Parietal Bone
Os Parietale
location_on Superior and lateral aspects of the cranium
The paired parietal bones form the majority of the calvaria, the roof and sides of the cranium. Each parietal bone is a gently curved quadrilateral plate with four borders and four angles. The inner surface bears grooves for the middle meningeal artery, which is clinically significant in epidural hematomas.
Key Anatomical Features
- Parietal eminence marks the point of maximum convexity on the external surface
- Superior and inferior temporal lines provide attachment for temporalis fascia and muscle
- Groove for the middle meningeal artery branches across the inner surface
- Parietal foramen near the sagittal suture transmits an emissary vein
- Four borders articulate with frontal, occipital, temporal, and the opposite parietal bone
Muscle Attachments
| Muscle | Attachment | Action |
|---|---|---|
| Temporalis | Inferior temporal line | Elevates and retracts the mandible |
| Superior auricular muscle | Temporal fascia over parietal bone | Draws the auricle superiorly |
| Epicranial aponeurosis | Covers the external surface | Connects frontalis and occipitalis muscles |
| Occipitalis | Superior nuchal line extending onto parietal region | Draws the scalp posteriorly |
Joints and Articulations
| Joint | Type | Connects to |
|---|---|---|
| Sagittal suture | Fibrous suture | Opposite parietal bone |
| Coronal suture | Fibrous suture | Frontal bone |
| Lambdoid suture | Fibrous suture | Occipital bone |
Common Pathologies
Epidural hematoma
Rupture of the middle meningeal artery beneath the parietal bone creates a lens-shaped blood collection between the skull and dura mater, a neurosurgical emergency.
Parietal fracture
The most common site of skull fracture due to the thin bone over the middle meningeal artery region. Linear fractures may cross vascular grooves.
Craniosynostosis (sagittal)
Premature fusion of the sagittal suture produces scaphocephaly, an elongated narrow skull shape, and is the most common single-suture craniosynostosis.
Clinical Relevance
The parietal bone is the most frequently fractured skull bone. A temporal region blow can fracture the thin bone and rupture the middle meningeal artery, causing epidural hematoma with the classic lucid interval. The parietal foramen emissary vein connects scalp veins to the superior sagittal sinus, providing a potential route for infection spread.
Development and Ossification
Each parietal bone ossifies intramembranously from a single center that appears near the parietal eminence around the 7th fetal week. The corners of the bone are the last to ossify, with fontanelles persisting at the angles until about 18 months of age.
Did You Know?
- The word parietal comes from the Latin paries meaning wall
- The anterior fontanelle at the junction of the parietal bones is used to assess intracranial pressure in infants
- Trepanation, one of the oldest surgical procedures, was most commonly performed on the parietal bone
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