Orbit

The orbit, or orbital cavity, is a bony space filled with the eye bulb (bulbus oculi), the surrounding fatty tissue (corpus adiposum orbitae), tear gland (glandula lacrimalis) and tear duct (ductus lacrimalis), orbital muscles (musculi bulbi), vessels and  nerves.

Walls
The space of the orbit has the shape of a four-sided pyramid, the base of which is the entrance to the orbit, the aditus orbitae, and the walls of which meet at the top of the orbit, the apex orbitae. So we can distinguish four walls in the orbit - medial, superior, lateral and inferior.

Aditus orbitae
The entrance to the orbit is bordered by the ``margo supraorbitalis and the ``margo infraorbitalis. They are formed by the following bones: cranially, the ``os frontale, laterally, the ``os zygomaticum, caudally, the ``maxilla, which extends medially to to the frontal bone with its processus frontalis.''

Media Wall
It is created in the sagittal plane, with the right and left walls being parallel. From front to back, it is made up of: processus frontalis maxillae, os lacrimale, lamina orbitalis ossis ethmoidalis and ala minor ossis sphenoidalis.It contains the  fossa sacci lacrimalis and canalis nasolacrimalis, in which the lacrimal duct - ductus lacrimalis is located. Then there is the foramen ethmoidale anterius and the foramen ethmoidale posterius, the openings between the lamina orbitalis of the olfactory bone and the os frontale. Nerves and vessels of the same name run through them.

Upper Wall
From front to back, it is formed by: pars orbitalis ossis frontalis and ala minor ossis sphenoidalis. glandulae lacrimalis.''

Lateral wall
It is formed from front to back: os zygomaticum, ala major ossis sphenoidalis.In this wall is the foramen zygomaticorbitale for the n. zygomaticus.

Lower wall
This wall is made up from front to back: os zygomaticum, corpus maxillae and processus orbitalis ossis palatini. The lower wall contains structures and openings: sulcus et canalis infraorbitalis, fissura orbitalis superior, fissura orbitalis inferior.

Relations to surroundings, passages

 * The topographic relations of the orbit are as follows:

Medially there is the nasal cavity' and the sinus ethmoidales of the olfactory bone. Above the orbit is the anterior cranial fossa and the sinus frontalis as part of the frontal bone. The fossa temporalis is located laterally. Below the orbit is the maxillary sinus.

Communications and their passing structures

 * Apex orbitae:

In the canalis opticus the n. opticus and a. ophthalmica.


 * Media wall:

In the "canalis nasolacrimalis" there is the already mentioned "ductus nasolacrimalis". In the foramen ethmoidale anterius and foramen ethmoidale posterius we find vessels and nerves of the same name. So n. ethmoidalis anterius and n. ethmoidalis posterius (somatosensitive innervation of part of the nasal mucosa) and then the vasa ethmoidalia anteriora and the vasa ethmoidalia posteriora.


 * Lateral wall:

In the foramen zygomaticoorbitale we find n. zygomaticus - it originates from the orbit and branches in the os zygomaticum to the n. zygomaticofacialis for sensitive innervation of the skin above the cheekbone and n. zygomaticotemporalis for sensitive innervation of the skin of the anterior temporal region and part of the frontal region.


 * Lower wall:

To the "canalis infraorbitalis" leads the "n. infraorbitalis, which branches in the course. Fissura orbitalis superior communicates with the middle cranial cavity, mediolaterally pass through it: n. oculomotorius, n. nasociliaris, n. frontalis and n. lacrimalis as branches of n. ophthalmicus, n. abducens, n. trochlearis and v. opthalmica superior. The Fissura orbitalis inferior communicates with the pterygopalatine fossa and the infratemporalis fossa. It passes through n. zygomaticus (here it enters the orbit, which it leaves through the foramen zygomaticoorbitale), n. infraorbitalis, a. infraorbitalis and v. opthalmica inferior''.