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Components of the blood
The blood in general is composed of plasma and cells, the plasma itself is composed
mainly of water and we can find a lot of elements in the plasma like hormones,
enzymes,plasma proteins, electrolytes or gases. All these things are dissolved orcarried in the blood either by being dissolved or carried by the plasma protein and
we can find the cells like erythrocytes, leucocytes and platelets.
So blood is composed mainly of plasma and formed elements, which we are going
to study. We are going to concentrate on the physical characteristic of the blood, its
functions and the viscosity of both the blood and lymph.
So as seen in slide 2; this is a sample of blood, which is venous, if it is spun in a
centrifuge, the heavier formed elements are packed down by centrifugal force and
the less dense plasma remains at the top, so if we take a sample of venous blood and if
we centrifuge it the dense/heavy elements of the blood (cells) will stay at the bottom
and plasma will go upwards.
PlasmaThe plasma has 2 components:
1) cellular components (formed elements) which includes erythrocytes2) the Buffy coat which is a whitish layer present at the site of the erythrocyte plasma
and it containsLeukocytes andplatelets.
We also have liquid components (plasma) which makes about 55% of the blood
making the cells about 45% of the blood.
Erythrocytes normally constitute 45% of the total volume of blood. This percentage is
known as the hematocritSO THE CELLS IN THIS PERCENTAGE ARE
KNOWN AS THE HEMATOCRIT-. In males and females, this percentage might
differ:
IMPORTANT: (in males: 45- 47% 5% , in females: 40-45% 5% )
Plasma is the fluid portion of the blood which contains proteins which are the most
important component of blood (albumins, globulins, and fibrinogens) these are the
plasma proteins and we can also find in the plasma nutrients, metabolic end products,
hormones, and mineral electrolytes.
Plasma is obtained when unclotted blood is centrifuged. The fluid which rises above
the cellular elements is in fact the PLASMA.
Serum is plasma from which fibrinogen and other coagulation proteins have
been removed as a result of clotting. It contains high level ofserotonin(released from platelets during clotting). It is obtained when clotted blood is
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centrifuged. The fluid above clotted blood is SERUM i.e. Serum is the liquid part of
the blood after the coagulation.
.
These are cellular elements in cell; they includeplatelets, Erythrocytes, different
types of leukocytes and the subtypes of leukocytes -1- granule -2- Agranule cytes.
The total plasma protein is 7-8 g/dl
Albumin about 4.5 g/dl
Globulin about 2.5 g/dl (alpha, beta and gamma globulins)
Fibrinogen about 0.3 g/dl
{Its important to know the amount of each protein}.
Most plasma proteins are produced by the liver, except for hormones and gamma
globulins (they are formed by plasma cells). Being 8% by weight of plasma
volume, plasma proteins serve a variety of functions, but they are not taken up bycells to be used as fuels or metabolic nutrients as are most other plasma solutes, such
as Glucose,fatty acids, andamino acids.
HypoproteinemiaHypoproteinemia is seen in:
a. liver disease(low production of protein- less formation-)
b. kidney diseases(loss of protein) such asNephritic syndrome you find signs
which are protein urea-means protein uric-
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In the liver hypoproteinemia; decreases the concentration of protein in blood.
Albumin: MW= 69000
It Accounts for about 60% of plasma protein
It acts as a carrier of many substances in the circulation,
It is an important bloodbuffer and the major bloodprotein contributing to the
ONCOTIC PRESSURE (plasma osmotic pressure).
This pressure helps to keep water in the bloodstream.
Globulins ( and ) act as enzymes and carriers.
- They are produced by the liver.
- Antibodies (gamma globulins, immunoglobulin) produced by plasma cells.
- Fibrinogen produced by liver forms fibrin threads of blood clot.
In the plasma we have:
nutrients and hormones and the difference between hormones and enzyme is that:
{hormones are secreted from specific organs and effects in the body directly, forexample: antidiuretic hormone (ADH)secreted from the hypothalamus it acts
on the connecting tubules in the kidney}.
{enzymes are secreted from one organ and acts locally in that organ, for example :
pepsinit is secreted from the stomach it acts locally in the stomach }.
Electrolytes; Ca++
, K+, Cl
-, HCO3
-, Na
+ions help to maintain the osmotic pressure.
Sodium ions are the major solute contributing to blood osmotic pressure and they helpin maintaining a normal blood pH.
(Normal pH is 7.35 or 7.45) it is a trump.
Above 7.45 we call it alkalosis
Below 7.35 we call it acidosis
- its danger leads to death that's why it is extremely important for patients to
get intensive per units of ABG (arterial blood gases) and they should be taking it
hourly in order to check if theyre blood is in the state of acidosis or alkalosis.
