Frontal bone

The frontal bone is an odd, flat, bent bone and partially pneumatized taking part in the formation of cranium and the face. It is articulated with the bone éthmoïde, the jawbone S, the parietal bones, the nasal bones, the Os sphénoïde and the lachrymal bones.

It is composed of a scale forming the dome of the skull and of an orbital blade which is articulated with the facial solid mass while supporting the former cranial pit.

The frontal bone is dug of two frontal sines.

frontal bone is a bone taking part in the formation of cranium and the face.
It is made of 2 parts:

  • a vertical, the scale (or left squameuse ), which corresponds to the area of the face
  • the orbital blade , which enters the composition of the roof of the orbits and the nasal cavities.

Scale

Also called left squameuse . It is the vertical part of the bone.

Surfaces

The face exocrânienne 1 of the scale is convex and usually comprises, in the low part of the line of centers, the remainders of the frontal joining (or sutures metopic); in childhood, this joining divides the bone into 2, this sometimes being able to persist all the life at certain people.
  1. One either side off this joining, butt 3 cm. above the supraorbital margin, has rounded rise, the Frontal eminence (Tuber frontal).
  2. Thesis eminences vary in size in different individuals, are occasionally unsymmetrical, and are especially prominent in Young skulls; the surface off the bone above them is smooth, and covered by the Galea aponeurotica.
  3. frontal Below the eminences, and separated from them by has shallow groove, are two arched rises, the Superciliary arches; thesis are prominent Medially, and are joined to one another by has smooth rise named the Glabella.
  4. male They are larger in the than in the female, and to their dismantles prominence off depend to nap extent one off the size the frontal Air sinuses; 28 prominent ridges are, however, occasionally associated with Small air sinuses.
  5. Beneath each superciliary arch has curved and prominent margin, the Supraorbital margin, which forms the upper boundary off the bases off the Orbit, and separates the orbital Squama from the portion off the bone.
  6. side The leaves off this margin is sharp and prominent, affording to the eye, in that situation, considerable protection from injury; the medial share is rounded.
  7. At the intermediate junction off its medial and thirds has notch, sometimes converted into has Foramen, the Supraorbital notch gold foramen, which transmits the supraorbital vessels and nerve.
  8. has small aperture in the upper share off the notch transmits has vein from the Diploë to join the Supraorbital vein.
  9. The supraorbital margin ends laterally in the Zygomatic process, which is strong and prominent, and articulates with the Zygomatic bone.
  10. Running upward and backward from this process has well-marked line, the Temporal line, which divides into the upper and lower temporal lines, continuous, in the articulated skull, with the corresponding lines one the parietal bone.
  11. temporal The area below and behind the line forms the anterior share off the Temporal fossa, and gives origin to the Temporalis muscle.
  12. Between the supraorbital margins the squama projects downward to has level below that off the zygomatic processes; this portion is known aces the Nasal leaves and present off has rough, uneven interval, the nasal notch, which articulates one either side the middle line with the nasal bone, and laterally with the frontal process off the Maxilla and with the Lacrimal.
  13. The term Nasion is applied to the middle off the Frontonasal sutures. From the center off the notch the nasal nasal process projects downward and forward beneath the bones and frontal processes off the Maxillæ, and supports the Bridge off the nose.
  14. nasal The process ends below in has sharp spine, and one either side off this has off small grooved surface which enters into the formation the roof off the corresponding nasal cavity.
  15. The spine forms share off the Septum off the nose, articulating in face with nasal the crest off the bones and behind with the perpendicular punt off the Ethmoid.

The internal concave surface 2 off the Squama is and present in the upper share off the middle line has vertical groove, the Sagittal sulcus, the edges off which unit below to form has ridge, the frontal crest; the Sulcus lodges the superior sagittal sine, while its margins and the crest afford attachment to the Falx cerebri.

  1. The crest ends below in has small notch which is converted into has foramen, the Foramen cecum, by articulation with the Ethmoid.
  2. This foramen vary in size in different subjects, and is frequently impervious; open when, it transmits has vein from the nose to the sagittal Superior sine.
  3. One either side off the middle line the bone present depressions for the convolutions off the brain, and numerous small furrows for the anterior branches off the middle meningeal vessels.
  4. Several small, irregular fossæ may also Sagittal Be seen one either side off the sulcus, for the reception off the Arachnoid granulations.

