Anatomic.us > Skeletal System > Axial Skeleton Skull

Frontal Bone

It is one of the flat bones of the skull (head bone). It is present at the anterior end of the skull, just above the orbits of eye (sockets for eye). It forms the forehead, the roof of nasal cavity and the upper part of orbital cavity of the eyes. It resembles the cockle shell in shape. It covers the brain and structures present beneath and inside it.

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Frontal Bone

GENERAL BONY FEATURES OF THE BONE

For the sake of study, we can divide it into three parts:

The vertical portion (also called squama) that forms the forehead. Its external surface is rough and convex. Its internal surface is concave. It has thick borders. This part has following features:

  • Almost 3 cm above the upper margin of the upper border of the orbits of eye, there are two rounded elevations present, which are called frontal eminence.

  • The superciliary arches (one on each side of face) are present below the frontal eminences. They are separated from these eminences by a shallow groove.

  • Glabella is a smooth elevation that is present medially, on front of the face, between the two superciliary arches. It is formed by joining of the two superciliary arches medially.

  • Supraorbital margins are curved and prominent margins that are present under each superciliary arch. These form the upper boundary of the orbital sockets. It divides the squamous potion from the orbital portion of the frontal bone.

  • Supraorbital foramen is an oval opening that is present in supraorbital margin. It transmits the vessels and nerves.

 

The nasal portion of frontal bone is the part of frontal bone between the two supraorbital margins and extends downwards to form the root of the nose.

  • It forms the root of the nose by making a joint with the nasal bones and the frontal process of maxilla.

  • It has a nasal notch that articulates on both sides of midline with the nasal bone.

  • The point, where nasal part of frontal bone and nasal bones meet is marked by frontonasal suture.

  • The middle point of frontonasal suture is called nasion.

 

The orbital (horizontal) part of frontal bone is the part that takes part in the formation of roof of each orbit of the face and nasal cavities.

  • This portion has two, thin triangular plates that are called orbital plates.

  • The two orbital plates are separated by from one another medially, by a gap, which is called the ethmoidal notch.

  • There are two air filled cavities present, which are called the frontal sinuses.

 

SOME CLINICAL ASPECTS

 

Pterion is a point where temporal, frontal, parietal and sphenoid bones meet. It is the weakest point of the skull hence it is very much liable to fracture. On fracture, the middle meningeal artery that travels below the pterion is ruptured. This results in collection of blood inside the skull thus creating increased intracranial pressure and is dangerous.

Any physical trauma to the face may result in fracture of frontal bone, frontal sinuses or upper border of the orbits of eye. In case the orbit of eye is involved, this may result in the blackening of eye due to collection of blood in eye region, under the effect of gravity, hence called the black eye.


GENERAL BONY FEATURES OF THE BONE

For the sake of study, we can divide it into three parts:

The vertical portion (also called squama) that forms the forehead. Its external surface is rough and convex. Its internal surface is concave. It has thick borders. This part has following features:

  • Almost 3 cm above the upper margin of the upper border of the orbits of eye, there are two rounded elevations present, which are called frontal eminence.

  • The superciliary arches (one on each side of face) are present below the frontal eminences. They are separated from these eminences by a shallow groove.

  • Glabella is a smooth elevation that is present medially, on front of the face, between the two superciliary arches. It is formed by joining of the two superciliary arches medially.

  • Supraorbital margins are curved and prominent margins that are present under each superciliary arch. These form the upper boundary of the orbital sockets. It divides the squamous potion from the orbital portion of the frontal bone.

  • Supraorbital foramen is an oval opening that is present in supraorbital margin. It transmits the vessels and nerves.

 

The nasal portion of frontal bone is the part of frontal bone between the two supraorbital margins and extends downwards to form the root of the nose.

  • It forms the root of the nose by making a joint with the nasal bones and the frontal process of maxilla.

  • It has a nasal notch that articulates on both sides of midline with the nasal bone.

  • The point, where nasal part of frontal bone and nasal bones meet is marked by frontonasal suture.

  • The middle point of frontonasal suture is called nasion.

 

The orbital (horizontal) part of frontal bone is the part that takes part in the formation of roof of each orbit of the face and nasal cavities.

  • This portion has two, thin triangular plates that are called orbital plates.

  • The two orbital plates are separated by from one another medially, by a gap, which is called the ethmoidal notch.

  • There are two air filled cavities present, which are called the frontal sinuses.

 

SOME CLINICAL ASPECTS

 

Pterion is a point where temporal, frontal, parietal and sphenoid bones meet. It is the weakest point of the skull hence it is very much liable to fracture. On fracture, the middle meningeal artery that travels below the pterion is ruptured. This results in collection of blood inside the skull thus creating increased intracranial pressure and is dangerous.

Any physical trauma to the face may result in fracture of frontal bone, frontal sinuses or upper border of the orbits of eye. In case the orbit of eye is involved, this may result in the blackening of eye due to collection of blood in eye region, under the effect of gravity, hence called the black eye.

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