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PCAT Biological Processes – Muscle Types

Mono-nucleated muscle cells are a predominant muscle fiber found in all of the following EXCEPT:

  1. the stomach
  2. the pharynx
  3. the heart
  4. the lungs
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This question is testing your familiarity with the predominant muscle cell types found in various structures or organs within the body. To answer this question, you must know the characteristics of the three different muscle types: 1) skeletal, 2) cardiac, and 3) smooth. Skeletal muscle is striated, multi-nucleated, and under voluntary control and is typically attached to bones and cartilages. Cardiac muscle is involuntary, striated, and mono-nucleated and is found only in the heart. Smooth muscle is involuntary, mono-nucleated and non-striated is generally associated with viscera.

Since skeletal muscles contain only multi-nucleated cells, the correct answer to this question must be a structure that is under voluntary control. The stomach and the lungs are internal organs found in the thoracic and abdominal cavities. These visceral organs are involuntary and consist primarily of smooth muscle fibers eliminating choices A and D. The heart is also involuntary and contains mostly cardiac muscle eliminating answer choice C.

The pharynx is part of the digestive tract and is located above the esophagus. Both the pharynx and the upper third of the esophagus consist mostly of skeletal muscle, while the rest of the digestive system is controlled by smooth muscle. Since the pharynx contains primarily skeletal muscle, the cells are multi-nucleated. Thus the correct answer is B.

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