Maximum contribution to the floor of orbit is by:
**Core Concept**
The floor of the orbit is a complex anatomical structure formed by the fusion of several bones. The maximum contribution to the floor of the orbit is primarily made by the maxillary bone, which forms a significant portion of the orbital floor.
**Why the Correct Answer is Right**
The maxillary bone, particularly its orbital surface, contributes significantly to the formation of the orbital floor. This is due to the presence of a thin, plate-like structure called the orbital floor plate, which is a part of the maxillary bone. The orbital floor plate is composed of compact bone and forms the thinnest point of the maxillary bone. This area is prone to fractures, especially in the presence of trauma or increased intraorbital pressure.
**Why Each Wrong Option is Incorrect**
**Option A:** The zygomatic bone contributes to the lateral aspect of the orbit but not the floor. While it forms part of the orbital rim, it does not participate in the formation of the orbital floor.
**Option B:** The ethmoid bone forms part of the medial wall of the orbit but does not contribute to the floor. Its role is in separating the nasal cavity from the orbit, rather than forming part of the orbital floor.
**Option C:** The lacrimal bone forms part of the medial wall of the orbit, specifically in the region of the lacrimal fossa, but does not contribute to the floor.
**Clinical Pearl / High-Yield Fact**
The orbital floor is particularly thin and prone to fractures, especially in the presence of a blow to the globe or increased intraorbital pressure. This can lead to herniation of orbital contents into the maxillary sinus.
**Correct Answer:** A. Maxilla.