The document summarizes hematopoiesis, the process of blood cell production. It notes that blood cells have short lifespans, ranging from a few days to 120 days for erythrocytes. The organ responsible for hematopoiesis changes with development - in embryos it is the yolk sac, in fetuses it is the liver and spleen, and in adults it is the bone marrow. The bone marrow contains pluripotent hematopoietic stem cells that can differentiate into all types of blood cells. Regulation of hematopoiesis involves cytokines, growth factors secreted by bone marrow stromal cells, as well as erythropoietin and thrombopoietin which stimulate red blood cell and platelet

1. Hematopoiesis

2. Blood cells have relativelly short lifespan
Erythrocytes – 120 days
Thrombocytes – 10 - 12 days
Leukocytes – only few days in the
blodstream, migrate to the connective tissue

3. Which organ is responsible for
hematopoiesis?
It´s depend on the period of development
 Yolk sac - embryo
 Liver and spleen - fetus
 Bone marrow
Yolk sac

4. Blood
 A special type of connective tissue
 The volume of blood in healthy adult human is
about 4.5 – 6 liters
 Is composed of blood cells suspended in a fluid
matrix called plasma
 Blood cells / elements:
 Red blood cells (erythrocytes)
 White blood cells (leukocytes)
 Platelets (thrombocytes)

5. Blood cells
leukocytes
erythrocytes
platelets
artery

6. Functions
 Transport of oxygen, carbon dioxide, nutrients
and hormones
 Maintance of acid-base balance
 Removal of waste products of cell metabolism
 Temperature control of the body
 Defense against infection (immune function)

7. Blood plasma
 yellowish fluid in which blood elements are
suspended,
 components :
water – 90%
inorganic salts – 3%
organic – proteins (albumins, globulins,
fibrinogen) – 7%
 after coagulation (some components leave
plasma) called serum

8. Blood cell production
(hematopoiesis)
 Blood elements are highly specialized
corpuscles („cells“) and can not divide
 Most of them have relatively short life span
 Are formed in a special type of connective
tissue called bone marrow

9. Bone marrow
 Hematopoietic tissue is derived from
mesenchyme
 In adults, the red bone marrow is located
in flat bones (skull, ribs, sternum, pelvis,
vertebrae) and ends of long bones
 Yellow bone marrow characteristic for
adult long bones does not form blood but it
stores fat

10. Pluripotential haematopoietic stem cells
 Undifferentiated cells („stem cells“), they
can give rise to ALL the different types of
specialized blood elements
 Differentiated to form progenitor cells in
two different ways:
Multipotential lymphoid stem cells
Multipotential myeloid stem cells

12. Regulation of hematopoiesis
 Erythropoietin – cortex of the kidney
 Thrombopoietin (megakaryocyte growth and
development factor) – liver, kidney
 Cytokines (protein signaling molecules) and
growth factors – stromal cells of bone marrow

13. Summary of blood elements function
Erythrocytes Hemoglobin Transport O2 and CO2
Neutrophils Neutrophil granules Destroy the
microorganisms by
phagocytosis
Eosinophils Eosinophil granules Allergy, agains
parasites
Basophils Basophil granules
Heparin and histamine
Anticoagulation effect
Lymphocytes Immunoglobulins
(antibodies)
Interaction of
antibodies with
antigens
Monocytes Lysosomes with
enzymes
Destroy the
microorganisms by
phagocytosis
Platelets Coagulation factors Blood coagulation

14. Thank You