Histology · Respiratory system
Serous membranes: pleura and peritoneum !
- Tissue
The lungs and belly organs are wrapped in thin, slippery membranes that let them slide; fluid builds up between the layers when they are diseased.
Updated 2026-11-01
See it in 3D: Pleura · Peritoneum · Greater omentum
What it is
Serous membranes line closed body cavities and cover the organs inside them. Each is a single layer of flat mesothelial cells over a thin connective tissue, arranged as a parietal layer on the wall and a visceral layer on the organ, with a thin film of fluid between them. The pleura, peritoneum and pericardium share this structure, so effusions, infections, tumour spread and mesothelioma follow the same rules.
Structure
- Mesothelium: simple squamous epithelium with microvilli that hold the lubricating fluid.
- Submesothelial connective tissue with elastic fibres, blood vessels, lymphatics and nerves.
- Visceral pleura covers the lung and dips into its fissures; parietal pleura lines the chest wall, mediastinum and diaphragm; they meet at the hilum.
- Visceral peritoneum covers intraperitoneal organs (forming their serosa); parietal peritoneum lines the abdominal wall; mesenteries and omenta are double folds carrying vessels.
Function
- The fluid film reduces friction and, in the chest, couples the lung to the chest wall so it expands with it.
- Mesothelial cells secrete and reabsorb fluid; lymphatics of the parietal layer drain it.
- The omentum walls off infections in the abdomen.
Transudate vs exudate
| Feature | Transudate | Exudate |
|---|---|---|
| Mechanism | Imbalance of hydrostatic or oncotic pressure | Inflamed or invaded membrane leaks protein |
| Protein and LDH | Low | High |
| Typical causes | Heart failure, cirrhosis, nephrotic syndrome | Pneumonia, tuberculosis, cancer, peritonitis |
| Cells | Few | Neutrophils, lymphocytes or malignant cells |
Clinical notes
- The parietal pleura and parietal peritoneum carry somatic pain fibres, so their inflammation gives sharp, well-localized pain.
- Tuberculous pleurisy, frequent in Colombia, produces a lymphocyte-rich exudate.
- Malignant mesothelioma arises from mesothelium after asbestos exposure.
- Peritonitis follows perforation or infection and spreads through the peritoneal spaces.
Test yourself
Think of the answer, then tap the question to see it.
Which epithelium lines the pleural and peritoneal cavities?
Mesothelium, a simple squamous epithelium with microvilli.
Why is pleuritic chest pain sharp and well localized?
The parietal pleura is supplied by somatic nerves of the chest wall, while the visceral pleura is insensitive to pain.
Which occupational exposure is classically linked to mesothelioma?
Asbestos.
What separates a transudate from an exudate in principle?
A transudate comes from pressure imbalance with an intact membrane; an exudate comes from an inflamed or invaded membrane leaking protein and cells.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- The alveolus: type I and II pneumocytes, surfactant, the blood–air barrier
- The GI tract wall: mucosa, submucosa, muscularis, serosa; enteric plexuses
- Simple, stratified, pseudostratified and transitional epithelium
Related conditions
Microorganisms
Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.
Sources: 22.2 The Lungs - Anatomy and Physiology 2e | OpenStax (OpenStax (Rice University), 2022); Membranes | SEER Training (National Cancer Institute (SEER Training), 2026); 23.1 Overview of the Digestive System - Anatomy and Physiology 2e | OpenStax (OpenStax (Rice University), 2022).
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Representative model, for educational purposes only.