Histology and Embryology: The Week You Became Three Layers
How the body's tissues are built and renewed, and how a single fertilized cell folds itself into a person, from germ layers to the placenta.
Try 3 questions
1. Epithelial tissue has no blood vessels of its own. How do its cells get nutrients?
- By absorbing them straight from the air
- By diffusion from the tissue beneath
- From internal glucose stores alone
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Answer: By diffusion from the tissue beneath
Epithelia sit on a basement membrane over vascular connective tissue, and nutrients and oxygen diffuse up from those capillaries.
2. The outermost layer of your skin consists mostly of what?
- A thin film of oil and sweat
- Living cells dividing rapidly
- Dead, flat cells full of keratin
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Answer: Dead, flat cells full of keratin
Skin cells are born in the deepest layer and move up over a few weeks, filling with keratin and dying to form a tough, waterproof surface that constantly flakes off.
3. Why do long-term smokers often develop a morning cough?
- Nicotine makes the lungs secrete acid
- Smoke dries out the throat overnight
- Smoke damages cilia that sweep mucus up
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Answer: Smoke damages cilia that sweep mucus up
Airways are lined by ciliated epithelium that moves mucus upward; when smoke paralyzes or destroys cilia, mucus pools and must be coughed out, especially after lying down.
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