Hematology 2 Lesson 1

LESSON 1
OVERVIEW MEGAKARYOPOIESIS
Intended Learning Objectives

After the completion of the chapter, students will be able to:
1. recall the pre-requisite course of the new course.
2. Illustrate the process of megakaryopoiesis
3. discuss the mechanism of platelet production and formation.
IF YOU HAVEN’T WATCH THE VIDEO SUPPLEMENT I SUGGEST WATCH IT FIRST!
MEGAKARYOPOIESIS
Historical Review of Hemostasis
 2nd century A.D. – hemophilia was first recognized.

 12th century A.D. – Moises Maimonides described 2 male siblings who died because of
excessive bleeding after circumcision.
 1803 – clinical description of families with hemophilia was first published. The disorder
was given the name HEMOPHILIA which means “love of hemorrhage” by Schonlein.
 1828 – the disorder was first described in a thesis published by Hoff.
 1842 – platelets were described.
 1905 – Theory on Blood Coagulation by Paul Morawitz was accepted.
 1913 – Lee & White WBCT was performed.
 1930 – Prothrombin time was introduced by Quick.
 1940 – Other tests for evaluating hemostatic mechanisms, like plt. Count & BT were
introduced
 1964 – “Cascade & Waterfall Theory” of coagulation was introduced.
HEMATOPOIESIS
-Process of blodd cell production in bone-forming organ
MEGAKARYOPOIESIS
-Process of platelet formation
Megakaryoblast  Earliest recognizable stage under light microscope

 14-18 um in diameter
 N:C ratio is 3:1
 Granules are absent
Promegakaryocyte  15-40 um in diameter

 Nuclear lobulation begins
 The cytoplasm has visible bluish-stained granules
 N:C ratio is 1:2
Megakaryocytes  Largest cell in BM

 Ranging up to 160 μ in size.
 Nucleoli are no longer visible
 Occasionally pseudopod/ irregular boarder
 N/C ratio = 1:1-1:12
Metamegakaryocyte  Disintegrated cell surrounded by platelet
Platelet/  Anucleate
Thrombocyte  Diameter: 2-4 µm
 MPV: 8-10 Fl
 Shape: disk-shaped or circular to irregular, lavender and
granular under Wright-stained wedge preparation
 NV: 150-450 x 109/L
 Very granular
 Life span: 5-10 days
Point of MK I MKII MKIII

Difference Megakaryoblast Promegakaryovyte Megakaryocyte
% precursors 20 25 55
Diameter 14-18 um 15-40 um 30-50 um
Nucleus Round Indented Multibilobed
Nucleoli 2-6 Variable Not visible
Chromatin Homogenous Condensed Deeply condensed
N:C Ratio 3:1 1:2 1:4
Mitosis Absent Absent Absent

Cytoplasm Basophilic Basophilic and granular Eosinophilic and
granular
a- granules Present Present Present
Dense granules Present Present Present
DMS(demarcation Present Present Present
System)
RECALL!
Major hormone involve in platelet production:

Thrombopoietin
 Is a glycoprotein hormone produced mainly by the liver and the kidney that regulates
the production of platelets by the bone marrow.
 It stimulates the production and differentiation of megakaryocytes.
PLATELET STRUCTURE
1. Peripheral Zone
2. Sol-Gel Zone
3. Organelle Zone
4. Membranous System
1. Peripheral Zone
o composed of the membranes and is responsible for platelet adhesion and aggregation
o originates from the plasma membrane of the megakaryocytes
2 Divisions:
o Glycocalyx – primarily composed of glycoproteins including factors V, VIII and

fibrinogen.
o Plasma Membrane – composed of a bilayer of asymetrically distributed phospholipids
imbedded with integral protein for surface receptors
2 Glycoprotein
**correction GP are found in plasma membrane**
0. Glycoprotein Ib (GP Ib)serves as the binding site for vWF, necessary for platelet
adhesion
0. Glycoprotein IIb-IIIa (GP IIb-IIIa; Integrin: αIIbβ3)calcium-dependent membrane protein

complex for fibrinogen receptor necessary for platelet aggregation
2. Sol-Gel Zone
o lies directly beneath the platelet membrane and is composed of:
Microtubules
 composed of protein tubulin which maintains the platelet disc shape
Microfilaments
 contain actin and myosin which upon stimulation of the platelet will interact to form
actomyosin (thrombosthenin) for clot retraction
3. Organelle Zone (Centromere) b. . Dense Granules “SCAAM”

