Blood

BLOOD
PREPARED BY:
DR. AKASH SUBEDI
PHARM.D
INSTRUCTOR (ANATOMY &PHYSIOLOGY )

Introduction
 Haematology, is the branch of medicine concerned with the study of the cause,
diagnosis, treatment, and prevention of diseases related to blood.
 It involves treating diseases that affect the production of blood and its
components, such as blood cells, hemoglobin, blood proteins, bone
marrow, platelets, blood vessels, spleen, and the mechanism of coagulation.
 Blood is a body fluid in humans and other animals that delivers necessary
substances such as nutrients and oxygen to the cells and transports metabolic
waste products away from those same cells.
 It is also the fluid connective tissue.
 Approximately 8% of an adult’s body weight is made up of blood.
 Females have around 4-5 liters, while males have around 5-6 liters. This difference
is mainly due to the differences in body size between men and women.
 Its mean temperature is 38 degrees Celsius.

 Blood is composed of Formed Elements and Plasma.
FORMED ELEMENTS:
About 45% of our blood is composed of formed elements also called as blood cells.
There are different types of blood cells found in our blood. They are listed below:
A. RBC (Red Blood Cells)/ erythrocytes: These are the most numerous of the three
types of blood cells. RBCs have the job of transporting oxygen and carbon
dioxide. There are approximately 4.2 to 6.2 million RBCs per cubic mm of blood.
B. WBC (White Blood Cells)/ Leukocytes: These are members of our body's
defense team since they protect us from invading bacteria and other pathogens.
There are anywhere from 5,000 to 11,000 per cubic mm of blood.
WBC can be classified into:
a) Granulocytes : Neutrophils (65%), eosinophils (4%) and basophils (1%). &
b) Agranulocytes: Lymphocytes (25%) and monocytes (5%).

C. Plateletes/ Thrombocytes: These are also the tiniest of the blood cells. Platelets
work in the body to help stop the bleeding whenever a blood vessel is damaged. We
have 140,000 to 340,000 platelets per cubic mm of blood.
PLASMA:
The other 55% of our blood is composed of plasma. It is the liquid portion of blood.
Water makes up about 91% of the plasma. Proteins make about 7% of plasma.
Different types of plasma proteins are albumins, globulins, fibrinogen and
prothrombin.
Different solutes make up the remaining 2% of the plasma. Different solute
includes ions, electrolytes such as potassium, sodium, and calcium. Various nutrients
needed by the body - like glucose, amino acids, and lipids - and waste products from
metabolism - like urea, uric acid, and creatinine - are also found in the plasma.
Oxygen and carbon dioxide are the blood gases which are found in the plasma as
well. The last of the solutes are hormones.

Functions of Blood:
 Transports gases, nutrients, waste, cells and hormones throughout the
body.
 Transports O2, CO2, nutrients, hormones, heat and wastes.
 Regulates pH, temperature, water content of cells.
 Protects against blood loss through clotting.
 Protects against disease through phagocytic white blood cells and
antibodies.

Structure and Functions of Formed Elements:
RBC/ Erythrocytes:
Red blood cells have a unique structure. They are biconcave in shape. Both sides of
the cell's surface curve inward like the interior of a sphere. This shape increases the
red blood cell's ability to penetrate through tiny blood vessels to deliver oxygen
to organs and tissues. Their flexible disc shape helps to increase the surface area of
these cells. This enables oxygen and carbon dioxide to diffuse across the red blood
cell's plasma membrane more easily.
Red blood cells contain enormous amounts of
protein called hemoglobin. This iron-containing molecule binds oxygen. Hemoglobin
is also responsible for the characteristic red color of blood. Unlike other cells of the
body, mature red blood cells do not contain a nucleus, mitochondria, or ribosomes.
The absence of these cell structures leaves space for the hundreds of millions of
hemoglobin molecules.

Platelets/ Thrombocytes:
They contain proteins on their surface that allow them to stick to the blood
vessel wall and also to stick to each other. They contain granules that can
secrete other proteins required for creating a firm plug to seal blood vessel
breaks. Also platelets contain proteins similar to muscle proteins that allow
them to change shape when they become sticky.
They are shaped like a plate. When platelets are stimulated by a
break in the blood vessel wall they change shape. They become round and
extend long filaments. They may even look like an octopus, with long
tentacles reaching out to make contact with the broken blood vessel wall or
with other platelets. With these long filaments, platelets then form a plug to
seal the broken blood vessel. Their main functions includes:
 Secretes clotting factors to promote blood clotting.
 Dissolve blood clots when they are no longer needed.

