Glandular & Compound Epithelium

Glandular Epithelium

• Glands are secretory structures formed by secretory epithelium.
• Some columnar or cuboidal epithelium gets specialized for secretion and is called glandular cells.

They are of 2 types.

1. Unicellular Glands: It consists of small isolated patches of secretory epithelium scattered in the inner lining. (E.g. Goblet cells in the intestinal mucosa.)
2. Muticellular glands: It consists of clusters of secretory cells (Salivary glands).

Based on the mode of releasing their secretions, glands are divided into two: Endocrine and Exocrine glands.

• Endocrine glands are ductless glands. Their secretions are released directly into blood or any other body fluids that bath the glands.
• Exocrine glands release their products through specific ducts.

Compound Epithelium

• Compound epithelium is composed of two or more layers of cells (multi–layered).
• It is mostly protective in function.                                               

 

• They are found on the dry skin surfaces, moist surface off buccal cavity, pharynx, inner lining of glandular ducts and pancreatic ducts.
• They protect the surfaces from mechanical and chemical stress.

 

Differences between Simple and Compound epithelium

Simple epithelium	Compound epithelium
Single layer of cells	Multi-layered (two or more layers)
All cells attached to the basal membrane	Only the bottom cells are attached to the basal membrane.
Function – secretion and absorption	Function – protection

Cell junctions

Adjacent cells in an epithelial tissue are held together by cell junctions. Three types of junctions are usually present.

1. Tight junctions: Prevents leaking of substances across two cells.
2. Adhering junctions: Cements adjacent cells to keep them together.
3. Gap junctions: Permits the communication of adjacent cells by connecting their cytoplasm. This allows movement of ions and some small molecules across the cells.