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We have 2 types of acidosis and alkalosis 1) We have metabolic acidosis or alkalosis
2) respiratory acidosis or alkalosis (the function of the respiratory system is in the acid
base balance, it is the moment to moment control of acid base balance determined by
CO2 or O2).
***when we study the GI we can ask about metabolic acidosis or alkalosis but once
we study the respiratory system we have to know by heart the respiratory acidosis and
alkalosis.***
The formula that makes a difference between acidosis and alkalosis is that when the is
shift in the hemoglobin-oxygen dissociation is curved to the right
It increases CO2
It increases the H ions which is the product of metabolism
It increases the temperature.
It increases 2,3 bisphosphoglycerate, all these factors shift the curve to the right.
Physical Characteristics and Volume:
Total blood volume: 8% of body weight, slightly alkaline pH between 7.35 and
7.45.
-Blood is denser than water and about 3-4 times more viscous. Why? Because of the
cells (cell components).
Blood functions:
There are six functions:
1) Transportation
O2lungs cells
CO2cells lungs
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-The formed elements are present in the buffy coat and the bottom red layer (RBCs,
WBCs and platelets).
-Erythrocytes have no nuclei or organelles and the platelets are cell fragments. Only
the leukocytes are true cells.
-Erythrocytes and platelets do not divide.
Blood viscosity:
It is Plasma protein, the main component of blood elements and is what sets the
principle of the blood viscosity. Viscosity is increased when hematocrit value or
Number of RBCs rise.
Erythrocytes
Plasma membrane is in an enclosed sac full of hemoglobin
(thats why they are called Bags of hemoglobin) with no
nucleus or organelles.
*whats the importance of RBCs ???
It contains hemoglobin which is responsible for the transfer of
oxygen (mainly), and at a lesser rate carbon dioxide and
hydrogen ions.
*Structural characteristics:
1) Small, biconcave shape which provides a large surface area for diffusion of oxygen
molecules across the membrane.
2) Concentration; in females 4.7-5 million per cubic mm, in Males 5.2-5.5 million per
cubic mm
3) Lacks nucleus; life span = 120 days
4) Thickness; 2.5/1 so oxygen can diffuse rapidly between exterior and innermost
regions of the cell
5) Relay on glycolysis for ATP production (not on oxidative phophorylation because
it has no mitochondria)
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*RBC Production:
1) During early weeks of pregnancyproduction of primitive nucleated RBCs in
yolk sac
(Wikipedia:- yolk sac: membrane sac attached to an embryo providing early
nourishment in the form of a yolk)
2) During the middle trimesterproduction of RBCs from the liver (mainly), spleen
and lymph nodes
(Wikipedia:- first trimester= months 1-3 of pregnancy, middle trimester= months
4-6, third trimester= months 7-9)
3) During the last month of pregnancy and after birth (0-5years)all from the bone
marrow.
4) 5-10 years from the shaft of long bones (then it becomes fatty and its
contribution in forming RBCs is reduced gradually and eventually stops completelyafter 20 years. The heads of long bones however, continue to form RBCs )
5) >20 years almost all in membranous bones.
*Relative rates of RBC production in bone marrow of different bones at different
ages.
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Hemoglobin
*Parts:
1) Globin Protein four highly folded polypeptide chains
2) Four iron containing non protein groups (heme groups), each can combine
reversibly with one oxygen molecule, thus each hemoglobin molecule binds with 4
oxygen molecules.
- The relationship between hemoglobin and oxygen is reversible (hemoglobin binds
oxygen and release it to tissues)
*Role:
1) Transfer oxygen molecule and carbon dioxide molecules
2) Buffer capacity
* Average values of hb:
Adult males 16 g/100ml
Adult females 14 g/100ml
Erythropoiesis
*Erythropoiesis: RBCs Production (because RBCs cant divide, the old ruptured
cells must be replaced by new cells produced in bone marrow). Although the various
formed elements have different function, they all arise from the same stem cell.
1) In children, most bones are filled with red bone marrow that is capable of blood
cell productions. Red bone marrow is the ultimate source for leukocytes and platelets
as well.
2) As a person matures,however, fatty yellow bone marrow that is incapable of
erythropoiesisgradually replaces red marrow, which remains only ina few isolated
places, such as the sternum (breastbone), ribs,and upper ends of the long limb bones.
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* Pluripotent hematopoietic stem cell (PHSC):
-The 'mother of all cells'the progenitor of all hematopoietic cellse.g. platelets,
RBCs, neutrophils, macrophages, lymphocytes.
-Derived from mesenchymeonce committed it follows its path.
*PHSC gives:
1. Committed stem cells that produce RBC, granulocytes, monocytes , platelets
2. Committed stem cells that give lymphocytes
3. PHSC that keeps a supply of committed stem cells
*Notes:1) growth inducers like interleukin-3 makes PHSC to give different committed stem
cells.