- the part where the secretory  Serotonin
 Calcium
products of platelet come from
 ADP
 ATP
 Magnesium
α Granules
 Platelet factor 4- heparin neutralizing
 β-thromboglobulin
 Platelet-derived growth factor
c. Mitochondria
 Fibrinogen
 Factor V  for ATP synthesis used for platelet metabolism
 vWF
 Thrombospondin-hemmaglu func d. Lysosomal Granules
 Fibronectin
1. acid phosphatase
2. hydolytic enzymes
3. Membranous System
Dense Tubular System

 derived from smooth endoplasmic reticulum and sequesters calcium for platelet
activation process
 it is also the site of platelet cyclooxygenase and of prostaglandin synthesis
b. Open Canalicular System

 Surface connecting system
 an invagination of the plasma membrane
 acts as a canal for the release of the granule constituents and cytoplasm to the exterior
of the platelet
PLATELET FUNCTION
 Participates in a sequence of events that lead to the formation of a platelet plug and
ultimately to the formation of a stable fibrin clot at the site of vessel interruption.
a.Primary hemostasis by adhesion, secretion and aggregation with the end view of
hemostatic plug.
b. Blood coagulation by releasing platelet factor 3 that plays a big role in forming fibrin
clot.
c.Clot retraction by its actomysin
d.Helps in localization of bacteria and other small objects and producing

aggregates too large to pass through capillaries.
Other Important Informations

Endomitosis  Multile mitotic division witout cell division;
generating giant-multinucleated polyploid
cell
2000-4000 platelts  Number of platelets produce by each
megakaryocytes
Platelet Shedding  Release of platelets into the bone marrow
sinus
 Process of platelet release
Demarcating Membrane System  Network formed by invagination of the
plasma membrane
 Function as future membrane system of
platelet (storage)
PLATELET ROLE IN HEMOSTASIS
Want to be more familiar with the cells?

Download this application so you could enjoy and learn
at the same time with this GAME!
CellaVision® CellAtlas
SELF-ASSESSMENT
1. What is the glycoprotein used by the platelets for adhesion?______________________
2. What is the glycoprotein used by the platelet for aggregation?_____________________
3. Part of platelet where you could find the cytoskeletal structure?____________________
4. Hormone responsible for platelet production?___________________________________
5. What are the 4 major platelet structures?______________________________________

ASSIGNMENT
1. ILLUSTRATE/DRAW THE STAGES OF PLATELET FORMATION (MEGAKARYOPOESIS)

2. DESCRIBE DISTINCT FEATURE FOR EACH STAGES
 SUBMISSION: SEE THE DOCUMENT ON OUR GOOGLE CLASSROOM

NOW YOU ARE DONE!
WHAT TO DO NEXT?
1. REMEMBER TO SUBMIT YOUR
MODULE
2. STUDY THIS MODULE WE WILL BE
HAVING POST TEST NEXT MEETING
DEADLINE FOR THIS MODULE: SEPTEMBER
14-18 ,2020
STUDY THE NEXT LESSON IN ADVANCE!
GODBLESS!

Hematology 2 Lesson 1

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LESSON 1

Intended Learning Objectives

1. recall the pre-requisite course of the new course.

2. Illustrate the process of megakaryopoiesis

3. discuss the mechanism of platelet production and formation.

IF YOU HAVEN’T WATCH THE VIDEO SUPPLEMENT I SUGGEST WATCH IT FIRST!

Historical Review of Hemostasis

 2nd century A.D. – hemophilia was first recognized.

-Process of blodd cell production in bone-forming organ

-Process of platelet formation

Megakaryoblast  Earliest recognizable stage under light microscope

Promegakaryocyte  15-40 um in diameter

Megakaryocytes  Largest cell in BM

Point of MK I MKII MKIII

Mitosis Absent Absent Absent

Major hormone involve in platelet production:

o Glycocalyx – primarily composed of glycoproteins including factors V, VIII and

0. Glycoprotein IIb-IIIa (GP IIb-IIIa; Integrin: αIIbβ3)calcium-dependent membrane protein

o lies directly beneath the platelet membrane and is composed of:

 composed of protein tubulin which maintains the platelet disc shape

3. Organelle Zone (Centromere) b. . Dense Granules “SCAAM”

Dense Tubular System

b. Open Canalicular System

c.Clot retraction by its actomysin

d.Helps in localization of bacteria and other small objects and producing

Other Important Informations

Want to be more familiar with the cells?

1. What is the glycoprotein used by the platelets for adhesion?______________________

2. What is the glycoprotein used by the platelet for aggregation?_____________________

3. Part of platelet where you could find the cytoskeletal structure?____________________

4. Hormone responsible for platelet production?___________________________________

5. What are the 4 major platelet structures?______________________________________

1. ILLUSTRATE/DRAW THE STAGES OF PLATELET FORMATION (MEGAKARYOPOESIS)

 SUBMISSION: SEE THE DOCUMENT ON OUR GOOGLE CLASSROOM

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