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- 1 Description and Overview
- 2 Structure
- 2.1 Frontal bone
- 2.2 Zygoma
- 2.3 Maxilla
- 2.4 Nasal bones
- 2.5 Mandible
- 2.6 Inferior Nasal Conchae
- 2.7 Lacrimal Bones
- 2.8 Resources
- 3 References
Description and Overview
The skull is the most intricate bony structure of the body. It is made up of 28 individual bones, out of which 11 are paired and 6 are single . The skull formation is divided into 2 parts:
- The Viscerocranium (the facial skeleton) - goes to develop the bones of the face. This is the portion of the skull related to the digestive and respiratory systems
- The Neurocranium (the brain case) - goes to develop the bones of the cranial base and cranial vault. This portion provides protection to the brain and to the 5 organs of special senses: Olfaction, vision, taste, vestibular function and auditory function.
The Viscerocranium is further divided into:
- The membranous viscerocranium, comprising the facial skeleton. It is the foundation on which the facial muscles attach.
- The cartilaginous viscerocranium, comprising the splanchnocranium.
In this article, we will cover the facial skeleton.
Since the facial skeleton is the foundation for the facial muscles, it is not inaccurate to say it helps in determining an individual's facial appearance.
It is made up of 14 bones which integrate to house the orbits of the eyes, nasal and oral cavities along with the sinuses. The facial skeleton consists of:
This forms the forehead region of the face housing the frontal sinuses. It forms the roof of the ethmoid sinuses, nose and orbit (for the eye)
- there is only 1 frontal bone
- it contains the frontal paranasal sinuses.
- in the 2nd year, houses 2 primary centres that ossify along the frontal suture.
- helps form the foramen cecum.
Parts and Ossification -
- has 3 parts and all the 3 parts have a membranous ossification.
- Squamous portion - forms the largest portion of the frontal bone, including forming majority of the forehead. Also forms the supraorbital margin and the superciliary arch.
- Orbital portion - forms the roof of the orbit and floor of the anterior cranial fossa.
- Nasal portion - articulates with the nasal bones and the frontal process of the maxilla to form the root of the nose. The trochlea of the orbit articulates with the orbital portion.
The zygoma forms the lateral rim and wall of the orbit, and forms the anterior zygomatic arch.
- also called the zygomatic bone, there are 2 of them.
- forms majority of the cheek skeleton.
- is the attachment for the masseter muscle.
- has 3 foramina : Zygomatico-orbital foramen, Zygomaticofacial foramen, Zygomaticotemporal foramen.
Parts and Ossification -
- has 3 processes and all the 3 ossify intramembranously.
- Frontal process - articulates with the frontal bone to help form the orbit.
- Temporal process - integrates with the zygomatic masseter process of the temporal bone to form the zygomatic arch.
- Maxillary process - articulates with the zygomatic process of the maxillary bone to help form the orbit.
This forms the roof of the oral sinus, as well as housing the upper teeth. It also forms part of the roof and lateral wall of the nasal cavity.
- 2 maxilla bones, called maxillae together.
- forms majority of the face and upper jaw skeleton.
- accommodates the maxillary paranasal sinus.
- articulates with the opposite maxilla and the frontal, nasal, sphenoid, ethmoid, and vomer bones; inferior nasal concha; palatine, zygomatic bones and lacrimal; and the septal and nasal cartilages.
Parts and Ossification -
- has a body and 4 processes, all with intra membranous ossification.
- Body - is the major part of the bone, which is shaped like a pyramid. Gives rise to 4 different regions: orbit, face, infratemporal fossa and nasal cavity. Houses the maxillary paranasal sinus. Infraorbital canal and foramen pass from the orbit region to the face region.
- Frontal process - forms the posterior border of the lacrimal fossa. It extends upwards to articulate with the frontal, ethmoid, nasal and lacrimal bones.
- Zygomatic process - extends outwards to hinge with the maxillary process of the zygomatic bone.
- Palatine process - in the anterior portion, has the incisive foramen located. This process extends medially to contour the majority of the hard palate. It concatenate with the palatine process of the opposite side and the horizontal plate of the of the palatine bone.
- Alveolar process - extends inwards into the maxilla and supports all the maxillary teeth. Each maxilla contains 5 primary and 8 permanent teeth. In the event of a tooth loss, the alveolar bone is resorbed.
