Histology of Glands

What is a gland?

An organ consisting of specialized secretory cells, usually producing a liquid secretion.

What is the embryological origin of glands?

Epithelial tissue.

How can glands be classified based on the number of cells?

Unicellular or multicellular.

What is a unicellular gland?

A single secretory cell distributed among non-secretory cells.

How are multicellular glands formed?

By invagination of an epithelial layer into deeper tissue.

In a multicellular exocrine gland, what does the proximal part of the invagination form?

The duct.

What does the distal part form?

The secretory element.

What is an exocrine gland?

A gland that releases its secretion onto an epithelial surface, directly or through ducts.

What is an endocrine gland?

A ductless gland that releases its secretion directly into the blood.

What are the three bases for classification of exocrine glands in the PDF?

Shape/branching of duct, mode of secretion, and nature of secretion.

What is the difference between a simple and compound gland?

→ Simple: unbranched duct.
→ Compound: branched duct.

What are the types of simple glands listed in the PDF?

Simple tubular, simple coiled tubular, simple branched tubular, and simple branched alveolar.

What are the types of compound glands listed?

Compound tubular, compound alveolar, and compound tubulo-alveolar.

What are the three modes of exocrine secretion?

Merocrine, apocrine, and holocrine.

What is merocrine secretion?

Secretion is released by exocytosis of secretory granules, with the cell remaining intact.

Give examples of merocrine glands.

Pancreas, parotid gland, and the protein component of milk from the mammary gland.

What is apocrine secretion?

The apical portion of the cell is pinched off along with the secretory product.

Give an example of apocrine secretion.

The lipid component of milk from the mammary gland.

What is holocrine secretion?

The entire cell is shed along with its secretory product.

Give an example of a holocrine gland.

Sebaceous gland.

What are the three types of glands based on the nature of their secretion?

Serous, mucous, and mixed glands.

What characterizes a serous gland?

Thin, watery, enzyme/protein-rich secretion; granular, dark-staining cytoplasm rich in rER; rounded basally placed nuclei.

What characterizes a mucous gland?

Mucopolysaccharide-rich secretion; lightly staining cytoplasm with an empty appearance; basally placed, flattened nuclei.

What is a mixed gland?

A gland containing both serous and mucous secretory units.

What is a serous demilune?

A crescent-shaped cap of serous cells around a mucous acinus.

What are the three major salivary glands?

Parotid, submandibular, and sublingual glands.

What type of glands are the major salivary glands?

Compound alveolar or compound tubuloalveolar glands.

Name four locations containing minor salivary glands.

Lips (labial), cheeks (buccal), soft palate (palatine), and tongue (lingual).

What are major components of saliva listed in the PDF?

Water, mucus, proteins, salts, salivary amylase (ptyalin), IgA, and lactoperoxidase.

What are the major functions of saliva?

Moistens food, lubricates/moistens the oral mucosa and lips, and initiates carbohydrate digestion.