Skull

Skull 

• Neurocranium and viscerocranium   

  • Neurocranium: part of skull that surrounds the brain  

    • One Frontal bone 

    • Two parietal Bones  

    • Occipital bone  

    • Lambdoid suture between occipital and parietal bones (looks like lambda Greek alphabet letter) 

    • In between single frontal bone and parietal bone: coronal/frontal suture  

    • Sagittal suture: between the two parietal bones, runs in the sagittal plane  

    • Pterion: small suture that connects the parietal, frontal, sphenoid and temporal bones 

    • Squamosal suture: connects parietal and temporal bones  

    • Coronal suture: connects parietal and frontal bones  

    • Cranial fossae: three large, stair like depressions in the floor of the cranial cavity  

      Anterior cranial fossa 

      • Inside the anterior cranial fossa is the ethmoid bone  

        • Cribriform foramina: holes within the ethmoid bone that allow for the transversing of the olfactory nerves to the olfactory bulb which brings the sensation of smell to the brain  

        • Lesser wing of sphenoid bone in also in anterior cranial fossa, separates our anterior and middle cranial fossa  

      • Anterior cranial fossa and middle cranial fossa are separated by the lesser wing  

    • Middle cranial fossa 

      • Two structures of the middle cranial fossa are the optic canal and superior orbital fissure (can be seen best through an anterior view of the orbit) 

        • Within the optic canal are two structures: cranial nerve II (optic nerve which allows us to see) and the Opthalmic artery: a branch off the internal carotid artery that supplies the orbit and the retina  

        • Within the superior orbital fissure: superior Opthalmic vein that drains to the cavernous sinus and also to the facial vein, the cranial nerve III, cranial nerve IV, cranial nerve V-1 (Opthalmic branch of the trigeminal nerve), and cranial nerve VI 

        • Within the inferior orbital fissure: inferior Opthalmic vein that goes to the cavernous sinus as well and the pterygoid plexus and facial vein and cranial nerve V-2 infraorbital nerve: the continuation of the V2 branch of the foreman rotundum, and the inferior orbital artery and vein 

      • sell 

      • Carotid canal: from the bottom of the skull and into the middle cranial fossa (where the carotid canal exits) 

        • Internal carotid artery  

      • Foreman rotundum: allows for cranial nerve five and V-2 (maxillary branch) (V-2 goes to the maxilla) 

      • Foreman Ovale: V-3 branch of trigeminal branch (v-3 goes to mandible) 

      • Foreman spinosum: small opening that is traversed by the middle meningeal artery that supplies the dura mater, and courses deep to pterion  

        • If you crack pterion (very thin portion of bone) could rupture meningeal artery and bleed separating the dura from the skull: epidural hematoma

Middle and posterior cranial fossa are separated by the petrous temporal bone  

Posterior cranial fossa 

• Internal acoustic meatus that goes into the Petris part of the temporal bone, traverses by cranial nerve VII (facial nerve) and VII vestibulocochlear nerve go into internal ear  

• Jugular foreman: traverses by internal jugular vein, cranial nerves IX, X, XI 

• Hypoglossal canal: CN XII hypoglossal nerve (tongue movement) 

Sphenoparietal suture between sphenoid and parietal  

Ethmoid bone is also part of the neurocranium  

• Part of bony orbit  

Temporal bone  

• External auditory meatus  

• Petris ridge of temporal bone: hard and more prominent part of temporal bone, in middle cranial fossa 

• Mastoid process  

• Styloid process: pointy  

• Internal acoustic meatus  

• Squamosal of temporal bone: thin portion of temporal bone  

Sphenoid bone: forms posterior portion of anterior cranial fossa and much of the middle cranial fossa  

• Lesser wing and greater wing  

• Sella turcica: portion in the middle of sphenoid bone where the hypophyseal gland or pituitary gland sits  

• Two bony projections off of lesser wing are anterior clinoid processes  

• Two bony projection off of Sella Turcica are the posterior projection processes  

• Optic foreman/optic canal through which the optic nerve travels through (2^nd cranial nerve)  

