Dr. Basim Al-Ka'abi
Blood Physiology
Second Lecture
1
Lecture Name: Blood Cellular Elements and Plasma
Lecturer Name: Dr. Basim A. Al-Ka'abi
Department: Medical Physiology
Stage: First Stage Medical Students
Lecture Objectives:
By the end of this lecture the students should be able to know the following:
The platelets and their various functions.
The concept of reticulo-endothelial system.
The plasma and its functions.
The types and functions of various plasma proteins, ions and enzymes.
References:
Barrett, K et al. (2018). Ganong's Review of Medical Physiology. Twenty
sixth edition. USA.
Guyton, A and Hall, J (2015). Text Book of Medical Physiology.
Thirteenth edition. Philadelphia, USA.
Dr. Basim Al-Ka'abi
Blood Physiology
Second Lecture
2
Cellular elements of the blood (cont'd)
(C) Platelets
-Blood platelets are small disks, which are non-nucleated, granulated
bodies, constitute about 150,000-450,000 in each cubic milliliters of blood.
-The primary role of the blood platelet is to arrest of blood loss. Adequate
number of functionally normal platelets are essential for optimal
hemostasis.
In their cytoplasm are such active factors as:
1. Actin and myosin molecules, which are contractile proteins similar to
those found in muscle cells, and still another contractile protein,
thrombosthenin, that can cause the platelets to contract.
2. Residual of both the endoplasmic reticulum and the Golgi apparatus that
synthesize various enzymes and especially store large quantities of
calcium ions.
3. Mitochondria and enzyme systems that are capable of forming ATP and
ADP.
4. Enzyme systems that synthesize prostaglandins, which are local
hormones that cause many vascular and other local tissue reactions.
5. An important protein called fibrin-stabilizing factor, which is essential
in blood coagulation process.
6. A growth factor that causes vascular endothelial cells, vascular smooth
muscle cells, and fibroblasts to multiply and grow, thus causing cellular
growth that eventually helps repairing damaged vascular walls.
Reticulo-endothelial system (monocyte-macrophage system)
-The monocytes act mainly as mobile cells that are capable of wandering
through the tissues.
Dr. Basim Al-Ka'abi
Blood Physiology
Second Lecture
3
-However, after entering the tissues and becoming macrophages, another
large portion of monocytes becomes attached to the tissues and remains
attached for months or even years until they called on to perform specific
local protective functions.
-They have the same capabilities as the mobile macrophages to
phagocytize large quantities of bacteria, viruses, necrotic tissue, or other
foreign particles in the tissue.
-When stimulated, they can break away from their attachment and once
again become mobile macrophages that respond to chemotaxis and all the
other stimuli related to the inflammatory process.
-The total combination of monocytes, mobile macrophages, fixed tissue
macrophages, and a few specialized endothelial cells in the bone marrow,
spleen, and lymph nodes is called the reticulo-endothelial system.
-The term reticulo-endothelial system is much better known in medical
literature than the term monocytes-macrophage system.
The plasma
-Plasma is a homogenous, slightly alkaline fluid, which contains waste
substances produce from the tissues, dissolved gases, inorganic salts,
protein, carbohydrate and lipids.
-Serum has the same composition as plasma except that its fibrinogen and
clotting factors have been removed.
Plasma proteins
-The plasma proteins consist of albumin, globulin and fibrinogen fractions.
-The globulin fraction is subdivided into numerous components, which are
alpha 1 (α1); α2; beta 1 (β1); β2 and gamma (γ) globulins.
-The albumin; α and β globulins and fibrinogen are manufactured in the
liver; while γ globulins are manufactured in plasma cells.
Dr. Basim Al-Ka'abi
Blood Physiology
Second Lecture
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-Normally, total plasma proteins in human adults range in concentration
from 6-8 g/dl.
-The capillary walls are relatively impermeable to the proteins in plasma,
and the proteins therefore exert on osmotic force of about 25 mm Hg across
the capillary wall (oncotic pressure) that tend to pull water into the blood.
-The plasma proteins are also responsible for 15% of the buffering capacity
of the blood.
Albumin
-Is the major protein of human plasma.
-Albumin, synthesized by the parenchymal cells of the liver, is normally
present at an average concentration of about 4 g/dl (range 3.5-5 g/dl).
