 Formed by two sets of bones. ◦ Cranium: encloses and protects the fragile brain tissue ◦ Facial bones: hold the eyes in an anterior position and allow the facial muscles to show our feelings

 Sutures are interlocking, immovable joints.  All but the mandible (jawbone) are joined together by sutures.

 Cranial “cavity” – houses brain  Smaller cavities ◦ Housing middle and inner ear ◦ Nasal cavity ◦ Orbits ◦ Sinuses  Openings (foramina, canals, fissures) for: ◦ Spinal cord ◦ Blood vessels ◦ Twelve cranial nerves: I-XII

 Composed of eight large, flat bones  Except for two paired bones ( the parietal and temporal), they are all single bones  1. Frontal bone – forms the forehead, the bony projections under the eyebrows, and the superior part of each eye’s orbit  2 &3. Parietal bones – paired bones that form the superior and lateral walls of the cranium, meeting at the midline of the skull

 4 & 5. Temporal bones – lie inferior to parietal bones and have several important bone markings ◦ External acoustic meatus – canal that leads to the eardrum ◦ Styloid process- attachment point for neck muscles ◦ Zygomatic process- thin bridge of bone that joins with the cheekbone (zygomatic bone) ◦ Mastoid process – behind ear, contains mastoid sinuses and point of attachment for neck muscles ◦ Jugular foramen, Internal acoustic meatus, and carotid canal – passageways for blood vessels and nerves

 6. Occipital bone – most posterior bone of the cranium, forms the floor and back wall of the skull ◦ In the base of there is a large hole, foramen magnum, that surrounds the lower part of the brain and allows the spinal cord to connect with the brain

 7. Sphenoid bone – butterfly- shaped bone that spans the width of the skull and forms part of the floor of the cranial cavity. ◦ Contains Turk’s saddle, which holds the pituitary gland in place ◦ Contains foramen ovale so the cranial nerves can pass through

 8. Ethmoid bone- irregular and lies anterior to the sphenoid, forms the roof of the nasal cavity and part of the medial walls of the orbits.

Facial bones (anterior aspect of skull) ◦ Form framework of face ◦ Form cavities for sense organs of sight, taste and smell ◦ Provides openings for passage of air and food ◦ Hold the teeth ◦ Anchor the muscles of the face

 Fourteen bones  Following are all paired: ◦ Maxillae, zygomatics, palatines, nasals, lacrimals, and inferior nasal conchae  Unpaired: ◦ Vomer and mandible  Hyoid: not really a skull bone, supported in the neck only by ligaments

 Only bone which does not articulate with any other bone  Moveable base for the tongue  Points of attachment for neck muscles that raise and lower the larynx during swallowing

 Maxillae : upper jaw  Palatine: posterior part of hard palate  Zygomatic: Cheekbones, form part of lateral orbital walls  Lacrimal: medial walls of orbits, groove serves as tear passage  Nasal bones: nose bridge

 Of bone and cartilage  Roof is ethmoid  Floor formed by palatine processes of the 2 maxillae and horizontal plates of palatine bones ◦ These nasal-floor structures form roof of the mouth, called the hard palate nasal bone ethmoid vomer inf nasal concha (part of slide 18) maxilla___________

 Vomer bone: forms nasal septum  Inferior conchae: lateral walls of the nasal cavity  Mandible: lower jaw

Remember that the Axial skeleton includes: Skull Vertebral column Thoracic cage Axial skeleton is shown in green

 Fetus and infant: 33 separate bones, or vertebrae  Adult: 24 vertebrae ◦ Inferior 9 have fused forming  The sacrum (5) and  The coccyx (4)

 Cervical – 7  Thoracic - 12  Lumbar - 5  Sacrum (5 fused)  Coccyx (4 fused)

 Cervical and lumbar are concave posteriorly* (lordosis)  Thoracic and sacral are convex posteriorly* (kyphosis)  Abnormal ◦ Too much of either ◦ Scoliosis (more than 10 degrees of lateral curvature) * when viewed from the side

C1 (atlas) C2 (axis)

 Smallest  Lightest  Most flexible  Triangular vertebral foramen  Transverse processes have foramina (transverse foramen)  Spinous process bifid (forked) except for C7 Cervical Vertebrae

 Heart shaped body  Additional small costal facets (costal=ribs)  Round or oval vertebral foramen  Form posterior part of rib cage Thoracic Vertebrae T1-T12

 Massive blocklike bodies  Short, thick hatchet-shaped spinous processes  Limited mobility Lumbar Vertebrae L1-L5

Shapes posterior wall of pelvis Composite bone of 5 fused vertebrae Sacral foramina allow passage of vessels & nerves Coccyx (the tailbone)

Remember that the Axial skeleton includes: Skull Vertebral column Thoracic cage Axial skeleton is shown in green

 Manubrium  Body  Xiphoid process  True ribs 1-7  False ribs 8-12  Floating ribs 11,12

 Skulls of newborns contain fontanels (membranous areas), which allow brain growth.  The infant’s facial bones are very small compared to the size of the cranium  Fetal skull ossifies after months

 Unossified remnants of membranes  Present at birth  Anterior fontanel largest  Called “soft spots”  Ossify by 1 ½ - 2 years Continue to ossify into adulthood; the sutures can become fused in old age