Lect_02_107_2025_epithelia_handout

What are the main functions of epithelial tissues?

Selective barriers, secretory functions, and providing protection.

What is the structure of epithelial tissues characterized by?

Cells arranged in continuous sheets as single or multiple layers, held together by various cell junctions.

What are the types of cell junctions found in epithelial tissue?

Tight junctions, adherens junctions, gap junctions, desmosomes, and hemidesmosomes.

What do tight junctions do?

They create an electrically tight barrier between cells, allowing selective permeability.

What role do adherens junctions play in epithelial tissue?

They prevent cell separation under tension and link cytoskeletal actin to cadherins.

What is the function of desmosomes?

They link the intermediate filaments of adjacent cells, providing structural integrity.

What are hemidesmosomes?

Structures that connect the basal surface of epithelial cells to the basement membrane.

What characterizes gap junctions?

Direct connections between cells that allow small molecules to pass through.

What is the basement membrane composed of?

Two layers: basal lamina (produced by epithelial cells) and reticular lamina (produced by connective tissue cells).

What are the two main types of epithelial tissue?

Covering and lining epithelium, and glandular epithelium.

What do exocrine glands secrete?

Substances onto external surfaces or into ducts.

What do endocrine glands secrete?

Hormones directly into the bloodstream.

What are the two arrangements of epithelial tissue?

Simple (single layer) and stratified (multiple layers).

Define pseudostratified epithelium.

It appears to have multiple layers due to varying cell heights but is actually a simple epithelium.

What is the primary function of simple squamous epithelium?

Facilitating diffusion and filtration.

How are simple cuboidal and columnar epithelia characterized?

Cuboidal epithelium is about as tall as wide, while columnar epithelium is taller than wide and often has specialized functions like secretion.

What are the characteristics of stratified squamous epithelium?

It has multiple layers for protection against abrasion.

What is the purpose of ciliated columnar epithelium?

To assist in moving materials, such as mucus.

What is notable about transitional epithelium?

It can change shape depending on the organ's status (e.g., bladder being full or empty).

What are goblet cells?

Modified columnar cells that secrete mucus.