Question

In man, intestinal haustra are
(A)Bulges of colon between plicae semilunares
(B)Bulges of colon between plicae circulares
(C)Bulges of colon between rectal columns
(D)Villi bearing innumerable microvilli

Answer 1

In man, intestinal haustra are small pouches that are present between the many folds which are present in the lower part of the duodenum and the jejunum. They are also known as valvulae conniventes.

Complete answer:
In man, intestinal haustra are the Bulges of the colon between plicae circulares. The plicae circulares are the numerous permanent crescentic folds of mucous membranes found in the small intestine. These are the large valvular flaps projecting into the lumen of the small intestine.

Additional Information: Structure of plicae circulares- The entire intestine has circular folds of the mucous membrane, also called the valves of Kerckring and plicae circulares. The bulk extends transversely around the cylinder of the small intestine for about one-half or two-thirds of its circumference, but some form complete circles, et al. have a spiral direction; the latter usually extend a bit more than once around the bowel, but occasionally two or 3 times. The larger folds are about 1 cm. thorough at their broadest part, but the greater numbers are smaller. The larger and smaller folds alternate with one another. Unlike the gastric folds within the stomach, they're permanent and aren't obliterated when the intestine is distended.
The spaces which are present between circular folds are smaller than that of the haustra of the colon and are opposite to haustra, circular folds reach around the whole circumference of the intestine. These differences help in distinguishing the small intestine from the colon on an abdominal x-ray.
So, the correct answer is ‘Bulges of colon between plicae circulares’.

Note: Many of us get confused between plicae circulares and plicae semilunares. The Plica Semilunaris, or is a small fold of tissue located in your inner eye and is also known as your third eyelid.