In this article we will discuss about the zygomatic and palatine bones which belongs to human skull.
Zygomatic Bone of the Human Skull:
It forms the bony prominence of the cheek. Shape is irregular. It takes part in the formation of lateral wall and floor of the orbit. Also forms the anterior wall of temporal and infra temporal fossa.
Parts:
It has three surfaces – lateral, medial and orbital surface and five borders – antero superior, antero inferior, postero superior, postero inferior and postero medial border.
Process:
These are frontal and temporal process, articulate with frontal and temporal bone.
Lateral Surface:
It is convex and prominent, shows zygomatico facial foramen which transmits zygomatico nerve and vessels.
Muscles attached are:
Origin of masseter near postero inferior border.
a. Zygomaticus Minor:
Originates inferior to the zygomatico facial foramen.
b. Zygomaticus Major:
Originates from the lateral surface behind the origin of zygomaticus minor.
Levator Labii Superioris :
Medial Surface:
Forms temporal and infra temporal fossae. Anterior part of this surface is rough and articulates with the zygomatic process of maxilla. This surface also shows zygomatico temporal foramen which transmits zygomatico temporal nerve and vessels.
Superior Surface:
Forms floor and lateral wall of orbit. It has a foramen called zygomatico orbital foramen leads to zygomatico temporal and zygomatico facial foramen.
Orbital Border:
It is non-articular, concave, gives attachment to the orbital septum.
Maxillary Border:
Articulates with maxilla, is also called as postero inferior border.
Temporal Border (Postero Superior Border):
It is sharp gives attachment to temporal fascia.
Posteromedial Border:
Upper part articulates with the greater wing of sphenoid and lower par articulates with the orbital surface of maxilla. Middle part is non-articular, forms inferior orbital fissure.
Postero Inferior Border:
It is non-articular, masseter muscle originates.
Frontal process has three surfaces- anterior, posterior and lateral surface, anterior surface takes part in formation of orbit. Close to the orbital border Whitnall’s tubercle lies.
It gives attachment to lateral check ligament, suspensory ligament of lockwood, lateral palpebral ligament, aponeurosis of the levator palpebrae superioris.
Frontal process has three borders- Anterior, posterior and medial border. Anterior border forms orbital margin, posterior border gives attachment to temporal fascia, while medial border joins the greater wing of sphenoid.
Temporal Process:
Upper part articulates with the zygomatic process of temporal bone, lower part gives origin to masseter muscle.
Ossification:
One center appears for the body of the bone at 8th week of intra uterine life and ossification spreads on all sides.
Palatine Bone of the Human Skull:
Lies between the maxilla and medial pterygoid plate. It takes part in the formation of lateral wall of nose and medial wall of pterygo palatine fossa.
Perpendicular plate has medial and lateral surface. Lateral surface shows a groove called greater palatine groove, it is converted into a canal by articulating with the maxilla. This canal transmits greater palatine nerves and vessels.
Processes of Palatine Bone:
They are pyramidal, orbital and sphenoidal process.
Pyramidal Process:
It lies in between posterior border of maxilla and medial and lateral pterygoid plates of the sphenoid bone. It gives origin to medial pterygoid muscle. Inferior surface has lesser palatine foramen – transmits lesser palatine nerves and vessels.
Orbital Process:
Lies along the upper part of perpendicular plate separated by a notch from the sphenoidal process. It is called spheno palatine notch. Orbital process lies in the floor of the orbit posteriorly; maxillary nerve grooves the lower part of this surface. It articulates with maxilla, sphenoidal concha and labyringh of the ethmoidal bone.
Sphenoidal Process:
It is a small plate, related to the lower surface of the body of sphenoid, extends upto ala of vomer.
Horizontal Plate:
It meets its fellow of opposite side and forms posterior 1/3 of hard palate. At the meeting point it forms nasal crest which articulates with vomer and projects back in the midline to form posterior nasal spine.
The anterior border of the horizontal plate meets the posterior border of palatine process of maxilla at palato maxillary suture.
The posterior border is sharp and concave.
Ossification:
One center of ossification appears by 8th week of intra uterine life on the perpendicular plate. Ossification spreads to the other parts of bone.
Vomer:
It is unpaired bone, lies in the midline of the nose and forms nasal septum, dividing the nose into two cavities. It has two surfaces right and left, grooved by nasopalatine nerves and vessels.
Superior border divides into two wings called alae.
Inferior border articulates with perpendicular plate of ethmoid bone above and septal cartilage below.
Ossification:
Two centers appear by 8th week of intra uterine life, one on either side. At puberty these plates fuse.