Lec 01: Megakaryopoiesis & Platelets Function

sinus endothelium

megakaryopoiesis takes place adjacent to

5 days

days megakaryopoiesis develop into platelets

150-400 × 10^9/L

platelets nonnucleated blood cells that circulate at (normal / reference value)

higher

ave platelets slightly ____ in women than in men

lower

platelets is slightly _____ in both sexes when over 65 y/o

megakaryocytes

largest cells in the bone marrow, this is where platelets arise

1. megakaryoblast (MK1)

2. promegakaryocyte (MK2)

3. granular megakaryocyte (MK3)

4. platelet / thrombocyte (MK4)

maturation of megakaryocyte

megakaryoblast

• small blunt pseudopods

• non-granular

increases

as the cell mature, the amount of cytoplasm _____

megakaryoblast

• round, oval, kidney-shaped

• fine chromatin

• stained blue

10:1

megakaryoblast NC ratio

promegakaryocyte

less basophilic and granules begin to form in the golgi region

promegakaryocyte

• irregular shape

• coarse chromatin

• slight lobulation

4:1 to 7:1

promegakaryocyte NC ratio

granular megakaryocyte

• pinkish

• very fine

• abundant

• reddish blue granules

• irregular border

granular megakaryocyte

• multiple nuclei & lobulation

• coarser chromatin

• no nucleolus

1:1

granular megakaryocyte NC ratio

platelet (thrombocyte)

• light blue to purple

• very granular with:

  • central granulomere/chromomere

  • surrounding hyalomere

granulomere/chromomere

located centrally in a platelet

hyalomere

surrounds the chromosome of a platelet

bone marrow; spleen and lungs

megakaryocytes are predominantly found in _______ and less number in ________

endomitosis

instead of mitosis, megakaryocytes undergo _______

megakaryocyte colony stimulating factor (Meg-CSF) and granulocyte colony stimulating factor (G-CSF)

stimulates the production of megakaryocyte progenitor cells

Meg-CSF

its production increases whenever the number of megakaryocytes decreases

thrombopoietin

megakaryocyte stimulating hormone

liver & kidneys

thrombopoietin are produced in _____

spleen

functions in the regulation of platelet numbers

splenic pool

rapid use of platelets through clotting or destruction rapidly empties it

marrow response

when the platelet count decreases, thrombopoietin causes maturation of the megakaryocyte to produce _______ equal to the number of platelets that was lost

platelets

true blood cells that maintain blood vessel integrity by initiating vessel wall repairs

platelets

major cells that control hemostasis

hemostasis

a series of cellular and plasma based mechanisms that se wounds, repair vessel walls, and maintain vascular patency (unimpeded blood flow)

platelets

• 2-4 um diameter

• round/oval

• anucleate

• “cell fragments”

• slightly granular

1. adhere to surfaces of damaged blood vessels

2. form aggregates with neighboring platelets to plug the vessels

3. secrete proteins and small molecules that trigger thrombosis or clot formation

platelets function steps

adhesion

platelets roll and cling to nonplatelet surfaces

ahesion

• reversible

• seals endothelial gaps

• some secretion of growth factors

• in arterioles vWF is necessary for adhesion

• dependent on vWF

von Willebrand factor

binds to exposed collagen at sites of injury and recruit platelets to the site

aggregation

• irreversible

• platelet plugs form

• platelet contents are secreted

• required fibrinogen

secretion

platelets discharge content of their granules

secretion

• irreversible

• occurs during aggregation

• platelet contents are secretes to coagulation

epinephrine & serotonin

promote vasoconstriction

ADP (Adenosine Diphosphate)

increases the adhesiveness of platelets

subendothelial connective tissues, especially collagen

platelet adhesion to _____ occurs within 1-2 mins after a break in the endothelium

platelet adhesion

if vascular injury exposes the endothelial surface and underlying collagen platelets adhere to the subendothelial collagen fibers, spread pseudopods along the surface, and clump together (aggregate)

pinkish purple

bm smear color

evenly

blood cells are ____ distributed

clear

areas between cells are

orange red

erythrocytes are

lilac

neutrophilic granules are

red orange

eosinophilic granules are

blue

lymphocytes cytoplasm is

purple

leukocytes nuclei are