blood histology

8/4/2019 Blood Histology

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BLOOD


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BLOOD...

y TISSUE

y Composed of: ERYTHROCYTES, LEUKOCYTES andTHROMBOCYTES

y Suspended in fluid : PLASMA (transparent yellow fluidthat constitute the extracellular matrix of the bloodtissue)

y Normal vol of blood in the body: 5-6 Liters (7% 0f thebody weight)

yErythrocytes = 45%

y Leukocytes and platelets = 1%

y Plasma = 54%


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Study of blood...

y Microscopic study of blood cells (PERIPHERAL

BLOOD STUDY) = uses stained blood smears

y Yields the following information: diseases that

primarily affect the blood; indirect evidences of

viral, bacterial, and parasitic infections

y This study will enable clinicians to identify the

disease, follow its course, and evaluate theeffectiveness of treatment


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PERIPHERAL BLOOD FILM ((Wrights

stained)

Elements of BLOOD:

Erythrocytes

Leukocytes

Thrombocytes


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RED BLOOD CELLS:Shape andSize

y Biconcave discs in shape;

y bag that can be deformed into almost any shape

y Normally, the RBCs have a great excess of cell membrane

relatively compared to the quantity of the material insidey With this, deformation does not stretch the membrane great

greatly and does cause rupture

y This shape can change remarkably as the RBCs pass thru the

capillaries


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Three Dimensional RBC


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The biconcave shape..

y This shape presents a surface area 20-30% greater in relation

to its volume than it would have if it were spherical

y This increased surface area favors the immediate saturation of

its hemoglobin with OXYGEN as the erythrocytes pass thruthe pulmonary capillaries

y Total surface AREA of the RBC in an average human:

3,800sqm3,800sqm (this is 2000X the surface area of the body)

y

This leads to great efficiency in oxygen and carbon dioxidetransport


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Areas ofthe bodythatproduce the

RBCs.

y Early embryonic life: in the YOLK SAC (primitive nucleated

RBCs)

y Middle trimester of gestation: in the LIVER,

majoritySPLEEN & LYMPH NODES, minorityy Last month of gestation and after birth: exclusively in the

BONE MARROW


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Amongthe bones.

y The marrow of essentially ALL BONES produces red bloodcells until the person is 5 years old5 years old

y The marrow of the long bones (except the proximal

portions of the humeri and tibiae) until20

years old20

years old

they become quite fatty

y After 20years of age, red blood cell production occur

only in the marrow of MEMBRANOUS BONES

(vertebrae, sternum, ribs, and ilia)y ***the marrow becomes less productive as age increases


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GENESIS OF RBCS

y Proerythroblast

y Basophil erythroblast (stain with basic dyes)

y Polychromatophil erythroblast

y Orthochromatic erythroblast y Reticulocyte

y Erythrocyte


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RETICULOCYTEy The RBC is already filled with hemoglobin to a concentration

of 34% in this stage

y The form of RBC wherein the nucleus is condensed to asmall size, with its remnant being extruded, while the ER is

reabsorbedy It still contains a small amount of basophilic material,

consisting of remnants of Golgi apparatus, mitochondria, andorganelles

yIts movement from the bone marrow to the capillaries:DIAPEDESISDIAPEDESIS (squeezing thru the pores of thecapillary membranes)


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Genesis ofRBC


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Before enteringthe circulation..

y Immature red blood cells extrude their nucleus =>

y Losing their capacity for DNA-directed protein synthesis =>

y Mitochondria and other organelles are also lost =>

y Reduced to a membrane-bound corpuscle cytoplasm thatconsists predominantly HEMOGLOBIN=>

y Perform their primary function


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RED BLOOD CELLS

y FUNCTIONS:

Transport ofHemoglobin => main or major function

Transport ofCarbonic anhydrase = this enzyme catalyzes,

hastens, and fastens the reaction between CO2 & H2O=>CO2 becomes transported from the tissues to the lungs

in the form of bicarbonate ion (HCO3-)

Hemoglobin is an excellent ACID BASE BUFFER (as most

protein is) => RBCs are responsible for most of thebuffering power of the whole blood


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Normal count ofRBC

y 5.4 M/mm in men

y 4.8M/mm in women

yy These values become slightly increased by residence in high altitudeThese values become slightly increased by residence in high altitude

placesplaces


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VARIETIESINSHAPEAND

MORPHOLOGY ofERYTHROCYTES

y Hypotonic solution can make the RBC swell => stretches

the membrane => leaky, permitting hemoglobin to escape

=> leaving behind an empty membrane =>

ERYTHROCYTE GHOSTERYTHROCYTE GHOST

y Conditions of low ATP => RBCs are transformed =>

become round up with 10-30 short conical projections

radiating from the surface => ECHINOCYTES,ECHINOCYTES, and theand the

adoption process is called CRENATIONadoption process is called CRENATION

yy CrenationCrenation: can be also induced during exposure to: can be also induced during exposure to

anionic compounds, fatty acids, oranionic compounds, fatty acids, or lysolecithinlysolecithin


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REGULATION OF RBC PRODUCTION

yy WHY IS THERE A NEED TO REGULATE RBCWHY IS THERE A NEED TO REGULATE RBC

PRODUCTION?????PRODUCTION?????

