The mesothelium

Last medical review:

The mesothelium is the membrane that lines cavities in the body and surrounds most of your internal organs. The mesothelium has different names depending on where it is in the body.

The pleura

The pleura is the part of the mesothelium in the chest.

Diagram of the pleura
Diagram of the pleura

The parietal pleura is the outer layer. It lines the inside of the chest wall and covers the top of the diaphragm.

The visceral pleura is the inner layer. It surrounds and supports each lung.

The pleural space is between the 2 layers of the pleura. It contains fluid that cushions the lungs and allows them to expand smoothly inside the chest.

The peritoneum

The peritoneum is the part of the mesothelium in the abdomen and pelvis.

Diagram of the peritoneum
Diagram of the peritoneum

The parietal peritoneum is the outer layer. It lines the abdominal wall and the pelvis.

The visceral peritoneum is the inner layer. It surrounds and supports most of the organs in the abdomen and pelvis. The omentum is a part of the visceral peritoneum.

The peritoneal space is between the 2 layers of the peritoneum. It contains fluid, which cushions the organs.

The mesothelium in other parts of the body

The pericardium is the membrane that covers and protects the heart.

The tunica vaginalis is the membrane that surrounds each testicle.

Expert review and references

  • John Cho, MD, PhD, FRCPC
  • American Cancer Society. Malignant Mesothelioma. Atlanta, GA: American Cancer Society; 2010:
  • National Comprehensive Cancer Network. NCCN Guidelines for Patients: Pleural Mesothelioma. 2022:

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