Epithelial Cell Polarity – Histology | Lecturio

Summary

This video provides an insightful overview of epithelial cell characteristics, focusing on their polarity and specialized structures. It highlights the role of microvilli, stereocilia, and cilia in enhancing absorption and facilitating movement across epithelial surfaces. Microvilli, found in the intestine and kidneys, increase surface area for absorption, while stereocilia, located in the male reproductive system and inner ear, are longer and branched. Cilia, equipped with a unique microtubule arrangement, help move substances along the respiratory tract. This foundational knowledge is essential for medical students preparing for exams.

Takeaways

• 😀 Epithelial cells exhibit polarity, having apical, lateral, and basal domains.
• 😀 Microvilli are specialized structures on epithelial surfaces that increase absorption efficiency.
• 😀 Microvilli are also referred to as brush borders in kidney tubes and striated borders in intestinal epithelial cells.
• 😀 Stereocilia, which are longer than microvilli, are found in the male reproductive system and ear hair cells.
• 😀 Cilia are hair-like structures that help move substances along the epithelial surface, particularly in the respiratory tract.
• 😀 The structure of microvilli includes a core of actin filaments connected to the plasma membrane.
• 😀 The actin filaments in microvilli can contract to increase surface area for absorption.
• 😀 Stereocilia are anchored using different proteins and also function to absorb fluids.
• 😀 Cilia are composed of axonemes with a unique arrangement of microtubules, allowing them to be motile.
• 😀 The coordinated beating of cilia helps in the movement of foreign bodies, secretory products, or cells along the epithelial surface.

Q & A

What are the three main characteristics of epithelial cells?

Epithelial cells have an apex, lateral borders, and a basal surface, which together establish their polarity.

What does it mean for epithelial cells to exhibit polarity?

Polarity refers to the distinct structural and functional differences between the apical surface, lateral domains, and basal surface of epithelial cells.

What are microvilli, and where are they commonly found?

Microvilli are fine projections on the apical surface of epithelial cells, commonly found in columnar epithelium in structures like the kidney and intestinal tract.

What is the function of microvilli?

Microvilli increase the surface area of epithelial cells, enhancing their ability to absorb nutrients and fluids.

What structural components make up microvilli?

Microvilli consist of a core of actin filaments, which are anchored to the cell membrane by proteins such as villin and myosin.

How do stereocilia differ from microvilli?

Stereocilia are longer and branched compared to microvilli, and they are found in areas like the male reproductive system and inner ear.

What is the primary role of stereocilia?

Stereocilia assist in the absorption of fluids, similar to microvilli but with a different structural composition.

What are cilia, and what function do they serve?

Cilia are long, hair-like structures that help move substances along the epithelial surface, particularly in the respiratory tract.

What is the structural arrangement of cilia?

Cilia consist of an axoneme, which is composed of nine pairs of microtubules arranged in a '9 + 2' pattern, allowing for coordinated motility.

How do cilia contribute to the movement of substances?

Cilia beat in unison to move foreign bodies, secretory products, or cells along the epithelial surface, aiding in clearance and transport.