[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Histology](https://durgical.com/en/histology/) › [Respiratory system](https://durgical.com/en/histology/#a-respiratory) › Serous membranes: pleura and peritoneum [Histology](https://durgical.com/en/histology/) · [Respiratory system](https://durgical.com/en/histology/#a-respiratory) # 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](https://durgical.com/en/anatomy/pleura/) · [Peritoneum](https://durgical.com/en/anatomy/peritoneum/) · [Greater omentum](https://durgical.com/en/anatomy/greater-omentum/) ## Key points - Serous membrane = mesothelium (simple squamous) + thin connective tissue. - Parietal layer on the wall, visceral on the organ, fluid between them. - Parietal layers feel pain; visceral pleura does not. - Mesothelioma: asbestos. - Exudate = inflamed or invaded membrane; transudate = pressure imbalance. ## 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](https://durgical.com/en/conditions/pleural-effusion/) | Imbalance of hydrostatic or oncotic pressure | Inflamed or invaded membrane leaks protein | | Protein and LDH | Low | High | | [Typical causes](https://durgical.com/en/conditions/tuberculosis/) | 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. ## Memory aid A serous membrane is a balloon pressed in by a fist: one layer touches the fist (organ), the other faces out (wall), and a drop of fluid lets them slide. ## 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. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/histology/serous-membranes-pleura-and-peritoneum/) ## See it in 3D The structures of Durgical's 3D anatomy where it is found. - [Pleura](https://durgical.com/en/anatomy/pleura/) - [Peritoneum](https://durgical.com/en/anatomy/peritoneum/) - [Greater omentum](https://durgical.com/en/anatomy/greater-omentum/) ## Related - [The alveolus: type I and II pneumocytes, surfactant, the blood–air barrier](https://durgical.com/en/histology/the-alveolus-type-i-and-ii-pneumocytes-surfactant-the-blood-air-barrier/) - [The GI tract wall: mucosa, submucosa, muscularis, serosa; enteric plexuses](https://durgical.com/en/histology/the-gi-tract-wall-mucosa-submucosa-muscularis-serosa-enteric-plexuses/) - [Simple, stratified, pseudostratified and transitional epithelium](https://durgical.com/en/histology/simple-stratified-pseudostratified-and-transitional-epithelium/) ## Related conditions - [Pleural effusion](https://durgical.com/en/conditions/pleural-effusion/) - [Peritonitis](https://durgical.com/en/conditions/peritonitis/) - [Pneumothorax](https://durgical.com/en/conditions/pneumothorax/) - [Tuberculosis](https://durgical.com/en/conditions/tuberculosis/) ## Microorganisms - [Mycobacterium tuberculosis](https://durgical.com/en/microbiology/mycobacterium-tuberculosis/) [← All of histology](https://durgical.com/en/histology/) 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](https://openstax.org/books/anatomy-and-physiology-2e/pages/22-2-the-lungs) (OpenStax (Rice University), 2022); [Membranes | SEER Training](https://training.seer.cancer.gov/anatomy/cells_tissues_membranes/membranes.html) (National Cancer Institute (SEER Training), 2026); [23.1 Overview of the Digestive System - Anatomy and Physiology 2e | OpenStax](https://openstax.org/books/anatomy-and-physiology-2e/pages/23-1-overview-of-the-digestive-system) (OpenStax (Rice University), 2022). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/histology/serous-membranes-pleura-and-peritoneum/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/histology/serous-membranes-pleura-and-peritoneum/