LSM3212_Lecture 2-4 Blood

8/3/2019 LSM3212_Lecture 2-4 Blood

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~ LSM3212 ~

A/Prof Wong Chong Thim

Department of Physiology

[email protected]

MD9, #03-08

A/Prof CT Wong LSM3212 Blood 1


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BLOOD

Composition of blood: plasma and

ce u ar e emen s o oo

Functions of BloodBlood Cells and their Production

Hemostasis: revention of blood loss



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Blood Cells & Plasma

Components

Plasma the liquid component of the blood

Cells

Some blood arameters Hematocrit

Hemoglobin concentration

Red blood cell (rbc, erythrocyte) count

White blood cell (wbc, leukocyte) count


Differential wbc count


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. , .



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p e s p s

Protein concentrations:Total 6.0-8.0 g/dL

Albumin 3.1-4.3 g/dL

o u ns . - . g

Fibrinogen 200-450 mg/dL

Transferrin 3.0-6.5 mg/dL

All the plasma proteins are

immunoglobulins, from B-

lymphocytes.



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Components of formed elements

thrombocytes

reticulocytes



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#14


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Main blood cell parameters of normal healthy adults

Cells/L (average) Approx. range Percentage of Total White Cells

Erythrocytes

MalesFemales

5.4 x 106

4.8 x 1064.4 5.8 x 10

6

4.1 5.2 x 106

,

Granulocytes

Neutrophils 5400 3000 6000 50 70

Eosinophils

Basophils35

150 300

10 - 100

1 4

0.4

Lymphocytes 2750 1500 4000 20 - 40

Monocytes 540 300 600 2 - 8

Platelets 300,000 200,000 500,000



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Main blood parameters

Test Measures Elevated Depressed

va ues va ues

Hematocrit (Hct) Percentage of formed

elements in whole blood.

Polycythemia Anemia

Reticulocyte count(retic) Circulating percentage ofreticulocytes Reticulocytosis

concentration (Hb)

hemoglobin in blood

RBC count Number of RBCs per l of Erythrocytosis/ Anemia

Male Female

Hematocrit (%) 40 to 54 37 to 47

Hemoglobin conc

( /dL)

14 to 17 12 to 16


Reticulocyte count ~0.8%


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Functions

Transport/Distribution

Metabolic wastes Various substances (eg. minerals, vitamins, etc)

Homeostasis/Regulation

Body temperature p

Fluid volume

Against blood loss (Hemostasis)

Against infection (Immunology) *



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Immune system

Leukocytes are the mobile units of the bodys immune

outside the blood.

They defend against the invasion of pathogens.

They identify cancer cells. They remove the bodys litter by phagocytosis.

They can leave the circulation and go to the sites of.


#09mmuno ogy


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15

Fig. 13-26, p. 487

A/Prof CT Wong


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Exchange of oxygen and carbon dioxide at tissue level

Diffusion

16A/Prof CT Wong LSM3212 Blood

Hb = hemoglobin


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Transport of oxygen



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1 Hb molecule = 4 Hb chains

1 Hb chain = 1 heme + 1 globin


abm3s6a.mov


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Oxygen carrying capacity of blood

In hemoglobin

~ 15 g Hb/dL blood

~ 1.34 ml oxygen/g Hb (fully saturated)

~ 20 ml oxygen/dl blood

In plasma ~ 0.003 ml oxygen/dL blood/mm Hg oxygen (partial

pressure of oxygen)

Systemic arteries = 100 mmHg

S stemic veins = 40 mm H



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Transport of carbon dioxide



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Transport of carbon dioxide

[carbaminoHb]

(~7%) (~23%)

(~70%)



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Blood Cell Production

An erythrocyte in the circulation cannot reproduce, as it lacks anucleus. Erythropoiesis (erythrocyte production) is the productionof new red cells, replacing the functionally worn-out cells in thecirculation. This occurs in the bone marrow in the adult.

Pluripotent stem cells in the red marrow differentiate into all thedifferent types of blood cells that we find in the circulation.

Regulatory factors act on hemopoietic (blood-producing) redmarrow to govern the type and number of cells produced and

discharged into the circulation. The average life span of an erythrocyte is 120 days. The final

demise of old erythrocytes is mainly in the spleen.

The number of erythrocytes normally remains constant.

Cell production = cell death.

However, a low level of oxygen delivery to the tissues stimulates


controlled by erythropoietin, a hormone produced by the kidneys.