Regulation is within narrow limits so that an adequate

number of red cells is always available to provide sufficienttissue oxygenation

Regulation is also not above the narrow limits so that the

cells do not become so concentrated that they impede blood

flow


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REGULATORS..y 1.Tissue Oxygenation basic regulator of RBC production

Any condition that causes the quantity of oxygentransported to the tissues to decrease increases therate of RBC production

Severe hemorrhage severe anemia BM begins toproduce large quantities of RBCs

Destruction of major portions of the bones ( byradiation) => BM works hard to produce RBCs =>hyperplasia of remaining BM tissue

Very high altitudes =>quantity of oxygen in the air isdecreased => insufficient O2 is transported to thetissues => RBC production becomes increased


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Remember.

yy Itis notthe concentration of RBCs inthe bloodthatItis notthe concentration of RBCs inthe bloodthat

controls the rate of RBCproduction,BUTthe functionalcontrols the rate of RBCproduction,BUTthe functional

ability ofthe RBCs to transport oxygento the tissues inability ofthe RBCs to transport oxygento the tissues in

relationto the tissue demand for oxygen.relationto the tissue demand for oxygen.


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Diseasedstates can also regulate

yy Some diseases ofthe circulationthat cause decreased bloodSome diseases ofthe circulationthat cause decreased blood

flowthru the peripheralvessels andthose that cause failureflowthru the peripheralvessels andthose that cause failure

of oxygen absorption bythe blood as it passes thru the lungsof oxygen absorption bythe blood as it passes thru the lungs

can also increase the rate of RBCproductioncan also increase the rate of RBCproduction.

y Examples: prolonged cardiac failure; lung diseases tissue hypoxia resulting from these diseased state

increases the rate of RBC production => increase in

hematocrit => increase in total blood volume


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REGULATORS. .

y 2. ERYTHROPOIETIN.This circulating hormone

(glycoprotein) is the principal factor that stimulates RBC

production

Hypoxia has little effect or no effect in stimulating RBCproduction in the ABSENCE of ERYTHROPOIETIN

If the erythropoietin system is FUNCTIONAL, hypoxia

can cause the marked increase in erythropoietin

production which in return enhances RBC productionuntil hypoxia is relieved


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ERYTHROPOIETIN

y 90% is formed in the KIDNEYSKIDNEYS (in the juxtaglomerular

portion or by the renal tubular epithelial cells)

y 10% is secreted or formed by the LIVERLIVER

yy When both kidneys are removed or destroyed by

When both kidneys are removed or destroyed by

disease, the person becomes invariably anemicdisease, the person becomes invariably anemic thethe

remaining 10% produced by the liver can cause orremaining 10% produced by the liver can cause or

effect only 1/3 to RBC formation as needed byeffect only 1/3 to RBC formation as needed by

the bodythe body


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ERYTHROPOIETIN

y It begins to be formed within minutes to hours and reaches a

maximum production at 24HRS when a person is placed in a

low oxygen condition

y

Yet no new RBCs appear circulating in the blood until about5days later

y Reason: erythropoietins important effect is to stimulate the

production of PROERYTHROBLASTS from the

hematopoietic stem cells in the BM


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ERYTHROPOIETIN

y This hormone also hastens the genesis of RBC

y Causes the proerythroblasts to pass more rapidly thru the

different erythroblastic stages than normally => speeding up

production of new cellsy This rapid production continues as long as the person

remains in a low oxygen state or until enough red cells are

produced to carry adequate amount of O2 to the tissues

despite the low oxygen


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ERYTHROPOIETIN

y In the absence of erythropoietin, few RBCs are produced by

the BM

y In the presence large quantities of erythropoietin and in the

presence of plenty of iron and other other nutrients => rateof RBC production can rise to 10X or more the normal

the ERYTHROPOIETIN CONTROL MECHANISM forRBC production is a powerful one


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MATURATION OF RED BLOOD CELLS

y NUTRITION plays and great affects the maturation and

rate of RBC production

y Two important VITAMINS: VITAMIN B12 and FOLIC

ACIDy Both are essential for the synthesis of DNA; both are

required for the formation of thymidine triphosphate, an

essential building blocks of DNA


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Lack ofVit B12/Folic Acid

Failure of nuclear maturation and division

Diminished DNA

Lack of Vit B12 and Folic Acid


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Consequence

y Failure to proliferate rapidly

y Type of cells produced: MACROCYTES

y Larger than normal, with flimsy membrane

y Irregular, large and oval, instead of the usual biconcave discy MACROCYTES are capable of carrying oxygen normally, but

are considered fragile

y Fragility causes them to have short life, one-half to one-third

normaly Vit B12 and Folic Acid Deficiency: causes MATURATION

FAILURE in the process of eryhtropoiesis


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What causesthe abnormality in the

function and morphology?

