3. Blood Cells

8/6/2019 3. Blood Cells

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BSC YEAR I

SEMESTER II

PERIPHERAL BLOOD


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INTRODUCTION

y The blood consists of a suspension of special cells in a liquid

called plasma.

y In an adult man, the blood is about 1/12th of the body weightand this corresponds to 5-6 litres.

y Blood consists of 55 % plasma, and 45 % by cells called formed

elements.


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THE PLASMA

y Cells free serum or plasma, can be obtained by centrifugation.

y It is a slightly alkaline fluid, with a typical yellowish color.

y It consists of 90 % water and 10% dry matter.

y Nine parts of it are made up by organic substances, whereas one part is made up byminerals.

y These organic substances are composed of glucose, lipids (cholesterol), triglycerides,phospholipids, lecithin, fats), proteins (globulins, albumins, fibrinogen), glycoproteins,hormones (gonadothropins, erythropoietin, thrombopoietin), amino acids and vitamins.

y The mineral substances are dissolved in ionic form, that is dissociated into positive andnegative ions.


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THE HEMATIC CELLS

y In the blood are special cells, classified into three :y Erythrocytes

y Leukocytes.

y Granulocytes: Neutrophils, Eosinophils, Basophils

y Aggranulocytes: Lymphocytes, monocytes

y Platelets which are not considered real cells.


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ERYTHROCYTES (red cells)

y The most numerous blood cells i.e. about 4-6 millions/mm3.

y In mammals, they are devoid of a nucleus and have biconcavedisc shape.

y In the other vertebrates (e.g. fishes, amphibians, reptilians andbirds),they are nucleated.

y Rich in hemoglobin, a protein that binds oxygen.

y Hence, responsible for providing oxygen to tissues and partly forrecovering carbon dioxide produced as waste.

y Most CO2

is carried by plasma, in the form of soluble carbonates.


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PLATELETS

y Main function: to stop blood loss from injuries (hematostasis).

y Granules: Alpha, Delta/dense, lysosomal

y They aggregate and release coagulation factors

y Serotonin: Vasoconstriction of lesioned vessels and slows downthe hematic flux, the fibrin which trap cells and forms the clotting.

y In the smears stained by Giemsa- an intense purple color.

y 2-3 m in diameter, -much smaller than RBCs.

yTheir density in the blood is 150,000-450,000/mm

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y Each type of leukocyte is present in the blood in

different proportions:

o Neutrophil 50 - 70 %

o eosinophil 2 - 4 %

o basophil 0.5 - 1 %

o lymphocyte 20 - 40 %

o monocyte 3 - 6 %


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y Neutrophils are very active in phagocyting bacteria and are present inlarge amount in the pus of wounds. Unfortunately, these cells are not ableto renew the lysosomes used in digesting microbes and dead after havingphagocytosed a few of them.


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y Eosinophils attack parasites and phagocyte antigen-antibody

complexes.


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y Basophil secrete anti-coagulant and vasodilatory substances

such as histamines and serotonin.

y They have a phagocytory capability, but their main function issecreting substances which mediate the hypersensitivity

reaction during allergies.


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y Lymphocytes are cells which, besides being present in the blood,populate the lymphoid tissues and organs too, as well as the lymph

circulating in the lymphatic vessel.y The lymphoid organs include thymus, bone marrow (in birds bursa),

spleen, lymphoid nodules, palatine tonsils, Peyer's patches andlymphoid tissue of respiratory and gastrointestinal tracts.


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y Monocytes are the precursors ofmacrophages.

yLarger blood cells, which upon maturity in thebone marrow, enter the blood circulation wherethey stay for 24-36 hours.

y Migrate into the connective tissue, and becomemacrophages and move within the tissues.

y In the presence of an inflammation, monocytesquickly migrate from the blood vessel and start anintense phagocytory activity.

y They also have an intense secretory activity.

y Secrete substances with defensive functions such aslysozymes, interferones and interleukines whichmodulate the functionality of other cells.


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PREPARATION OF THE BLOOD SMEAR

y MATERIALS

- sterilized lancet or needle- 20 clean microscope slides and coverslips

- Canada balsam or other medium for permanent

preparations

- 95% ethyl or methyl alcohol- distilled water

- Giemsa stain

- low containers (you can make them with aluminum sheet

also)- microscope which magnifies 200 times at least


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TAKING THE BLOOD

FINGER PRICKy Clean the part of the finger to be punctured using soap and water .

y With a sterile lancet or needle, make a puncture on a fingertip.

y In the meantime, keep all the materials needed ready and protected

from dust, particularly the clean microscope slides.

