Histology4: Apical & Lateral Surface Features

Summary

This educational video script delves into the characteristics of epithelial tissues, focusing on the differentiation between cilia and microvilli, their functions, and how to identify them in histology slides. It also introduces goblet cells and their role in mucus production, as well as the importance of lateral cell junctions like tight junctions, desmosomes, and gap junctions in maintaining tissue integrity and function. The script aims to enhance understanding and recognition of these structures for effective study.

Takeaways

• 🔬 Epithelial tissues can be identified by features on the apical and lateral surfaces of their cells.
• 🌟 The difference between cilia and microvilli is crucial for tissue identification; cilia have a wiggling motion for moving substances along the cell surface, while microvilli increase surface area for enhanced transport.
• 👀 Simple columnar epithelium can be either non-ciliated or ciliated, with ciliated types having cilia for movement and non-ciliated types having microvilli for increased surface area.
• 🔍 On histology slides, microvilli appear uniform and highlighted, resembling a pink edge, while cilia look messy and resemble bed head, indicating protein projections.
• 📚 Students are typically taught to recognize only two ciliated tissues: simple columnar and pseudostratified columnar epithelium.
• 🧪 Goblet cells are unique to epithelial tissues, with a clear top part that produces mucin, which, when mixed with water, forms mucus for lubrication or breakdown of substances.
• 📡 Goblet cells are commonly found in simple columnar epithelium without cilia, particularly in the small intestine, and in ciliated pseudostratified columnar epithelium in the respiratory tract.
• 💧 Lateral surface features of epithelial tissues include tight junctions, desmosomes, and gap junctions, which serve different functions such as impermeability, strength, and communication between cells.
• 🛡️ Tight junctions act as a waterproof barrier, preventing substances from passing between cells, which is important in areas like the stomach lumen.
• 🔗 Desmosomes provide strength and resistance to stretching, found in areas that require structural integrity like the skin and cardiac muscle.
• 🔄 Gap junctions facilitate instant communication between cells, allowing for coordinated actions such as wave-like contractions in the heart.

Q & A

What are the two main features of the apical surface of epithelial cells discussed in the video?

The two main features are cilia and microvilli. Cilia are protein projections with mitochondria at their base that can move substances along the cell surface, while microvilli are folded cell membranes that increase the surface area for transport in and out of the cell.

How do cilia function in epithelial tissues?

Cilia function by moving substances along the surface of the cell. They can wave in a coordinated direction to transport materials effectively.

What is the primary purpose of microvilli on the apical surface of epithelial cells?

The primary purpose of microvilli is to increase the surface area at the apical surface, which enhances the transport of substances in and out of the cell.

How can one differentiate between cilia and microvilli in a histology slide?

In a histology slide, microvilli often appear as a uniform, highlighted edge of the apical surface, resembling a pink highlighter. Cilia, on the other hand, appear more messy and resemble protein projections, often described as 'bed head'.

What is the difference between simple columnar epithelium and ciliated simple columnar epithelium?

The difference lies in the presence of cilia. Simple columnar epithelium lacks cilia, while ciliated simple columnar epithelium has cilia on the apical surface.

What are the two types of ciliated tissues that are typically learned?

The two types are ciliated simple columnar epithelium and ciliated pseudostratified columnar epithelium.

How can one distinguish between pseudostratified and simple columnar epithelium?

Pseudostratified columnar epithelium appears to have a layered structure due to the nuclei of the cells being positioned at different heights, creating a false impression of stratification, whereas simple columnar epithelium has a uniform arrangement of cells with nuclei at the same level.

What is the function of goblet cells in epithelial tissues?

Goblet cells produce mucus, which is a mixture of mucin and water. This mucus is secreted onto the tissue surface for lubrication or to aid in the breakdown of substances.

What are the lateral surface features of epithelial tissues?

The lateral surface features include tight junctions, desmosomes, and gap junctions. These junctions serve different functions such as impermeability, strength, and communication between cells.

What is the role of tight junctions in epithelial tissues?

Tight junctions act like a waterproof zipper, preventing substances from passing between cells and ensuring that transport occurs through the cells themselves, thus controlling the passage of substances.

How do desmosomes contribute to the integrity of epithelial tissues?

Desmosomes provide strength by acting like spot welds between cells, allowing them to resist stretching and twisting, which is crucial in tissues like the skin and cardiac muscle.

What is the primary function of gap junctions in epithelial tissues?

Gap junctions facilitate instantaneous communication between cells, allowing for coordinated behaviors such as wave-like contractions in the heart, through connected channel proteins.