The pterygoid processes of the sphenoid (from Greek ''pteryx'', ''pterygos'', "wing"), one on either side, descend perpendicularly from the regions where the
body and the
greater wings of the
sphenoid bone
The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of the occipital bone. The sphenoid bone is one of the seven bones that articulate to form the o ...
unite.
Each process consists of a
medial pterygoid plate and a
lateral pterygoid plate
The pterygoid processes of the sphenoid (from Greek ''pteryx'', ''pterygos'', "wing"), one on either side, descend perpendicularly from the regions where the body and the greater wings of the sphenoid bone unite.
Each process consists of a me ...
, the latter of which serve as the origins of the
medial and
lateral pterygoid muscles. The medial pterygoid, along with the
masseter
In human anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it ...
allows the jaw to move in a vertical direction as it contracts and relaxes. The lateral pterygoid allows the jaw to move in a horizontal direction during mastication (chewing). Fracture of either plate are used in clinical medicine to distinguish the
Le Fort fracture classification for high impact injuries to the
sphenoid and
maxillary bones.
The superior portion of the pterygoid processes are fused anteriorly; a vertical groove, the
pterygopalatine fossa
In human anatomy, the pterygopalatine fossa (sphenopalatine fossa) is a fossa in the skull. A human skull contains two pterygopalatine fossae—one on the left side, and another on the right side. Each fossa is a cone-shaped paired depression deep ...
, descends on the front of the line of fusion. The plates are separated below by an angular cleft, the
pterygoid notch, the margins of which are rough for articulation with the pyramidal process of the
palatine bone
In anatomy, the palatine bones () are two irregular bones of the facial skeleton in many animal species, located above the uvula in the throat. Together with the maxillae, they comprise the hard palate. (''Palate'' is derived from the Latin ...
.
The two plates diverge behind and enclose between them a V-shaped fossa, the
pterygoid fossa, which contains the
medial pterygoid muscle
The medial pterygoid muscle (or internal pterygoid muscle), is a thick, quadrilateral muscle of the face. It is supplied by the mandibular branch of the trigeminal nerve (V). It is important in mastication (chewing).
Structure
The medial pteryg ...
and the
tensor veli palatini
The tensor veli palatini muscle (tensor palati or tensor muscle of the velum palatinum) is a broad, thin, ribbon-like muscle in the head that tenses the soft palate.
Structure
The tensor veli palatini is found anterior-lateral to the levator ve ...
.
Above this fossa is a small, oval, shallow depression, the
scaphoid fossa, which gives origin to the tensor veli palatini.
The anterior surface of the pterygoid process is broad and triangular near its root, where it forms the posterior wall of the pterygopalatine fossa and presents the anterior orifice of the
pterygoid canal.
In many mammals it remains as a separate bone called the
pterygoid bone
The pterygoid is a paired bone forming part of the palate of many vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and ...
.
Its name is Greek for "resembling a fin or wing", from its shape.
Medial pterygoid plate
The medial pterygoid plate (or medial pterygoid lamina) of the
sphenoid bone
The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of the occipital bone. The sphenoid bone is one of the seven bones that articulate to form the o ...
is a horse-shoe shaped
process that arises from its underside.
It is narrower and longer than the
lateral pterygoid plate
The pterygoid processes of the sphenoid (from Greek ''pteryx'', ''pterygos'', "wing"), one on either side, descend perpendicularly from the regions where the body and the greater wings of the sphenoid bone unite.
Each process consists of a me ...
and curves lateralward at its lower extremity into a hook-like process, the
pterygoid hamulus, around which the tendon of the
tensor veli palatini
The tensor veli palatini muscle (tensor palati or tensor muscle of the velum palatinum) is a broad, thin, ribbon-like muscle in the head that tenses the soft palate.
Structure
The tensor veli palatini is found anterior-lateral to the levator ve ...
glides.
The lateral surface of this plate forms part of the
pterygoid fossa, the medial surface constitutes the lateral boundary of the
choana
The choanae (singular choana), posterior nasal apertures or internal nostrils are two openings found at the back of the nasal passage between the nasal cavity and the throat in tetrapods, including humans and other mammals (as well as crocodili ...
or posterior aperture of the corresponding nasal cavity.
Superiorly the medial plate is prolonged on to the under surface of the body as a thin lamina, named the vaginal process, which articulates in front with the
sphenoidal process of the palatine and behind this with the ''ala'' (wing) of the
vomer
The vomer (; lat, vomer, lit=ploughshare) is one of the unpaired facial bones of the skull. It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right max ...
.
The angular prominence between the posterior margin of the vaginal process and the medial border of the
scaphoid fossa is named the
pterygoid tubercle, and immediately above this is the posterior opening of the
pterygoid canal.
On the under surface of the vaginal process is a furrow, which is converted into a canal by the sphenoidal process of the
palatine bone
In anatomy, the palatine bones () are two irregular bones of the facial skeleton in many animal species, located above the uvula in the throat. Together with the maxillae, they comprise the hard palate. (''Palate'' is derived from the Latin ...
, for the transmission of the pharyngeal branch of the
internal maxillary artery and the pharyngeal nerve from the
sphenopalatine ganglion
The pterygopalatine ganglion (aka Meckel's ganglion, nasal ganglion, or sphenopalatine ganglion) is a parasympathetic ganglion found in the pterygopalatine fossa. It is largely innervated by the greater petrosal nerve (a branch of the facial ner ...
.
The
pharyngeal aponeurosis is attached to the entire length of the posterior edge of the medial plate, and the
constrictor pharyngis superior takes origin from its lower third.
Projecting backward from near the middle of the posterior edge of this plate is an angular process, the processus tubarius, which supports the pharyngeal end of the Eustachian tube.
The anterior margin of the plate articulates with the posterior border of the vertical part of the palatine bone.
In many animals it is a separate bone called the
pterygoid bone
The pterygoid is a paired bone forming part of the palate of many vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and ...
.
Lateral pterygoid plate
The lateral
pterygoid plate of the
sphenoid (or lateral lamina of pterygoid process) is broad, thin, and everted and forms the lateral part of a horseshoe like process that extends from the inferior aspect of the sphenoid bone, and serves as the origin of the lateral pterygoid muscle, which functions in allowing the mandible to move in a lateral and medial direction, or from side-to-side.
Its lateral surface forms part of the medial wall of the infratemporal fossa, and gives attachment to the
lateral pterygoid muscle; its medial surface forms part of the pterygoid fossa, and gives attachment to the
medial pterygoid muscle
The medial pterygoid muscle (or internal pterygoid muscle), is a thick, quadrilateral muscle of the face. It is supplied by the mandibular branch of the trigeminal nerve (V). It is important in mastication (chewing).
Structure
The medial pteryg ...
. Posterior edge is sharp, and often has sharp projection -
pterygospinous process (Civinini process).
References
External links
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Bones of the head and neck