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Blood cell production in boneTwo important properties of

stem cells:

. ep cat on2. Differentiation

A/Prof CT Wong LSM3212 Blood 24Fig. 11-9, p. 404


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Ifoxygen delivery to the tissues,and kidneys, is decreased, the

kidneys detect this and increase theoutput oferythropoietin. The rate oferythropoiesis increases.

An increase in the rate of

erythropoiesis increases the number-carrying capacity to the tissues.

Once the oxygen delivery to the

tissues, and kidneys, is sufficient,the kidneys detect this. Theydecrease their output oferythropoietin.


[Negative feedback system]


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Hemoglobin is a molecule consisting of two parts.

The heme part is nonprotein.

Each of its four iron atoms is

bound to one of the

polypeptides and cancombine with one molecule

o oxygen gas. s mo ecu e

is bright red when combined

with oxygen. e g o n s our, o e

polypeptide chains.

Hemoglobin can also

com ne w t car on ox e,hydrogen ions, carbon

monoxide, and nitric oxide.


emog o n can u er p y

binding with hydrogen ions.


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Type of globin chain determines

.Each consist of a tetramer of

globin polypeptide chains., each

with an attached heme.

-like chains 141 aa long

-like chains 146 aa long

HbF (), fetal Hb

HbA (), adult HbHbA2 ( ), adu t Hb, norma

variant, very small %.

-

HbE () abn aa26 glu-lys



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Iron metabolism

Iron absorption occurs predominantly in the duodenum and upper jejunum.

Iron must traverse both the apical and basolateral membranes of absorptive

.

the oxidation state of iron.

Iron that is present in food (particularly in red meat, pulses (legumes) and dairy

roducts rimaril occurs as Fe III or as heme. There is evidence that heme

may be transported into the intestine by a specific carrier (heme carrier protein 1;

HCP1) although the nature of the carrier is unknown. Iron from heme is better

absorbed compared to non-heme iron.

Iron that is exported from cells into plasma by ferroportin becomes bound to

- - -,

iron-binding domains that is synthesized in the liver, retina, testis and brain.At the neutral pH of blood, transferrin can bind two atoms of Fe(III) with a

dissociation constant Kd of 1023 M. Fe III binds transferrin onl in the


presence of an anion, usually carbonate, that bridges iron and transferrin.


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Iron transport across the enterocyte

of the intestines).


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Amount of available iron is de endent on

(1)Amount of iron in food we ingest main source is meat

(2)Form of iron present in the food

Ferric iron (Fe(III)) in the diet is

converted to ferrous iron (Fe(II))by a ferroreductase (DCYTB,

duodenal cytochrome B) that is

located on the apical surface of

enterocytes of the duodenal mucosa.

Amount of iron absorbed is well controlled by feedback system(many hypotheses, no complete agreement), absorbing enough to


.

Liver stores a ready supply of iron.


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iron, transferrin and the

transferrin receptor.

The plasma protein transferrin

(Tf) binds Fe(III) with high

affinity. At the neutral pH (7.2)in plasma, TfFe(III) binds to

the cell surface from where it is

internalized by receptor-

mediated endocytosis throughclathrin-coated pits.

The internalized vesicle (an endosome) becomes acidified (pH 5.5) by the action of

an H+ ATPase not shown . As the H of the endosome decreases the structure of the

TfTfR complex changes and Fe(III) is released from TfFe(III). Fe(III) is converted toFe(II) by the endosomal reductase STEAP3 (six-transmembrane epithelial antigen of the

prostate 3) and is then transported out of the endosome into the cytosol by divalent metal


ranspor er- . e can e s ore n err n n nonery ro ce s or ncorpora e

into haemoglobin in erythroid cells. The TfTfR complex is exocytosed by a recycling

endosome.


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In liver

A/Prof CT Wong LSM3212 Blood 32In maturing rbc


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Synthesis of Porphobilinogen and Heme

1* ALA synthase; 2 PBG synthase/ALA dehydratase; 3 PBG deaminase/Uroporphyrinogen


III synthase; 4 Uroporphyrinogen decarboxylase; 5 coproporphyrinogen III oxidase;

6 protoporphyrinogen IX oxidase; 7 Ferrochelatase (Addition of iron occurs at this step)


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The largest repository of heme in the human

body is in red blood cells, which have a lifeHeme Catabolismspan o a out ays. ere s t us aturnover of about 6 g/day of hemoglobin,

which presents 2 problems. Breakdown of rbc

system, mainly in the spleen and liver (Kupffercells).