abnormality

Inability of the cells to synthesize adequate quantities of DNA

Slow production of the cells, but does not prevent excess formation ofRNA by the DNA in those cells that do not succeed in being produced

Cellenlargement

Quantity of RNA in each cell becomes greater than normal

Excess production of cytoplasmic Hgb and other constituents

Abnormalshape

Abnormalities of all the cells DNA

Structural components of the cell membrane andcytoskeleton are also malformed=> abnormal cell shapes andincreased cell membrane fragility


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MATURATION FAILURES (Diseases)

y PERNICIOUS ANEMIA

Causes maturation failure due to failure to absorb Vit

B12 from the GIT

Basic abnormality is an atrophic gastric mucosa => fails

to secrete normal gastric secretions

One of the important secretions of the parietal cells of

the gastric glands: INTRINSIC FACTOR

Intrinsic Factor: combines with Vit B12 from the food,

and makes the B12 available for absorption by the GIT


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Upon absorption ofVit B12

y Once Vit B12 has been absorbed from the GIT, it is stored in

large quantities in the liver (stores up to 1000x the normal

level)

y It is released slowly as needed to the bone marrow and other

tissues of the body

y RDR to maintain normal RBC maturation:1-3microgram

y 3-4years of defective B12 absorption are requiredto

cause maturation failure anemia


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MATURATION FAILURES (Diseases)

y FOLIC ACID DEFICIENCY

(PTEROYLGLUTAMIC ACID) CAUSED BY GIT absorption abnormalities, like sprue

(small intestinal disease) Difficulty in absorbing both the Vit B12 and Folic Acid


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SYNTHESIS/FORMATION OF

Hemoglobin

y Begins in the proerythroblasts

y Continues slightly even into the reticulocyte stage

y When the retic leaves the BM and passes into the blood

stream => continue to form minute quantities of HgB foranother day or so


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SYNTHESIS OF HgB

Protoporphyrin IX

Combines with IRON

Formation of Pyrrole molecule

Four Pyrrole molecules combine

Succinyl-CoA (formed in the Krebs Cycle

Binds with glycine


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SYNTHESIS ofHgB

Four Hemoglobin chain bind together loosely toform

WHOLE HEMOGLOBIN MOLECULE

Formation of subunit of hemoglobin, calledHemoglobin chain

Formation of HEME MOLECULE

Each heme molecule combines with a long peptide chain , GLOBIN


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Hemoglobin structure

y Because each chain has a heme prosthetic group => (4) four

iron atoms in each hemoglobin molecule

y Each one can bind with 1 molecule of oxygen => making a

total of 4 molecules of oxygen (or a total of8 oxygen atoms)

that can be transported by each hemoglobin molecule


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Hemoglobin variants

y Variations in the different subunit hemoglobin chains

y Depending on the amino acid composition of the polypeptide

portion

y

Types of chains: alpha chain, beta chain, gamma chain, deltachain

y Most common form of hemoglobin in the adult human being:

HEMOGLOBIN A

y

Hemoglobin A is a combination oftwo alpha chains andtwo beta chains


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Combination ofHEMOGLOBIN with O2

y Hemoglobin combines loosely and reversibly with oxygen

y Primary function of hemoglobin in the Body: ability to

combine with oxygen in the lungs, and then release the

oxygen readily in the tissue capillaries where the gaseous

tension oxygen is much lower than in the lungs


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Combination ofHEMOGLOBIN with O2

y O2 does not combine with the two positive bonds of the ironin the hemoglobin molecule

y Instead, it binds loosely with one of the so-calledcoordination bonds of the iron atom

y Loose bond =} combination is easily reversibley Oxygen does not become ionic oxygen,but is carried as

molecular oxygen, composed of two oxygen atoms, to thetissues, where, because of the loose, readily reversible

combinationy O2 is released into the tissue fluids in the form of dissolved

molecular oxygen, rather than ionic oxygen


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Iron Storage

y Total quantity of iron in the body: averages 4-5 grams

y 65% is in the form of hemoglobin, 4% in the form of

myoglobin, 1% in the form of various heme compounds that

promote intracellular oxidation, 0.1% is combined with the

protein transferrin in the blood plasma, 15-30% is stored

mainly in the RES and liver parenchyma in the form of

FERRITIN


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Daily Loss ofIron

y Human excretes about 1mg of iron each day => feces

y Additional quantities of iron are lost whenever bleeding

occurs

y

Menstrual loss brings about iron loss of average: 2mg/day


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DESTRUCTION OF RED BLOOD CELLS

y Normally, RBCs circulate an average of 120 days before they

are destroyed == due to wearing out of life processes

y As they age, RBCS BECOME FRAGILE!!!

