circulatory systems because they have many cells with high metabolisms. Without an efficient means of delivering vital substances like oxygen, water, and nutrients, complex and active life forms like ourselves could not exist. Blood delivers the following essential substances to our cells:

• Oxygen: Constant supply needed for cellular respiration.
• Water: Correct balance needed for enzymatic activity.
• Nutrients: Fuel for cellular respiration and materials for cellular maintenance.
• Biological building blocks: Molecules for making replacement parts and daughter cells.
• Chemical messages: Allows cells to alter their activity in response to environmental changes.

Removing Dangerous Wastes Most living organisms produce waste products that, at certain concentrations, become toxic. High-metabolism organisms like us have developed ways to manage these waste products, allowing many cells to coexist in a single organism. The liver and kidneys break down toxic substances and expel them as urine. Blood transports toxins from tissues to these organs for processing and removal. Blood also releases unwanted gases in the lungs, exchanging them for fresh oxygen. Waste products blood helps remove include:

• Carbon dioxide gas: Byproduct of cellular respiration that must be removed to prevent blood acidification.
• Excess water, salt, and other substances: Necessary to maintain balance.
• Debris from dead cells: Especially red blood cells, which have a short lifespan.
• Toxic waste products of metabolism: Safely transported to the liver and kidneys.
• Ingested toxins: Managed by the liver and kidneys.

In addition to transporting substances, blood also contains its own cells and performs unique functions:

Contains and Transports Immune Factors 

Blood contains antibodies and white blood cells that fight viruses, bacteria, and other invaders. These cells are crucial for preventing infections and fighting cancers that originate within the body. The lymphatic system also plays a role in the movement, storage, and creation of immune factors.

Contains and Transports Clotting Factors 

One of the most serious risks of injury is blood loss. All organs, including the brain, rely on constant blood flow to stay alive. Large amounts of blood loss can be devastating and is a common cause of death from trauma. Blood contains a response system to injuries. Platelets, clotting factors, and other blood components form clots and scabs to stop bleeding. While this system cannot save us from major injuries like artery ruptures, its effectiveness is evident in individuals with clotting disorders. People with certain cancers, vitamin deficiencies, and other diseases have blood that does not clot normally, leading to easy bruising, bleeding without apparent cause, and sometimes death from minor injuries or spontaneous bleeding. A properly functioning clotting system is crucial for survival.

Components of Blood

Blood, although appearing uniform, consists of several major components. When centrifuged, these components separate based on density.

Here, we will explore the essential components of blood, including plasma, white blood cells (leukocytes), red blood cells, and platelets.

Plasma

Plasma is the liquid that carries red blood cells, white blood cells, platelets, and other substances found in blood. It makes up more than half of the blood's volume. Plasma is mostly water, but it also contains salts, proteins, and other substances, making it appear thick and syrupy even when the red and white cells are filtered out.

One important protein in plasma is albumin, which helps keep the blood thick and syrupy, ensuring that blood doesn't leak out of vessels and slows bleeding during injury. Other substances in plasma include:

• Antibodies: Proteins that attack invading pathogens.
• Clotting factors: Prevent bleeding.
• Hormones: Chemical messages sent between different tissues.
• Electrolytes: Such as salt.
• Nutrients: Such as sugar, vitamins, and minerals.
• Lipids: Including cholesterol.

Red Blood Cells

Red blood cells are the body's cargo ships, designed to carry oxygen from the lungs to cells and return carbon dioxide to the lungs for exhalation. They contain hemoglobin, a protein that binds aggressively to oxygen in the lungs and releases it slowly and steadily as it passes through the body. Hemoglobin is a pigment that changes color depending on whether it is bound to oxygen, causing blood from veins to appear dark red and blood from arteries to appear bright red.

White Blood Cells

White blood cells perform immune and clean-up functions in the body. They are produced by stem cells in the bone marrow. Different types of white blood cells include:

• Neutrophils: Target bacteria and fungi.
• Eosinophils: Target larger parasites and play a role in allergic responses.
• Basophils: Release chemicals that enhance inflammatory responses.
• B Lymphocytes: Release antibodies and assist in activating T cell lymphocytes.
• T Lymphocytes: Help the immune system recognize and respond to infections and target virus-infected and tumor cells.
• Natural Killer Lymphocytes: Target virus-infected and tumor cells.
• Monocytes: Mature into macrophages, which engulf harmful cells and cellular debris; some become Kupffer cells in the liver, breaking down and recycling dying red blood cells.

Platelets

Platelets are cell fragments that stop bleeding by clumping together to form clots and scabs. Produced in the bone marrow, platelets have two states: active, which are ready to create clots, and inactive, which do not. Normally, healthy blood vessels produce chemicals that keep platelets inactive. When an injury occurs, a chemical cascade activates the platelets, starting the clotting process. Incorrect activation of platelets can happen if the endothelial lining is damaged, leading to clots in healthy blood vessels, which can occur in some metabolic disorders and cardiovascular diseases.

Blood Types

Early medical history suggested that blood transfusions between people might be impossible due to fatal reactions. Scientists later discovered "blood types," proteins on the surface of blood cells that help the immune system distinguish between self and foreign cells. Transfusing incompatible blood can cause a fatal clotting reaction. Today, doctors use rapid tests to determine blood types and store blood for transfusions sorted by type.

The three common blood type protein markers are A, B, and Rh. The A/B protein group gives rise to blood types A, B, AB, or O. "O" is used to describe the absence of A and B markers. Each blood type can be positive or negative for the Rh protein, resulting in types like "AB+" or "AB-."

"O negative" is known as the universal donor type, as it lacks A, B, and Rh proteins, making it compatible with any recipient. However, "O negative" individuals can only receive blood from other "O negative" donors due to their lack of these proteins.

Platelet deficiency or absence increases the risk of catastrophic bleeding events, including spontaneous bleeding and bleeding from minor injuries.