What is a mesentery? For each of the mesenteries listed below found indicate whether it is derived from the dorsal mesentery (D) or ventral mesentery (V) developmentally. (5pts) A. Greater Omentum B. Lesser Omentum C. Falciform ligament D. Transverse mesocolon E. The mesentery F. Sigmoid mesocolon 4
The Correct Answer and Explanation is:
A mesentery is a double layer of peritoneum (the membrane lining the abdominal cavity) that connects the intestines to the posterior wall of the abdomen. It serves several important functions, including supporting the blood vessels, nerves, and lymphatic vessels that supply the intestines, and it also helps in the movement and stability of the organs. Mesenteries are essential structures in fetal development and postnatal life, ensuring that abdominal organs are properly positioned and nourished.
Now, let’s look at the specific mesenteries and whether they are derived from the dorsal or ventral mesentery during development:
A. Greater Omentum
- Derived from: Dorsal Mesentery (D)
- Explanation: The greater omentum is a large, fatty apron that hangs down from the stomach and covers the intestines. It is derived from the dorsal mesentery, specifically from the part of the mesogastrium that attaches to the stomach and later drapes down and over the intestines.
B. Lesser Omentum
- Derived from: Ventral Mesentery (V)
- Explanation: The lesser omentum is a small fold of tissue connecting the lesser curvature of the stomach and the first part of the duodenum to the liver. It is derived from the ventral mesentery, which originates from the foregut during embryonic development.
C. Falciform Ligament
- Derived from: Ventral Mesentery (V)
- Explanation: The falciform ligament is a flat, fibrous ligament that connects the anterior surface of the liver to the anterior abdominal wall and the diaphragm. It is also derived from the ventral mesentery, specifically from the portion that connects the liver to the abdominal wall.
D. Transverse Mesocolon
- Derived from: Dorsal Mesentery (D)
- Explanation: The transverse mesocolon attaches the transverse colon to the posterior abdominal wall. It is derived from the dorsal mesentery, specifically from the mesocolon, which provides support to the colon.
E. The Mesentery
- Derived from: Dorsal Mesentery (D)
- Explanation: The mesentery, which supports the small intestine (mainly the jejunum and ileum), is derived from the dorsal mesentery. This structure provides a stable connection between the intestines and the posterior abdominal wall.
F. Sigmoid Mesocolon
- Derived from: Dorsal Mesentery (D)
- Explanation: The sigmoid mesocolon attaches the sigmoid colon to the posterior abdominal wall. Like the transverse mesocolon, it is derived from the dorsal mesentery.
Summary of Developmental Origins:
- Ventral Mesentery (V): Lesser omentum, falciform ligament
- Dorsal Mesentery (D): Greater omentum, transverse mesocolon, mesentery, sigmoid mesocolon
