A student looks at sections of four organs under the microscope: the skin, the stomach, the pharynx…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A student looks at sections of four organs under the microscope: the skin, the stomach, the pharynx and a tubule of the kidney.
- Which two are lined or covered by compound epithelium?
- Which one has a lining of simple columnar epithelium?
- Which one has a simple cuboidal lining?
- Why does the skin need more layers than an air sac?
Need a reminder? The key ideaShow
Epithelial tissue forms sheets that cover the body and line its cavities and tubes. It has little matrix and no blood vessels, and it rests on a basement membrane. Simple epithelium has one layer, and compound epithelium has more. The cells are squamous (flat), cuboidal (cube shaped) or columnar (tall). Simple squamous epithelium lines blood vessels and air sacs and forms a thin boundary for diffusion. Cuboidal epithelium lines gland ducts and kidney tubules and helps in secretion and absorption. Columnar epithelium lines the stomach and intestine. Ciliated epithelium moves mucus or particles. Compound epithelium protects, as in the skin. The rate of diffusion across a layer is inversely proportional to its thickness.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) The skin and the pharynx. Both are exposed to wear and have many layers. The inside of the mouth is another example.
Step 2. (b) The stomach. Its tall cells secrete and absorb.
Step 3. (c) The kidney tubule, which has cuboidal cells for secretion and absorption.
Step 4. (d) The skin protects against wear, germs and loss of water, so layers help. The air sac must let gases through quickly, and a thin layer does this. A thick layer would slow the diffusion.
Answer: (a) skin and pharynx; (b) stomach; (c) kidney tubule; (d) protection needs layers, and diffusion needs thinness.
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