MCAT Biology : Epithelial Tissue and Integumentary System

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

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Example Question #11 : Epithelial Tissue And Integumentary System

Which term refers to the top layers of cells in the epidermis?

Possible Answers:

Subcutaneous layer

Dermis

Stratum corneum

Sebaceous layer

Stratum germinativum

Correct answer:

Stratum corneum

Explanation:

The stratum corneum encompasses the very top two layers of cells in the epidermis. It consists almost entirely of dead, keratinzed skin cells that have been pushed to the outermost layer. The stratum corneum forms a protective, waterproof barrier against the outside environment.

Example Question #11 : Connective Tissue And Epithelium

The parietal cells of the stomach are vital for both food digestion and as a defense mechanism against pathogens. When the parietal cells are not functioning properly, diseases such sepsis due to Clostridium difficile and malnutrition may occur. To keep the digestive system healthy, proper nutrition as well as a balanced diet is vital.

The parietal cells of the stomach secrete hydrochloric acid via the hormone gastrin. Gastrin is released when the stomach distends, via the presence of proteins and/or indirectly by the vagus nerve from the parasympathetic nervous system. Hydrochloric acid breaks down certain ingested food as well as activates certain zymogens for further digestion of macromolecules. The high acidity of the stomach due to the release of hydrochloric acid by parietal cells also destroys most pathogens. When the parietal cell is not functioning properly, opportunistic pathogens may create health problems.

Parietal cells also secrete intrinsic factor, a glycoprotein which binds to vitamin B12 to prevent destruction of the vitamin by the hydrochloric acid. Down the gastrointestinal tract, the vitamin is absorbed by the ileum of the small intestine. Vitamin B12 is essential for red blood cell production. A diet low in vitamin B12 may lead to anemia.

The prolonged use of aspirin will significantly decrease the production of bicarbonate in the mucosal layer of the stomach. How might this lead to a gastric ulcer?

Possible Answers:

When the production of bicarbonate in the stomach is low, the body tries to maintain homeostasis by producing more hydrochloric acid by the parietal cell. Excess acid in the stomach will result in gastric ulcer.

The inability to neutralize the high acidity of the stomach leading to gastric ulcer.

Aspirin promotes the production of prostaglandin leading to excess secretion of hydrochloric acid by the parietal cell. Excess hydrochloric acid secretion lead to gastric ulcer.

Excess in ability to neutralize the high acidity of the stomach leading to gastric ulcer.

Aspirin inhibits prostaglandins leading to excess secretion of hydrochloric acid by the parietal cell. Excess hydrochloric acid secretion lead to gastric ulcer.

Correct answer:

The inability to neutralize the high acidity of the stomach leading to gastric ulcer.

Explanation:

The stomach produces bicarbonate along the mucosal layer to neutralize the high acidity of the stomach. Without proper neutralization of the acid along the mucosal layer, the acid can directly destroy the barrier. When the acid destroys the mucosal layer, gastric ulcers may occur.  

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