Overview of Structure and Functions of Blood Components:

Production of Blood Cells
Within the bone marrow, all blood cells originate from a single
unspecialized precursor cell called as “pluripotent hematopoietic
stem cell”. As they specialize, First, they become uncommitted
stem cells (immature Steam cells). And then into progenitor
cells which then differentiate into erythroblast, lymphocyte stem
cells other white blood cells and megakaryocytes (the parent
cells of platelets). Which then further divides into blood
circulation to form RBC, WBC and Platelets.
It is estimated that only about one out of every
100,000 cells in the bone marrow is an uncommitted stem cell,
making it difficult to isolate and study these cells.

Hemostasis
Hemostasis or haemostasis is a process which causes bleeding to stop or
to keep the blood within a damaged blood vessel. It is the first stage of wound
healing.
Hemostasis has three major steps:
 Vascular Spasm (Vasoconstriction).
 Temporary blockage of a ruptured blood vessels by a platelet plug
formation.
 Blood coagulation, or formation of a fibrin clot. These processes seal the
hole until tissues are repaired.

 Vascular spasm (Vasoconstriction) :
It is produced by vascular smooth muscle cells, and is the blood
vessel's first response to the injury. The damaged vessels will constrict which reduces
the amount of blood flow through the area and limits the amount of blood loss.
Collagen is exposed at the site of injury, which promotes
platelets to adhere to the injury site. Platelets releases serotonin, ADP and
thromboxane A2 which increase the effect of vasoconstriction. The spasm response
becomes more effective as the amount of damage is increased. Vascular spasm is
much more effective in smaller blood vessels.

 Platelet plug formation:
Platelets adheres to the damaged endothelium to form a
platelet plug. Plug formation is activated by a glycoprotein called Von Willebrand
factor (VWF), which is found in plasma. When platelets come across the injured
endothelium cells, they change shape and ultimately become ‘sticky’. release
cytoplasmic granules such as ADP, serotonin and thromboxane A2. Adenosine
diphosphate (ADP) attracts more platelets to the affected area, serotonin is a
vasoconstrictor and thromboxane A2 assists in platelet aggregation. As more
chemicals are released more platelets stick and release their chemicals; creating a
platelet plug. Platelets alone are responsible for stopping the bleeding of unnoticed
wear and tear of our skin on a daily basis. This step is also referred as primary
hemostasis.

 Clot formation:
Once the platelet plug has been formed by the platelets, the clotting
factors (a dozen of proteins that travel along the blood plasma in an inactive
state) are activated in a sequence of events known as 'coagulation cascade'
which leads to blood clotting. Clotting factors are synthesized by liver and
released in blood stream. This step is also called as "Secondary Hemostasis".
During this process the primary hemostasis plug becomes harder:
the resultant plug is called as 'thrombus' or 'Clot'. This mechanism is the
primary step of wound healing.
This process occurs via three major Pathways:
a. Intrinsic Pathway,
b. Extrinsic Pathway and.
c. Common pathway.

Homeostatic imbalance of blood :
An inability to maintain homeostasis of blood which may lead to death or a
disease is known as homeostatic imbalance of blood.
Some diseases which are caused by homeostatic
imbalance of blood are listed below:
 Anemia.
 Polycythemia
 Leukemia
 Hemophilia

Anemia:
It is the condition which develops when the blood lacks enough healthy red blood
cells or hemoglobin.
There are many different types of anemia and depending on the type,
symptoms of anemia can be mild to severe and the duration of symptoms can
range from mild to a chronic condition.
Symptoms:
 Fatigue.
 Weakness.
 Pale skin.
 Shortness of breath.
 Dizziness.
 Chest pain.
 Headache.
 Cold hands and feet etc.

Anemia can be classified into various types which are listed below:
1. Iron deficiency anemia
2. Megaloblastic anemia/ Folate deficiency anemia.
3. Pernicious anemia/ Vitamin B12 deficiency anemia.
4. Aplastic anemia
5. Sickle cell anemia
6. Hemolytic anemia
7. Other anemias.

