6.a: The Digestive System

10/10/2013 § Leave a comment

Hahahahaha 7 pages, no.

Judge me all you want, but no.


Page 214, the wall of the oesophagus

1. Draw a plan diagram to show the layers of tissue in the wall.

I can’t do that if I don’t know what a plan diagram even is.

2. The inner tissue consists of many layers of epithelium cells, whereas in the stomach and intestines there is only a single layer of epithelium cells. Suggest reasons for the difference.

If there is only one layer of epithelium cells, then food molecules and monosaccharides only have to diffuse through one layer during absorption. 

3. There are two layers of muscle fibres in the wall, labelled X and Y. One of them contains circular muscle fibres and the other contains longitudinal muscle fibres. Deduce from the appearance of the muscle fibres in the micrograph which layer is which.

X indicates the circular muscle fibres, Y indicates the longitudinal muscle fibres.

4. Food only remains in the oesophagus for a few seconds. There are small glands in the wall of the oesophagus, with ducts leading from the glands to the lumen of the oesophagus. Suggest a fluid that would be useful for the small glands to secrete, and its function.

Water… would be a useful fluid… because it would make it easier… for food to go down…?

5. There are small blood vessels in the wall of the oesophagus. Suggest two reasons for the oesophagus wall needing a supply of blood.

Honestly, I’m not sure, but maybe because a) blood contains enzymes and proteins needed to help the food make its way to the stomach, and also b) blood helps maintain the preferred temperature for the process of digestion (then absorption and assimilation…?). 

6. In the lower part of the oesophagus, the outer layer of muscle fibres is smooth muscle, but in the upper part of the oesophagus, nearest to the mouth, this outer layer is striated muscle. Suggest reasons for this difference. You may need to research this question.

Wouldn’t the striated muscle be in charge of our ability to swallow, then? Also – wouldn’t it then be a big part of our gag reflex?


Also, just for kicks.

Chapter 19, Digestion, Question 9


i. State the highest percentage of transgene that was recovered. –> 3.7%

ii. Calculate the percentage of transgene that was not recovered from this person. –> 96.3%


i. Explain what has happened to transgenes not recovered from food. The transgenes not recovered from food were digested into the small intestine. (by nucleases, as they are broken up into nucleotides)

ii. Predict what happens to the subunits of the transgenes. —> Since the subunits of transgenes are nucleotides, they could be used for DNA replication, necessary for all cells.

c. Suggest two reasons for the variation in results between the seven people. —> The speed of movement of food going through the oesophagus as well as the amount of DNA the digesting enzymes have secreted.

d. Explain why an indigestible marker was used in the experiment. —> If the marker was digestible, it wouldn’t be able to provide information. This way, DNA and nucleotide concentration can be tracked, as well as the rate of digestion.

e. Evaluate the reasons of this experiment in terms of the safety of eating genetically modified food. —> If genetically modified food is digested in the gut, they wouldn’t cause harm to the human body. But this was only between 7 individuals so the evidence we have at our hands isn’t totally reliable.

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