The parietal bone ( lat.os parietále ) is the paired bone of the medulla of the skull . The right and left parietal bones are connected by a suture and form the upper and lateral parts of the cranial vault. The parietal bones are also connected by sutures to the frontal , occipital , temporal and sphenoid bones.
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Content
Description
The parietal bone has the shape of a convex outward quadrangular plate in which there are two surfaces, the outer and inner, four edges, the frontal, sagittal, occipital and scaly, and the four corners, frontal, occipital, mastoid and sphenoid. At the edges, the parietal bones are connected with each other and with four other bones by six sutures: coronoid, sagittal, lambdoid, parietal-mastoid, scaly and sphenoid-parietal [1] .
Surfaces
The outer surface , fácies extérna [2] , is smooth and convex, with the parietal tubercle , túber parietále protruding in its center, from which the ossification of the parietal bone begins. Slightly lower than the tubercle, lying one below the other, the parietal bone arches intersect two curved lines: the upper temporal line , línea temporális supérior and the lower temporal line , línea temporális inférior . The first is a continuation of the same line of the frontal bone, and the temporal fascia , fáscia temporális is attached to it; the temporal muscle, músculus temporális , is attached to the second line. The upper part of the outer surface of the parietal bone is covered with a tendon helmet . In the back part near the upper edge there can be a parietal opening , forámen parietále , which is a graduate , emissárium (through it a venous parietal graduate leaves and sometimes the branch of the occipital artery comes to the dura mater).
The inner surface , fácies intérna [3] , is concave, finger impressions are clearly visible on it - fingerprints of the adjacent dura mater - and arterial grooves, súlci arteriósi - traces of the adjoining branches of the middle meningeal artery that extend up and back from the wedge-shaped corner and the back of the scaly the edges. Along the upper edge of the inner surface passes a clearly visible groove of the superior sagittal sinus. On the whole skull, it is connected to the furrow of the paired parietal bone and forms the complete furrow of the superior sagittal sinus , súlcus sínus sagittális superióris . A large crescent process of the dura mater , fálx cérebri májor, is attached to the edges of this groove. On the sides of the furrow, especially noticeable in old age, there are shallow dimples of granulations, fovéolae granuláres - imprints of granulations of the arachnoid membrane of the brain. In the area of the mastoid angle there is a sigmoid sinus groove, sulcus sínus sigmoídei , on the whole skull passing along the inner surface of three adjacent bones, temporal, parietal and occipital.
Edges and seams
The sagittal region (upper), márgo sagittális [3] is the longest. Along this edge, the right and left parietal bones are connected to each other by a serrated sagittal suture , sutúra sagittális .
The occipital margin (posterior), márgo occipitális [4] , is also serrated, combining with the lambdoid margin of the occipital bone, it forms a lambdoid suture , sutúra lambdoídea .
The scaly edge (lower), márgo squamósus [4] , is divided into three sections. The front edge is thin and pointed, it is beveled due to the outer surface and is covered by the edge of the large wing of the sphenoid bone. The middle section is curved and also beveled, it is covered with scales of the temporal bone. The posterior portion is thicker than others, it is connected by teeth with the mastoid process of the temporal bone. In these three areas, the scaly margin forms three sutures: the sphenoid-parietal suture , sutúra sphenoparietális , the scaly seam , sutúra squamósa , and the mastoid-parietal suture , sutúra parietomastoídea .
The frontal margin (anterior), márgo frontális [4] , is connected by teeth with the parietal edge of the frontal bone scales, forming a coronal suture , sutúra coronális .
Corners and Feature Points
The frontal angle (anteroposterior), ángulus frontális [4] , is almost straight, located at the intersection of the sagittal and frontal margins. At the intersection of the sagittal and coronal sutures, a special point of bregma , bregma , is distinguished . During the first two years of the baby’s life, the frontal and parietal bones do not fuse to the end, this site does not ossify and remains webbed. It is called the anterior fontanel , fontículus antérior .