Orbital but horizontal leaves

This portion ( leave orbitalis ) consists off two thin triangular punts, the Orbital punts, which form the vaults off the orbits, and are separated from one another by has median gap, the Ethmoidal notch.

Surfaces

  1. orbital The inferior surface 2 off each punt is smooth and concave, and present, laterally, under cover off the Zygomatic process, has shallow depression, the Lacrimal fossa, for the Lacrimal nipple; near the nasal leaves has depression, the Fovea trochlearis, but occasionally has small trochlear spine, for the attachment off the cartilaginous pulley off the Obliquus oculi superior.
  2. The superior surface is convex, and marked by depressions for the convolutions off the Frontal lobes off the Brain, and faint grooves for the meningeal branches off the Ethmoidal vessels.
  3. The Orbital Ethmoidal notch separates the two punt S; it is quadrilateral, and filled, in the articulated skull, by the Cribriform punt off the ethmoid.
  4. present The margins off the notch several half-concealments which, when united with corresponding half-concealments one the upper surface off the ethmoid, supplements the ethmoidal air concealments.
  5. Two grooves cross-country race thesis edges transversely; they are converted into the anterior and posterior ethmoidal canals by the Ethmoid, and open one the medial wall off the Orbit.
  6. The Anterior channel transmits the Nasociliary nerve and Anterior ethmoidal vessels, the posterior, the Posterior ethmoidal nerve and vessels.
  7. In face off the Ethmoidal notch, one either side off the Frontal spine, are the openings off the Frontal air sinuses.
  8. Thesis are two irregular cavities, which extend backward, upward, and lateralward for has variable distance between the two tables off the skull; they are separated from one another by has thin bony septum, which often deviates to one gold other side, with the result that the sinuses are rarely symmetrical.
  9. Absent At birth, they are usually fairly well-developed between the seventh and eighth years, goal only reach to their full size after Puberty.
  10. They vary in size in different let us persons, and are larger in men than in women.
  11. They are lined by Mucous membrane, and each communicates with the corresponding Nasal cavity by means off has passage called the Frontonasal duct.

Borders

To border off the Squama is thick, strongly serrated, bevelled At the expense off the inner table above, where it rests upon the parietal bones, and At the expense off the outer table one either side, where it receives the side presses those bones off; this to border is continued below into has triangular, rough surface, which articulates with the great wing off the Sphenoid. Orbital The posterior borders off the punts are thin and serrated, and articulate with the small wings off the sphenoid.

Structure

The Squama and the Zygomatic processes are very thick, consisting off compact Diploic tissue contained between two Laminæ; the diploic tissue is absent in the areas occupied by the frontal air sinuses. Orbital The portion is thin, translucent, and composed entirely off Compact bone; hence the facility with which instruments edge penetrate the cranium through this share off the orbit; when the frontal sinuses broad are exceptionally they may extend backward for has considerable distance into the orbital portion, which in such boxes also consists off only two Tables.

Ossification

Frontal The bone is ossified 3 in membrane from two primary centers, one for each half, which appear toward the end off the second month off fetal life, one above each supraorbital margin.
  1. From each off thesis centers ossification extends upward to form the corresponding half off the squama, and backward to form the orbital punt.
  2. The spine is ossified from has off even secondary centers, one either side off the middle line; similar centers appear in the nasal leaves and zygomatic processes.
  3. At birth the bone consists off two parts, separated by the frontal sutures, which is usually obliterated, except At its lower share, by the eighth year, goal occasionally persists throughout life.
  4. frontal It is generally maintained that the development off the sinuses begins At the end off the first gold beginning off the second year, goal Onodi' S researches indicate that development begins At birth.
  5. The sinuses are off considerable size by the seventh gold eighth year, goal C not attain to their full proportions until after puberty.

Articulations

Frontal The Articulates with twelve bones: the Sphenoid, the Ethmoid, the two Parietal S, the two Nasals, the two Maxillæ, the two Lacrimals, and the two Zygomatics.

See also

  • Bone terminology
  • Terms for anatomical hiring

Category: Skeletal system

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