Platelets, also called thrombocytes, are small cell fragments (not full cells) produced from large bone-marrow cells called megakaryocytes. Blood normally has 1,50,000 to 3,50,000 platelets per mm³, and they release substances that help blood clot; a fall in their number causes clotting disorders and heavy blood loss. Memory hook: "Thrombocytes = broken bits from mega cells that STOP the bleed."
Platelets are fragments pinched off from megakaryocytes in bone marrow (1.5–3.5 lakh/mm³); they release substances that drive blood coagulation to stop bleeding.
Your doubts, answered
Are platelets true cells or cell fragments?
Platelets are cell FRAGMENTS, not complete cells. NCERT says they are 'cell fragments produced from megakaryocytes'. They have no nucleus. This is a favourite NEET trap, so never call platelets 'cells' in the strict sense.
Where are platelets produced?
Platelets are pinched off from megakaryocytes, which are special large cells present in the bone marrow. So the source cell is the megakaryocyte and the place is the bone marrow. If an option says 'made from megakaryocytes in bone marrow', that is correct.
What is the normal platelet count?
NCERT gives 1,50,000 to 3,50,000 platelets per mm³ of blood (written as 1,500,00–3,500,00 in the book). Learn this exact range; NEET has asked count values for RBC, WBC and platelets.
Do platelets clot blood by themselves?
No. Platelets RELEASE a variety of substances, most of which are involved in the coagulation (clotting) of blood. They start and help the clotting process but do not act alone; the clotting cascade with factors like thrombin and fibrinogen does the actual clot.
What if platelet number drops?
A reduction in platelet number leads to clotting disorders, which cause excessive loss of blood from the body. This low count is called thrombocytopenia (NCERT states the effect, not the term).
⚠️ The NEET trap ✗ Platelets are complete, nucleated blood cells made in the spleen. ✓ Platelets are non-nucleated cell FRAGMENTS produced from megakaryocytes in the BONE MARROW. 🧠 Fragment, not cell; megakaryocyte, not spleen. NEET swaps the source organ and calls them 'cells' to trick you.
Real NEET questions
NEET 2016 Phase 2
Name the blood cells, whose reduction in number can cause clotting disorder, leading to excessive loss of blood from the body.
A · Erythrocytes
B · Leucocytes
C · Neutrophils
D · Thrombocytes ✓
Solution: Platelets, also called thrombocytes, release substances involved in the coagulation or clotting of blood. A reduction in their number leads to clotting disorders, causing excessive loss of blood. NCERT Ch 15, p.195: 'a reduction in their number can lead to clotting disorders.'
Solved Body Fluids and Circulation NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
