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Blood PhysiologyBlood Physiology

Blood Physiology Lecture 1Dr. A-M Zagrean

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Blood Physiology - Syllabus

Lecture 1 Functions of the blood Composition and physico chemical- Functions of the blood. Composition and physico-chemical

properties of blood. The hematocrit. Blood volume. HematopoiesisLecture 2

- Erythrocytes. Respiratory gases transportation. Blood groups. Lecture 3Lecture 3

- Physiology of Immune System. Function of specific defense. Lymphocytes. Function of nonspecific (cellular) defense. Leukocytes.

Lecture 4- Function of maintaining the fluid- coagulant balance. Hemostasis. Fibrinolysis. Therapeutic uses of blood. Transfusions.

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Blood = ?

- component of the internal medium

internal medium - Cl. Bernard - 1865

- component of the circulatory system

- liquid tissueq

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Functions of the blood1) Because of the blood volume and pressure, blood flow,

tissue perfusion and capillary exchanges are maintained.

2) Transport through the body of:2) Transport through the body of: -oxygen and carbon dioxide -food molecules (glucose, lipids, amino acids) -ions: Na+, Ca2+, HCO3−

-wastes (e.g., urea) -hormones -heat

3) Defense of the body against infections and other foreign materials. All the WBCs participate in these defenses.

4) Acid-base buffering power RBC: CA HCO3-; Hb (>deoxyHb); phosphate; plasma proteins (polyanions at plasmatic pH)

5) Wound repair… blood clotting…

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Blood components1 - blood cells / cell fragments – hematocrit

1) red blood cells (RBCs) or erythrocytes) ( ) y yThe fraction occupied by the red cells is called the hematocrit. Normally it is

approximately 45%. Values much lower than this are a sign of anemia.2) platelets or thrombocytes3) five kinds of white blood cells (WBCs) or leukocytes

- 3 kinds of granulocytest hilneutrophils

eosinophilsbasophils

- 2 kinds of leukocytes without granules in their cytoplasm lymphocytesmonocytes

2 – plasma - plasmatic volumePlasma is the non-cellular part of the blood and communicates continuouslywith the interstitial fluid through pores of the capillary membranes

monocytes

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Blood (5 l or 7%BW)= 60% plasma (ESF) + 40% blood cells (ICF)

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Composition of Blood

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Plasma (mOsm/l H2O) Interstitial (mOsm/l H2O) Intracellular (mOsm/l H2O)N + 142 139 14

Plasma composition: comparison with other fluid compartments

Na+ 142 139 14K+ 4.2 4 140Ca++ 1.3 1.2 0Mg+ 0.8 0.7 20Cl- 108 108 4HCO-

3 24 28.3 10HPO4

-,H2PO-4 2 2 11

Amino acids 2 2 8Creatine 0.2 0.2 9Lactate 1.2 1.2 1.5Glucose 5.6 5.6Proteins 1 2 0 2 4Proteins 1.2 0.2 4Urea 4 4 4Others 5.3 4.4 70Total mOsm/l 301.8 300.8 301.2

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Osmotic pressure of the plasma

• Relation between osmotic pressure – osmolarity ex: albumin, glucose, NaCl

• Van’t Hoff’s law for osmotic pressure (Π)Π = CRT

C = concentration of solutes (osmoles/L)R = ideal gas constantT= absolute temperature (Kelvin degrees)

Π (mmHg) = 1 osm/L x R x (37+273) = 19,300 mmHg1 mosm/L 19.3 mmHg

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Plasma Proteins : albumin (oncotic press), globulin (Ig), and fibrinogen (clotting).

Essentially all the albumin and fibrinogen of the plasma proteins, as well as 50 -80 % of the globulins, are formed in the liver (30 g/day). The remainder of the globulins (mainly the gamma globulins) are formed in the lymphoid tissue.

Conditions that cause rapid loss of plasma proteins: severe burns that denude large surface areas of the skin; severe renal disease;denude large surface areas of the skin; severe renal disease; cirrhosis of the liver, large amounts of fibrous tissue develop among the liver parenchymal cells, causing a reduction in their ability to synthesize plasma proteins this leads to decreased plasma colloid osmotic pressure, which causes generalized edema.

