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Cellularity:
- Epithelial tissues are highly cellular, meaning they are composed mainly of closely packed cells with very little extracellular matrix.
- Connective tissues, on the other hand, have a lower cellularity, consisting of a greater amount of extracellular matrix which forms the structural framework of the tissue.
Functionality:
- Epithelial tissues primarily function in protection, absorption, secretion, and sensation. Their location and structure allow them to form barriers and lining for organs and surfaces within the body.
- Connective tissues provide support, binding other tissues together, and play roles in transportation (e.g., blood), immune response (e.g., lymph), and storage (e.g., adipose tissue).

Plexuses that Form the Enteric Nervous System:
1. Myenteric Plexus (Auerbach's Plexus):
- Located between the circular and longitudinal muscle layers of the gastrointestinal tract. It primarily controls gastrointestinal motility and coordination of muscle contractions.
1. Submucosal Plexus (Meissner's Plexus):
- Found in the submucosal layer of the gastrointestinal tract. Its main role is to regulate enzyme secretion, blood flow, and nutrient absorption in the gut.

Three Major Modes of Secretion:
1. Merocrine Secretion:
- Involves the exocytosis of secretion products; the gland cells remain intact. This mode does not involve any loss of cellular material.
- Example: Salivary glands release enzymes via merocrine secretion.
1. Apocrine Secretion:
- Involves the release of a portion of the cell's cytoplasm along with the secretion. The apical part of the cell pinches off to release its contents into the duct.
- Example: Mammary glands secrete milk through the apocrine process.
1. Holocrine Secretion:
- Involves the entire cell disintegrating to release its secretion, resulting in the loss of the cell. This type of secretion typically involves cells that are shed and replaced continuously.
- Example: Sebaceous glands secrete sebum in this manner.