Platelet Structure And Function

Question 1

Where are megakaryocytes found?

Answer 1

Only in bone marrow and not in peripheral blood

Question 2

Largest cell in the bone marrow

Answer 2

Megakaryocytes

Question 3

Megakaryocyte mission is to proliferate and release fragments of _____________ Into circulation. 

Answer 3

Cytoplasm (Platelets) 

Question 4

 Megakaryocytopoiesis Is controlled by growth factors such as….

Answer 4

Interleukins and thrombopoietin (TPO, a renal hormone)

Question 5

From the kidneys (Also from liver and spleen) Is a major growth factor for megakaryocytic progenitor cells to mature and release Platelets

Answer 5

Thrombopietin (TPO) 

Question 6

What is the old name for platelets?

Answer 6

Thrombocytes

Question 7

What is the normal platelet range? 

Answer 7

150 to 450,000 µL

Question 8

Where are megakaryoblasts or MK-I found? 

Answer 8

In bone marrow only

Question 9

megakaryoblasts or MK-I nucleus undergoes __________. 

Answer 9

Endomitosis

Question 10

megakaryoblasts (MK-I) nucleus…

Answer 10

Overlapping nuclear lobes (Can only see one)

Question 11

megakaryoblasts (MK-I) cytoplasm…

Answer 11

Contain scanty, blue cytoplasm, and no granules yet*

Question 12

megakaryoblasts (MK-I) N:C ratio is _______

Answer 12

High

Question 13

megakaryoblasts (MK-I) size?

Answer 13

14 to 18 micrometers

Question 14

can megakaryoblasts (MK-I) be classified by visual morphology? 

Answer 14

No! Cannot be classified by visual morphology alone! 

Question 15

How to Promegakaryocytes (MK-2) composite to megakaryoblasts (MK-I) in size?

Answer 15

Larger (14 to 30 µm) 

• an exception to the rule that older cells get smaller

Question 16

Promegakaryocytes (MK-2) nucleus…

Answer 16

Becomes lobulated or indented

Question 17

Promegakaryocytes (MK-2) N:C ratio?

Answer 17

Moderate 

Question 18

Promegakaryocytes (MK-2) cytoplasm?

Answer 18

Begins to develop dense, alpha and lysosomal granules (Red-pink)

Question 19

Promegakaryocytes (MK-2):

demarcating membrane system (DMS) develops; Importance?

Answer 19

Forms eventual “perforations” where platelets break off

Question 20

The largest cell in the bone marrow? What’s the size? 

Answer 20

Basophilic/granular megakaryocyte (MK-3)

16 to 56 µm

Question 21

Basophilic/granular megakaryocyte (MK-3) N:C ratio?

Answer 21

Moderate

Question 22

Basophilic/granular megakaryocyte (MK-3) nucleus…

Answer 22

Intensely lobulated

Question 23

Basophilic/granular megakaryocyte (MK-3) cytoplasm…

Answer 23

Has distinct granulation (Eosinophilic and granular)

Question 24

what do Basophilic/granular megakaryocyte (MK-3) have on their surface?

Answer 24

Various platelet specific receptors expressed

Question 25

At what stage is shedding of platelets?

Answer 25

Mature megakaryocyte

Question 26

Mature megakaryocyte nucleus….

Answer 26

Multi lobed nucleus

Question 27

Mature megakaryocyte N:C ratio?

Answer 27

Low

Question 28

Mature megakaryocyte cytoplasm…

Answer 28

-basophilia of cytoplasm has disappeared -pink granules in the cytoplasm are now clustered into small aggregates called platelet fields

Question 29

Pink granules in the cytoplasm of mature megakaryocytes that cluster into small aggregates are called….

Answer 29

Platelet fields

Question 30

Mature Megakaryocytes buds/sheds between ____________ cytoplasmic Fragments which become the platelets

Answer 30

2000 to 4000

Question 31

Maturation time from blast stage to platelet formation is typically _____ days. 

Answer 31

5

Question 32

Normal marrow contains approximately __________ Megakaryocytes

Answer 32

15 million

Question 33

Normal circulation life of a platelet is ______ days 

Answer 33

8 to 10

Question 34

Platelets are removed or destroyed by ______________ In the liver and spleen, or by active use. 

Answer 34

Macrophages

Question 35

Circulating platelets are distributed between the spleen and blood. What proportion is always in the spleen? 

Answer 35

1/3

Question 36

Under normal conditions, the platelet count or mass is consistent even with active use. What does this indicate?

Answer 36

A feedback system adjust production to consumption

Question 37

_______ stimulates production of platelets

Answer 37

TPO

Question 38

___________ activates platelets.

Answer 38

Thrombin

Question 39

A single megakaryocyte may shed _________ Platelets

Answer 39

2000 to 4000

Question 40

___________ is the primary serine protease of coagulation. 

Answer 40

Thrombin