This document summarizes hemapoiesis, the formation of blood cells in the bone marrow. It discusses the different phases of hemapoiesis, types of bone marrow, and the hierarchy of cells involved - from hematopoietic stem cells down to precursor cells. It also provides details on the components of blood, including red blood cells, white blood cells, platelets. Platelets are described as non-nucleated cell fragments formed from megakaryocytes, and their structure is examined through light microscopy and electron microscopy.

1. BLOODBLOOD
By
Hanaa S. E. Mousa
Lecturer of Histology

2. HEMOPOIESIS
 Definition
 The formation of blood elements(RBCs,
white blood cells, and platelets) from
immature precursor stem cells
 Site in healthy adults:
 Bone marrow

3.  Phases:
 Before birth ( Mesoplastic Phase in
mesoderm)
Hepatic Splenic Myeloid
After birth:
Bone barrow normally
Extramedullary in liver and spleen
when needed

4. Types of Bone Marrow
Red bone marrow:
 Predominant in intrauterine life and
children
 Present in flat bone in adults (scapula,
vertebrae, ribs, skull, sternum)
Yellow bone marrow:
 Present in shaft of long bone ( can revert to
red bone marrow in hemorrhage)

5. Red Bone marrow

7. Red Bone marrow

9. Blood cells in the bone
marrow
Hematopoietic stem cells
Progenitor cells
Precursor cells

10.  Hematopoietic stem cells
 Pluripotential stem cells
 Give all types of cells
 Progenitor cells
 Multipotent
 Precursor cells
Unipotent, can’t self renew
First cell to be recognized

11.  Blood is composed of
 Plasma
 Formed elements:
 Platelets
 Blood cells:
 RBCs
 WBCs
 Granulocytes:Neutrophils , Eosinophils, Basophils
 Agranulocytes:Lymphocytes , Monocytes
BloodBlood

15. PLATELETS
 Small, disc-shaped non-nucleated cell
fragments
 From megakaryocytes
 2-4 micrometer in blood smears
 250,000-400,000 / cubic mm

16. LM of platelets
 It has no nucleaus
 Cytoplasm :
 Hyalomere: pale blue peripheral
zone
 Granulomere:dark central region
contain purple granules

18. EM of platelets
 Hyalomere:Hyalomere:
 electron-lucent
Thick cell membrane with glycocalyx
(covering)
 10-15 parallel microtubules and
microfilaments forming a ring just
below the cell membrane

19.  GranulomereGranulomere::
 Granules+ Few Ribosomes , Some
Mitochondria , and Glycogen Particles
 Three types of granules
 Alpha (α )
 Delta (δ )
 Lambda( λ )

21. Blood Film, leishmanBlood Film, leishman
stainstain