---
title: "Inferior Orbital Fissure | Anatomy I"
description: "Inferior orbital fissure is the skull opening that links the orbit to nearby fossae and transmits nerves and vessels in Anatomy and Physiology I."
canonical: "https://fiveable.me/anatomy-physiology/key-terms/inferior-orbital-fissure"
type: "key-term"
subject: "Anatomy and Physiology I"
unit: "Unit 7"
---

# Inferior Orbital Fissure | Anatomy I

## Definition

The inferior orbital fissure is an opening at the floor of the orbit that connects the eye socket to nearby facial spaces. In Anatomy and Physiology I, it is the passageway for nerves and blood vessels traveling between the orbit, maxillary region, and pterygopalatine fossa.

## What It Is

The inferior orbital fissure is a gap in the skull at the back floor of the orbit, or eye socket. In Anatomy and Physiology I, you can think of it as a doorway between the orbit and deeper facial spaces rather than a bone itself. It sits where the maxilla and sphenoid bones meet, so it is part of the bony architecture that makes the orbit open in specific places for vessels and nerves to pass through.

Its main job is to let structures move between the orbit and the pterygopalatine and infratemporal regions. That is why this fissure shows up when you study the skull as a three dimensional system, not just a list of bone names. The orbit is not sealed off like a box. It has openings that connect the eye region to the face, nasal area, and cranial base.

Several important structures travel through the inferior orbital fissure. The infraorbital nerve passes through this area after branching from the maxillary division of the trigeminal nerve, and it carries sensation from the lower eyelid, cheek, side of the nose, and upper lip. Blood vessels also pass here, including venous drainage from the orbit through the inferior ophthalmic vein and related vessels.

That anatomy matters because the fissure is a route, not just a landmark. If the orbital floor is fractured, swollen, or compressed by a mass, the structures that use this passage can be affected. A person might notice numbness in the cheek or upper lip, pain around the orbit, or changes in drainage and movement depending on the injury.

A common mistake is mixing up the inferior orbital fissure with the inferior orbital foramen. The fissure is the larger opening region in the skull, while the infraorbital foramen is the smaller exit on the maxilla where the infraorbital nerve emerges onto the face. In class diagrams, the fissure usually looks like a slit or gap deeper in the orbit, while the foramen is the visible opening on the facial surface.

## Why It Matters

Inferior orbital fissure shows how the skull is built for protection and communication at the same time. The orbit protects the eye, but it also needs paths for nerves and veins to enter and leave. When you study this fissure, you are really tracing how the trigeminal nerve, facial sensation, and venous drainage connect across the skull.

This term also comes up in the skull unit because the orbit is one of the best examples of how different bones create spaces and openings. If you can identify the inferior orbital fissure on a model, diagram, or CT image, you are showing that you can read the skull as an anatomical map. That skill carries over to other skull openings too, especially when you compare the fissure with nearby foramina and fossae.

It also helps explain symptoms. Numbness of the upper lip or cheek, for example, makes more sense once you know the infraorbital nerve passes through this region. In anatomy lab, that connection between structure and function is exactly what turns memorized labels into usable knowledge.

## Connections

### Orbit

The inferior orbital fissure is part of the orbit’s bony floor and back wall, so you need the orbit to place it correctly. When you study the orbit, you are learning how the eye socket is shaped and why certain openings are left for nerves, veins, and muscles to pass through. The fissure is one of those openings.

### [Pterygopalatine Fossa](/anatomy-physiology/key-terms/pterygopalatine-fossa)

This fissure connects the orbit with the pterygopalatine fossa, so the two spaces are linked in skull anatomy. The pterygopalatine fossa acts like a small crossroads for nerves and vessels in the deep face. If you trace structures through the inferior orbital fissure, you are often tracing their route into or out of this fossa.

### [Temporal Fossa](/anatomy-physiology/key-terms/temporal-fossa)

The inferior orbital fissure is described as a connection to deeper facial spaces near the temporal region, which makes the temporal fossa useful for orientation. Even though the temporal fossa is not the same space, it helps you place the orbit in relation to the side of the skull and nearby muscle attachment areas. That spatial sense makes skull diagrams easier to read.

### [Anterior Cranial Fossa](/anatomy-physiology/key-terms/anterior-cranial-fossa)

The anterior cranial fossa is another skull region that shows how the skull base is divided into compartments and openings. Comparing it with the inferior orbital fissure helps you separate cranial cavity structures from facial openings. That contrast matters when you are identifying what protects the brain versus what routes structures through the face.

## On the AP Exam

A labeled skull image, bone model quiz, or CT-based question may ask you to identify the inferior orbital fissure and explain what passes through it. You might also need to connect a symptom, like cheek or upper lip numbness, to the infraorbital nerve traveling through this opening. In lab practicals, the trick is to place it in the orbit’s floor and notice that it is a passage, not a separate bone. If a question compares openings, use its location to distinguish it from the infraorbital foramen and from other orbital spaces.

## Inferior Orbital Fissure vs infraorbital foramen

These are easy to mix up because both relate to the infraorbital nerve. The inferior orbital fissure is the deeper opening in the orbit that transmits the nerve and vessels through the skull region, while the infraorbital foramen is the opening where that nerve emerges on the anterior maxilla to supply the face. If you are looking at a skull, the fissure sits deeper and more posterior than the foramen.

## Key Takeaways

- The inferior orbital fissure is a skull opening at the back of the orbit, not a bone or muscle.
- It connects the orbit with deeper facial spaces, especially the pterygopalatine region.
- The infraorbital nerve and orbital blood vessels pass through this area, which is why injury here can affect facial sensation.
- You should be able to place it on a skull diagram and distinguish it from the infraorbital foramen.
- In A&P I, this term is a good example of how skull openings protect the eye while still letting nerves and vessels move through.

## FAQs

### What is the inferior orbital fissure in Anatomy and Physiology I?

It is an opening in the skull at the back floor of the orbit that connects the eye socket with deeper facial spaces. It acts as a passage for nerves and blood vessels, especially the infraorbital nerve and orbital veins. In A&P I, it shows up when you study the bones of the orbit and how the skull routes structures through them.

### What passes through the inferior orbital fissure?

The infraorbital nerve passes through it, along with blood vessels such as the inferior ophthalmic vein and related branches. These structures travel between the orbit and the pterygopalatine region. If you are tracing facial sensation or venous drainage, this fissure is one of the routes you need to know.

### How is the inferior orbital fissure different from the infraorbital foramen?

The fissure is the deeper slit-like opening in the orbit, while the foramen is the opening on the front of the maxilla where the infraorbital nerve comes out onto the face. They are connected in the same nerve pathway, but they are not the same landmark. This is a common lab practical confusion.

### Why would an injury near the inferior orbital fissure cause facial numbness?

Because the infraorbital nerve travels through this area on its way to the face. If the fissure or nearby orbital floor is fractured, that nerve can be compressed or damaged. The result can be numbness or tingling in the lower eyelid, cheek, side of the nose, or upper lip.

## Related Study Guides

- [7.2 The Skull ](/anatomy-physiology/unit-7/2-skull/study-guide/UlZ8y25gzC1E8srV)

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