Pl P t i S f A i A id f th TiPlasma Proteins as a Source of Amino Acids for the Tissues.Protein tissues depletion – plasmatic proteins pinocytosis by macrophages intracell split into amino acids that are transported back into the blood (plasma proteins function as a labile protein storage medium)

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Hematocrit (packed red cell volume)- definition: fraction of the blood composed of RBCp- functional significance- methods of determination: centrifuging blood in a calibrated ‘hematocrit tube’- values ~ 35% – 45%;

~ up to 10% in severe anemia up to 10% in severe anemia~ up to 65% in polycytemia

- corrected Ht = 0,96 Ht (3-4% from the measured Ht is represented by entrapped plasma)

- venous vs. arterial hematocrit …l ti h t it bl d i it- relation hematocrit – blood viscosity…

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Effect of hematocrit on blood viscosity10

9polycythemia

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7

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=1)

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2

1Vis

cosi

ty(w

a

Plasma viscosity (1.5)

Normal blood viscosity (~ 3)

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00 10 20 30 40 50 60 65 70 %RBC

Hematocrit

Water viscosity (1)

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From Guyton, 2006

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The erythrocyte sedimentation rate (ESR)- commonly used, inexpensive, but non-specific laboratory test (Westergren, 1921)

measures the speed of sedimentation of RBC/RBC aggregates in- measures the speed of sedimentation of RBC/RBC aggregates in plasma over a period of 1 hour in a vertical column of anticoagulated blood under the influence of gravity

- sialic acid-rich glycoproteins on cell surface membranes contribute to g y pcreating a negative charge on the cells’ surface cellular repel …

- a raised ESR is assoc with marked rouleaux formation of RBCs- mainly depends on plasma concentration of large proteins (fibrinogen, Ig)

- ESR raised in systemic inflammatory & neoplastic diseases; useful in chronic diseases, for monitoring disease activity/response to therapy

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The basic factors influencing the ESR- increased ESR

with elevated fibrinogen (e.g., pregnancy, collagen vascular diseases, malignancy).

decreased albumin conc.anemia (hematocrit is reduced, red blood cell aggregates fall

faster); macrocytic red cells also settle more rapidly.

– a decreased ESR is associated with:hypofibrinogenemia, hypergammaglobulinemia associated with

dysproteinemia, and hyperviscosity blood diseases in which RBC have an irregular or smaller shape

that causes slower settling; increased albumin concentration polycythemia

– an abnormal value remains a nonspecific finding

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ESR normal valuesAdults mm/hrAge < 50 years

– Men 1 - 15 – Women 5 - 15

Age > 50 years – Men up to 20 – Women up to 30

ESR increases in inflammatory & neoplastic diseases; >100mm.hr in chronic infections (e.g., tuberculosis)

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Blood volume

- values: 5000 ml; 65-70 ml/kg; 7-8% BW- changes:

1. physiological: pregnancy, water loss/gain 2. pathological: hemorrhage

- circulating blood volume, ‘stagnant’ blood volume - blood volume: plasma volume and cell volume

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Determination of blood volume

- Dilution method:- volume = mass of substance injected / concentration

- plasmatic volume -T1824 (Evans Blue ), I125 albuminbl d l C 51 k d RBC- blood volume - Cr 51 marked RBC

- Blood volume = plasma volume / (1 – Ht)

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Blood cells

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Red blood cells are seen as biconcave disks

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E

WBC - LeukocytesThi h t h i hil (E) d t hil (N) R f RBCThis photo shows an eosinophil (E) and a neutrophil (N). R for RBCs.The eosinophil is distinguished by its red granules and bilobed nucleus.

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WBC – LeukocytesA basophile is characterized by a lobed nucleus and it is filled by large blue-blackp y y ggranules that sometimes cover the nucleus.Here you can see the distinct granules against the purple nucleus.

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Monocytes are phagocytic and may have vacuoles in the cytoplasm.They also have a horseshoe shaped nucleus or in immature monocytesThey also have a horseshoe shaped nucleus or, in immature monocytes, they may have an indented nucleus.

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Lymphocytes are only slightly larger than red blood cells and they havea relatively large nucleus / cytoplasm ratio.Note that the lymphocyte in the above photo has only a thin rim of light purple cytoplasm around the dense nucleus.

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Fibrin clot with platelets and red blood cells

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Hematopoiesis: the formation of blood cellsHematopoiesis is the process that generates blood cells of all lineages. Calculations based on the blood volume and the level and half-life of each type of blood cell in the circulation indicate that each day an adult produces ~ 200 billion erythrocytes, 100 billion leukocytes and 100 billion platelets These rates can increase by a factor of 10 orbillion leukocytes, and 100 billion platelets. These rates can increase by a factor of 10 or more when the demand for blood cells increases (Kaushansky, 2006).Stages:

- embryonic: up to 2 months – yolk sac- fetal: 2-7 months – liver, spleen, lymph nodes

after birth: exclusively in the bone marrow- after birth: exclusively in the bone marrow- up to 5 years: bone marrows of essentially all bones- after 20 years: bone marrows of the membranous bones (vertebrae, sternum,

ribs, ilia); proximal portions of the humeri and tibiae

Relative rates of red blood cell production in the bone marrow of different bones at different ages

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Hematopoiesis in the bone marrow

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All the various types of blood cells:

the formation of blood cellsHematopoiesis:

All the various types of blood cells:- are produced in the bone marrow - arise from a single type of cell called a pluripotential hematopoietic stem cell (PHSC)- the path that is taken, to a committed stem cell, is regulated by the p , , g yneed for more of a certain type of blood cell which is, in turn, controlled by grows inducers (cytokines: IL-3, IL-7, IL-11, etc.) - committed cells colony forming units (CFU): CFU erythrocytes (E)/ granulocytes & monocytes (GM)/ megakaryocytes (M)- differentiation inducers then act on CFUs final adult blood cells-hypoxia, infectious diseases: control grows & differentiation inducers

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Pluripotential hematopoietic stem cell

- attached (probably by adherens junctions) to osteo-blasts lining the inner surface of bone cavities;

- produce, by mitosis, two kinds of progeny:produce, by mitosis, two kinds of progeny:1) more stem cells (a mouse that has had all its blood

stem cells killed by a lethal dose of radiation can besaved by the injection of a single living stem cell !).

