Morphological Differentiations of the Apical Pole

Flashcards covering the morphological differentiations of the apical pole, including microvilli and ciliary vibratiles, their structure, function, and molecular components.

What are microvilli and where are they observed?

Microvilli are cylindrical cytoplasmic expansions observed in absorptive epithelia, such as the duodenum and renal convoluted tubule.

What is the primary purpose of microvilli?

To expand the plasma membrane surface area for enhanced absorption, like nutrient absorption in the small intestine.

Name some key proteins found in the actin cytoskeleton of microvilli.

Villin, spectrin, fimbrin, α-actinin, fascin, myosin I, and myosin II.

What are ciliary vibratiles and what is their primary function?

They are mobile structures that allow the movement of certain particles or fluids.

Provide an example of ciliary vibratile function in the human body.

In the bronchial epithelium, synchronous movement of ciliary vibratiles transports inhaled dust towards the throat for swallowing.

What is the typical length of ciliary vibratiles?

5-10 micrometers.

What is the structural organization of ciliary vibratiles concerning microtubules?

They consist of a central pair of microtubules surrounded by doublets of microtubules.

What protein is crucial for the movement of ciliary vibratiles, and how does it act?

Dynein, which generates the force causing displacement between microtubule doublets.

What links the microtubule doublets in cilia and helps maintain their structure?

Nexin links the doublets, and radial spokes attach to the central sheath.

How do dynein molecules facilitate ciliary movement?

Dynein molecules induce a force that causes tubule B to displace relative to tubule A, leading to the inclination of the microtubules and thus the entire cilium.

What are microtubules composed of, and what is their approximate diameter?

Microtubules are polymers of tubulin units, arranged into 13 protofilaments, with an approximate diameter of 24 nm.