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PLATELETS
Prepared By : Zahid Ali
Baqai medical unniversty
PLETELET PHYSIOLOGY
Platelets Production:
Hematopoietic stem cell
↓
Megakaryoblast
↓
Megakaryocyte
↓ Fragmentation
of cyto...
 Thrombopoietin:
 Regulator

of platelet production.
 Produced by the liver and kidneys.
 Levels are increased in
thro...
PLATELET CIRCULATION
Normal count is 250,000.
 Normal life span 7-10 days.
 About 1/3 are trapped in the spleen.

STRUTURE
Mucopolysacch.
coat

α Granules
Dense core
granules

Mucopolysacch. Coat: Glycoprotein content
which are importan...
Function
Formation of mechanical plug during
normal hemostatic response to
vascular injury.
The main steps involved are:
a...
PLATELETS ADHESION
Adhesion of platelet to subendothelial
collagen.
Dependent on the VW factor (Von
Willebrand part of Fac...
RELEASE (SECRETION)
Collagen exposure results in the
release of granules contents (ADP,
serotonin, fibrinoen).
Collagen an...
Membrane Phospholipid
↓
Arachidonic acid
↓ Cyclo-oxygenase
Thromboxane synthetase ↓
Thromboxane A2
Thromboxane A2: Potenti...
Platelets Disorders
Platelet disorders are the most
common cause of bleeding. The
disorder could be ↓ number
(thrombocytop...
THORMBOCYTOPENIA
Loss of platelets from the circulation faster
than the rate of their production by the bone
marrow. So th...
are ↑ or normal
in the bone marrow I.e production
is normal but platelets are
destroyed e.g. by antibodies.

 Megakaryocy...
Causes of Thrombocytopenia
Congenital
• Megakaryocytic hypoplasia
• TAR syndrome
• Wiscott Aldrich syndrome

Acquired
• Im...
Immunothrombocytopenia (ITP)
Autoimmune disorder characterized by
platelets bound antibodies:
Classification:
• Acute: Usu...
Pathogenesis of
Immunothrombocytopenia
1.

Platelets are sensitized with
autoantibodies.

2.

Premature removal of platele...
Acute Immunothrombocytopenia
 Self limiting usually weeks.
 In children.
 Usually preceeded by viral infection.
 Bone ...
Chronic Immunothrombocytopenia
Pathogenesis:
Autoimmune. Antibodies are formed
against antigens on platelet surface.
Clini...
Manifestations
Skin purpura, superfacial bruising,
epistaxis, menorrhagia.
• Mucossal hemorrhage is seen in
severe cases a...
Laboratory Findings
Thrombocytopenia with giant forms.
Count usually 10-50,000.
• Bone marrow shows normal or
increased me...
Other Causes of Thrombocytopenia
Bone Marrow Suppression:
Due to effect of infections (viral) or toxins or due
to replacem...
Aplastic Anemia
Splenomegaly:
• Normally 1/3 of body platelets are in the
spleen and 2/3 in the peripheral circulation.
• ...
Infections
•

Decreased platelets can be seen with many
infections, e.g., intra-uterine infections: best
examples are cong...
Defective Platelets Function
•

A defect in function is suspected if
there is prolonged bleeding time with or
without skin...
Disorders of Platelets Function
Congenital
• Glanzman’s disease
• Bernard Soluier’s
• Storage granules defect

Acquired
• ...
Glanzman’s Disease (Thrombasthenia)
•
•
•
•

•

•

Autosomal recessive inheritance.
Normal platelets count and appearance....
Acquired Disorders of Platelet
Function
Causes:
• Drugs e.g., Aspirin
• Myeloproliferative disorder.
• Paraproteinemias e....
Acquired Disorders of Platelet Function
(Cont…)

Drugs:
• Best example is ASPIRIN which is the MOST
COMMON cause of acquir...
Thank You For Your
Attention!
Platelets and platelets disorderz
Platelets and platelets disorderz
Platelets and platelets disorderz
Platelets and platelets disorderz
Platelets and platelets disorderz
Platelets and platelets disorderz
Platelets and platelets disorderz
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Transcript of "Platelets and platelets disorderz"

