Heamotology

Hematology

Introduction to Hematology

Hematology is the branch of medicine that deals with the study of blood, blood-forming organs, and blood diseases. It encompasses various aspects of blood, including its formation, components, and functions, as well as diseases related to blood.

Blood is a crucial fluid that performs many essential functions, including transporting oxygen, nutrients, hormones, and waste products throughout the body. Hematologists diagnose and treat blood disorders such as anemia, clotting disorders, leukemia, lymphoma, and more.

Illustration of blood components and their functions in hematology

Table of Contents

• Blood Volume
• Blood Composition
• Blood Clotting
• Blood Disorders
• Blood Types
• Blood Banks
• FAQ

Blood Volume in Human Body

The blood volume in a human body varies based on several factors, including age, sex, and overall health. On average:

• Men have about 5-6 liters of blood.
• Women have about 4-5 liters of blood.

Blood Composition

Blood consists of two main components: plasma and blood cells.

Plasma

Plasma is a light-yellowish or straw-colored liquid that makes up approximately 55% of the total volume of blood. It serves as the liquid base for whole blood, excluding red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes)

Composition of Plasma:

Plasma contains about 91% to 92% water and 8% to 9% solids.

The solids in plasma include various components such as coagulants (mainly fibrinogen) that aid in blood clotting .

Plasma also contains important dissolved proteins, including albumin and globulin, which help maintain the colloidal osmotic pressure.

Additionally, plasma transports nutrients like glucose, fatty acids, vitamins, and minerals.

Functions of Plasma:

Plasma plays a crucial role in blood clotting, as it contains coagulants like fibrinogen .

It serves as a transport medium for nutrients, carrying substances like glucose, fatty acids, vitamins, and minerals throughout the body.

Plasma also supports the immune system by transporting antibodies and other immune-related molecules.

Furthermore, plasma helps maintain the colloidal osmotic pressure, which is important for maintaining fluid balance between blood vessels and tissues.

Blood Cells

Blood cells make up about 45% of the blood volume. There are three types of blood cells:

• Red Blood Cells (RBCs) - Carry oxygen from the lungs to the rest of the body and return carbon dioxide to the lungs to be exhaled.
• White Blood Cells (WBCs) - Part of the immune system; they help the body fight infection and other diseases.
• Platelets - Help with blood clotting to prevent excessive bleeding.

Blood Clotting

Blood clotting, or coagulation, is a crucial process that prevents excessive bleeding when a blood vessel is injured. This process takes 2-5 minutes and occurs in three distinct stages:

1. Formation of Prothrombinase: Initiated by damage to blood vessels, leading to a cascade of reactions resulting in the formation of prothrombinase.
2. Conversion of Prothrombin to Thrombin: Prothrombinase converts prothrombin, a plasma protein produced in the liver, into thrombin, an enzyme.
3. Formation of Fibrin: Thrombin converts fibrinogen, a soluble plasma protein, into insoluble fibrin threads that form a mesh, trapping blood cells to form a clot.

Blood Disorders

Blood disorders are medical conditions that affect the blood cells and proteins, causing various health problems. Some common blood disorders include:

Anemia

A condition in which there is a deficiency of red blood cells or hemoglobin, leading to fatigue, weakness, and shortness of breath.

Leukemia

A type of cancer that affects white blood cells, leading to an overproduction of abnormal white blood cells.

Hemophilia

A genetic disorder in which blood does not clot properly, leading to excessive bleeding from even minor injuries.

Thrombocytopenia

A condition characterized by a low platelet count, leading to an increased risk of bleeding and bruising.

Blood Types

Blood types are classified based on the presence or absence of specific antigens on the surface of RBCs. The most well-known blood group systems are ABO and Rh.

ABO System

• Austrian scientist Karl Landsteiner discovered the ABO blood group system in 1900 while working at the University of Vienna. 
• This system defines four main blood groups: A, B, AB, and O. 
• Each group is identified by its own set of antigens, and a person's blood group is determined by a pair of genes, one inherited from each parent. 
• The antigens on the RBCs determine the blood type, and the plasma contains antibodies that react with the antigens:
• Blood group A: Has A antigens on the RBCs and anti-B antibodies in the plasma
• Blood group B: Has B antigens on the RBCs and anti-A antibodies in the plasma
• Blood group O: Has no antigens on the RBCs, but both anti-A and anti-B antibodies in the plasma
• Blood group AB: Has both A and B antigens on the RBCs, but no antibodies

Blood Group	Antigen	Antibody	Can Donate To	Can Receive From
A	A	Anti-B	A, AB	A, O
B	B	Anti-A	B, AB	B, O
AB	A, B	None	AB	A, B, AB, O
O	None	Anti-A, B	A, B, AB, O	O

Rh Factor

• The Rh factor, discovered by Karl Landsteiner and Alexander S. Wiener in 1940, classifies blood as either Rh-positive (Rh+) or Rh-negative (Rh-). 
• The presence of the Rh antigen on RBCs determines this classification.
• The Rh factor is a protein that can be present (+) or absent (–), and Rh positive is much more common than Rh negative. 
• Erythroblastosis Fetalis: A condition where an Rh-mother carries an Rh+ fetus, potentially leading to severe anemia in the fetus due to the mother's antibodies attacking the fetal RBCs. It can be prevented with anti-Rh antigen vaccination.

Blood Banks

Blood banks store blood at 4-6 degrees Celsius to preserve it for future use in transfusions. These facilities ensure that blood and its components are available for patients who need them, such as those undergoing surgery, suffering from trauma, or having blood disorders.

FAQ

Question	Answer
Which component of blood is responsible for clotting?	Platelets
What is the primary function of hemoglobin?	Transporting oxygen
What is the liquid part of blood called?	Plasma
Which blood group is known as the universal donor?	O
Which blood type is known as the universal recipient?	AB
What is the primary function of white blood cells?	Fighting infection
Which organ is primarily responsible for the production of blood cells?	Bone marrow
Which vitamin is necessary for blood clotting?	Vitamin K
What is the normal pH range of blood?	7.35 to 7.45
Which protein in the blood helps in identifying and neutralizing pathogens?	Antibodies