Skull Flashcards
Major parts of skull
2 parts of the cranium: neurocranium and
visceral cranium: Neurocranium (cranial vault) = bony covering of brain and its meninges, contains proximal parts of cranial nerves and vasculature of brain.
1. Calvarium (skullcap – a dome-like roof)
2. Basi cranium (cranial base)
bones - frontal, ethmoid, sphenoid,
occipital and 2 paired: parietals and
temporals)
Visceral cranium
bones of facial skeleton (derived from mesenchyme of embryonic pharyngeal arches).
- Forms A part of cranium.
- Consists of bones that surround mouth, nose, and most of orbits.
bones - 3 unpaired (mandible, ethmoid, vomer), 6 paired bones (maxillae, I nasal conchae, zygomatics, palatines, nasals, and lacrimals)
Frontal bone
Forms the forehead, roofs of orbits, and superciliary arches S to orbital apertures.
- Contains frontal paranasal sinuses
Parietal bones
Forms S and L parts of skull, 4 largest sutures of cranium are located at sites where PBs articulate with other cranial bones
4 sites of cranium (PBs)
- coronal suture – runs in coronal plane, is A where Pbs meet frontal bone.
- squamous suture – occurs where each PB
meets temporal bone I - sagittal suture – occurs where right and left PBs meet S in the midline.
- lambdoid suture – occurs where PBs meet OB P
Sutural bones
Small bones, occur within sutures, especially in lambdoid suture
- Irregular in shape, size, and location
- Sutural (wormian) bones develop between major cranial bones during fetal period, persist throughout life
Occipital bone
Forms P portion of cranium & cranial base.
- Articulates with TBs and PBs
- foramen magnum is located at its base – I part of brain connects w/spinal cord
OB features
Occipital condyles – articulate w/C1 vertebra.
- External occipital protuberance
- Nuchal lines – anchor muscles of neck and back
Temporal bones
Lie I to PBs
- Forms IL region of skull and parts of cranial floor.
- Houses ear and associated structures: external acoustic meatus opening
Sphenoid bone
Spans width of cranial floor
- Situated between bones of cranial vault and those of face, central body and 3 paired processes:
- greater wings
- lesser wings
- pterygoid processes or plates (M & L)
Ethmoid bone
light and spongy bone, lies between nasal and sphenoid bones.
- Forms most of M bony region between NC and orbit
Mandible
largest and strongest facial bone
2 parts of mandible
- horizontal body – anchors lower teeth and forms chin.
- 2 upright rami – project SL from body, mandibular angle.
- coronoid process – provides insertion for t temporalis (a muscle of mastication).
- mandibular condyle – articulates with TB to form temporomandibular joint
Maxillary bones
Forms UJ and central part of facial skeleton.
- Functionally, hold tooth roots and form most of nasal aperture and floor, most of HP, and floors of orbits.
- Contains maxillary sinuses – largest paranasal air sinuses
Zygomatic bones
forms L wall of orbits and prominences of cheeks
Nasal bones
form bridge of nose
Lacrimal bones
delicate bones located in M orbital walls
Palatine bones
P to maxillae and complete P part of HP
Vomer and I nasal conchae
Vomer - slender bone that lies in NC and forms I part of nasal septum.
Inferior nasal conchae – thin, curved bones that project M from L walls of NC
Skull geography
Prominent bony ridges internally divide
neurocranium into distinct fossae: A, middle, and P
Small cavities in skull
middle and inner ear cavities – in L aspect of skull.
NC – lies in and P to nose.
orbital cavities – house the eyeballs
air-filled sinuses – occur in several bones L and S to NC
Pathways within skull
Foramina (openings) in skull accommodate
passage of nerves and blood vessels between cavities and skull interior and exterior, also potential pathways for spread of infections and cancerous cells
Postnatal skull growth
At birth, the bones of calvarium ossify outward from their centers of ossification and bones are connected to one another by fibrous membranes, called fontanelles,
which allow skull compression during
childbirth and brain expansion during postnatal growth, A fontanelle (soft spot) remains open until middle of the 2nd year
Postnatal skull growth part 2
At birth, cranial vault is large, and face is small, bony paranasal sinuses are undeveloped, teeth have not erupted, and 2 halves of mandible are unfused
Cranial joints
Sutures are immovable, fibrous joints between bones of calvarium
- Synchondroses are immovable, cartilaginous joints between bones of
skull base (sphenooccipital, synchondrosis)