Iron deficiency anemia:
It is the most common form of anemia. It occurs when your iron
levels are too low.
Low iron levels can be due to blood loss, lack of iron in the diet or an
inability to absorb iron . Blood loss can occur due to heavy or long menstrual
periods, ulcers, colon cancer, infections, severe injury etc.
Megaloblastic anemia:
Anemia due to folate/folic acid deficiency is called as
megaloblastic anemia. It is normally caused due to problems with absorbing
vitamins or a diet lacking in folate. In this type of anemia the red blood cells
are larger than their normal size.

Pernicious anemia:
Anemia due to vitamin B12 deficiency is called pernicious anemia and
usually occurs when the body is not able to absorb vitamin B12 properly or
due to intestinal problems. This type can also be caused by a lack of vitamin
B12 in the diet.
Aplastic anemia:
This is a rare type of anemia in which the bone marrow decreases its
production of all types of blood cells (including red blood cells, white blood
cells, and platelets). The cause is uncertain but it may be due to an
autoimmune disorder, a viral infection, cancer treatments, or exposure to toxic
chemicals. It may also be inherited.

Sickle cell anemia
This type of anemia is due to a problem with hemoglobin that causes red
blood cells to have an abnormal crescent shape. The body destroys these cells quickly
and new red blood cells cannot be made fast enough. Sickle cell anemia is a genetic
disorder.
Hemolytic anemia
This is due to red blood cells being destroyed faster than the bone marrow can
produce new ones. The reason for the premature death of red blood cells may be
inherited or because of outside factors such as blood diseases, autoimmune disorders
etc.
Other anemias
There are other rare forms of anemia, including thalassemia and hereditary
spherocytosis.

Polycythemia:
Polycythemia/ polyglobulia is a disease state in which
the hematocrit (the volume percentage of red blood cells in the blood) is elevated. It
can be due to an increase in the number of red blood cells or due to a decrease in the
volume of plasma.
They are of two types:
1. Polycythemia vera (Primary Polycythemia) and
2. Secondary polycythemia.
1. Polycythemia vera / Primary polycythemia: It is a rare growth disorder of the
bone marrow, occurring when the marrow is overactive and produces more blood
cells than the body needs.
2. Secondary polycythemia: It affects some people as a result of limited oxygen due
to smoking or living at high altitudes.

Sign and symptoms:
Polycythemia may not cause any symptoms, It's often discovered only if a
hemoglobin test or a red blood cell count is done. Some people do experience
symptoms that appear gradually. These may include:
 itching following bathing.
 dizziness.
 Flushing of the face and hands.
 Visual disturbances.
 Some people may have high blood pressure.

Leukemia
Leukemia is a group of cancers that usually begin in
the bone marrow and result in high numbers of abnormal white blood
cells. These white blood cells are not fully developed and are
called blasts or leukemia cells.
The exact cause of leukemia is unknown. A
combination of genetic factors and environmental factors are believed
to play a role.
Risk factors include smoking, ionizing radiation, some
chemicals (such as benzene), exposed to chemotherapy etc. People with
a family history of leukemia are also at higher risk.

Types:
The major types of leukemia are:
 Acute lymphocytic leukemia (ALL): This is the most common type of leukemia
in young children. It affects lymphoid cells (lymphocytes), it can also occur in
adults.
 Acute myelogenous leukemia (AML): It is a common type of leukemia. It affects
myeloid cells. It occurs in children and adults but it is the most common type of
acute leukemia in adults.
 Chronic lymphocytic leukemia (CLL): It is the most common chronic adult
leukemia, you may feel well for years without needing treatment.
 Chronic myelogenous leukemia (CML): This type of leukemia mainly affects
adults. A person with CML may have few or no symptoms for months or years
before entering a phase in which the leukemia cells grow more quickly.

Sign and Symptoms:
Common leukemia signs and symptoms include:
 Fever or chills.
 Persistent fatigue, weakness.
 Frequent or severe infections.
 Losing weight without trying.
 Swollen lymph nodes, enlarged liver or spleen.
 Easy bleeding or bruising.
 Recurrent nosebleeds.
 Tiny red spots in your skin.
 Excessive sweating, especially at night.