VENIPUNCTURE

y Assemble all your requirements together

y Clean the are to be punctured using clean water and soap and let it dry

y Tie the upper arm above the puncture site using a torniquette

y Puncture the site as soon as possible and draw the blood


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MAKING A BLOOD SMEAR

y

Place a small drop of blood near an end of a slide.

y Bring the edge of another slide in contact with the drop and allow thedrop to bank evenly behind the spreader.

yThe angle between the two slides has to be 30-40 degrees.

y Now, push to the left in a smooth, quick motion.

y The smear should cover about half the slide.

NB: It is important that the quantity of blood is not excessive, otherwisethe red cells could hide the leukocytes.


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FIXING

y Main function: maintain cell morphologypost-staining

y Prevents osmotic or hypotonic shock.

y Fixing is done before staining

y A simple and effective fixing technique consists of dipping the smear ina vessel containing 95% ethyl or methyl alcohol for *1-2 minutes.

y A dropper or a bottle dispenser can also be used to flood the fixativeover the smear.


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OBSERVATION/EXAMINATION

y Scan the smear with a low power objective x10

y A magnification of 200 times is enough to allow you to

observe and identify the different types of cells.

y If you use a higher power, you can also see the cells details

better.

y You can examine either with dry objectives or with the oil

immersion technique.


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ERYTHROCYTESy The red cells are numerous in the blood.

y Usually, measure 6.5-8.0 m in diameter.

y They are annucleate

y Under the microscope, they look like pink discs clearer in the middle

y Poikilocytsosis: Variation in shape of the red cells

y Anisocytosis: Variation in the red cell size

y Sometimes, this depicts an underlying conditions like diseases

y It may also be due to poor preparation and staining of the smear.


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PLATELETS

y

Platelets are not true cells.

y They originate from large cells called megakaryocytes.

y They are small sized, disk-shaped, about 3m in diameter.

y They appear a purple color and are more intense than red

cells


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LEUKOCYTES

y All white cells have a nucleus.

y Easily visible under the microscope, if stained with acidic and basicdye.

y Usually, the shape of the nucleus of various kind of leukocytes isdifferent.

y Some may show multiple lobes, or indented/kidney-shaped.

y Together with the different colors of granules, the shape of nucleushelps us to recognize these cells.

y Leukocytes are divided into granulocytes and lymphoid cells.


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GRANULOCYTES

y Granulocytes originate from the marrow bone.

y Cytoplasm is rich in granules which take typical colorswhich help their recognition.

y In the blood, there are immature cells as well.

y They distinguish themselves by having a less segmentednucleus.

y There are three types of granulocyte: neutrophil,eosinophil, basophil.


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NEUTROPHIL Granulocytes

y The neutrophil are the most common leukocytes.

y They have a diameter of 12-15 m.y nucleus is divided into 3-5 lobes connected by a fine nuclear strand/filament

y The cytoplasm is pinkish because its granules are small and faintly pink colored.

y Immature neutrophils have a band-shaped or horseshoe-shaped nucleus and are known as bandcells.

y In the nucleus of the neutrophil from females, you may see an appendage like a little drumstick(Barr body). It is the second X chromosome, inactivated.


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EOSINOPHIL Granulocytesy The eosinophils are quite rare in the blood.

y Same size as the neutrophils.

y Usually their nucleus is bi-lobed.

y Nuclei with three or four lobes have been observed but rare observation.

y The cytoplasm is full of granules which assume a characteristic pink-orange color

y As for the neutrophil, the nucleus is still easily visible.


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BASOPHIL Granulocytes

y

Basophils are the rarest leukocytes: less than 1 %.y They are quite small: 9-10 m in diameter.

y Cytoplasm has large granules of a dark purple color.

y The nucleus is bi- or tri-lobed, but it is hard to see because of thenumber of granules which hide it


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LYMPHOID CELLS (or agranulocytes)

y Because usually these cells appear lacking in granules, they arealso named agranulocytes.

y They have a compact nucleus and a transparent cytoplasm.

y There are two types of agranular cells: lymphocytes and

monocytes.

y Their look is similar, but their origin is different. \

y lymphocytes spring from lymphatic organs, monocytes have

the same origin as the granulocytes.


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LYMPHOCYTESy Lymphocytes are quite common in the blood: 20-40%, 8-10 m in diameter and

generally they are smaller than the other leukocytes but they are still a few largerthan red cells

y The nucleus is round and large in comparison to the cell and it occupies most of it.

y According to the quantity of cytoplasm, lymphocytes are divided into small,medium and large.

y With Giemsa stain, we cannot distinguish the different types of lymphocyte (B, T,

NK), either in the blood because they are not activated, or because it would benecessary to perform special immunochemical staining.


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MONOCYTES

y

Monocytes are the largest leukocytes: 16-20 m.y They have a great reniform or horseshoe-shaped nucleus, in

some cases even bi-lobed.

y The cytoplasm is transparent, but with an appearance of

"ground glass" (fig. 12).

3. Blood Cells

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