A&P 101: Epithelial tissue in structure and function

Think of your body like a crowded lunchroom full of feisty, fidgety systems—it needs order to function. That’s where epithelial tissue comes in. In this lesson, you’ll explore the roles of epithelial tissue in protecting, organizing, and regulating your body’s boundaries—from your skin to your stomach lining. This video introduces how different cell shapes and layers serve different functions, and how this tissue also builds glands that manage secretions like sweat, mucus, and hormones. Understanding epithelial tissue is a first step toward understanding everything from wound healing to hormone release.

Watch the CrashCourse video “Epithelial Tissue Crash Course A&P #2” (~10 minutes). The video explains the role of epithelial tissue in lining and protecting the body, introduces cell shapes and layering, and connects these structures to their functions—including real clinical examples. After watching the video, answer the interactive questions that follow.

Sample answers:

Question 1: 

Strong answer:

Epithelial tissue plays a key role in lining, covering, and organizing the body’s internal and external spaces. It forms the outer layer of the skin and also lines internal surfaces like the stomach, lungs, blood vessels, and body cavities. One of its most important jobs is to create physical boundaries between different areas of the body, helping to keep organs and systems separated and properly arranged. In addition to providing protection, epithelial tissue also plays roles in absorption (like taking in nutrients in the intestines), secretion (such as producing sweat or mucus), and selective permeability (controlling what passes into and out of tissues). It also forms glandular tissue, which creates both endocrine and exocrine glands for releasing hormones and other substances. Without epithelial tissue, the body wouldn’t be able to maintain order or interact safely with the external environment.

Weak answer:

Epithelial tissue covers the body and keeps everything together. It helps protect you and makes sure things stay in place. It’s like a wall for your organs and is really important.

Question 2:

Strong answer:

Epithelial tissue is classified by both the shape of its cells (squamous, cuboidal, columnar) and the number of layers (simple, stratified, or pseudostratified), and these structural features directly relate to their function. For example, simple squamous epithelium is a single layer of thin, flat cells that makes it easy for substances like oxygen to pass through. That’s why it lines the alveoli in the lungs, where fast gas exchange is critical. Because the cells are so thin, they allow efficient diffusion, which wouldn’t be possible with thicker or multilayered cells.

Weak answer:

Squamous cells are flat and columnar cells are tall. It depends on where they are in the body. Some are layered and some are not. They have different shapes for different jobs.