Biological Systems MCAT Practice Exam

What type of tissue lines the surface of all organs?

1. Connective tissue

2. Epithelial tissue

3. Nervous tissue

4. Muscle tissue

The correct answer is: Epithelial tissue

Epithelial tissue is the correct choice because it serves as the protective layer that lines the surfaces of all organs and body cavities. This type of tissue functions as a barrier, protecting underlying structures from injury, pathogens, and dehydration, as well as playing critical roles in absorption, secretion, and sensation. Epithelial tissue exhibits distinct characteristics such as polarity, meaning it has an apical surface that faces the lumen or external environment, and a basal surface that attaches to the underlying connective tissue. Additionally, epithelial tissue is avascular (lacking blood vessels) and receives nutrients through diffusion from the underlying connective tissues. This specialization allows it to maintain its integrity and perform various functions efficiently, ranging from the selective absorption in the intestines to the secretion of hormones by glandular epithelium. Other tissue types have different primary roles: connective tissue supports and binds other tissues; nervous tissue processes and transmits signals; and muscle tissue facilitates movement. Therefore, epithelial tissue's unique properties and functions distinctly qualify it as the type of tissue that lines the surfaces of all organs.