2) cells that begin to differentiate along the pathsleading to the various kinds of blood cells.

- their number decrease with age;

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CFU-B CFU-E Erithrocytes

Committed stem cells

Pluripotential hematopoietic

t ll

Colony forming unit(CFU)

CFU-GM Granulocytes

Monocytes/Macrophages

CFU-M Megakaryocytes platelets

stem cell(PHSC)

Lymphoid stem cell(LSC)

T Lymphocytes

B LymphocytesPHSC (LSC) B Lymphocytes

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Hematopoiesis

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Growth and differentiation inducers (cytokines, hormones) for the formation of blood cells …

Interleukin-3 (IL-3) promotes growth of most of the different types of stem cellstypes of stem cells

Interleukin-7 (IL-7) - major cytokine in stimulating bone marrow stem cells to start down the path leading to the various lymphocytes(mostly B cells and T cells).

Erythropoietin (EPO), produced by the kidneys, enhances the production of red blood cells

Thrombopoietin (TPO/ megakaryocyte growth and development factor)Thrombopoietin (TPO/ megakaryocyte growth and development factor), assisted by Interleukin-11 (IL-11), stimulates the production of megakaryocytes. Their fragmentation produces platelets.

Granulocyte-monocyte colony-stimulating factor (GM-CSF), as its name suggests, sends cells down the path leading to both those cell types. In due course, one path or the other is taken. - Under the influence of granulocyte colony-stimulating factor (G-g y y g (

CSF), they differentiate into neutrophils. - Further stimulated by interleukin-5 (IL-5) they develop into

eosinophils. - Stimulated by macrophage colony-stimulating factor (M-CSF)

the granulocyte/macrophage progenitor cells differentiate into monocytes, the precursors of macrophages.

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Hematopoiesis

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Genesis of Red Blood Cells

CFU-E

w

PROERYTHROBLAST

BASOPHIL ERYTHROBLAST (Hb )

POLYCHROMATOPHIL ERYTHROBLAST

Bon

e M

arro

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ORTHOCHROMATIC ERYTHROBLAST (34% Hb)

RETICULOCYTE (remnants of cytoplasm. organells)

BB

lood passes the capillary wall through diapedesis;

mature in 1-2 days;

ERYTHROCYTE

B y ;~1% in the blood

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Regulation of RBC genesisRBC precursors mature in the bone marrow closely attached to a macrophage. Time for the transition from proerythroblast to reticulocitocyte:

5 days (2 days in anemic stress macrocytes with >25 % HbF)Erythropoiesis rate: 5 x 104 RBC / day / µl, stimulated by erythropoietin (EPO)

Reticulocytes in the blood: 0,5 –1%

RBC life-time: 120 days

6. Low atm O2 /High altitude

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ErythropoietinGlycoprotein, MW = 34.000, T1/2 = 6 - 9 hoursMechanism of action:

↑↑ the committment of stem cells to proerythroblasts↑ the differentiation of erythroblastic stages

Synthesized - 90% kidneys (renal tubular* epithelial cells?),the rest of 10% formed mainly in the liver- stimulus = renal hypoxiayp

↑ in EPO conc. after minutes to hours, with a maximum level after 24 h

after 3 - 5 days: ↑ RBC number. 10 x- other non-renal hypoxia sensors act through E NE PG (+) EPO productionE, NE, PG (+) EPO production

Regulation of erythropoietin control mechanism…Therapeutically used: 50 – 300 U / kg, 3 times / week

in kidneys diseases, transplant, anemia, pulmonary diseases, blood loss…

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B12 Vitamin & Folic acid

Act on the final maturation of RBC.B th ti l f DNA th i th h th f ti fBoth are essential for DNA synthesis through the formation of an essential DNA building block, thymidine triphosphat

B12 Vitamin:- the body uses 1-3 µg/day of B12 vitamin

h i 1000 3000- hepatic stores amounts 1000-3000 µg (enough for 3-4 years…)- intrinsic factor needed for absorption …

Vit. B12 & folic acid deficiency proliferation & maturation failure:

- pernicious anemia macrocytes (large, oval, fragile) short life - causes: atrophic gastric mucosa intrinsic factor deficiency no B12 absorption