Red blood cells (RBCs) are made in the red bone marrow of adults. Each RBC lives about 120 days, then is destroyed in the spleen — which NCERT calls the "graveyard of RBCs." Erythropoietin, a hormone from the juxtaglomerular (JG) cells of the kidney, stimulates RBC formation. Memory hook: "Marrow makes, 120 days age, Spleen buries the cage — Kidney sends the erythropoietin wage."
RBCs form in red bone marrow, circulate for about 120 days, and are destroyed in the spleen (graveyard of RBCs). Erythropoietin from kidney JG cells signals the marrow to make more RBCs.
Your doubts, answered
Where are RBCs formed in an adult?
In adults, RBCs are formed in the red bone marrow. This is the NCERT-stated fact for humans. (In the foetus, other organs like the liver also make RBCs, but for NEET the adult answer is red bone marrow.)
What is the exact lifespan of an RBC?
An RBC has an average life span of 120 days. After this it is destroyed. Remember the number 120 days exactly — NEET often gives close wrong options like 100 or 140.
Why is the spleen called the 'graveyard of RBCs'?
After about 120 days, old RBCs are destroyed in the spleen. Because RBCs go there to be broken down and removed, NCERT calls the spleen the 'graveyard of RBCs.'
Which hormone stimulates RBC formation and where is it made?
Erythropoietin is the hormone that stimulates RBC formation (erythropoiesis). It is produced mainly by the juxtaglomerular (JG) cells of the kidney, not by the bone marrow. The kidney senses low oxygen and releases erythropoietin, which then acts on the red bone marrow to make more RBCs.
Is erythropoietin made by the bone marrow?
No. This is a classic trap. The bone marrow is only the SITE where RBCs are made. Erythropoietin (the signal) comes from the JG cells of the kidney. Two different organs — do not mix them up.
⚠️ The NEET trap ✗ Erythropoietin is produced by the red bone marrow because that is where RBCs are made. ✓ Erythropoietin is produced by the juxtaglomerular (JG) cells of the kidney. The red bone marrow is only the SITE of RBC formation; the kidney sends the erythropoietin signal that tells the marrow to make RBCs. 🧠 Marrow = the factory (makes RBCs). Kidney = the boss (sends erythropoietin). NEET swaps these two to trick you.
Real NEET questions
2021
Erythropoietin hormone which stimulates R.B.C. formation is produced by
A · The cells of bone marrow
B · Juxtaglomerular cells of the kidney ✓
C · Alpha cells of pancreas
D · The cells of rostral adenohypophysis
Solution: Erythropoietin stimulates erythropoiesis (RBC formation in the red bone marrow). It is secreted mainly by the juxtaglomerular (JG) cells of the kidney in response to low oxygen. The bone marrow is only the site where RBCs are made, not where the hormone is produced — so option (a) is the classic trap.
2022
Given below are two statements: Statement I: The coagulum is formed of a network of threads called thrombins. Statement II: Spleen is the graveyard of erythrocytes. In the light of the above statements, choose the most appropriate answer.
A · Both Statement I and Statement II are correct
B · Both Statement I and Statement II are incorrect
C · Statement I is correct but Statement II is incorrect
D · Statement I is incorrect but Statement II is correct ✓
Solution: Statement II is correct: RBCs are destroyed in the spleen, which NCERT calls the 'graveyard of RBCs.' Statement I is wrong because the clot (coagulum) is a network of threads called fibrins, not thrombins — thrombin is only the enzyme that converts fibrinogen to fibrin. So Statement I is incorrect but Statement II is correct.
Solved Body Fluids and Circulation NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A healthy adult man has, on average, 5 million to 5.5 million RBCs per mm³ (cubic millimetre) of blood. RBCs are the most abundant cells in blood.
What is the average lifespan of an RBC?
About 120 days. After this, RBCs are destroyed in the spleen.
Which organ is called the graveyard of RBCs?
The spleen. Old RBCs are broken down here after their 120-day lifespan, so NCERT names it the graveyard of RBCs.
Where is erythropoietin produced and what does it do?
Erythropoietin is produced by the juxtaglomerular (JG) cells of the kidney. It stimulates the red bone marrow to form more RBCs, usually when blood oxygen is low.
Where are RBCs made in adults?
In the red bone marrow. For NEET, the adult site of RBC formation is always the red bone marrow.