First, the porphyrin ring is hydrophobic and

must be solubilized to be excreted.

Second, iron must be conserved for new heme

synthesis. Normally, senescent red blood cells

and heme from other sources are engulfed by

cells of the reticuloendothelial system. Theglobin is recycled or converted into amino

acids, which in turn are recycled or catabolized


as requ re . ron s re ease n o e c rcu a on

for reuse by the body.


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eme s ox ze , w t t e eme r ng e ng opene y t e

endoplasmic reticulum enzyme, heme oxygenase. The oxidation step

requires heme as a substrate, and any hemin (Fe3+) is reduced to heme


.


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bridging methylene (between

rings III and IV) is reduced by

biliverdin reductase roducin

bilirubin.

Bilirubin is released into the

circulation. It is transported in theplasma bound to albumin. This is

the free or unconjugated

bilirubin, and it is quite insoluble.



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Albumin bound bilirubin is

transport to hepatocytes, where

UDP glucuronyl transferase adds 2

equivalents of glucuronic acid to

bilirubin to produce the more

water soluble, bilirubindiglucuronide derivative.

The increased water so ubi ity of

the tetrapyrrole facilitates its

excretion with the remainder of the.


Destruction of rbc and reutilization of breakdown products


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Destruction of rbc and reutilization of breakdown products

A/Prof CT Wong 38


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Jaundice

,

bacteria to produce the final porphyrin products, urobilinogensand urobilins, that are found in the feces.

Bilirubin and its catabolic products are collectively known as

the bile pigments.

In individuals with abnormall hi h red cell l sis or liverdamage or obstruction of the bile duct, the bilirubin and its

precursors accumulate in the circulation; the result is

,

pigmentation known asjaundice.



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Anemia

Anemia is a reduction below the normal capacity in the blood to carry

oxygen. ere are many n s o anem a.

Nutritional anemia is caused by a dietary deficiency of a factor neededfor erythropoiesis (eg. iron, vitamins).

Aplastic anemia is due to the failure of the bone marrow to make

adequate numbers of RBCs.

Renal anemia is due to kidney disease; lack of Epo. Hemorrhagic anemia is due to the loss of significant amounts of blood

(and production cannot keep up with loss).

Hemolytic anemia is due to the rupture of many RBCs. Sickle cell

disease can make red cells fragile and vulnerable to hemolysis.


PRODUCTION vs LOSS/DESTRUCTION


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Polycythemia

Polycythemia is an excess in circulating erythrocytes.

.

Primary polycythemia is caused by an tumor-like condition in the bone

marrow.

-

mechanism to improve the oxygen-carrying capacity in the blood.

Relative (spurious) polycythemia: Other conditions can elevate the

, .


PRODUCTION vs LOSS/DESTRUCTION


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Leukocytes are produced at varying rates.

Their rates change depending on the changing defense needsof the body.

They are produced from pluripotent stem cells in the bonemarrow. These cells can differentiate and proliferate into

different cell lines, producing the different kinds of white bloodce s.

Granulocytes and monocytes are produced only in the bonemarrow.

Lymphocytes are originally produced from precursor cells in thebone marrow. Most new ones are produced from lymphocytesin lymphoid tissue (eg lymph nodes).



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Hemostasis Primary hemostasis

Vesse wa s

Platelets

Coagulation factors

Extrinsic pathway Intrinsic pathway

Common pathway

ontro o emostas s Anticoagulants



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e s s s p eve s ss evessels.

The first two steps to stop escaping blood from a vessel

are: vascular spasm - This reduces blood flow through a damaged

vessel.

platelet plugging - An aggregation of platelets forms a plug.Platelets aggregate on contact with exposed collagen in thedama ed wall of a vessel. The latelet lu seals a break in avessel.

Platelets releases numerous substances when activated.Some of these substances will enhance the aggregation

process. Among t ese are ADP, t rom oxane A2, ca ciumions. Other substances from the endothelium of a bloodvessel inhibit platelet aggregation, keeping the process


.


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Normal and damaged vessel wall


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No a a d da aged vesse wa



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factors. They lead to the final conversion of fibrinogen into fibrin.

e c o ng ac ors serve as pro eo y c enzymes n a ser es o

reactions, the clotting sequence. One factor in the sequence isactivated which in turn activates another factor and so on. This

.

