Which of these is NOT part of the dorsal cavity?

A. Microvilli: Microvilli are tiny, finger-like projections on the apical surface of some cells, especially in the small intestine. They increase the surface area of the plasma membrane, allowing the cell to absorb more nutrients efficiently.

B. Stereocilia: Stereocilia are long, non-motile projections found in certain specialized cells, such as in the epididymis, and are primarily involved in mechanosensation and absorption, but they are less widespread than microvilli.

C. Primary cilia: Primary cilia are single, non-motile organelles present on many cells that function mainly as sensory structures to detect environmental signals rather than increase nutrient absorption.

D. Flagella: Flagella are long, whip-like structures used for cell motility, such as in sperm cells. They do not contribute significantly to nutrient absorption.

A. Vitamin D: Vitamin D is fat-soluble and is absorbed along with dietary fats. It is stored in the liver and adipose tissue and plays a key role in calcium and phosphorus regulation.

B. Vitamin C: Vitamin C is water-soluble, not fat-soluble. It dissolves in water, is not stored extensively in the body, and must be obtained regularly through the diet. Its main functions include collagen synthesis and antioxidant protection.

C. Vitamin E: Vitamin E is a fat-soluble antioxidant that protects cell membranes from oxidative damage. It is stored in adipose tissue and the liver for long-term use.

D. Vitamin A: Vitamin A is fat-soluble and essential for vision, immune function, and epithelial tissue health. It is stored in the liver and released as needed.

E. Vitamin K: Vitamin K is fat-soluble and plays a critical role in blood clotting and bone metabolism. It is absorbed with dietary fats and stored in the liver.