The nasal bones are a pair of bones which form the upper part of the nasal cavity. They articulate with the maxilla and the frontal bone.
- 2 nasal bones.
- forms the bridge of the nose.
- inferior portion forms the superior margin of the nasal aperture.
Articulation and ossification -
- intramembranous ossification.
- joins with the nasal bone of the opposite side, the frontal process of the maxilla, nasal portion of the frontal bone and the perpendicular plate of the ethmoid.
- The septal cartilage and the lateral nasal cartilage articulates with the inferior portion of the nasal bones.
Also known as the Jaw Bone, the mandible is the only mobile bone of the facial skeleton. It houses the lower teeth.
- only 1 mandible. Largest and strongest bone of the face.
- forms the lower jaw and is horseshoe shaped.
- all the muscles of mastication attach to this bone.
Parts and ossification -
- has a body, a ramus and 3 processes. Ossification is around the Meckel's cartilage and is intramembranous.
- Body - on the anterior part of the lateral surface of the body lies the mental foramen. Medial side of the body houses the mylohyoid line, which helps divide a sublingual from a sub mandibular fossa. The posterior border of this line, provides attachment to the pterygomandibular raphe. On the lateral side is the external oblique line. At the midline on the medial side are the superior and inferior genial tubercles, as well as the digastric fossa.
- Ramus - meets the body of the mandible at the angle of the mandible on each side. Lateral side attachment include the masseter muscle and the medial side being medial pterygoid muscle and sphenomandibular ligament. The superior part of the ramus divides into a coronoid process anteriorly and a condylar process posteriorly, separated by a mandibular notch. The mandibular foramen is placed on the medial side of the ramus.
- Coronoid process - it is the anterior most superior extension of each ramus and the gives its attachment to the temporalis muscle.
- Condylar process - superiorly has a neck which forms a condyle. In the temporomandibular joint, joins with the temporal bone. Lateral pterygoid muscle attaches to pterygoid fovea on the neck.
- Alveolar process - it is constructed by a thick buccal and a thin lingual plate of bone. It is also the part of the mandible that supports the mandibular teeth. Extends superiorly from the body of the mandible.
Small bones of the face
Inferior Nasal Conchae
This pair of small bones form part of the lateral wall of the nasal cavity.
- 2 inferior nasal conchae.
- curved bone
- forms part of the lateral wall of the nasal cavity.
Articulation and ossification -
- Ossification is endochondral in nature.
- lies with in the a curve in the lateral wall of the nasal cavity.
- articulates with the maxilla and the perpendicular plate of the palatine, ethmoid and lacrimal bones.
These small, fragile bones lie in the antero-medial part of the orbit.
Together with the maxillae, these form the hard palate.
This is an single bone (unpaired) which forms the inferior portion of the nasal septum.
Resources2 part tutorial on Bones of the Facial Skeleton:
- Neil S. Norton, Ph.D. and Frank H. Netter, MD, Netter’s Head and Neck Anatomy for Dentistry, 2nd Edition, Elsevier Saunders, 2012
- Bron AJ, Tripathi RC, Tripathi BJ. Wolff's Anatomy of the Eye and Orbit. 8th ed. Philadelphia: Lippincott Williams & Wilkins. 1997
- Anatomy of Frontal Bone - Animated Osteology , MBBS , FMGE & NEET PG. Available from: http://www.youtube.com/watch?v=9yOp0lvVF_0
- Zygomatic Bone. Available from: http://www.youtube.com/watch?v=_jN4R18ophg
- Skull Maxilla Bone. Available from: http://www.youtube.com/watch?v=I3TGO-dphfg
- Lang J. Clinical Anatomy of the Nose, Nasal Cavity, and Paranasal Sinuses. NY: Thieme Medical Publishers. 1989
- Nasal bone - Anatomy, Function & Diagram - Human Anatomy | Kenhub. Available from: http://www.youtube.com/watch?v=i9ImrUiKvp8
- Mandible | Skull Anatomy. Available from: http://www.youtube.com/watch?v=_lHosB-c_fQ
- Inferior Nasal Concha. Available from: http://www.youtube.com/watch?v=iwnxM5AQ0u4