The last two steps in the cascade are:

prothrombin is converted to thrombin

fibrinogen is converted to fibrin

intrinsic pathway - This uses the sequence of factors in the cascade.

extrinsic pathway - This requires only four steps and requires

contact with tissue factors external to the blood.



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Fig. 11-13, p. 408


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Coagulation factors

I FibrinogenII Prothrombin

III Thromboplastin/tissue factor*

V Proacclerin, labile factor, accelerator globulin

VII Proconvertin, SPCA, stable factorVIII Antihemophilic factor (AHF), antihemophilic factor A,

*

anti emop ilic glo ulin (AHG)

IX Plasma thromboplastic component (PTC), Christmas factor,

antihemophilic factor B

X Stuart-Prower factor

*

*XI Plasma thromboplastin antecedent (PTA), antihemophilic

factor C

XII Hageman factor, glass factor

- - ,

HMW-K High-molecular-weight kininogen, Fitzgerald factorPre-K Prekallikrein, Fletcher factor

Ka Kallikrein


PL Platelet p osp olipi

* Vitamin K dependent coagulation factors


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Vitamin K acts as a cofactor

in the formation of g-

carboxyglutamyl residues

(gla components) fromlutam l residues lu

components) in the

coagulation factors listed.

in the formation ofcalcium

binding sites. The next slide

show the events that will

lead to the conversion of

rothrombin to thrombin.

LSM3212 Blood 50A/Prof CT Wong

Coagulation cascade


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Coagulation cascade

Common pathway


Fig. 11-14, p. 409


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Prothrombin activator

The figure on the left is the situation at the start of the common pathway.

Factor Xas gla components are attracted to the ionised Ca that are in contact

with latelet factor 3 also called latelet hos holi ids . These lateletphospholipids have negative charges that attract the Ca in the plasma. This

builds up the concentration of Xa in the damaged area. Prothrombin, which

also possesses gla components are also attracted by the Ca present. This thus

increases its concentration and also brings it in close proximity with Xa (seefigure on right). Xa then can act on the prothrombin and convert it to thrombin.

Same sort of reaction occurs in the activation of factor X by IXa (intrinsic

52

pathway) or VIIa (extrinsic). Next 2 slides show how inactive coagulation

factors are activated mainly by loss of part of the protein molecule, change in

3D structure, exposure of active sites in the molecule.


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(Either VIIa com lex or IXa com lex)

(active site)

Figure on left is the normal circulating inactive factor X. Removal of part of

the molecule by either IXa (intrinsic pathway) or VIIa complexes (extrinsic

pathway) allows for changes in 3D conformation, leading to exposure of

active site, converting it into an active enzyme. Similar events occur during

activation of IX, VII and conversion of prothrombin to thrombin.

LSM3212 Blood 53

( = gla components)

A/Prof CT Wong

(Xa, V, Ca, PL)


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( = gla com onents)

(Thrombin removes part of the fibrinogen molecule,

which allows the fibrin monomer to bind to one

another)

LSM3212 Blood 54A/Prof CT Wong

Anticoagulants


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Anticoagulants

Heparin/heparan

Heparin in plasma; heparan on endothelial surface

Functions as co-factor to anti-thrombin III

Normal constituent of plasma Anti-thrombin III

Plasma protein that binds to and inactivates thrombin,IXa, Xa

One of the many plasma proteins normally present inblood

Warfarin (coumarin) drugs

Drugs affecting vitamin K dependant coagulationfactors

Removal of calcium ions (in vitro)

Chelates/binds to calcium ions e . citrate, oxalate,


EDTA)


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Additional notes on blood clottin :

1. Clot retraction occurs after the clot is formed.

2. Amplification occurs in the clotting process. One moleculecan activate one hundred molecules in the next step and soor .

3. Whether a clot will form or not is dependent on the balanceo e ac ors promo ng c o orma on an a o c odestruction (fibrinolysis)

http://www.mhhe.com/biosci/esp/2002_general/Esp/folder_str


ucture/tr/m1/s7/trm1s7_3.htm

Balance between clot formation and destruction


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Aims & Objectives


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Aims & Objectives

1. Describe the composition of blood.

. .

3. Describe the process of normal erythropoiesis.

factors required for normal erythropoiesis.

. .involved in hemostasis.

Reference: Sherwood L 2010 Human Physiology. 7th ed


Chapter 11

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LSM3212_Lecture 2-4 Blood