Cuboidal epithelium tissue is the tissue present in the lining of kidney tubules and ducts of salivary glands.

- The kidney tubules and ducts of salivary glands are responsible for the secretion and reabsorption of substances. Therefore, they require a specific type of tissue that can perform these functions efficiently.
- Cuboidal epithelium tissue is made up of specialized cells called cuboidal cells. These cells are cube-shaped and have a central nucleus. They are tightly packed together, forming a single layer.
- The shape and arrangement of the cuboidal cells provide several advantages for their function in the kidney tubules and salivary gland ducts. Let's discuss these advantages in detail:

1. Absorption and Secretion:
- The cuboidal cells have microvilli on their apical surface, which increases the surface area available for absorption and secretion.
- The cells also have a high number of mitochondria, which provide energy for active transport processes involved in absorption and secretion.

2. Selective Permeability:
- The cuboidal epithelium tissue regulates the movement of substances across the lining of kidney tubules and salivary gland ducts.
- The cells have specialized transport proteins and ion channels that allow specific substances to pass through while preventing the passage of others.

3. Protection:
- The cuboidal cells provide a protective barrier against harmful substances and pathogens.
- They form a tight seal between adjacent cells, preventing the leakage of substances and maintaining the integrity of the tubules and ducts.

4. Secretion of Mucus:
- Some cuboidal cells in the salivary gland ducts secrete mucus, which lubricates and protects the ducts.

5. Reabsorption of Water and Solutes:
- In the kidney tubules, the cuboidal cells are involved in the reabsorption of water and solutes from the filtrate back into the bloodstream.
- These cells have specialized transporters that actively reabsorb essential substances while allowing waste products to be excreted.

In conclusion, the presence of cuboidal epithelium tissue in the lining of kidney tubules and ducts of salivary glands is essential for their proper functioning. This tissue's unique characteristics, such as its shape, arrangement, and specialized features, allow it to perform absorption, secretion, selective permeability, protection, and reabsorption functions efficiently.

Mention kn ncert 11 bio ch 7 page no 101 .