Bone: Parietal bone
Figure 1 : Left parietal bone. Outer surface.
Figure 2 : Left parietal bone. Inner surface.
Latin	os parietale
Gray's	subject #32 133
MeSH	A02.835.232.781.651

The parietal bones are bones in the human skull and form, by their union, the sides and roof of the cranium. Each bone is irregularly quadrilateral in form, and has two surfaces, four borders, and four angles. Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. ... Trinomial name Homo sapiens sapiens Linnaeus, 1758 Humans, or human beings, are bipedal apes belonging to the mammalian species Homo sapiens (Latin for wise man or knowing man) under the family Hominidae (known as the great apes). ... It has been suggested that temporal fenestra be merged into this article or section. ...

Surfaces

External

The external surface [Fig. 1] is convex, smooth, and marked near the center by an eminence, the parietal eminence (tuber parietale), which indicates the point where ossification commenced. The external surface of the parietal bone is convex, smooth, and marked near the center by an eminence, the parietal eminence (parietal tuber), which indicates the point where ossification commenced. ... Ossification is the process of bone formation, in which connective tissues, such as cartilage are turned to bone or bone-like tissue. ...

Crossing the middle of the bone in an arched direction are two curved lines, the superior and inferior temporal lines; the former gives attachment to the temporal fascia, and the latter indicates the upper limit of the muscular origin of the temporalis. The temporalis muscle is one of the muscles of mastication. ...

Above these lines the bone is covered by the galea aponeurotica (epicranial aponeurosis); below them it forms part of the temporal fossa, and affords attachment to the temporalis muscle. The Galea aponeurotica is connective tissue at the back of the head. ...

At the back part and close to the upper or sagittal border is the parietal foramen, which transmits a vein to the superior sagittal sinus, and sometimes a small branch of the occipital artery; it is not constantly present, and its size varies considerably. The superior sagittal sinus lies within the superior border of the falx cerebri, a two-layered dural structure separating the two cerebral hemispheres. ... occipital artery ...

Internal

The internal surface [Fig. 2] is concave; it presents depressions corresponding to the cerebral convolutions, and numerous furrows for the ramifications of the middle meningeal artery; the latter run upward and backward from the sphenoidal angle, and from the central and posterior part of the squamous border. In geometry, concavity is a property of certain geometric figures, and in calculus, a property of certain graphs of functions. ... The middle meningeal artery is typically the first branch of the first part (retromandibular part) of the maxillary artery; one of the two terminal branches of the external carotid artery. ...

Along the upper margin is a shallow groove, which, together with that on the opposite parietal, forms a channel, the sagittal sulcus, for the superior sagittal sinus; the edges of the sulcus afford attachment to the falx cerebri. The internal surface of the squama frontalis of the frontal bone is concave and presents in the upper part of the middle line a vertical groove, the sagittal sulcus, the edges of which unite below to form a ridge, the frontal crest; the sulcus lodges the superior sagittal sinus, while... The superior sagittal sinus lies within the superior border of the falx cerebri, a two-layered dural structure separating the two cerebral hemispheres. ... The falx cerebri (Latin: scythe of the brain) is an extension of the protective dura mater that projects into the longitudinal fissure that seperates the two cerebral hemispheres. ...

Near the groove are several depressions, best marked in the skulls of old persons, for the arachnoid granulations (Pacchionian bodies). Arachnoid granulations (and arachnoid villi) are small protrusions of the arachnoid (the thin second layer covering the brain) through the dura (the thick outer layer). ...

In the groove is the internal opening of the parietal foramen when that aperture exists.

Borders

• The sagittal border, the longest and thickest, is dentated and articulates with its fellow of the opposite side, forming the sagittal suture.

• The squamous border is divided into three parts: of these:
  • the anterior is thin and pointed, bevelled at the expense of the outer surface, and overlapped by the tip of the great wing of the sphenoid;
  • the middle portion is arched, bevelled at the expense of the outer surface, and overlapped by the squama of the temporal;
  • the posterior part is thick and serrated for articulation with the mastoid portion of the temporal.

