Platelet Production, Structure and Function Flashcards by Ruth Joy De Guzman

activated platelets are those that have released their contents such as

a-granules, ATP and ADP,
lysosome granules

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what is platelets?

anucleate cells that circulate at a concentration of 150 to 400x10^9 /L

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What does platelet triggers?

primary hemostasis

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this involves the
coagulation factors.

Secondary Hemostasis

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this involves your platelet
and your blood vessels.

Primary Hemostasis

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Platelets arise from a unique bone marrow cell known as

megakaryocyte

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When the megakaryocyte is mature, they can now
______.

shed off platelets

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1 Mature Megakaryocyte can shed off

2000-4000 of platelets

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Life Span of Platelets

8-9 days

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What is megakaryocytes?

Megakaryocytes are the largest cells in the bone marrow, and possess multiple chromosomes copies

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Megakaryocytes also known as

Polypoid

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Diameter of megakaryocytes

30-50 um

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Do not undergo mitosis

megakaryocytes

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3 STAGES OF MEGAKARYOCYTE PROGENITORS

Proliferative stage
Terminal Megakaryocytes Differentiation stage
Thrombopoiesis stage

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continuous cell production

Hematopoiesis

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multipotential hematopoietic stem cell progenitor cell

Common Lymphoid Progenitors
Common Myeloid Progenitors

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undifferentiated/ immature
hematopoietic cell that is committed to a cell lines.

progenitor

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Multiplication of cells

Proliferative Stage

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3 megakaryocyte lineage are derived from myeloid
progenitors.

o burst-forming unit (BFU-Meg)
o colony forming unit (CFU-Meg)
o light-density CFU (LD-CFU-Meg)

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3 megakaryocyte lineage resembles to

lymphocyte

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– least matured

BFU-Meg

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more mature progenitor

LD-CFU-Meg

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intermediate colony

CFU-Meg

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characteristics of BFU & CFU

diploid (paired chromosome) and
has mitosis

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last stage of cell division

LD-CFU

Has no capacity to divide but it retains its DNA replication, instead of mitosis

LD-CFU

LD-CFU is now called

ENDOMITOSIS

It is called differentiation because each characteristic of these three in terms of percent precursor, nucleoli, etc.

Terminal Megakaryocyte Differentiation Stage

growth factor that will help to stimulate of the production of the platelets

TPO (Thrombopoietin)

least differentiated megakaryocyte

MK-I

the hallmark is the present of indentation

MK-II

most abundant, easily to recognize, largest bone cells and they are capable now of shredding of platelets

MK-III

cytoplasm of MK-I

basophilic or bluish

major function of alpha granules

adhesion

without this a-granules, it will result to

GRAY PLATELET SYNDROME

Has cleavage

MK-II

immature hematopoietic cell that is morphologically identifiable compared to progenitors that are not identifiable

precursor

appearing as pale blue cells with azurophilic granules

platelets

reference value of platelets

150 to 400x10^9 /L

Reference value in women

140 to 379 3x10^9 /L

Reference value in men

220 to 350 3x10^9 /L

RETICULATED PLATELETS or also known as

stress platelets

Larger than normal platelet

RETICULATED PLATELETS

MPV of reticulated platelets

12-14 fl

MPV of platelets

8-10 fl

mRNA for TPO has been found in

kidney, liver, and smooth muscle cells

Acts in synergy with TPO to induce early differentiation of stem cells.

Interleukin-3 (IL-3)

Enhance the later phenomena of endomitosis and platelet release

Interleukin-6 (IL-6) and Interleukin-11 (IL-6 and IL-11)

The star for the coagulation is

platelets

Composed of the membranes and is responsible for platelet adhesion and aggregation

PERIPHERAL ZONE

Stimulate platelet aggregation

a) Epinephrine b) Collagen c) Ristocetin d) Thrombin

2 DIVISIONS OF PERIPHERAL ZONE

Glycocalyx Plasma Membrane

primarily composed of glycoproteins including factors V, VIII and fibrinogen, albumin

glycocalyx

MAJOR STRUCTURAL FEATURES OF PLATELET

1. PERIPHERAL ZONE 2. SOL-GEL ZONE 3. ORGANELLE ZONE (CENTROMERE)

it has blebs or pseudopods that is used for locomotion

MK-I

serves as the physical and chemical barrier between the intracellular and extracellular constituents of the platelets. composed of a bilayer of asymmetrically distributed phospholipids imbedded with integral for surface receptors

Plasma Membrane

serves as the binding site for vWF, necessary for platelet adhesion.

Glycoprotein Ib

– calciumdependent membrane protein complex for fibrinogen receptor necessary for platelet aggregation.

Glycoprotein IIb-IIIa

Lies directly beneath the platelet membrane and is composed of: Microtubules and Microfilaments

SOL-GEL ZONE

Composed of protein tubulin which maintains the platelet disc shape

Microtubules

Contain actin and myosin which upon stimulation of the platelet will interact to form actomyosin (thrombosthenin) for clot retraction.

Microfilaments

The part where the secretory products of platelet come from

ORGANELLE ZONE (CENTROMERE)

a-granules stain

medium gray

neutralizes heparin

Platelet factor 4 (Anti-heparin function)

aside from the adhesion, will promote smooth muscle growth for vessel repair

β-thromboglobulin

promote platelet to platelet interaction and for adhesion

Thrombospondin

promotes smooth muscle growth, cell growth division, healing of the wound, repair and growth of the blood vessel.

Platelet-derived growth factor

Dense Granules/delta also known as

dense bodies

d-granules stain

black or opaque

involves in aggregation and activation of platelets

ADP

energy source of the platelet to achieve the 8-9 days

ATP

for vasoconstriction which binds endothelial cells and platelet membranes

serotonin

For ATP synthesis used for platelet metabolism

Mitochondria

Lysosomal Granules

✓ Acid phosphatase ✓ Hydrolytic enxymes

Site of the arachidonic acid metabolism and provides small amounts of calcium to the resting platelet.

. Dense Tubular System

control center of the platelet activation

dense tubular system (DTS)

platelet function participates in a sequence of events that lead to the formation of a

platelet plug

platelet factor for Hemophilia A

Platelet factor VIII`

platelet factor for Hemophilia B

PLatelet factor IX

platelet factor for Hemophilia C –

Platelet factor XII

Accelerates the conversion of PT to thrombin

PF1

Accelerates the clotting of purified fibrinogen by thrombin

PF2

Phospholipid needed i

PF3

– part of alpha granules, and we also seen inside the platelets that neutralized the heparin

PF4

Necessary for normal fibrin formation

PF5

Antifibrinolysis

PF6

Necessary in the formation of intrinsic thromboplastin (also known as FII or tissue factor)

PF7

described 2 male siblings who died because of excessive bleeding after circumcision

Moises Maimonides