How do epithelial cells differ from other cells?

Epithelial cells are a type of specialized cells that form the lining of various body surfaces and cavities, both internal and external. They differ from other cells in several distinct ways:

• Arrangement: Epithelial cells are closely packed together with tight junctions that hold the cells more tightly than other cells. This arrangement provides a tight protective barrier and helps withstand mechanical stress. 
• Avascular nature: Epithelial cell tissues do not house capillaries. 
• Specializations: Epithelial cells have specialized structures such as microvilli (small finger-like projections) and cilia (hair-like structures) that aid in absorption and movement of substances, respectively.
• Gliding surface area: Epithelial cells replace dead cells by sloughing off and gliding, enabling them to maintain a tightly closed barrier to the external environment. 
• Function: Epithelial cells have diverse functions, including protection, absorption, secretion, and sensory reception. For instance, they line the respiratory tract to protect underlying tissues from pathogens, and they line the intestines to absorb nutrients.
• Transitional nature: Multi-layered epithelia have the ability to stretch when necessary and return to their normal state afterwards. This property is beneficial in allowing organs such as the urinary bladder to distend or contract as necessary without compromising its structure or function.