BLOOD

Platelets – enucleated and have little
organelles.
Functions of Blood
1. Transportation
2. Regulation of pH and Body Temperature
3. Protection and Immune Defense
Composition of Blood
Hematopoiesis
- The first 8 weeks: they start at the embryonic
yolk sac and they begin to settle in the liver,
spleen, thymus, and bone marrow. They
become stem cells.
- Form the 8th week to 5th month: in the liver
and spleen are the primary sites of
hemopoiesis.
Plasma
Plasma Proteins
- 7g/100ml of plasma
 Albumin: 58% of plasma proteins. Osmotic
balance.
 Globulin: 38%. Immunoglobulins, lipoproteins
and transport proteins: antibodies and thyroid
hormone-binding proteins.
 Fibrinogen: 4%. Can form large fibrins to form
blood clot.
- 50% of plasma proteins are produced by
plasma cells.
The other substances in plasma
- In addition of dissolved proteins, plasma
contains ions, nutrients, waste products, gases and
regulatory substances.
Formed Elements
- The hematocrit refers to the percentage of blood
cells ( in practice the formed elements).
- The hematocrit is about 46% for male and about
42% for females.

Red blood cells – 99.9 % of the formed
elements in volume or 4.2 – 6.2 million/mm³.
Erythrocytes are enucleated and have little
organelles.
 White blood cells (leukocytes) – have nuclei
Granulocytes are: neutrophils, eosinophils and
basophils.
Agranulocytes are: lymphocytes, monocytes.
Recycling of RBC/hemoglobin Components
 Globular proteins are broken down to amino
acids for resumption.
 Heme is separated from its iron and becomes
biliverdin (green) then to bilirubin to be
absorbed in the liver, there conjugated and
then excreted in bile from the intestines.
 A build up of bilirubin in the circulation and
intestinal spaces is known as jaundice.
Erythrocytes
 99.9% in volume of the formed elements.
 5.4 million cells/ one microliter (ul or mm³) of
blood for a man.
 4.8 million cells/ one microliter (ul or mm³) for
a woman.
 260 million RBC/drop of blood.
 25 trillion RBCs in the blood of an adult = 1/3
of all the cells in the human body. (75 trillion
cells)
 The diameter is 7.5 microns and the thickness
varies at the edge (thick, 1.5 -2.5 microns) and
the center (thinner, 1 micron).
Functions of Erythrocytes
- 33% of RBC is hemoglobin, Hb, an oxygen and
CO2 carrying protein.
- Each Hb consist of two pairs of subunits
(alpha and beta) and each subunit has an
oxygen binding heme.
Leukocytes
 Nucleus is present and hemoglobin is absent.
Granulocytes: Neutrophils, eosinophils, basophils
Agranulocytes: monocytes, lymphocytes
 There are as many as 6-8,000 leukocytes in 1
microliter of blood, but most of the
leukocytes are found on peripheral tissues.
Functions of Leukocytes
General defense:
1. neutrophils,
2. eosinophils,
3. basophils and
4. monocytes
Specific immunity:
1. lymphocytes
Neutrophils: polymorphonuclear
 Live in the circulatory
system for only 10-12
hours, then move into
tissues, where they live
up to 1-2 days.
 Phagocytic and secrete
lysozymes to digest
bacteria and others.
Eosinophils: reduce inflammation and parasitic
reaction
Basophils: releases histamines, which promotes
inflammation also release heparin, which inhibits
blood clotting.
Monocytes – live 2-3 days in circulation and migrate
in the tissues as macrophages, which phagocytose
foreign bodies. An increased number of monocytes is
an indication of an infection.
Lymphocytes
They are about the size of an RBC and they contain a
nucleus.
There are three types:
 T-cells: attack foreign bodies.
 B-cells: differentiate into plasma cells, which
secrete antibodies.
 Natural Killer cells (NK cells): destroys the
bodies own abnormal cells.
Thrombocytes
 Megakaryocytes in bone marrow, which
release their fragments into circulation, then
called platelets.
 Platelets have no nuclei.
 Participate in blood clotting.
 Platelets survive about 10-12 days in
circulation and are about 150,000 –
300,000/ul
 Thrombocytopenia is a loss of platelets and is
a sign of bleeding etc..
 Thrombocytosis is excess platelets and is a
sign of infection.
Hemostatis
Prevents loss of blood in three phases
1. The vascular phase: immediate temporary
closure of a blood vessel by constriction of
vascular smooth muscles.
2. The platelet phase: formation of a platelet
plug by platelet adhesion and aggregation.
Platelets bind to collagen in damaged tissues.
Platelets are adhered and form a plug.
3. The coagulation phase: for a large blood clot
formation by the network of fibrin from
fibrinogen. A large number of steps involving
many factors are required, some of which
require thrombin and Ca++.
Clotting Process
 Clotting is the phenomenon where blood cells
are trapped in the framework of fibers.
 The clotting process requires Ca++ and 11
different plasma proteins, mostly enzymes
The process goes through 3-stages:
1. Activation of prothrombinase by
either the extrinsic or intrinsic
pathway.
2. Prothormbinase converts
prothrombin to thrombin.
3. Thrombin converts fibrinogen to
fibrin.
Extrinsic pathway: the process is triggered by a tissue
factor of damaged endothelial cells, the other
enzymes are successively activated to complete the
clotting process- a cascade. The process is fast and
takes only 15 seconds.
Intrinsic pathway: starts with the activation of factor
XII by contacting the damaged blood vessels and is a
slower process.
Blood Collection and Analysis
• Collection of human blood is usually
performed from a superficial vein via
venipuncture or from the finger tip or sole.
• Only when needed an arterial puncture may
be performed.
• The temperature of blood is about 38°C and is
slightly higher than that of the body
temperature.
• Having a large quantity of proteins in plasma
(7g/100ml) and corpuscles, bloods’ viscosity is
more than five times higher than that of
water.
• The pH of blood is about 7.4.
Blood Tests
• Genetically determined RBC antigens
(glycoproteins) rest on the surface of the
membrane.
• There are at least 50 different kinds of
antigens on the surface of an RBC.
• Their antibodies are found in plasma.
• One set of important antigens are A and B,
typed ABO. Although A/B antibodies are not
found in the blood until about 2 months after
birth.
Blood Typing
Hemolytic Disease of the Newborn