Hemophilia:
Hemophilia is a mostly inherited genetic disorder that
impairs the body's ability to make blood clots because it lacks
sufficient blood-clotting proteins (clotting factors).
There are two main types of hemophilia:
1. Hemophilia A: It occurs due to lack of clotting factor VIII.
2. Hemophilia B: It occurs due to lack of clotting factor IX.
Hemophilia A is more common occurring then Hemophilia B.

Sign and Symptoms:
Most common signs and symptoms includes:
 Unexplained and excessive bleeding from cuts or injuries, or after
surgery or dental work
 Unusual bleeding after vaccinations
 Pain, swelling or tightness in your joints
 Blood in your urine or stool
 Nosebleeds without a known cause
 In infants, unexplained irritability

Blood Groups:
A blood group is a classification of blood, based on the
presence and absence of inherited antigenic substances on the surface
of red blood cells (RBCs). Blood is categorized into various blood
groups. There are at least 24 blood groups and more than 100 antigens
that can be detected on the surface of RBC’s.
Among different blood groups only two types are detected in
human which are listed below:
1. ABO Blood Group and
2. Rh Blood Group.

1. ABO Blood Group:
The ABO Blood Group is based on two antigens called A antigen and B
antigen.
 People who have only antigen A have type A blood.
 People who have only antigen B have type B blood.
 People who have both A & B antigen have type AB blood.
 People who neither have antigen A nor B have type O blood.
Blood plasma usually contains antibodies called agglutinins that react
with the A and B antigens if the two are mixed. These are anti-A antibody, which
reacts with antigen A, and anti-B antibody, which reacts with antigen B.

The antibodies present in each of the four blood types are listed below:

2. Rh Blood Group:
Rh Blood Group contains Rh antigen and does not contain anti-Rh antibody hence, it
agglutinates when anti Rh serum is mixed and vice versa.
Once the patient blood type is known, then Rh factor is determined, for determining
Rh factor, a drop of blood is mixed with the anti-Rh serum, if agglutination is seen
then it is Rh +ve, if not seen then it is Rh –ve.

Blood Transfusion:
A blood transfusion is a safe, common procedure in which blood is given to a
patient through an intravenous (IV) route.
It is done to replace blood lost during surgery or due to a serious injury. A
transfusion also may be done if your body can't make blood properly because of an
illness.
Every person has one of the following blood types: A, B, AB, or O. Also,
every person's blood is either Rh-positive or Rh-negative. The blood used in a
transfusion must work with your blood type. If it doesn't, antibodies (proteins) in your
blood attack the new blood and leads to transfusion reaction.

Types:
Blood is transfused either as whole blood (with all its parts)
or, more often, as individual parts. The type of blood transfusion
you need depends on your situation. Types of blood transfusions
are:
 Whole Blood Transfusion.
 Red Blood Cell Transfusions
 white blood cell transfusions
 Platelets and Clotting Factor Transfusions
 Plasma Transfusions

Body Fluids:
Total amount of fluids present in human body is termed as body fluids, about 60% of
body fluids are present in males and about 55% of body fluids are present in females.
Body fluids can be classified into two main types:
 Extracellular Fluid (ECF) and
 Intracellular Fluid (ICF).

Extracellular Fluid(ECF):
ECF denotes all body fluid outside the cells. About one third of total body
fluid consists of extracellular fluid. It can be divided into three major components:
 Interstitial Fluid
 Intravascular Fluid and
 Transcellular fluid.
Interstitial Fluid:
The interstitial fluid surrounds tissue cells. It provides the
immediate microenvironment that allows for the movement
of ions, proteins and nutrients across the cell barrier. This fluid is not static, but is
continuously being refreshed by the blood capillaries and recollected by lymphatic
capillaries.

Intravascular Fluid:
The main intravascular fluid in mammals is blood. The other
intravascular fluid is lymph. The average volume of plasma in the
average (70 kg) male is approximately 3.5 liters. The volume of the
intravascular fluids are regulated by hydrostatic pressure gradients, and
by reabsorption by the kidneys.
Transcellular Fluid:
Transcellular fluid is the portion of total body water that
represents all body fluids which are formed from the transport activities
of cells. It is the smallest component of extracellular fluid. For
example, aqueous humor, CSF, synovial fluid etc.

