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Haematology > Platelet structure and formation > Flashcards

Platelet structure and formation Flashcards

1
Q

Platelets derived from

A

Megakaryocytes

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2
Q

Function of platelets

A

Hemostasis

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3
Q

Shape of inactivated platelets

A

biconvex

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4
Q

size of platelets

A

2-3 micrometers in diameter

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5
Q

Hormone that regulates megakaryocyte and platelet formation

A

Thrombopoietin

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6
Q

Thrombopoietin is produced by

A

liver and kidney

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7
Q

How many platelets does one megakaryocyte produce

A

1000-3000

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8
Q

How many platelets are produced in an adult in a day

A

10 raised to the power 11

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9
Q

Percentage of platelets stored in the spleen at any point in time

A

30-40%

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10
Q

Why does splenic contraction occur

A

To release sequestered platelets through induction by sympathetic system

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11
Q

Why do sickle cell patient have higher platelet count

A

By the time they reach their teens, they undergo autosplenectomy hence platelets are released into the circulation

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12
Q

Average lifespan of circulating platelet

A

8-10 days

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13
Q

How are platelets destroyed

A

By phagocytosis by the reticular activating system

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14
Q

How many lobes does megakaryocyte have

A

multiple lobed

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15
Q

When is a megarkaryocyte said to be active

A

When it has tiny dots or platelets present on it

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16
Q

How many zones are platelets seperated into

A

4.

Peripheral zone
Sol gel zone
Membranous zone
organelle zone

POMS

17
Q

What do you find in the peripheral zone

A

It has glycoproteins required to platelet adhesion, aggregation, activation

18
Q

Sol gel zone contains

A

Microfilaments and microtubules which maintain discoid shape of platelet.

19
Q

Under what conditions do platelets turn round

A

Under cold conditions when microfilaments dissasemble.

Under warm conditions they go back to their original shape

20
Q

Membranous zone contains

A

Membranes derived from the smooth endoplasmic reticulum of megakaryocytic cells.

These membranes form a tube to the surface of the platelet membrane and synthesize and release thromboxane A2

21
Q

Organelle zone contains

A

2 types of platelet granules.

  1. Alpha granules which contain clotting factors like factor V,VIII, Fibrinogen
  2. Delta granules or dense bodies ; Contain ADP, calcium. serotonin which are platelet activating mediators
22
Q

Normal platelet count

A

150-450 times 10 raised to the power 9 L

23
Q

Thrombocytopenia

A

Low platelet count

< 150 TIMES TEN RAISED TO THE POWER 9 L

24
Q

Causes of thrombocytopenia( Not producing enough)

A 
Bone marrow faluire
Hereditary
Marrow infiltration
Chemotherapy
Radiation therapy
25
Q

Causes of Increased destruction of platelets

A 
Immune thrombocytopenic purpura ( autoantibodies against platelets)
DIC
Von willebrands disease type 2b
Heparin induced
Mechanical destruction
Neonatal alloinduced thrombocytopenia
26
Q

Other causes of thrombocytopenia

A 
hypersplenism
drugs
gestational-Increased plasma volume will affect platelets
infections
Hemophagocytosis
27
Q

Thrombocytosis

A

Increased platelet count

28
Q

Types of thrombocytosis

A

Primary

Secondary- due to a disease

29
Q

Causes of primary thrombocytosis

A 
Polycythemia vera
myelofibrosis
myelodysplastic syndromes
chronic myeloid leukemia
essential thrombocytosis
30
Q

Secondary thrombocytosis

A 
infection
inflammatory disorders
Acute/ chronic blood loss
tissue damage from trauma/surgery
medicines
splenectomy
malignancy
rebound from chemotherapy
31
Q

Spurious platelet counts

A

A situation where full blood count will give a false low or high platelet count

32
Q

Causes of false thrombocytosis

A

Anything that causes red cell fragmentation so machine counts it as smaller sized platelets

burns
microangiopathic hemolytic anemia
Microorganisms
Fragments of white cells in patients with leukemia

33
Q

Causes of false thrombocytopenia

A

Platelet aggregation by EDTA, myeloma etc.

Larger than normal platelets

Platelet satellitism where they surround WBCs and are counted as one

Haematology (29 decks)

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