L.1:A Haemopoiesis & - PowerPoint Presentation

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L.1:AHaemopoiesis & Red Blood Cells Disorders

أ.م.د.ميسم مؤيد علوش

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Objectives:1-Define haemopoiesis , main site of haemopoiesis and

exteamedulary

haemopoiesis

2-Define the surface markers of

haemopoietic

stem cell

3-Know the function of erythropoietin and stimulants for its

production

4-Know

haemoglobin

types in normal subjects and the red

cell

indicies

5-Define

anaemia

and classify of

anaemia

6-Know the differential diagnosis of

hyochromic

microcytic

anaemia

7-.Know the main dietary sources of iron ,site of absorption

of iron ,distribution of iron in the body and daily

requirement.

8-Know the causes of iron deficiency

anaemia

.

9-Know the clinical and laboratory findings of iron deficiency

anaemia

 

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Blood film from a healthy subject

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Haematology   Haemopoiesis:

It is the process of blood cells formation (red blood

cells,white

blood cells and platelets).

 

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Site of haemopoiesis:-In the first few weeks of gestation

the

yolk sac

is the main site of

haemopoiesis

.

-From

6 weeks until 6-7 months of fetal life

the

liver and spleen are the major

haemopoietic

organs

and continue to produce blood cells until about 2 weeks after birth.

-

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The bone marrow is the most important

site from

6 to 7 months of fetal life.

-

During normal childhood and adult life the marrow is the only source of new blood cells.

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HaemopoeisisاااااااااااااااااااااااHAEMOPOEISIS

Haemopoiesis

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In infancy all the bone marrow is haemopoietic but during childhood there is progressive fatty replacement of marrow throughout the long bones so that in adult life haemopoietic marrow is confined to the central skeleton and proximal ends of the femurs and humeri .

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Even in these haemopoietic areas, approximately 50% of the marrow consists of fat . The remaining fatty marrow is capable of reversion to haemopoiesis and in many diseases there is also expansion of haemopoiesis down the long bones.

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Normocellular

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Bone Marrow fragment

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Hypocellular Normocellular

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Hypercellular Bone Marrow

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Moreover, the liver and spleen can resume their fetal haemopoietic role (Extramedullary haemopoiesis').

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All the blood cells are derived ,in the bone marrow ,from a pluripotent haemopoietic stem cell that is capable of giving rise to both lymphoid and myeloid progeny via a common lymphoid progenitor cell and a common myeloid progenitor cell respectively.

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This haemopoietic stem cell is rare, perhaps 1 in every 20 million nucleated cells in bone marrow. Although its exact phenotype is unknown, on immunological testing it is CD34+ CD38-

and has the appearance of a small or medium-sized lymphocyte.

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Haemopoiesis

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Erythroblasts (normoblasts) at varying stages of development..

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Megakaryocyte

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Megakaryocyte

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The haemopoietic growth factors:are glycoprotein hormones that regulate the proliferation and differentiation of haemopoietic progenitor cells and the function of mature blood cells e..g. erythropoietin , thrombopoietin, and Interleukin 3 ( IL-3).

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We each make approximately 1012 new erythrocytes (red cells) each day by the complex and finely regulated process of Erythropoiesis.The first recognizable erythrocyte precursor in the bone marrow, is

the

pronormoblast

.

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Erythropoiesis -Red cell formationErythropoiesis is regulated by the hormone Erythropoietin.. Normally, 90% of the hormone is produced in the kidney and 10% in the liver and elsewhere.

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There are no preformed stores and the stimulus to erythropoietin production is the oxygen (02) tension in the tissues of the kidney

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Erythropoietin production therefore increases in: -Anaemia- haemoglobin for some metabolic or structural reason is unable to give up 02 normally, -atmospheric 02 is low

-defective cardiac or pulmonary function

-damage to the renal circulation affects 0

2

delivery to the kidney.

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Erythropoietin production

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The marrow requires many other precursors for effective erythropoiesis. These include metals such as iron or cobalt, vitamins (especially vitamin B12, folate, vitamin C, vitamin E, vitamin B6, thiamine and riboflavin) and hormones such as androgens and thyroxine.

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Haemoglobin4 haem

4

globin

Protoporphyrin

ring+ferrous

iron in centre=hem

2

α

+2 non

α

Globin

chain

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Haemoglobin synthesisNormal adult blood contains three types of haemoglobin: 1. Adult haemoglobin (Hb A

) 96-98 % :

Hb

A :α

2

β

2

'

 

2.

Fetal

Hb

(

Hb

F )

0.5-0.8 % :

Hb

F α

2

γ

2

3.

Hb

A2

1.5-3.2 % : α

2

δ

2

 

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At birth Hb F is the dominant haemoglobin in the blood. The major switch from fetal to adult haemoglobin occurs 3-6 months after birth .

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Red blood cell indicies:1.Red blood cell count (RBC).2. The Hb concentration (Hb).13.5 – 17.5 g/dL ♂

11.5 – 15.5 g/

dL

♀

 

3.The

haematocrit

(

Hct

) or packed cell volume

PCV.

PCV 0.39-0.50 male, 0.36-0.46 female

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4.The mean cell volume (MCV): PCV/RBC. MCV 80-95 fimtoliter( fl) 5.The mean cell haemoglobin (MCH): the average amount of haemoglobin

in an individual red cell.

MCH 27-32(

pigogram

) pg

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6.The maen cell haemoglobin concentration(MCHC)is the average concentration of haemoglobin ,rather than the absolute amount,in an individual red cell.

MCHC 32-36 gm/dl

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AnaemiaDefinition: a state of low hemoglobin concentration for age & sex.

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Classification of anemias: According to the RBC indices anaemias are classified into:

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  1. Hypochromic microcytic: low MCV, low MCH.2. Normochromic normocytic anemia:

MCV

normal

MCH

, normal

.

3.

Macrocytic

anemia:

high MCV.

 

 

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Microcytic anaemias:A microcytic anaemia is one in which the erythrocytes are smaller than normal (i.e. microcytic

).

Often they also

hypochromic

(i.e. they appear paler than normal in a stained blood film).The

anaemia

may thus be referred to as a

hypochromic

microcytic

anaemia

.

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Hypochromic microcytic Normochromic normocytic RBCs RBCS

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Microcytic anaemias result from a reduced rate of synthesis of haemoglobin.This, in turn results from a reduced rate of synthesis of either

haem

or

globin

.

 

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Microcytic anaemias:

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