Occipital angle (posterior), ángulus occipitális [4] , obtuse, rounded, located at the intersection of the sagittal and occipital margins. In the place where the sagittal suture and lambdoid sutures meet, a special point lambda , lambda , stands out. On the skull of a newborn, there is a posterior fontanel , fontículus postérior , which usually closes at the beginning of the first year of life.
The mastoid angle (posterior lower), ángulus mastoídeus [4] , is obtuse, located at the intersection of the occipital and scaly margins. Here the parietal bone is connected with the occipital bone and with the mastoid process of the temporal bone. In the place of convergence of the lambd - shaped , occipital-mastoid and parietal-mastoidal sutures, a special point, asterion , stands out . On the skull of a newborn is a mastoid fontanel , fontículus mastoídeus , which usually closes immediately after birth or by two or three months of the baby’s life.
The tapered angle (anteroposterior), ángulus sphenoidális [4] , acute, located at the intersection of the frontal and scaly edges. At the convergence of the frontal and scaly sutures, a special point pterion , pterion , stands out. On the skull of the newborn, there is a wedge-shaped fontanel , fontículus sphenoidális , which also usually closes at the same time as the mastoid fontanel.
Development
The parietal bone is primary, it develops from connective tissue through direct ossification . Two ossification points, one above the other, form at the site of the future parietal tubercle, around the seventh week of fetal development. They quickly merge, and ossification rays radially propagate from the center of ossification towards the edges. The corners of the parietal bone, being the most distant from the center, are ossified by the latter, and in the newborn, fontanelles remain in their place [5] . Sometimes the parietal bone can be divided by the anteroposterior suture into the upper and lower parts or have an even more complex structure, being divided into several parts [6] .
In the case of premature closure of the sagittal suture, scaphocephaly (sagittal craniosynostosis) occurs: the skull begins to elongate in the anteroposterior direction and narrows in the temporal and parietal region. This pathology is treated surgically [7] .
Image Gallery
Parietal Bone Animation
Parietal bone, location in the skull
Parietal bone (highlighted in yellow)
Parietal bone with temporal fascia and muscle
See also
- Anatomical terminology
Notes
- ↑ All names are given in accordance with , adopted in 1998. Russian-language terms are compared with the official list of Russian equivalents (see references).
- ↑ Sinelnikov et al., 2009 , p. 39.
- ↑ 1 2 Sinelnikov et al., 2009 , p. 40.
- ↑ 1 2 3 4 5 6 7 Sinelnikov et al., 2009 , p. 41.
- ↑ Standring, 2015 , p. 478.
- ↑ Bergman RA, Afifi AK, Miyauchi R. Parietal Bone . Illustrated Encyclopedia of Human Anatomic Variation: Opus V: Skeletal Systems: Cranium . Anatomy Atlases. Date of treatment June 10, 2017.
- ↑ Koltunov D.E., Belchenko V.A. Methods of treating scaphocephaly in children with syndromic craniosynostosis : [ Russian ] // Pediatrics : Journal. - 2013. - T. 92, No. 5. - S. 163-164. - ISSN 1990-2182 .
Literature
- International Anatomical Terminology / Ed. L. L. Kolesnikova . - M .: Medicine , 2003 .-- 424 p. - 5,000 copies. - ISBN 5-225-04765-3 . - ISBN 3-13-114361-4 . - ISBN 3-13-115251-6 .
- Sinelnikov R. D. , Sinelnikov Ya. R., Sinelnikov A. Ya. Atlas of human anatomy: in 4 volumes . - 7th ed., Revised. - M .: Novaya Volna, Umerenkov, 2009.- T. 1. - S. 39–41. - 344 p. - ISBN 978-5-7864-0199-9 .
- Standring S. Gray's Anatomy: The Anatomical Basis of Clinical Practice . - 41st Edition. - L .: Elsevier Health Sciences, 2015 .-- P. 477—478. - 1592 p. - ISBN 978-0-7020-5230-9 .
- White TD, Black MT, Folkens PA Human Osteology . - 3rd Edition. - N. Y .: Academic Press , 2011 .-- P. 64-66. - 662 p. - ISBN 978-0-12374134-9 .