Which tissue lines kidney tubules and many glands, and is specialized for absorption and secretion?

Which tissue lines kidney tubules and many glands, and is specialized for absorption and secretion?

• A. Simple cuboidal epithelium
• B. Simple squamous epithelium
• C. Pseudostratified epithelium
• D. Transitional epithelium

Answer: (A)

Absorption and secretion are best carried out by a single, continuous layer of cells with enough cytoplasm to host the machinery needed for both processes. Simple cuboidal epithelium fits this role: a single layer of roughly cube-shaped cells, each with a central nucleus, provides a compact yet active surface. In kidney tubules, this arrangement supports reabsorption of water, ions, and nutrients, and the proximal tubule even has a brush border of microvilli to greatly increase surface area for uptake. Glands use the same tissue type to produce and release secretions into ducts or surrounding fluids. Other epithelial forms serve different purposes: simple squamous is thin and specialized for diffusion, not bulk absorption; pseudostratified is often ciliated and geared toward protection and mucus movement; transitional epithelium lines organs that stretch, like the bladder, rather than functioning primarily in absorption and secretion.

Absorption and secretion are best carried out by a single, continuous layer of cells with enough cytoplasm to host the machinery needed for both processes. Simple cuboidal epithelium fits this role: a single layer of roughly cube-shaped cells, each with a central nucleus, provides a compact yet active surface. In kidney tubules, this arrangement supports reabsorption of water, ions, and nutrients, and the proximal tubule even has a brush border of microvilli to greatly increase surface area for uptake. Glands use the same tissue type to produce and release secretions into ducts or surrounding fluids. Other epithelial forms serve different purposes: simple squamous is thin and specialized for diffusion, not bulk absorption; pseudostratified is often ciliated and geared toward protection and mucus movement; transitional epithelium lines organs that stretch, like the bladder, rather than functioning primarily in absorption and secretion.