The lens is avascular but metabolically active. Which statement best explains nutrient delivery?

The lens is avascular but metabolically active. Which statement best explains nutrient delivery?

• A. It has direct capillary supply to the lens fibers
• B. It relies on aqueous humor for nutrient exchange and waste removal
• C. It receives nutrients from blood vessels in the capsule
• D. It obtains nutrients via the vitreous humor

Answer: (B)

The lens is avascular, so it must obtain nutrients by diffusion from surrounding fluids rather than from blood vessels. In the eye, nutrients diffuse from the aqueous humor, which is produced by the ciliary body and flows through the posterior chamber into the anterior chamber. The lens’ metabolically active anterior epithelium and deeper fiber cells take up these nutrients (glucose, amino acids, oxygen) from the aqueous humor, while waste products diffuse back into the same fluid to be removed via the outflow pathways. This diffusion-based nourishment from the aqueous humor best explains how the lens stays nourished without direct blood supply. Direct capillary supply to lens fibers isn’t present, the capsule has no blood vessels, and the vitreous humor isn’t the primary nutrient source for the lens.

The lens is avascular, so it must obtain nutrients by diffusion from surrounding fluids rather than from blood vessels. In the eye, nutrients diffuse from the aqueous humor, which is produced by the ciliary body and flows through the posterior chamber into the anterior chamber. The lens’ metabolically active anterior epithelium and deeper fiber cells take up these nutrients (glucose, amino acids, oxygen) from the aqueous humor, while waste products diffuse back into the same fluid to be removed via the outflow pathways. This diffusion-based nourishment from the aqueous humor best explains how the lens stays nourished without direct blood supply. Direct capillary supply to lens fibers isn’t present, the capsule has no blood vessels, and the vitreous humor isn’t the primary nutrient source for the lens.