Overview
This lecture introduces the basic anatomy of the skull, focusing on the classification and identification of its bones, their articulations, key sutures, anatomical landmarks, and the different aspects/views of the skull.
Skull Bones: Classification and Overview
- The skull is the bony skeleton of the head, composed of 22 bones.
- Of these, 21 are immovable and 1 is movable (the mandible).
- The mandible is movable due to its synovial joint with the temporal bone (temporomandibular joint).
- The 21 immovable bones consist of 8 paired bones (16 total) and 5 unpaired bones.
Paired and Unpaired Skull Bones
- Paired bones (right and left): parietal, temporal, zygomatic, nasal, maxilla, lacrimal, palatine, inferior nasal concha.
- Unpaired bones: frontal, occipital, sphenoid, ethmoid, vomer.
- Sutures (immovable joints) connect the skull bones; only the mandible is connected via a movable joint.
Anatomical Aspects and Views of the Skull
- The skull can be viewed from several standard perspectives:
- Anterior (Norma frontalis)
- Superior (Norma verticalis)
- Lateral (Norma lateralis)
- Posterior (Norma occipitalis)
- Inferior (Norma basalis)
- Cranial cavity (interior)
Norma Verticalis (Superior View)
- Shows 4 bones: frontal (1), parietal (2), occipital (1).
- Major sutures: coronal (frontal & parietal), sagittal (between parietals), lambdoid (parietal & occipital).
- Key landmarks: bregma (coronal & sagittal meet), vertex (midpoint of sagittal), lambda (sagittal & lambdoid meet).
- Fontanels (in newborns): anterior (closes ~18 months), posterior (closes ~6 months).
- Eminences: frontal and parietal (convexities), parietal emissary foramina (vein passage).
Norma Occipitalis (Posterior View)
- Shows occipital, parietal (2), and mastoid part of temporal bones.
- Sutures: lambdoid, occipitomastoid, parietomastoid.
- Features: external occipital protuberance, inion (center), external occipital crest, nuchal lines (highest, superior, inferior).
- Attachments: trapezius (superior nuchal line), nuchal ligament (crest).
Norma Frontalis (Anterior View)
- Shows frontal, zygomatic (2), maxilla (2), mandible, nasal bones (2).
- Important sutures: metopic, frontonasal, frontomaxillary, zygomaticomaxillary, intermaxillary, internasal, zygomaticofrontal.
- Divided into forehead (upper), orbits/nasal cavity (middle), and jaws (lower).
- Special features: frontal eminence, superciliary arches, glabella, nasion (suture intersection), supraorbital notch/foramen (passage for nerve/vessels).
Key Terms & Definitions
- Suture — an immovable joint between skull bones.
- Fontanel — a soft membrane-filled space in the fetal skull.
- Bregma — point where coronal and sagittal sutures meet.
- Lambda — point where sagittal and lambdoid sutures meet.
- Eminence — a convex, prominent area on a bone.
- Protuberance — a projection or bulge on a bone.
- Nasion — intersection of frontonasal and internasal sutures.
- Norma — standard view/aspect of the skull.
Action Items / Next Steps
- Review the names, positions, and connections of all skull bones.
- Memorize key sutures and anatomical landmarks.
- Prepare for detailed study of individual bones in upcoming lectures.