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Bones of Head

The bones of head include:

Parietal Bone

The parietal bone creates the major portion of the vault of the skull and is a curved plate of bone. It’s quadrilateral in shape.

The parietal bone has:

 

  • 2 surfaces: external and internal.
  • 4 edges: superior (sagittal), inferior, anterior and posterior.
  • 4 angles: frontal, sphenoidal, occipital and mastoid.

 

Sometimes, the parietal bone is split into 2 parts: upper and lower by an anomalous anteroposterior suture. The physician may mistake this state using a fracture. But it can be ruled out easily as the anomalous parietal suture is bilateral.

Sphenoid Bone

It is an unpaired bone situated at the base of the skull. Its resemblance is of the shape of a butterfly or bat with outstretched wings.

It is composed of the following 7 parts:

  • A body.
  • 2 lesser wings.
  • 2 greater wings.
  • 2 pterygoid processes.
  • 2 pterygoid processes represent the legs of the bat.

The craniopharyngeal canal sometimes exists in the floor of the pituitary fossa. It symbolizes the remnant of Rathke’s pouch which creates the anterior lobe of the pituitary gland

The observation of sella turcica in radiographs of skull is of great clinical importance because pathological changes in it represent intracranial space-occupying lesions like pituitary tumor.

Zygomatic Bone

The zygomatic bone is also referred to as malar bone because it forms the visibility of the cheek that is termed mala in Latin.

The zygomatic bone is composed of the following 3 parts:

  • A body
  • 2 processes: frontal and temporal.

It presents 3 surfaces, viz. orbital surface, lateral surface and temporal surface.

  • A part of the lateral wall and floor of the Orbital surface. It’s a foramen, the zygomatico-orbital foramen, which carries a zygomatic nerve.
  • Lateral surface is subcutaneous and presents a zygomaticofacial foramen via which zygomatico-facial nervecomes out.
  • Temporal surface creates the part of anterior wall of the temporal fossa and presents a zygomaticotemporal foramen, which carries the zygomaticotemporal nerve.

Mandible

It is the lower jaw bone. It has lower teeth and is the biggest, strongest and lowermost bone of the face.

It is composed of 3 parts: a horizontally-oriented body and 2 vertically oriented rami and is horseshoe shaped bone.

Ramus of the mandible is more or less a quadrilateral vertical plate of bone that projects upwards from the posterior part of the body.

The meeting point between posterior and inferior edges of the ramus of mandible is named the angle of the mandible.

Maxilla

There are totally 2 maxillae, 1 on every side of midline. The 2 together create the upper jaw. They have uneven pneumatic bone structure.

It is the second largest bone of the face. It consists of 5 parts: a body and 4 processes.

Maxilla is pyramidal in shape and has a large cavity inside called maxillary air sinus. The body presents the subsequent 4 surfaces:

  • Nasal (medial) surface
  • Orbital (superior) surface
  • Temple (posterior) surface
  • Anterior (facial) surface

Frontal Bone

The frontal bone lies in the region of the brow. Its shape is similar to a shell.

It includes the following 6 parts:

Squamous part (main part)

The frontal bone ossifies in membrane. The primary centers appear 1 for every half of the frontal bone in the region of frontal tuberosity. At birth, frontal bone is created from 2 halves, divided by a median frontal suture. The union between the 2 halves starts at second year and generally finishes by the end of the eighth year.


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By | 2018-02-01T06:36:57+00:00 November 4th, 2017|Anatomy, Bones and Cartilages, Head and Neck|0 Comments