What is Maxilla
Maxilla (plural: maxillae) is one of the eight facial bones that form the facial skeleton. It is the second largest bone of the face. The bone is commonly known as upper jaw bone as it forms the upper jaw holding the upper set of teeth. It also forms the lower parts of eye sockets and nasal cavities.
Though the maxilla looks like a single bone, it is actually a paired bone, joined by a delicate suture in the middle called intermaxillary suture or median palatine.
Where is the Maxilla Located
The bone is positioned in the mid-face, just above the mandible. It starts from the middle of the forehead, and extends on either side of the nose, reaching up to the cheekbones. You can easily feel the bone by pressing the skin just under your cheekbones.
|How many are there in the human body||1|
|Articulates with||9 bones: frontal, ethmoid, sphenoid, nasal, zygomatic, lacrimal, inferior nasal concha, palatine, vomer.|
The left and right maxilla, collectively help to:
- Hold the upper set of teeth in place.
- Increase the volume and depth of voice.
- Form a part of the eye socket, nasal cavity, and hard palate.
- Play an important role in mastication and communication.
The bone consists of a body and four projections or processes, namely, frontal, zygomatic, palatine, and alveolar.
It is the largest part of the bone, having a roughly pyramidal shape and four surfaces: anterior, orbital, nasal, and infratemporal surfaces.
i. Anterior surface
The anterior surface of the body features a curved margin of the bony anterior nasal aperture, called the nasal notch. This surface also partly forms the lower margin of the eye socket, named as infra-orbital margin, along with the zygomatic bone. Below the infra-orbital margin, there is an opening on the anterior aspect of the maxilla, the infra-orbital foramen. This foramen is the outer opening of the infra-orbital canal that serves as the passage for the infraorbital nerve and blood vessels. Just below the infra-orbital foramen, there is another depressed area on the anterior surface of the body, called the canine fossa. The levator anguli oris muscle originates from here.
ii. Orbital surface
This surface forms most of the floor of the eye socket and features the infra-orbital groove leading into the infra-orbital canal. This canal ends with an opening on the anterior surface of the maxilla and serves as the passage for the infraorbital nerve and blood vessels.
iii. Nasal surface
The nasal surface of the body of the maxilla forms part of the lateral wall of the nasal cavity and features a large opening, the maxillary hiatus. The maxillary hiatus is an opening to the maxillary sinus, located below the middle nasal concha. The maxillary sinus is a paranasal sinus, an air-filled cavity located within the body of the maxilla.
iv. Infratemporal surface
The infratemporal surface of the body of the maxilla forms the anterior wall of the infratemporal fossa. It also features the maxillary tuberosity on the inferior aspect of lateral margin. The maxillary tuberosity or maxillary eminence has several small openings, called alveolar foramina that lead into the alveolar canals. These canals transmit the posterior superior alveolar nerves, and posterior superior alveolar arteries and veins to the upper teeth. A few fibers of the medial pterygoid muscle originate from this maxillary tuberosity.
It is an inferior crested extension of the maxilla with a rather porous structure. It forms the maxillary dental arch containing eight cavities where the upper teeth are held. The curved free margin of the alveolar process is called the alveolar arch, featuring dental alveoli, interalveolar septa, interradicular septa, and alveolar yokes. The dental alveoli are sockets in the alveolar process where the roots of the upper set of teeth lie. In between the adjacent dental alveoli, there is a bony ridge, called the interalveolar septa. On the other hand, there are some bony ridges, known as interradicular septa that form compartments in dental alveoli for the roots of the teeth. The dental alveoli also produce some projections on the outer side of the bone, called alveolar yokes or juga alveolaria.
The frontal process lies superiorly and medially relative to each maxillary bone. Each frontal process articulates with the frontal bone superiorly and the nasal bones medially. It forms the anterior wall of the nasolacrimal groove and contributes in shaping the inferior and central portion of the forehead as well as to the nasal bridge through its union with the frontal and nasal bone. The frontal process has a vertical ridge which constitutes the medial border of the orbit (anterior lacrimal crest). Posteriorly it forms the lacrimal groove together with the lacrimal bone. Superomedially it is in close contact with the anterior ethmoidal sinuses.
The zygomatic process is the most lateral portion of the maxilla, growing laterally to meet the zygomatic bone. It forms the superolateral border of the maxillary sinus and is superior to the first maxillary molar. The process also shares a border with the alveolar process inferiorly and with the frontal process superomedially. Along with the alveolar process, the zygomatic process also plays a crucial role in providing structure to the midface. On the anterior surface, lateral to the zygomatic process, a depression is formed known as the canine fossa, which constitutes the anterior surface of the maxilla. Another depression called the zygomaticoalveolar crest is located below the zygomatic process and just above the alveolar process.
Lastly, the palatine process is a horizontal extension on the medial side of the bone constituting the roof of the mouth and the floor of the nasal cavity. Together with the palatine bone it forms the hard palate. Anteriorly it features a small process, the anterior nasal spine. The incisive foramen can be found on the median line just posteriorly to the incisor teeth. The nasopalatine nerve and greater palatine vessels pass through this foramen.
Following are the muscles that attach to the maxillae.
Muscles originating from the maxillae
- Levator labii superioris alaeque nasi
- Levator labii superioris
- Levator anguli oris
Muscles inserting into the maxillae
- Zygomaticus minor
- Orbicularis oris
As stated, each maxilla articulates with the following 9 bones:
- Frontal bone: superiorly
- Sphenoid, palatine, lacrimal, and ethmoid bones: posteriorly
- Nasal bone, and vomer: medially
- Nasal concha: inferiorly
- Zygomatic bone: laterally
The left and right maxilla also articulate with each other, appearing like a single unpaired bone.
Ossification and Development
All five parts of the maxilla undergo intramembranous ossification through two ossification centers.