Podcast
Questions and Answers
What is the primary function of thrombosthenin in platelets?
What is the primary function of thrombosthenin in platelets?
Platelets have a nucleus that helps them in their functioning.
Platelets have a nucleus that helps them in their functioning.
False
What are the types of granules found in platelets?
What are the types of granules found in platelets?
Alpha granules, Dense granules, Lysosomes
Platelets originate from the fragmentation of __________.
Platelets originate from the fragmentation of __________.
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Which of the following is NOT a component found in alpha granules?
Which of the following is NOT a component found in alpha granules?
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Match the types of granules with their contents:
Match the types of granules with their contents:
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Microscopic tubular systems in the cytoplasm of platelets assist in communication with plasma.
Microscopic tubular systems in the cytoplasm of platelets assist in communication with plasma.
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What maintains the shape of a platelet cell?
What maintains the shape of a platelet cell?
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What is the normal platelet count range?
What is the normal platelet count range?
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Platelets have an average lifespan of 7-10 days in circulation.
Platelets have an average lifespan of 7-10 days in circulation.
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What is the process by which damaged platelets are removed from circulation?
What is the process by which damaged platelets are removed from circulation?
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Thrombocytopenia refers to a condition characterized by a __________ in the number of platelets.
Thrombocytopenia refers to a condition characterized by a __________ in the number of platelets.
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Match the following platelet disorders with their causes:
Match the following platelet disorders with their causes:
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Which of the following factors may regulate the production of platelets?
Which of the following factors may regulate the production of platelets?
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Macrophages are involved in the destruction of old platelets.
Macrophages are involved in the destruction of old platelets.
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Platelets are essential in the __________ of bleeding.
Platelets are essential in the __________ of bleeding.
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Study Notes
Platelets
- Smallest blood cells, forming a creamy layer on top of white cells after centrifugation
- Round or oval shaped, approximately 1.5 µm in diameter
- No nucleus, but packed with granules, bound by a membrane
- Shape maintained by microtubules, extensive folded membrane, and tubular system in cytoplasm
- Membrane receptors for collagen, activators, von Willebrand factor for adhesion to vessel walls and to each other during haemostasis
- Contractile proteins (thrombosthenin) involved in shape changes, aggregation, and clot retraction
- Cytoplasmic granules (alpha, dense, lysosomes) with various factors for vasoconstriction, aggregation, coagulation, wound healing
- Alpha granules: fibrinogen, factor V, thrombaspondin, von Willebrand factor, platelet-derived growth factor
- Dense granules: ADP, serotonin, calcium
- Lysosomes: hydrolytic enzymes
Platelet Development
- Originate from megakaryocytes, which stem from pluripotent stem cells in the bone marrow
- Megakaryoblast -> pro-megakaryocyte -> megakaryocyte -> platelet
- Megakaryocyte maturation: reduplication of nucleus, maturation of cytoplasm, and loss of basophilia
- Platelets formed by cytoplasmic pseudopodia penetrating sinusoids, or vesicle formation within cytoplasm, fragmenting and releasing platelets, leaving behind the nucleus
Platelet Functions
- Arrest bleeding through platelet plug formation, secretion of substances for coagulation and clot retraction.
Normal Platelet Values
- Normal range is 150-400 x 10³/µL, mean around 250 x 10³/µL
Platelet Lifespan
- Approximately 9-12 days
Platelet Destruction
- Phagocytosis by macrophages in the spleen
Platelet Regulation
- Number fairly constant, production matches destruction, but mechanism unclear
- Factors like thrombopoietin related to colony stimulating factors may be involved.
Platelet Disorders
- Thrombocytopenia (low platelet count) can result from various mechanisms, such as failure of maturation, marrow hypoplasia, infiltration, consumption (DIC), or drug-induced effects
- Platelet Function Disorders:
- Defective adhesion (low/absent von Willebrand factor or receptors)
- Defective aggregation (e.g., aspirin)
- Defective release reaction (e.g., aspirin)
- Excessive destruction (e.g., enlarged spleen in certain conditions like malaria or portal hypertension)
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Description
This quiz covers the anatomy and function of platelets, the smallest blood cells critical for hemostasis. It also explores their development from megakaryocytes in the bone marrow. Test your knowledge on the features, granules, and roles of platelets in the body.
