Question

multiple choice question
what happens to the fragments of old red blood cells after they rupture?

they circulate in the plasma.

they are recycled by macrophages.

they are excreted by the kidney.

they are degraded by plasma enzymes.

Explanation:

Old red blood cells are removed from circulation when they age or are damaged. Macrophages (a type of white blood cell) in the spleen, liver, and bone marrow play a key role in phagocytosing (engulfing) and recycling the components of ruptured or old red blood cells. The iron from hemoglobin is recycled, and the heme is broken down further.

• "They circulate in the plasma" is incorrect because the fragments of old RBCs are not meant to circulate but are removed.
• "They are excreted by the kidney" is incorrect as the kidney filters blood but does not excrete RBC fragments directly (though some breakdown products like bilirubin are eventually excreted in bile and urine after processing, but the fragments themselves are processed by macrophages first).
• "They are degraded by plasma enzymes" is incorrect because plasma enzymes do not primarily degrade RBC fragments; macrophages are the main cells involved in this process.

Answer:

B. They are recycled by macrophages.