Where are platelets formed?

Appeared in: SGPGI Nursing Officer-2024

Explanation

Platelets (thrombocytes) are produced in the bone marrow, which is the primary site for the formation of all blood cells in adults (a process called hematopoiesis).
They are not true cells but are small, anucleated fragments that break off from the cytoplasm of very large precursor cells known as megakaryocytes.
This specific process of platelet formation is called thrombopoiesis.

Option A: The small intestine's primary function is the digestion and absorption of nutrients. It does not produce blood cells.
Option B: The large intestine is mainly involved in water absorption and the formation of feces. It has no role in hematopoiesis.
Option D: The liver does not form platelets in adults. Its role is to produce thrombopoietin (TPO), the hormone that signals the bone marrow to produce more platelets.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain The physiological site of platelet production (thrombopoiesis) as background academic context rather than a clinical decision trigger.
Understanding that platelets are made in the bone marrow is crucial for diagnosing conditions like thrombocytopenia (low platelet count). The cause could be decreased production in the marrow (e.g., due to leukemia, aplastic anemia, or chemotherapy) or increased destruction elsewhere.
Nurses monitor platelet counts (normal range: 150,000-450,000/µL) to assess a patient's risk for bleeding. Low counts require bleeding precautions.
What if? If a patient has severe liver failure (cirrhosis), their platelet count may be low. This is not because the liver makes platelets, but because a diseased liver produces less thrombopoietin (TPO), leading to reduced stimulation of the bone marrow. Also, cirrhosis often causes an enlarged spleen (splenomegaly), which can trap and destroy platelets, further lowering the count.

How to Approach the Question

This is a factual recall question testing fundamental knowledge of hematology.
First, identify the key term in the question: 'platelets' and 'formed'. The question asks for the origin site.
Recall the general process of blood cell formation, known as hematopoiesis.
Remember that in adults, the bone marrow is the factory for all major blood components: red blood cells, white blood cells, and platelets.
Evaluate each option: The intestines are for digestion. The liver has many roles, including producing the regulatory hormone for platelets (thrombopoietin), but it's not the production site in adults. This leaves the bone marrow as the correct location.

Concept Tested & Keywords

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E6 Nursing Brunner Adult Health 3SA Vol 1 Part 3 p. 110-112

E6 Anatomy Grays 43e Vol 1 Part 1 p. 103-105

E6 Physiology Ganong 27e Vol 1 Part 1 p. 97-99

Practise the full SGPGI Nursing Officer-2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.