2) Differentiation of different colonies into different blood cells is done by different
inducers
3) Erythropoiesis begins when a stem cell is transformed into a proerythroblast
(committed cell)
Committedstem cell thatform RBC,Granulocytes,monocytes,platelets
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RBCs Maturation Stages
Time needed for committed stem cells to develop to mature erythrocytes is about 5-7
days.
1) Proerythroblast: is the first cell belonging to the red blood series.
2) Early Erythroblast: (ribosome synthesis) little of Hb starts to accumulate
3) Late Erythroblast: (hb accumulation) Hb concentration is increased until it forms
almost 34% of volume of the cell.
4) Normoblast: (ejection of nucleus)
5) Reticulocyte: Very few Hb is formed. It is the last stage which does not contain
nucleus and the cytoplasmic organelles are disappearing and the only remnants of
these remained. They leave the bone marrow and stay in the blood for 1-2 days and
finally they form mature RBC. Normal reticulocytes number in circulation is about
1% of total RBC number
6) Mature Erythrocyte
Erythropoiesis control* low O2 levels do not stimulate erythropoiesis by acting directly onthe red bonemarrow. Instead, it reduces O2 delivery to the kidneys,stimulates them to secrete thehormone erythropoietininto the blood and this hormone in turn stimulateserythropoiesisby the bone marrow.
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*Erythropoietin (EPO):A hormone produced mainly by tubular epithelial cells in
the kidney (90%) and hepatocytes in liver (10%) that promotes the formation of red
blood cells in the bone marrow. EPO is a glycoprotein (a protein with a sugar attached
to it). Human EPO has a molecular weight of 34,000.
1) Stimulus: A drop in normal oxygen levels (hypoxia) triggers erythropoietin
formation. Hypoxia is the most potent stimulus for erythropoietin production. Other
factors that increase erythropoietin production are Androgen, alkalosis and
Catacholamines.
2) When less O2 is delivered to the kidneys, they secrete the hormone erythropoietin
into the blood.
3) Erythropoietin stimulates erythropoiesis (erythrocyte production) by the bone
marrow
4) The additional circulating erythrocytes increase the O2-carrying capacity of the
blood.
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Fragile Membrane
Cells Rupture as they pass through
narrow spaces in spleen
5) The increased O2-carrying capacity relieves the initial stimulus that triggered
erythropoietin secretion.
Destruction of Erythrocytes
The anucleated condition of erythrocytes carries with it some important limitations.
-Red blood cells are unable to synthesize new proteins, to grow, or to divide.
-Erythrocytes become old as they lose their flexibility and become increasingly
rigid and fragile, and their contained hemoglobin begins to degenerate.
-Aged RBCs have:
Metabolic activity
Enzyme activity
ATP
Membrane Lipids
*Process:
1) In the red pulp of the spleen, RBC rupture when they try to squeeze through
because of their fragile old membrane.For this reason, the spleen is sometimes calledthe red blood cell graveyard.
2) Macrophages in spleen, liver and red bone marrow phagocytize dying RBC.
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-Globinbreaks into amino acids, which can be reused to produce other proteins
-Hemeiron and porphyrin
-Fe removed and recycled in spleen
-Porphyrinconverted to bilirubin (bile pigment)
Yellow pigment secreted by liver into bile, which is excreted in urine and feces
Diseases of Red Blood Cell
Anemia :
*Definition; a decrease in the number of red blood cells (RBCs) (less than the normal
quantity of hemoglobin in the blood). However, it can include decreased oxygen-
binding ability of each hemoglobin molecule.
*Causes:
1) Insufficient number of RBC
2) Low hemoglobin content
3) Abnormal hemoglobin
*Effects:
anemia
Decreased
viscosity
Decreased
resistance to
blood flow
hypoxiaDilatation of
blood vessels
More blood
returns to the
heart
More cardiac output
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Polycythemia Lea
Blood volume
Hematocrit
viscosity
decreased blood flow Increased blood pressure
Decreased venous
return to the heart
Decreased cardiac output
Increased
venous return
Increased cardiac
output
More O2 is extracted from Hb and
thus deoxygenated blood is
increased leading to bluish
discoloration of the skin (cyanosis)
Polycythymia:
*Definition: a disease state in which the proportion of blood volume that is occupied
by red blood cells increases.
*Types:
1) Primary Polycythemia: Due to increased activity of hemocytoblastic cell of bone
marrow.
2) Secondary Polycythemia: Due to hypoxia.
*Effects:
We are sorry for any mistake in this lecture ,,,
We want to thank ANMAR HADAD , and we wish to
you all the success in medicine