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Mesentery: Medical Definition & Function

Instructor: Lori Haag

Lori has teaching experience in the health care setting. She has an associate's degree in Nursing and a bachelor's degree in Psychology.

In this lesson, you will learn about the mesentery, its functions, its characteristics, and its classifications. You will also become familiar with the difference between true mesenteries and specialized mesenteries.

Suspended by Silk

Addy needed a break from her anatomy homework. She thought she might go blind if she had to look at another diagram of the human digestive system. She already knew all the organs by heart, including their functions. What she didn't quite understand is how they all stayed in place. She needed to take a walk outside to clear her head.

As Addy walked along the wooded path, she looked closely at the black spider hanging in the middle of the thin web. The wind was blowing it all over the place, but the web remained suspended. The unique matrix stretched in all different directions to where it tethered securely onto surrounding structures. Addy traced each silk thread to where it was anchored, and marveled at the complexity and strength of this seemingly flimsy architecture. How was this possible?

The Mesentery

In order to understand the mesentery, it is necessary to be familiar with the peritoneum. The peritoneum has two parts. The parietal peritoneum lines the outer walls of the abdominal cavity, and the visceral peritoneum lines the abdominal organs. The peritoneum is a serous membrane that is highly vascular.

The mesentery is a continuation of the peritoneum that is made of connective tissue. It secretes serous fluid, providing lubrication and decreasing the friction between abdominal organs. The connective tissue of the mesentery contains lymph vessels, nerves, arteries, and veins creating a communication pathway between the abdominal wall and internal organs. It is also responsible for holding the abdominal organs in place.

The mesentery is made of connective tissue
The mesentery

True Mesenteries

There are two classifications of mesenteries: true mesenteries and specialized mesenteries. While the latter do not connect to the posterior wall, true mesenteries connect organs to the posterior wall of the peritoneum.

The true mesenteries include:

  • the small bowel mesentery
  • the transverse mesocolon
  • the sigmoid mesentery, also referred to as the mesosigmoid

The Small Bowel Mesentery

The small bowel mesentery is a wide fan-shaped mesentery that attaches the jejunum and the ileum to the posterior wall of the abdomen. It runs obliquely from the duodenojejunal junction (the point where the end of the duodenum meets with the beginning of the jejunum) to the ileum where it attaches at the ileocecal junction (the end of the ileum and beginning of the cecum).

The Transverse Mesocolon

The transverse mesocolon connects the transverse colon of the large intestine to the posterior abdominal wall. It encloses the transverse colon, and it divides the abdominal cavity into two compartments. The superior compartment contains the stomach, liver, and spleen. The inferior compartment harbors the small intestines, and the descending and ascending colon of the large intestines.

The Sigmoid Mesentery

The sigmoid mesocolon can also be referred to as the mesosigmoid. It is an inverted v-shape and attaches the sigmoid colon to the abdominal wall.

The mesentery holds abdominal organs in place
Abdominal Cavity

Specialized Mesenteries

Specialized mesenteries are also extensions of the peritoneum, but they do not attach to the posterior wall of the abdomen. They too are made of connective tissue and connect organs to each other. The specialized mesenteries include the greater omentum, the lesser omentum, and the mesoappendix.

The greater omentum connects the stomach to the colon. It is an apron-like structure that hangs from the curve of the stomach and is composed of mainly fatty tissue. This helps keep the intestines warm. The greater omentum is filled with macrophages (cells produced by the immune system to destroy invaders), which aid in the fight against abdominal infections.

The lesser omentum is a double-layered extension of the peritoneum that connects the stomach to the liver. Some parts of the lesser omentum are extremely thin while other parts are fatty. The mesoappendix is the fold of peritoneal tissue around the appendix. It connects the appendix to the ileum.

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