Question

Sequence of events in the formation of eye are
(A) Formation of optic grooves
(B) Optic vesicles formation
(C) Optic cup formation
(D) Formation of lens placodes
Choose the correct answer from the options given below:

• A. (A), (B), (C), (D).
• B. (A), (C), (B), (D).
• C. (A), (B), (D), (C).
• D. (A), (D), (C), (B).

Hint:

Remember: Inductive interaction is key in eye development. The optic vesicle (neuroectoderm) must contact the surface ectoderm to induce the lens placode, which then invaginates to form the optic cup.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The development of the eye involves coordinated interactions between the neuroectoderm of the forebrain, the overlying surface ectoderm, and the surrounding mesenchyme.

Step 2: Detailed Explanation:
Let us analyze the embryological sequence of events during ocular development:
1. Formation of optic grooves (A):
The first morphological sign of eye development occurs before the neural tube closes.
Two bilateral depressions, called optic grooves (sulci), appear on the inner surface of the neural folds of the future diencephalon.
2. Optic vesicles formation (B):
As the neural tube closes, these grooves evaginate laterally to form bulb-like outpocketings called optic vesicles, which remain connected to the forebrain via the optic stalk.
3. Formation of lens placodes (D):
As the optic vesicle expands, its outer wall comes into close contact with the overlying surface ectoderm.
This contact induces the surface ectoderm to thicken and differentiate into the lens placode.
4. Optic cup formation (C):
Simultaneously, the outer wall of the optic vesicle and the lens placode invaginate together.
The vesicle collapses to form a double-walled structure called the optic cup, while the lens placode pinches off to form the lens vesicle within the mouth of the cup.
Therefore, the chronological sequence of events is:
Optic grooves (A) $\rightarrow$ Optic vesicles (B) $\rightarrow$ Lens placodes (D) $\rightarrow$ Optic cup (C).

Step 3: Final Answer:
The correct option is (C), representing (A), (B), (D), (C).