physiology of blood lec1

8/14/2019 Physiology of Blood Lec1

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Lect 1

2006-2007


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WHAT IS BLOOD?

Blood consists of: a fluid,plasma

a cellular component madered cells (erythrocytes)

white cells (leucocytes


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Plasma is aqueous solution contaions (Na+, K+, Ca2+, Mg2+, Cl-,

HCO3)The concentration of these ions iswithin very narrow limits to enthe proper functioning of the tissthe body.

The kidney plays a central role. small moleculeswhich are bei

transported (e.g. glucose)


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Review of blood as a CT.Elements of blood.

General functions of blood.

Elemental functions of formed elementsblood.

Plasma and its constituents.

Hemostasis.


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Transport (O2 , CO2, Glucose, AA, hormone

proteins,..and wastes like urea and creatTemperature regulation.

pH regulation (Buffer system).

Electrolyte balance.

Defense mechanism.

Hemostasis (Arrest of bleeding).

Others


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Unlike the heart and the bloodvessels, which are organs, bloo

complex tissue. It is one of theconnective tissues based on itsderivation, from mesenchyme

and its structure, which contaithe intercellular matrix knownthe plasma.


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Plasma proteins may ha

specialized functions, they also contribute, a

with other solutes, to tosmolarity and viscosof the blood.


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THE FORMED ELEMENTThese are blood cells and cell

derivatives. All the formed elemeoriginally derived from apleuripotential(multiple potentiastem cell known as a hemocytobl

These cells are derived frommesenchyme cells which give riseother types of connective tissue as


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Pleuripotential stem cells are

known as colony forming u(CFU) because their presencmarrow and other locations

permits the formation of alltypes of blood cells.


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These are the most abundant cells (about 5000

per millilitre) in the blood.Their principal function is to transport O2 andThis is facilitated by the presence of haemowithin the cell.

O2 binds avidly to haemoglobin in the lungs.Off-loading at the tissues is facilitated by a falpH (e.g. due to CO2 production) and a rise

temperature.


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Haemoglobin also facilitates CO2 carriageIt is a very good H+ buffer which encourag

solubilisation of CO2.

Anaemia is a condition when the O2 carryicapacity of the blood is reduced.

e.g. reduction in red cell numbers, iron, foor vitamin B12 deficiencies, defectivehaemoglobin (sickle-cell anaemia).


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They have no nuclei or otherorganelles and only rudimenta

enzyme systems. But they do prcertain substances of importance, fexample carbonic anhydrase.

RBCs carry hemoglobin which caoxygen and carbon dioxide.


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Erythrocytes - red blood cells, 5 tomillion/mm3 arebiconcave disk

which function in transporting oxand carbon dioxide to and from ti

Their shape facilitates both volum

surface area. Their structure is thaflexible membrane sack.


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Sickle cellsA single point mutation in the gen

codes for globin produces hemogwith a single amino acid differencthe beta chains. This results inaggregation of the HbS hemoglobcausing a loss of plasticity of the c

and the formation of comma shapcells at low oxygen tension.


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Substitution at position 6 of thhydrophobic valine for hydropglutamic acid causes an abnorhemoglobin (HbS) whichcrystallizes when oxygen tenslow, and the RBC's changeshalong, thin sickle forms thatsludge in capillaries, furtherdecreasing blood flow and oxytension.


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Sickled cells are prone to stitogether, plugging smallervessels and leading to decre

blood flow with ischemia.


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H l bi i f f


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Hemoglobin consists of fourpolypeptide chains, 2 alpha and 2each of which contains a heme gr

Each heme group is composed of porphyrin ringwith an iron atomcenter.

The iron atoms each bind to an oxmolecule. They can also bind to camonoxide.

physiology of blood lec1

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