• The frontal border is deeply serrated, and bevelled at the expense of the outer surface above and of the inner below; it articulates with the frontal bone, forming half of the coronal suture. That point where the coronal suture intersects with the sagittal suture forms a T-shape and is called the bregma.

• The occipital border, deeply denticulated, articulates with the occipital, forming half of the lambdoid suture. That point where the sagittal suture intersects the lambdoid suture is called the lambda, because of its resemblance to the Greek letter.

Mastoid can mean: Of, relating to or in the region of the mastoid process. ... The temporal bones (os temporales) are situated at the sides and base of the skull. ... The frontal bone (os frontale, TA: A02. ... The coronal suture (sutura coronalis) is a dense, fibrous connective tissue joint that separates the frontal and parietal bones of the skull. ... The occipital bone [Fig. ... The lambdoid suture (sutura lambdoidea) is a dense, fibrous connective tissue joint that separates the parietal and temporal bones of the skull from the occipital bone. ... Look up Λ, λ in Wiktionary, the free dictionary. ...

Angles

• The frontal angle is practically a right angle, and corresponds with the point of meeting of the sagittal and coronal sutures; this point is named the bregma; in the fetal skull and for about a year and a half after birth this region is membranous, and is called the anterior fontanelle.

• The sphenoidal angle, thin and acute, is received into the interval between the frontal bone and the great wing of the sphenoid. Its inner surface is marked by a deep groove, sometimes a canal, for the anterior divisions of the middle meningeal artery.

• The occipital angle is rounded and corresponds with the point of meeting of the sagittal and lambdoidal sutures—a point which is termed the lambda; in the fetus this part of the skull is membranous, and is called the posterior fontanelle.

• The mastoid angle is truncated; it articulates with the occipital bone and with the mastoid portion of the temporal, and presents on its inner surface a broad, shallow groove which lodges part of the transverse sinus. The point of meeting of this angle with the occipital and the mastoid part of the temporal is named the asterion.

The anterior fontanelle (bregmatic fontanelle, frontal fontanelle) is the largest, and is placed at the junction of the sagittal suture, coronal suture, and frontal suture; it is lozenge-shaped, and measures about 4 cm. ... The middle meningeal artery is typically the first branch of the first part (retromandibular part) of the maxillary artery; one of the two terminal branches of the external carotid artery. ... The posterior fontanelle (or occipital fontanelle) is triangular in form and is situated at the junction of the sagittal suture and lambdoidal suture. ... In Greek mythology, Asterion (ruler of the stars), called king of Crete, was the consort of Europa and stepfather of her sons by Zeus, who had to assume the form of the Cretan bull of the sun to accomplish his role: Minos the just king in Crete, Rhadamanthus, presiding over...

Ossification

The parietal bone is ossified in membrane from a single center, which appears at the parietal eminence about the eighth week of fetal life.

Ossification gradually extends in a radial manner from the center toward the margins of the bone; the angles are consequently the parts last formed, and it is here that the fontanelles exist.

Occasionally the parietal bone is divided into two parts, upper and lower, by an antero-posterior suture.

Additional images

Facial bones.	Cranial bones	Sphenoid bone visible center right.	Side view of the skull. Image File history File links Gray188. ...
Left infratemporal fossa. Image File history File links Gray189. ...	Base of the skull. Upper surface. Image File history File links Download high resolution version (719x1057, 150 KB) File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...	Sagittal section of skull. Image File history File links Gray194. ...

See also

• Bone terminology
• Terms for anatomical location
• It is one of the areas of the head that can be used as a weapon in a headbutt.

This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained herein may be outdated. Please edit the article if this is the case, and feel free to remove this notice when it is no longer relevant. Grays Anatomy illustration of a human femur. ... In zootomy, several terms are used to describe the location of organs and other structures in the body of bilateral animals. ... A headbutt to the chest A headbutt is a strike with the head, typically involving the use of robust parts of the cranium as area of impact. ... The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ... An illustration from the 1918 edition Henry Grays Anatomy of the Human Body, commonly known as Grays Anatomy, is an anatomy textbook widely regarded as a classic work on human anatomy. ...