Anatomy of the Face - Flipbook - Page 43
Sphenoid Bone
The sphenoid bone is the most complex bone of the human body. Because of its shape, it is also known as the "wasp bone". It
makes up most of the middle part of the base of the skull and contributes to the floor of the middle cranial fossa of the skull.
The sphenoid is just one of the twenty-two bones that form the skull and essentially helps to connect the neurocranium to the
facial skeleton. It is a single bone in the midline of the cranial cavity situated posterior to the frontal bone but anterior to the
occipital. Its name derives from the Greek 'sphenoeides,' which means wedge-shaped. It has several foramina and fissures present
in its surface that allow the entry and exit of nerves and blood vessels to and from the cranial cavity. Shaped like a butterfly or a
bat, it has a central body and two lateral wings on either side. It is one of the bones that make up the orbit, in particular, forming
the posterior surface. The articulations of the sphenoid are with 12 skull bones - the frontal (2), parietal (2), ethmoid, zygomatic (2),
temporal, occipital, palatine (2), and vomer bones. There may be several morphological variations in the relationship between
the sphenoid, the ethmoid, and the frontal bone. Together, these give rigidity and stability to the skull making it the ideal place to
house the brain.
The soft tissue structures such are the cranial nerves and parts of the brain are associated with this bone and have intense relations
to it. The sphenoid bone also takes part into the forming of the many of the foramina and canals of the cranium. There are four
main parts to the sphenoid bone: the body (corpus), the lesser and greater wings (alae minores et majores) and the pterygoid
processes. The sella turcica (Latin for Turkish saddle) is a saddle-shaped depression in the body of the sphenoid bone and is home
to pituitary gland.
MUSCLE ATTACHMENTS
The temporalis muscle, which serves as one of the muscles of mastication, is attached to the temporal surface of the greater wing
of the sphenoid.
The upper fibers of the lateral pterygoid muscle attach to the infratemporal surface of the greater wing of the sphenoid as well as
the infratemporal crest.
The lateral pterygoid muscle attaches to the lateral aspect of the lateral plate of the pterygoid process.
The medial pterygoid muscle is attached to the medial aspect of the lateral plate as well as the pterygoid fossa.
The medial division of the pterygoid process, called the medial plate, serves as a site of attachment to the superior pharyngeal
constrictor muscle.
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