Multiple Choice
Which of the following is true for microfilaments?
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2. Cell Chemistry & Cell Components
Introduction to the Cytoskeleton
1:58 minutesProblem 11
Textbook Question
Cells lining the trachea have whiplike motile extensions on their free surfaces. What are these extensions, what is their source, and what is their function?
Verified step by step guidance1
Identify the extensions: The whiplike motile extensions on the free surfaces of cells lining the trachea are called cilia. These are specialized cellular structures found in certain epithelial cells.
Understand their source: Cilia are formed from microtubules, which are part of the cytoskeleton. Specifically, they arise from basal bodies located just beneath the cell membrane. Basal bodies are derived from centrioles and serve as the organizing centers for the microtubules that make up the cilia.
Describe their structure: Cilia are composed of microtubules arranged in a '9+2' pattern. This means there are nine pairs of microtubules forming a ring around two central microtubules. This arrangement is critical for their motility.
Explain their function: The primary function of cilia in the trachea is to move mucus and trapped particles (such as dust, bacteria, and other debris) upward toward the throat. This process is known as the mucociliary escalator and helps keep the respiratory tract clean and free of harmful substances.
Relate to physiology: The coordinated beating of cilia is powered by dynein, a motor protein that facilitates the sliding of microtubules against each other. This movement is essential for maintaining respiratory health and preventing infections by clearing foreign particles from the airway.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Cilia
Cilia are hair-like structures that extend from the surface of certain cells, including those lining the trachea. They are motile extensions that beat in a coordinated manner to move substances across the cell surface, such as mucus and trapped particles, helping to keep the airways clear.
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Epithelial Tissue
The trachea is lined with epithelial tissue, specifically pseudostratified ciliated columnar epithelium. This type of tissue is characterized by cells of varying heights, giving the appearance of multiple layers, and is crucial for respiratory function, providing protection and facilitating the movement of mucus.
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Mucociliary Escalator
The mucociliary escalator is a defense mechanism of the respiratory system, where cilia work in conjunction with mucus to trap and transport inhaled particles and pathogens out of the airways. This process is vital for maintaining respiratory health and preventing infections.
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