Intracellular Fluid (ICF):
ICF denotes all body fluid inside the cells. About two
third of total body fluid consists of intracellular fluid. It contains
water and dissolved solutes and proteins. The solutes are
electrolytes, which help keep our body functioning properly.
There are a lot of electrolytes inside the cell, but potassium,
magnesium, and phosphate have the greatest concentrations.

Lymphatic System:
Lymphatic system is the network that primarily consists of lymph,
lymphatic vessels, and lymphatic tissues, that helps body to get rid of
toxins, waste and other unwanted materials.
Lymph:
It is a clear fluid that passes from intercellular spaces of body tissue
into the lymphatic vessels, it is discharged into the blood and resembles
blood plasma in containing white blood cells and
especially lymphocytes but normally few RBC and no platelets.
Lymphatic Tissue:
Lymphatic tissue is rich in lymphocytes. The lymphatic
tissue includes the lymph nodes, spleen, tonsils, adenoids and the
thymus.

Lymph nodes: They are small, encapsulated bean-shaped structures
composed of lymphatic tissue.
About 600 lymph nodes are found throughout the body along the
lymphatic routes, and they are especially prevalent in areas around the
armpits (axillary nodes), neck (cervical nodes), knees (popliteal nodes) etc.
The nodes contain lymphocytes(T & B lymphocytes), which enter from the
bloodstream.

Spleen
It is the largest lymphatic tissue in body, measuring about 12cm in length. It is
located underneath the left part of the diaphragm, and has a smooth, convex
surface that faces the diaphragm. A capsule of dense connective tissues
surrounds the spleen.
it consists of lymphocytes, Macrophages, RBC, plasma cells and
granulocytes.
FUNCTION:
 Removal of ruptured, worn out and defective blood cells and platelets.
 Storage of platelets up to one-third of body’s supply.
 Production of blood cells during fetal life.
 Filtering and phagocytic function.

Tonsils
Tonsils are collections of lymphoid tissue present at aerodigestive tract.
Normally, each tonsil measures up to 2.5 cm in length, 2.0 cm in width and
1.2 cm in thickness. Humans have four tonsils:
 Pharyngeal tonsil (1); present at the posterior part of nasopharynx.
 Tubal tonsil (1 pair): present at the posterior part of nasopharynx
 Palatine tonsil (1 pair): present at the posterior region of oral cavity.
 Lingual tonsil (1): present at the base of the tongue.
FUNCTION:
 Participates on the immune response against inhaled or ingested foreign
substances.

Function of Lymph/Lymphatic System:
 Drains excess interstitial fluid from tissue spaces and return it to the blood.
 Transports dietary lipids: It transports lipids and lipid soluble vitamins
absorbed by GIT.
 Carries out immune response: it initiates immune response against
particular antigens.

Reticuloendothelial System/ Mononuclear phagocyte
system:
Reticuloendothelial system is a network of cells and tissues found through out
the body especially in the connective tissues, spleen, liver, lungs,
blood, bone marrow, and lymph nodes. It is a part of the immune
system that consists of the phagocytic cells located in reticular connective
tissue.
Spleen is the largest unit of the reticuloendothelial system. The
monocyte is formed in the bone marrow and transported by the blood; it
migrates into the tissues, where it transforms into a histiocyte or a macrophage.
Macrophages are scattered in the connective tissues, liver (Kupffer
cells), spleen lymph nodes, lungs (alveolar macrophages) and central nervous
system (microglia).

Various reticuloendothelial cells are involved in phagocytic function, some of
the cells are listed below:
Cells Location
Adipose tissue
macrophages
Adipose tissue
Monocyte Bone marrow/Blood
Kupffer Cells Liver
Intraglomerular mesangial
cell
Kidney
Osteoclasts Bones
Microglia CNS
Alveolar Macrophages Alveoli

FUNCTION OF RETICULOENDOTHELIAL SYSTEM:
 phagocytosis
 Formation of new red blood cells (RBCs) and white blood cells (WBCs).
 Destruction of old RBCs and WBCs.
 Formation of plasma proteins.
 Formation of bile pigments.
 Storage of iron: In liver, Kupffer cells store excess iron
from catabolism of heme from the breakdown of RBC’s.

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