Physiology · Blood, hemostasis and basic immunity

The red cell life cycle and the spleen !

Concept
Exam priority: medium

A red cell lives about four months. Old, stiff cells are caught in the spleen, eaten, and their iron is reused; the rest becomes bilirubin.

Updated 2026-11-01

Also called: Red cell destruction, Hemolysis, Splenic function

See it in 3D: Spleen · Liver · Splenic artery

What it is

Mature red cells have no nucleus or mitochondria, so they cannot repair themselves and run on glycolysis alone. After about 120 days they become stiff and are removed mainly by macrophages in the splenic red pulp. The spleen also filters blood for damaged cells, inclusions and encapsulated bacteria, and holds a reserve of platelets.

Key facts

The cords of the red pulp force cells through slits only a few micrometres wide: rigid or coated cells are trapped.
'Pitting' removes inclusions (Howell–Jolly, Heinz bodies) without destroying the cell; 'culling' removes whole cells.
The spleen holds about a third of the platelets; hypersplenism lowers all counts.
Oxidant stress (fava beans, some drugs, infection) in G6PD deficiency denatures hemoglobin into Heinz bodies → bite cells.

Where the red cell is destroyed

Feature	Extravascular	Intravascular
Site	Splenic and hepatic macrophages	Inside blood vessels
Typical causes	Spherocytosis, IgG-coated cells, sickle cells	ABO mismatch, complement (PNH), mechanical valves, malaria
Haptoglobin	Normal or mildly low	Very low
Urine	Dark from urobilinogen; no hemoglobin	Hemoglobinuria, later hemosiderinuria

Clinical notes

Sickle cell disease: repeated splenic infarcts cause 'autosplenectomy' in childhood, hence pneumococcal risk.
Splenic injury is the most common solid-organ injury in blunt abdominal trauma.
Plasmodium invades and ruptures red cells; in Colombia malaria (P. vivax and P. falciparum) is a common cause of hemolysis in endemic regions.

Test yourself

Think of the answer, then tap the question to see it.

Why is the red cell entirely dependent on glycolysis?

It has no mitochondria, so it cannot use oxidative phosphorylation; ATP comes only from glycolysis, which is why pyruvate kinase deficiency causes hemolysis.

Why does G6PD deficiency cause hemolysis only under oxidant stress?

G6PD makes NADPH to regenerate reduced glutathione. Under normal conditions enough is made; with oxidants (infection, fava beans, some drugs) the cell cannot detoxify peroxide and hemoglobin denatures.

Why is haptoglobin low in intravascular hemolysis?

Free hemoglobin released in the plasma binds haptoglobin, and the complex is quickly cleared by the liver, using up haptoglobin.

Why does a person without a spleen face a higher risk from encapsulated bacteria?

The spleen filters blood-borne bacteria and makes IgM and opsonizing antibodies against capsular polysaccharides; without it, organisms like pneumococcus are cleared poorly.

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See it in 3D

The structures of Durgical's 3D anatomy where it happens.

In Biochemistry

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Educational physiology content; not a diagnostic or treatment guide and no substitute for a health professional's advice. Values are approximate references. No doses are given.

Sources: 18.3 Erythrocytes (OpenStax (Rice University), 2022); Anatomy, Abdomen and Pelvis, Spleen (StatPearls (NCBI Bookshelf), 2024); Hall JE. Guyton and Hall Textbook of Medical Physiology, 13th ed. (ch. 33). Reference book used to check facts; its text and figures are not reproduced (Elsevier, 2016).

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