  1. 1. PLATELETS Prepared By : Zahid Ali Baqai medical unniversty
  2. 2. PLETELET PHYSIOLOGY Platelets Production: Hematopoietic stem cell ↓ Megakaryoblast ↓ Megakaryocyte ↓ Fragmentation of cytoplasm Platelets
  3. 3.  Thrombopoietin:  Regulator of platelet production.  Produced by the liver and kidneys.  Levels are increased in thrombocytopenia,and reduced in thrombocytosis.  It increases the no. & rate of maturation of the megakaryocytes.
  4. 4. PLATELET CIRCULATION Normal count is 250,000.  Normal life span 7-10 days.  About 1/3 are trapped in the spleen. 
  5. 5. STRUTURE Mucopolysacch. coat α Granules Dense core granules Mucopolysacch. Coat: Glycoprotein content which are important for interaction of platelets with each other or aggregating agents. − α Granules: - Dense core:
  6. 6. Function Formation of mechanical plug during normal hemostatic response to vascular injury. The main steps involved are: adhesion, release, aggregation.
  7. 7. PLATELETS ADHESION Adhesion of platelet to subendothelial collagen. Dependent on the VW factor (Von Willebrand part of Fact VIII). Also dependent on glyoproteins.
  8. 8. RELEASE (SECRETION) Collagen exposure results in the release of granules contents (ADP, serotonin, fibrinoen). Collagen and thrombin activate prostaglandin synthesis.
  9. 9. Membrane Phospholipid ↓ Arachidonic acid ↓ Cyclo-oxygenase Thromboxane synthetase ↓ Thromboxane A2 Thromboxane A2: Potentiase aggregation and vasoconstrictor. Aggregation: Release ADP+thromboxane A2 →aggregation. This is followed by more secration →secondary aggregation. →platelet mass or plug.
  10. 10. Platelets Disorders Platelet disorders are the most common cause of bleeding. The disorder could be ↓ number (thrombocytopenia) or defective function.
  11. 11. THORMBOCYTOPENIA Loss of platelets from the circulation faster than the rate of their production by the bone marrow. So thrombocytopenia is due to: A. Failure of platelets production, most common cause, Megakaryocytes are ↓ in the bone marrow e.g. drugs. B. ↑ rate of removal of platelets from the circulation.
  12. 12. are ↑ or normal in the bone marrow I.e production is normal but platelets are destroyed e.g. by antibodies.  Megakaryocytes
  13. 13. Causes of Thrombocytopenia Congenital • Megakaryocytic hypoplasia • TAR syndrome • Wiscott Aldrich syndrome Acquired • Immunothrombocytopenia • Thrombotic thrombocytopenic purpura • DIC • Drugs • Infections • Splenomegaly • Bone marrow suppression or infiltration • Aplastic anaemia
  14. 14. Immunothrombocytopenia (ITP) Autoimmune disorder characterized by platelets bound antibodies: Classification: • Acute: Usually in children, self limiting preceeded by infection usually viral. • Chronic: Usually in adults, more common in female. Etiology: • Idiopathic
  15. 15. Pathogenesis of Immunothrombocytopenia 1. Platelets are sensitized with autoantibodies. 2. Premature removal of platelets from the circulation by macrophages of the R-E system and destroyed mainly in the spleen.
  16. 16. Acute Immunothrombocytopenia  Self limiting usually weeks.  In children.  Usually preceeded by viral infection.  Bone marrow shows normal or increased megakaryocytes.  Due to immune complexes bound to platelets. (Complex = viral antigenantibody complex). These complexes are removed by the reticuloendothelial system (RE system).  5-10% can go into chronic ITP.
  17. 17. Chronic Immunothrombocytopenia Pathogenesis: Autoimmune. Antibodies are formed against antigens on platelet surface. Clinical: • Usually adults, young female 15-50 yrs. • Insidious onset. • Chronic: last months or years. • No precipitating causes. • Shows fluctuating (cyclical) course with periods in which platelets number return to normal.
  18. 18. Manifestations Skin purpura, superfacial bruising, epistaxis, menorrhagia. • Mucossal hemorrhage is seen in severe cases and intra-cranial hemorrhage is rare. • Splenomegaly: 10% of cases. •
  19. 19. Laboratory Findings Thrombocytopenia with giant forms. Count usually 10-50,000. • Bone marrow shows normal or increased megakaryocytes. • Platelet bound IgG is +. • . •
  20. 20. Other Causes of Thrombocytopenia Bone Marrow Suppression: Due to effect of infections (viral) or toxins or due to replacement e.g., by malignancy e.g., leukemias, metastatic tumors, or due to fibrosis of the bone marrow e.g., due to irradiation. DIC: • Due to consumption of platelets. Drugs: • Due to suppression e.g., phenylbutazone, Gold, Thiazide. • Other mechanisms of action are immune, or by causing direct aggregation of platelets. • May be accompanied by other signs e.g., fever, joint pain, rash, leukopenia.
  21. 21. Aplastic Anemia Splenomegaly: • Normally 1/3 of body platelets are in the spleen and 2/3 in the peripheral circulation. • With spleen enlargement, up to 80-90% of body platelets will pool in the spleen decreased platelets in the peripheral circulation. • This spleen enlargement could due to many causes, e.g., thalassemia, portal hypertension, Gaucher’s, malaria, Kalaazar, lymphomas, etc. • Life span of the platelets is normal.
  22. 22. Infections • Decreased platelets can be seen with many infections, e.g., intra-uterine infections: best examples are congenital syphilis, toxoplasmosis, rubella, cytomegalo virus (CMV), herpes. Also seen with other infections e.g., influenza, chicken pox, rubella, infectious mononucleosis. • The effect is due to suppression of bone marrow, immune mediated or due to DIC in fulminant infections.
  23. 23. Defective Platelets Function • A defect in function is suspected if there is prolonged bleeding time with or without skin or mucosal hemorrhage in the presence of normal platelet count.
  24. 24. Disorders of Platelets Function Congenital • Glanzman’s disease • Bernard Soluier’s • Storage granules defect Acquired • Drugs • Uremia • Myeloproliferative disorders • Multiple myeloma
  25. 25. Glanzman’s Disease (Thrombasthenia) • • • • • • Autosomal recessive inheritance. Normal platelets count and appearance. No clumps are seen on peripheral blood film (I.e., no platelets clumps). Due to decreased surface membrane glycoproteins 11b + 111a failure of primary aggregation. Platelets do not aggregate with all aggregating agents but they aggregate with ristocetin. Bleeding time is prolonged.
  26. 26. Acquired Disorders of Platelet Function Causes: • Drugs e.g., Aspirin • Myeloproliferative disorder. • Paraproteinemias e.g., multiple myeloma. • Cardiopulmonary bypass. • Autoimmune diseases e.g., SLE (Systemic Lupus Erythromitosis) • Uremia (renal failure).
  27. 27. Acquired Disorders of Platelet Function (Cont…) Drugs: • Best example is ASPIRIN which is the MOST COMMON cause of acquired platelet function disorder. • Aspirin irreversibly affect the cyclooxygenase enzyme. The effect last 4-7 days and it takes about 10 days before the platelets are replaced. • Presents as elevated bleeding time but purpura is unusual.
  28. 28. Thank You For Your Attention!
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