Which structure does not serve to increase surface area in the small intestine?

Lymph nodes

The small intestine has several structural adaptations that serve to increase its surface area for efficient absorption of nutrients. These include:

* Villi: Small, finger-like projections that line the inner surface of the small intestine.

* Microvilli: Microscopic, hair-like structures that cover the surface of the villi.

* Crypts of Lieberkühn: Tube-like structures that are located between the villi and contain stem cells that produce new cells to replace those that are shed.

* Circular folds: Folds in the inner lining of the small intestine that help to slow down the passage of food and increase the contact time with the absorptive surface.

Lymph nodes are not directly involved in increasing the surface area of the small intestine. They are part of the lymphatic system and play a role in immune surveillance and the removal of waste products from the body.