-When the concentration of albumin is severely reduced (as in liver disease
because of protein synthesis is depressed; in renal disease because large
amounts of albumin are lost in the urine or in malnutrition), this leads to
a decrease in the plasma oncotic pressure, so excess extracellular fluid may
accumulate, a medical condition called edema.
-Whereas in closed body cavities it is described as either ascites (in the
peritoneal cavity) or effusion (in the pleural or pericardial cavities).
-Albumin is also the carrier for substances; these substances include
normal components of blood, such as bilirubin and fatty acids as well as
exogenous agents such as drugs.
Haptoglobins
-Haptoglobin is composed of two α chains and only one form of β chain of
polypeptides.
-The β chain contains the site with which the molecule binds hemoglobin.
-Their biological function is in the metabolism of plasma Hb by preventing
its glomerular filtration and confining its uptake to the liver.
Dr. Basim Al-Ka'abi
Blood Physiology
Second Lecture
5
Ceruloplasmin
-Ceruloplasmin is a copper-containing protein that has enzymatic
activities.
-It is important in maintenance of Cu
+2
homeostasis and serve in Cu
+2
transport, and carries 90% of the copper present in plasma.
-Albumin carries the other 10% of plasma copper.
- Wilson’s disease, an inherited condition, in which plasma ceruloplasmin
is markedly reduced and Cu
+2
levels increase in the brain and the liver with
resultant neurological changes and liver damage.
Transferrin
-The major function of transferrin is the transport of iron in the circulation
to the sites where it is required, and to prevent iron loss through the kidney.
-Two molecules of ferric iron (Fe
+3
) bind to each molecule of transferrin.
Ferritin
-Ferritin is the storage form of iron in the tissues, which is found principally
in the reticulo-endothelial cells of the liver, spleen and bone marrow.
-It contains approximately 23% iron.
-Normally, there is a little ferritin in human plasma.
-However, in patients with excess iron, the amount of ferritin in plasma is
markedly elevated.
Fibrinogen
-Fibrinogen is about six times more viscous than albumin and is mainly
responsible for blood viscosity. It is also essential in blood clotting process.
-Serum has no fibrinogen, so total plasma protein minus serum proteins
give a measure of fibrinogen.
Dr. Basim Al-Ka'abi
Blood Physiology
Second Lecture
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Immunoglobulins
-The antibodies are gamma globulins called immunoglobulins; usually
they constitute about 20% of all plasma proteins.
-There are five major groups of immunoglobulins in the serum, which are
IgA, IgG, IgM, IgD and IgE; they are produce by the lymphocyte-plasma
cell system.
-All the immunoglobulins are composed of combinations of light and
heavy polypeptide chains, most of which are a combination of two light
and two heavy chains, some of the immunoglobulins have combinations of
as many as ten heavy and ten light chains, which gives rise to a much larger
molecular weight immunoglobulin.
-Yet, in all immunoglobulins, each heavy chain is paralleled by a light
chain at one of its ends, thus forming a heavy-light pair and there are
always at least two such pairs in each immunoglobulin molecule.
-Antibodies provide a major defense against infectious agents.
Functions of plasma proteins
1. They act as protein reserve to the body, mainly in case of starvation.
2. The plasma proteins increase the viscosity of the blood.
3. Plasma proteins exert an oncotic pressure of about 25 mm Hg, which
plays an important role in the reabsorption of tissue fluid.
4. They are important in transporting certain hormones, drugs and other
substances in the blood.
5. They also have the ability to neutralize both acids and alkalis that is they
act as buffers.
6. Globulins acts as defense mechanism by forming antibodies.
Dr. Basim Al-Ka'abi
Blood Physiology
Second Lecture
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The ionic constituents of plasma
-The ionic constituents of plasma maintain the pH of blood within
physiological limits.
-The chief inorganic cation of plasma is sodium.
-Plasma also contains small amounts of potassium, calcium, magnesium
and hydrogen ions.
-The principal anion of plasma is chloride, and ionic equilibrium is
maintained by the presence of other anions, including bicarbonate,
phosphate, sulfate, plasma protein and organic acids.
Enzymes of plasma
-Most plasma enzymes do not have metabolic roles, except for the enzymes
concerned in blood coagulation.
-Serum enzyme levels are often useful in the diagnosis of particular
diseases or abnormal physiological conditions, such as the level of plasma
acid phosphatase becomes very high in cases of prostatic cancer, and high
alkaline phosphatase is found in cases of hepatic obstruction.