Structural Classification of exocrine glands and their examples.

Exocrine glands can be classified into three main structural categories based on their shape and arrangement of secretory units:

1. Simple glands: These glands have a single unbranched duct that connects the secretory unit to the surface. Examples include:
- Sweat glands
- Sebaceous glands

2. Compound glands: These glands have a branched duct system that connects multiple secretory units to the surface. Examples include:
- Salivary glands
- Mammary glands

3. Tubular glands: These glands have a tubular shape, with secretory units that are long and narrow. Examples include:
- Intestinal glands
- Gastric glands

Overall, exocrine glands play a crucial role in the body by secreting substances such as enzymes, hormones, and sweat to help regulate various physiological processes.

Based on the shape and arrangement of the secretory portion:

1. Unicellular exocrine glands:
- Consists of a single cell that secretes substances directly into the lumen of an organ
- Example: Goblet cells in the digestive tract

2. Multicellular exocrine glands:
- Consists of clusters of secretory cells that are connected to a duct that carries the secretions away from the gland

Based on the branching of the duct system:

1. Simple glands:
- Have ducts that do not branch
- Example: Splenic glands in the immune system

2. Compound glands:
- Have ducts that branch into smaller and smaller ducts
- Example: Salivary glands

Based on the structure of the secretory portion:

1. Tubular glands:
- Have a duct that is lined with secretory cells, forming a tube-like structure
- Example: Intestinal glands

2. Acini (or alveolar) glands:
- Have a duct that opens into a sac-like structure (acinus) that is lined with secretory cells
- Example: Pancreatic glands

3. Tubuloacinar glands:
- Have a duct that branches into both tubular and acinar structures
- Example: Mammary glands

4. Holocrine glands:
- Secretory cells accumulate secretions within their cytoplasm and eventually rupture, releasing their contents into the duct
- Example: Sebaceous glands in the skin

5. Apocrine glands:
- Secretory cells release secretions by pinching off their apical portion into the duct
- Example: Sweat glands in the skin

6. Merocrine glands:
- Secretory cells release secretions by exocytosis into the duct without cellular damage
- Example: Most exocrine glands in the body, such as salivary glands and pancreatic glands