y

They rupture during passage through some tight spot of thecirculation as they squeeze through the red pulp of the

SPLEEN


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Normally..

yEventhough mature RBCs do not

have nucleus,mitochondria, orER

yettheyhave cytoplasmic enzymesthat are capable of metabolizing

glucose and small amounts ofATP

andNADPH


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Roles ofNADPH

y Maintain the pliability of the cell membrane

y Maintain membrane transport of ions

y Keep the iron of the hemoglobin in theferrous form (rather

than the ferric form)y Prevent oxidation of the proteins in the RBC

y * ferric form of iron causes formation of methemoglobin,

which can not carry OXYGEN


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Asthe RBCs become old

yThese metabolic systems become

also progressively less active with

timeyThe RBCs become more and

more fragile>>> presumably

because their life processes wearout


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ROLE OF THESPLEEN?

y Many of the RBCs fragment in the spleen (red

pulp), most specifically in the structural trabeculae

y WHEN THE SPLEEN IS REMOVED, THE NUMBER OF

ABNORMAL RED BLOOD CELLS AND OLD CELLS

CIRCULATING IN THE BLOOD ALSO INCREASES

CONSIDERABLY


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DESTRUCTION OF HEMOGLOBIN

y Once the RBC bursts, the HEMOGLOBIN is phagocytosed

almost immediately by macrophages

y Liver (Kupffer cells), spleen, bone marrow

y

After few hours to days, the macrophages release the ironfrom the hemoglobin back into the blood to be carried by the

TRANSFERRIN either to:

y BONE MARROW for production of new RBC, or

y

LIVER and other tissues for storage in the form ofFERRITIN


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DESTRUCTION OF HEMOGLOBIN

yThe porphyrin portion/molecule is

converted by the macrophages (thru

a series of stages) into the bile

pigment called BILIRUBIN

yBILIRUBIN is released into the blood

and later secreted by the liver into

the bile


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ANEMIASMajor classification

y BLOOD LOSS ANEMIA

usually after hemorrhage which is NOT corrected after

appropriate time

If this becomes chronic blood loss, a person frequently cannot absorb enough iron from the intestines to form

Hemoglobin as rapidly as it lost

RBCs are then produced with too little hemoglobin inside

themMICROCYTIC, HYPOCHROMIC ANEMIA


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Normal replacement

y After rapid hemorrhage, the body replaces the plasma within

1-3 days (plasma replacement)

y But this leaves a low concentration of rbcs

y

If no second hemorrhage occurs, the rbc concentrationreturns to normal within 3-6 weeks (RBC concentration

replacement)


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y APLASTIC ANEMIA

Bone marrow aplasia

Lack of a functioning bone marrow

May be due to: gamma ray radiation, excessive x-raytreatment, chemotherapeutics drugs which are suppresants


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y MEGALOBLASTIC ANEMIA

Vit B12 and folic acid deficiency, and lack of secretion of

INTRINSIC FACTOR (due to pernicious anemia) => slow

reproduction of the erythroblasts in the bone marrow

The RBCs formed are grow too large (oversized) with odd

shapes (bizzarre) megaloblasts

The RBCs formed are also fragile rupture easily

Causes: intestinal atrophy or absence of stomachdue to gastrectomy; intestinal sprue which leads to

poor absorption of important vitamins and minerals


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y HEMOLYTIC ANEMIA- shortRBC lifespan

y 1. HEREDITARY SPHEROCYTOSIS the RBCs are small

and spherical rather than being biconcave discs=> cant be

compressed because they are not loose, and are not baglike in

consistency => ruptures easily even with slightest

compression.

y 2. SICKLE CELL ANEMIA abnormal type of hemoglobin

called HEMOGLOBIN S

Leads to serious decrease of RBC mass DEATH


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HEMOGLOBINS

y When this hemoglobin is exposed to low concentrations of

oxygen, it precipitates into long crystals inside the RBC

y The crystals elongate the RBC give the appearance of beinga sickle rather than biconcave disc

y The precipitated hemoglobin also damages the cell

membrane making the RBC highly fragile


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THANK YOU

END

blood histology

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