Chapter 38, Problem 1TYK

Which tissue type consisting of sheetlike layers of cells can both exchange oxygen and act as a barrier to bacteria?

a. nervous

b. epithelial

c. connective

d. muscle

e. heart

Summary Introduction

Introduction:

All the distinct cells of our body can be broadly classified into four different tissue groups. These four groups are epithelial, connective, muscle and nervous tissues. These groups differ in their structure and thus the functions that they perform. Epithelial tissue is involved in transport, protection, secretion and absorption. Connective tissue provides structural support, muscle tissues aids in movement whereas nervous tissues are responsible for communication, coordination and control.

Answer to Problem 1TYK

Correct answer:

Epithelial tissue consists of sheet-like layers of cells that exchange oxygen and act as a barrier to bacteria.

Explanation of Solution

Explanation/justification for the correct answer:

Option (b) is epithelial. Epithelial tissue also known as epithelium. It consists of sheet-like layers of cells that line the outer surface of organs and vessels in the body. These tissues depending upon their different subtypes perform distinct functions like protection, secretion, transport and absorption. However, the epithelium that forms the outer layer of a fish’s gill, apart from acting as a barrier to pathogens, also aids in exchange of oxygen, carbon dioxide and ions with the aqueous environment. Hence, option (b) is correct.

Explanation for the incorrect answers:

Option (a) is nervous. The nervous tissue is not the correct answer as these tissues are involved in communication and control between the body parts. So, it is an incorrect option.

Option (c) is connective. These tissues provide structural support, strength and elasticity to the various body parts. So, it is an incorrect option.

Option (d) is muscle. The muscle tissue is composed of cells that can be contracted and thus helps in the movement of the body parts or the entire body. So, it is an incorrect option.

Option (e) is heart. The heart is not a tissue. Instead, it is an organ that is composed primarily of cardiac muscles (a form of muscle tissues), whose function is to pump blood within the circulatory system. So, it is an incorrect option.

Hence, options (a), (c), (d) and (e) are incorrect.

Conclusion

Hence, it can be concluded that the epithelial tissue acts as a barrier to pathogens. Moreover, in organisms like fish, the outer layer is composed of epithelial tissues, which functions in exchanging gases like oxygen and carbon dioxide and ions with the aqueous environment.