Chapter 4, Problem 1MC

Select the one false statement about mucous and serous membranes.

a. The epithelial type is the same in all serous membranes, but there are different epithelial types in different mucous membranes.

b. Serous membranes line closed body cavities, whereas mucous membranes line body cavities open to the outside.

c. Serous membranes always produce serous fluid, and mucous membranes always secrete mucus.

d. Both membranes contain an epithelium plus a layer of loose connective tissue.

Summary Introduction

Introduction:

The body surface is covered by several membranes and these membranes also line the body cavity. Body membranes often form lubricating protective sheets around the organs. Epithelial membranes and connective tissue membranes are the two major groups constituting the body membranes.

Answer to Problem 1MC

Correct answer:

The statement that the serous membrane always produces serous fluid and mucous membrane always secrete mucus is incorrect.

Justification for the correct answer:

Option (c) is given that the serous membranes and the mucous membrane always produce the serous fluid and mucous respectively. The mucosa of the digestive tract and respiratory tract are also capable of producing a large amount of lubricating mucus, which is protective in nature. On the other hand, the mucous membrane of the urinary tract cannot secrete mucous.

The serous membrane is composed of a simple squamous epithelial layer, which rests on the thin layer of areolar connective tissue. The serosa occurs in a pair of the parietal and visceral layer. Both of these serous membranes secrete a thin, clear fluid called the serous fluid. Hence, option (c) is correct.

Explanation of Solution

Explanation for incorrect answers:

Option (a) is given that all the serous membranes are made up of same type of epithelial, but different mucous membranes are made up of different epithelial types. The epithelial membrane mainly constitutes the cutaneous, mucous, and serous (serosa) membranes. The serosa is composed of a simple squamous layer existing on a loose connective tissue. However, the mucous lines the body cavities opened to the exterior environment. Therefore, it is composed of either simple columnar epithelial or stratified squamous existing on a loose connective tissue. So, it is an incorrect option.

Option (b) is given that the closed body cavities are lined by the serous membranes, whereas the mucous membranes majorly lines the body cavities, which open to the outside. The body cavities, which are close to the exterior environment, are lined by the serosa of the epithelial membrane. The serous layers are separated by the serous fluid secreted by those layers, not by air. So, it is an incorrect option.

Option (d) is given that both the membranes are made up of an epithelium as well as the layer of the loose connective tissue. The epithelial membrane of the serosa and the mucosa is made up of a simple squamous epithelium, which exists on the layer of a loose connective tissue. So, it is an incorrect option.

Hence, options (a), (b), and (d) are incorrect.

Conclusion

Thus, the serosa always produces serous fluid, but the mucosa does not always secrete mucus in the body.