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zygomatic Bone

[ Author:Fushun Ma | Time:2011-10-20 09:57:34 |  Font Size: [Large Medium Small]
Tags: zygomatic bone function surgery anatomy

 Zygomatic Bone is the important human facial bone. The bones in a human head can be divided into two categories the cranium and the maxilla. The cranium is composed of 8 bones which contain and protect the brain. The maxilla indicates the other 14 bones of the human head except the cranium. There are two zygomatic bones located on right and left side of the face separately. They are two of the 14 maxillary bones. They are the third largest maxillary bones next to the mandible and upper maxillary bones. They are located on the lower lateral part of the obit in a irregular diamond shape with a rough surface. The zygomatic bone constitute the highest peak pointing to the front lateral direction. The diamond shaped zygomatic bone has four processes. They are the frontosphenoidal process, the maxillary process, the temporal process and the orbital process. The temporal process reaches backward to the zygomatic process of the temporal bone. These two processes joined together forming the zygomatic arch. The zygomatic arch located on each side of the skull, shaped in an lateral directed arch. Its upper edge is sharp and it can be easily pulped on the side of the face.

zygomatic bone location of the zygomatic bone
The relationship of the zygomatic bone in the human head. The zygomatic bone is in the green line on the right side picture. It is located on the lateral inferior of the obital cave and the most laterally protruding bone in a human face.

 The zygomatic bone categories in flat bone is composed of the surface hard shell and the loose core. The zygomatic bone surface under the skin also known as the cheek surface is convex with a zygomatic facial foramen in the middle of the bone letting the zygomaticofacial nerve and vessels to pass through. Below this foramen is a slightly elevation which indicates the origin of the zygomatic arch. The zygomatic bone surface facing the brain is the temporal surface concaved inner posteriorly.

The frontal bone is located superiorly to the zygomatic bone, the maxilla inferior and proximately, the temporal bone and the sphenoid bone lateral posteriorly. The zygomati bone's anterior margin, smooth and rounded, is part of the circumference of the orbit. Its superior margin, rough, and directed horizontally, the attachment potion of the origin of the masseter muscle.

front view of the left zygomatic bone左侧颧骨后面观
Posterior and anterior view of the left zygomatic bone shows the bone is in a diamond shape with two foramens, four processes and two free edges on it. From the rare point of view the surface of the zygomatic bone is concave and irregular.  Figs from Gray's Anatomy.

The special shape and structure grants the zygomatic bone characters of hard and durability. So the bone can take great impact from different directions, thus providing protection of the face. When a facial injury happens complete fractures scarcely  occurs on body of the zygomatic bone. While fractures often occur on the other facial bones and the articulation line of the other facial bones with the zygomatic bone.

The function of the zygomatic bone

1.Protection function. Its hard nature and the most protruding position provide protection for the important facial organs from the external impact as a car bumper does for a car.

2.Supporting function. The zygomatic bone provides supporting for the whole facial bone and soft tissue structure by articulating with the other connection facial bones. If a zygomatic bone is damaged by injury or other causes, facial bony structure deformity and atrophy of the connecting bones on the infected side may occur because of the lose of the supporting effect from the zygomatic bone during the growing and maturity period.

3.Forming the facial outline. The mid portion of the facial outline is composed of the zygomatic bone. The position, size and degree of protrusion determine the human facial style. The facial outline differences between various ethnic groups mainly comes from the structural character of the zygomatic bone.

4.Participating the formation of the obitus occular. Most part of the lateral and inferior orbit is composed of the zygomatic bone. The strong zygomatic bone protect the eye and provide attachment of the external occulary muscle.

5.Muscle attachment and muscle protection. The inferior edge of the zygomatic bone give origin to the masseter muscle. The masseter muscle, the muscle bulging out when we bite tightly, originates from the inferior edge of the zygomatic bone and runs inferior posteriorly to the terminating point of  the angle of mandible providing power of chewing. Any kind of instability and damage of the zygomatic bone caused by various reasons may interfere the function of the masseter muscle. Forthermore the zygomatic arch, formed by the connection of zygomatic process of the temporal bone and temporal process of the zygomatic bone, protects the underline temporal muscle and separates the muscle from the overlying  skin, so that the muscle movement could not be shown on the face. When we eat movements in the temporal area can be noticed.  However there is no chew related movement can be noticed in the cheek.

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