The correct option is (c) 1 and 3 only.
Explanation
Glandular epithelium consists of specialized epithelial cells capable of synthesizing and secreting substances such as enzymes, hormones, mucus, and sweat. These cells can exist individually or form complex multicellular structures.
Statement-wise Analysis:
- Statement 1 is Correct: Multicellular glandular epithelium is typically formed during development when a portion of the epithelial tissue folds inward (invaginates) into the underlying connective tissue. This invagination creates a multicellular gland.
- Statement 2 is Incorrect: Glandular epithelium does not always constitute a unicellular gland. It is classified into two types based on the number of cells:
- Unicellular: Consisting of isolated glandular cells (e.g., goblet cells of the alimentary canal).
- Multicellular: Consisting of clusters of cells (e.g., salivary glands).
- Statement 3 is Correct: The primary function of glandular epithelium is secretion. These cells are specialized to produce and release substances at the epithelial surface (exocrine) or directly into the fluid bathing the gland (endocrine).
Key Takeaway:
Glandular epithelium is specialized for secretion and can be either unicellular (goblet cells) or multicellular (salivary glands). Multicellular glands arise from the invagination of epithelial tissue.