PLATELETS Flashcards
LXCTURE 6
How are platelets formed?
Platelets are formed in the bone marrow by fragmentation of megakaryocytes.
What role do platelets play in blood coagulation?
Platelets trigger and control blood coagulation by participating in the formation of blood clots
What happens when platelets adhere to damaged surfaces of blood vessels?
Platelets rapidly adhere to damaged surfaces of blood vessels and secrete proteins and small molecules that trigger thrombosis or clot formation.
what is the size of platelets
2-4 micrometer
how do platelets maintain blood vessel integrity
by instigating vessel wall repair.
how do platelets accomplish their clot formation process
Platelets rapidly adhere to damaged surfaces of blood vessels, and secrete proteins and small molecules
what are the effects of uncontrolled platelet
Uncontrolled platelets can refer to two different conditions:
Thrombocytosis (High Platelet Count) and Platelet Function Disorders:
Platelet function disorders occur when platelets don’t work as they should.
Deep vein thrombosis
Pulmonary emboli
Acute myocardial infarction(heart attacks), Celebrovascular accidents (strokes)
Peripheral artery disease
Repeated spontaneous abortions (miscarriage).
Deep vein thrombosis (DVT) occurs when a blood clot (thrombus) forms in one or more of the deep veins in the body, usually in the legs. Pulmonary embolism (PE) occurs when one of the arteries in the lungs becomes blocked by a blood clot. Peripheral artery disease (PAD), also known as peripheral arterial disease, is a common vascular disorder characterized by the abnormal narrowing of arteries
What is the mean platelet volume (MPV) and how is it generated?
indicating the average volume of platelets in blood
What does an elevated MPV value indicate?
An elevated MPV value, resulting from the presence of predominantly larger platelets, can sometimes signal a regenerative bone marrow response to increased platelet consumption.
Can you explain what Essential Thrombocythaemia (ET) is
ET is a rare malignant condition characterized by extremely high platelet counts and uncontrolled platelet production, making it a life-threatening haematological disorder.
What does thrombocytosis refer to and what does it indicate
Thrombocytosis refers to elevated platelet counts in the blood, which can be a signal of inflammation or trauma but generally carries small intrinsic significance
What is thrombocytopenia?
Thrombocytopenia is a condition characterized by a low platelet count, which can be a common consequence of drug treatment and may be life-threatening
Why does thrombocytopenia occur?
Thrombocytopenia occurs due to a decreased number of platelets in the blood. These platelets play a crucial role in maintaining normal blood vessel function and repair
What symptoms are associated with thrombocytopenia?
bruising
uncontrolled hemorrhage
What role do thrombocytes (platelets) play in blood vessel maintenance
Thrombocytes are responsible for maintaining and repairing blood vessels. They help form blood clots to prevent excessive bleeding and promote healing
What conditions might lead to thrombocytopenia
Thrombocytopenia can occur in response to drug treatments, certain diseases, or other medical conditions. It’s essential to identify the underlying cause for appropriate management
What is the normal range for platelet counts in circulation?
Platelets typically circulate in amounts of 150 to 400 x 10⁹/L.
How do mean platelet counts differ between women and men?
Mean platelet counts are slightly higher in women compared to men
What is the distribution pattern of platelets on a Wright-stained wedge preparation blood film
On a Wright-stained wedge preparation blood film, platelets are distributed throughout the red blood cell monolayer at a rate of 7 to 21 per 100x field.
What is the average diameter of platelets
2.5µm
What does the mean platelet volume (MPV) correspond to
The mean platelet volume (MPV) corresponds to a range of 8 to 10 fL
How would you describe the internal structure of platelets under a light microscope?
The internal structure of platelets is complex and granular
What are platelets, and from which bone marrow cells do they arise?
Platelets are small, disc-shaped blood cells involved in clotting. They arise from megakaryocytes, which are unique bone marrow cells
Describe the process of megakaryocyte maturation. What makes it mysterious?
Megakaryocyte maturation involves a form of mitosis called endomitosis. Unlike typical mitosis, endomitosis lacks telophase and cytokinesis. This mysterious process results in megakaryocytes with multiple sets of chromosomes.
What is endomitosis, and how does it differ from typical mitosis?
Endomitosis is a cell division process where the cell replicates its DNA without undergoing full cell division. Unlike regular mitosis, endomitosis skips the final stages of cell division, resulting in cells with multiple nuclei.
Explain the role of spindle fiber orientation during endomitosis
During endomitosis, the loss of spindle fiber orientation at the point of telophase prevents chromosomes from proceeding to polar bodies. Instead, they duplicate in place within the cell.
Why do chromosomes duplicate in place during endomitosis instead of proceeding to polar bodies?
The altered spindle fiber orientation disrupts the normal movement of chromosomes, causing them to remain in place. This unique adaptation ensures that cytokinesis (cell separation) is arrested.
What makes this cell cycle adaptation in megakaryocytes unique?
The lack of cytokinesis during endomitosis is specific to megakaryocytes and is not observed in other normal human cells. It allows these cells to produce platelets efficiently.
What is endomitosis, and how does it differ from regular cell division?
Endomitosis is a cell division process where DNA replication occurs without subsequent cell division. Unlike typical mitosis, endomitosis lacks cytokinesis, resulting in cells with multiple sets of chromosomes.
what does “polyploid” mean?
Polyploid refers to possessing multiple copies of chromosomes within a single cell.
What ploidy levels are achieved during endomitosis
Endomitosis leads to ploidy levels of 8N, 16N, or 32N
Why is reaching 128N ploidy unusual in megakaryocytes?
Megakaryocytes, which replicate their nuclei up to 128N, exhibit unusually high ploidy. Such levels may indicate hematologic diseases.
How do megakaryocytes utilize their abundant DNA?
Megakaryocytes use their copious DNA to synthesize abundant cytoplasm, which eventually differentiates into platelets
How many platelets can a single megakaryocyte shed?
A single megakaryocyte can shed 2000 to 4000 platelets.
What is the daily platelet production by megakaryocytes in an average-sized healthy human?
An average-sized healthy human has approximately 10⁸ megakaryocytes, producing 101¹¹ platelets per day.
