Facial skeleton

Overview

The facial skeleton, also known as the viscerocranium, is a complex structure that forms the framework of the face. It consists of several bones that are intricately connected to provide support and shape to the face, as well as to protect vital sensory organs such as the eyes, nose, and mouth. The facial skeleton is a crucial component of the human skull and plays a significant role in functions such as mastication, respiration, and communication.

Anatomy of the Facial Skeleton

The facial skeleton is composed of 14 bones, which are divided into paired and unpaired bones. These bones are:

Paired Bones

**Maxillae**: The maxillae are the two upper jawbones that form the central part of the facial skeleton. They house the upper teeth and form the floor of the orbits, the sides and floor of the nasal cavity, and the roof of the mouth.
**Zygomatic Bones**: Also known as the cheekbones, the zygomatic bones are located on either side of the face and articulate with the maxillae, temporal bones, sphenoid bones, and frontal bones.
**Nasal Bones**: These small, rectangular bones form the bridge of the nose and articulate with the frontal bone, maxillae, and each other.
**Lacrimal Bones**: The smallest bones of the face, the lacrimal bones are situated in the medial wall of each orbit and contain the lacrimal fossa, which houses the lacrimal sac.
**Palatine Bones**: These L-shaped bones are located at the back of the nasal cavity and contribute to the formation of the hard palate, the floor of the nasal cavity, and the floor of the orbits.
**Inferior Nasal Conchae**: These thin, curved bones are located within the nasal cavity and help to filter and humidify the air we breathe.
**Vomer**: The vomer is a thin, flat bone that forms the lower part of the nasal septum, dividing the nasal cavity into two nostrils.

Unpaired Bones

**Mandible**: The mandible, or lower jawbone, is the largest and strongest bone of the face. It holds the lower teeth and is the only movable bone of the skull, playing a key role in mastication and speech.

Development of the Facial Skeleton

The development of the facial skeleton begins in the embryonic stage and continues through childhood and adolescence. The process involves both intramembranous and endochondral ossification.

Intramembranous Ossification

Intramembranous ossification is the process by which flat bones, such as the maxillae and zygomatic bones, are formed directly from mesenchymal tissue. This process begins around the sixth week of embryonic development and continues postnatally.

Endochondral Ossification

Endochondral ossification involves the replacement of a cartilage template with bone. This process is responsible for the formation of bones such as the mandible and the base of the skull. It begins in the early fetal period and continues into adolescence, with the growth plates closing around the age of 18-25 years.

Functions of the Facial Skeleton

The facial skeleton serves several critical functions, including:

**Protection**: The facial bones protect the brain, eyes, nasal cavity, and oral cavity from injury.
**Support**: The bones of the face provide structural support for the soft tissues of the face, including muscles, skin, and mucous membranes.
**Mastication**: The mandible and maxillae play a vital role in chewing by providing attachment points for the muscles of mastication and housing the teeth.
**Respiration**: The nasal cavity, formed by the nasal bones, maxillae, and other facial bones, is essential for breathing and filtering the air we inhale.
**Communication**: The facial skeleton supports the muscles involved in facial expressions and speech, enabling non-verbal communication and articulation.

Clinical Significance

The facial skeleton is susceptible to various conditions and injuries that can affect its structure and function. Some of the most common issues include:

Fractures

Facial fractures can occur due to trauma, such as car accidents, falls, or sports injuries. Common types of facial fractures include:

**Nasal Fractures**: The most common type of facial fracture, often resulting from direct impact to the nose.
**Maxillary Fractures**: These fractures can affect the upper jaw and the surrounding structures, potentially impacting the orbits and nasal cavity.
**Zygomatic Fractures**: Fractures of the cheekbone can affect the shape of the face and the function of the orbit.
**Mandibular Fractures**: Fractures of the lower jaw can impair chewing and speech and may require surgical intervention.

Congenital Anomalies

Congenital anomalies of the facial skeleton can result from genetic factors or developmental disruptions. Some common congenital conditions include:

**Cleft Lip and Palate**: These conditions result from incomplete fusion of the maxillae and palatine bones during embryonic development, leading to gaps in the upper lip and/or palate.
**Craniosynostosis**: Premature fusion of the cranial sutures can affect the shape of the skull and face, potentially leading to increased intracranial pressure and developmental delays.

Infections

Infections can affect the bones of the face, leading to conditions such as:

**Osteomyelitis**: A bacterial infection of the bone that can result in inflammation, pain, and bone destruction.
**Sinusitis**: Inflammation of the paranasal sinuses, often caused by bacterial or viral infections, can affect the maxillae and other facial bones.

Surgical Interventions

Surgical interventions may be necessary to address various conditions affecting the facial skeleton. Some common surgical procedures include:

Orthognathic Surgery

Orthognathic surgery involves the correction of jaw deformities to improve function and aesthetics. This surgery can address issues such as malocclusion, facial asymmetry, and obstructive sleep apnea.

Facial Reconstruction

Facial reconstruction surgery aims to restore the appearance and function of the face following trauma, congenital anomalies, or tumor resection. Techniques may include bone grafting, the use of implants, and soft tissue reconstruction.

Rhinoplasty

Rhinoplasty, or nose surgery, can be performed for both cosmetic and functional reasons. It may involve reshaping the nasal bones and cartilage to improve the appearance of the nose or to correct breathing issues.

References

Gray, Henry. Gray's Anatomy: The Anatomical Basis of Clinical Practice. 41st ed., Elsevier, 2015.
Moore, Keith L., et al. Clinically Oriented Anatomy. 8th ed., Wolters Kluwer, 2018.
Standring, Susan. Gray's Anatomy: The Anatomical Basis of Clinical Practice. 40th ed., Elsevier, 2008.