The human body contains various cavities that house and protect internal organs. One such space is lined by the peritoneum, a smooth, transparent serous membrane. This membrane forms a continuous lining, covering certain organs and the inner walls of a specific body cavity. It plays a role in the health and function of the organs it encloses.
The Peritoneum’s Location
The peritoneum is located within the abdominopelvic cavity. This expansive cavity extends from the diaphragm, which separates it from the chest cavity, down to the upper pelvic cavity. It is bordered by the anterior abdominal muscles, vertebrae, pelvic floor, and the diaphragm. The peritoneum lines the walls of this cavity and covers most of the organs within it.
Understanding the Peritoneal Layers
The peritoneum consists of two continuous layers. The outer layer, called the parietal peritoneum, adheres to the internal surface of the abdominopelvic cavity walls. The inner layer, known as the visceral peritoneum, wraps around and covers the internal organs. Between these two layers lies the peritoneal cavity, which normally contains a small amount of slippery serous fluid (typically 50 to 100 milliliters). This fluid, secreted by mesothelial cells, allows the parietal and visceral layers to glide smoothly against each other.
Crucial Roles of the Peritoneum
The peritoneum performs several functions that support the health and proper functioning of abdominal organs. One primary role is lubrication, facilitated by the serous fluid within the peritoneal cavity. This fluid reduces friction between organs as they move during digestion and other bodily processes, enabling their smooth sliding. The peritoneum also provides support by helping to hold abdominal organs in their proper positions. It forms various folds and ligaments that connect organs to each other and to the abdominal wall, providing structural stability. The peritoneum offers a degree of protection by acting as a barrier against the spread of infection within the abdominal cavity and can help localize inflammation. It also has capabilities for absorption and secretion. Its cells can absorb fluids and certain substances, such as medications, into the bloodstream, and it plays a role in fluid exchange.
Organs and Their Peritoneal Relationships
Organs relate to the peritoneum in different ways, classifying them as either intraperitoneal or retroperitoneal.
Intraperitoneal organs are almost completely enveloped by the visceral peritoneum and suspended within the peritoneal cavity. These organs are more mobile due to their peritoneal covering. Examples include:
Stomach
Liver
Spleen
Jejunum
Ileum
Parts of the large intestine (transverse and sigmoid colon)
Retroperitoneal organs are situated behind the parietal peritoneum, covered only on their anterior surface, and are more fixed in position. Common retroperitoneal organs include:
Kidneys
Adrenal glands
Pancreas (except its tail)
Most of the duodenum
Ascending and descending colon
Aorta
Inferior vena cava
Ureters
Specialized peritoneal folds, such as mesenteries and omenta, connect organs to the abdominal wall and each other, providing pathways for blood vessels, nerves, and lymphatic vessels.