• Superior orbital fissure: transmits the third ocular motor nerve, the fourth trochlear, 6^th abducens, the first part of the trigeminal nerve, Opthalmic 

• Foreman rotundum: transmits maxillary nerve (2^nd branch of trigeminal nerve  

• Foreman Ovale: transmits mandibular nerve, third branch of trigeminal nerve  

• Pterygoid processes: two processes together are called the pterygoid plate (lateral and medial)  

  • Attachments for muscles of mastication (chew) 

Viscerocranium  

• 14 total bones  

  • Nasal concha  

  • Ethmoid bone: perpendicular plate and superior nasal concha  

  • Cauchy: shells in nasal cavity that allow for circulation of air as you breathe in (part of neural cranium) 

  • Within nasal cavity is the superior and middle nasal concha (part of the ethmoid bone) there is a small bone known as the inferior nasal concha (part of the viscera cranium) 

  • Lacrimal bone: a visceral cranium bone that it part of the bony orbit  

  • Mandible  

    • Coronoid process  

    • Condyle of the mandible  

    • The ramus of the mandible  

    • Angle of the mandible  

    • Body of mandible  

    • Two foramina  

      • Mental foreman: transmits the mental nerve, branch of the mandibular branch of the trigeminal  

      • Mandibular foreman: on the inside of mandible), it  transmits the inferior alveolar nerve, a branch of the mandibular division of trigeminal 

  • Maxilla bone, there are two (also part of bony orbit), maxilla atin for jaw 

    • Many bones come together to make the bony orbit 

  • Vomer: part of the visceral cranium that makes up the middle part of nasal cavity and meets with the perpendicular plate of the ethmoid bone  

  • Nasal septum is made up of two bones: the perpendicular plate of the ethmoid and the Velma 

  • Zygomatic bones (2): another portion of the bony orbit, cheek bone 

  • Orbital plate of the palatine bones: A very small portion of the bony orbit   

  • Bony orbit is made up of the frontal bone, the lacrimal bone, the maxillary bone, zygomatic bone, the sphenoid bone, and the palatine bone  

Anterior cranial fossa: made up of frontal bone and ethmoid bone  

• Portion of the ethmoid bone called the cribriform plate contain olfactory foramina that allow the olfactory nerve or first cranial nerve to pass through 

The middle cranial fossa is divided from the anterior cranial fossa by the lesser wing of the sphenoid  

• Made up of the sphenoid bone and the temporal bone  

Posterior cranial fossa is made up of the occipital bone and temporal bone  

• Petris ridge of temporal bone separates the posterior cranial fossa and middle cranial fossa 

Cranial nerve two goes through the optic canal  

Superior orbital fissure: the third cranial (oculomotor nerve) nerve fourth cranial nerve (trochlear nerve)  and sixth cranial nerve (abducens) will move the muscles of the eye, involved in innervating the extraocular muscles; also transmits the 51 nerve which is the first part of the trigeminal nerve and is Opthalmic and is purely sensory (takes sensation from the upper part of the face to the brain) 

Foreman rotundum: transmits the maxillary nerve (transmits sensation from the lower part of the face meaning maxilla, upper part of the nose, upper lip) 

Foreman Ovale: transmits the mandibular division of the trigeminal nerve that involves taking sensation from the lower part of the face involving the lower teeth the lower lip the chin the mandible to the brain  

• Upper teeth are innervated by the maxillary nerve  

Foreman lacerum does not transmit anything  

Foreman spinosum: transmits middle meningeal artery which is important in suppling blood to the calvaria if this is injured one will have an epidural hematoma  

Internal acoustic meatus: transmits the facial nerve (cranial nerve seven, muscles of facial expression are innervated by the facial nerve) and the vestibulocochlear nerve (cranial nerve eight, hearing and balance and innervated by the vestibulocochlear nerve) 

Jugular foreman: transmits cranial nerve 9 (glossopharyngeal nerve: innervates our tastes to the back of the tongue, pharynx innervates stylopharyngeus muscle ), 10 (vagus nerve that innervates to the heart, the gut, the larynx ), and 11 (accessory nerve: innervates the sternocleidomastoid muscle and the trapezius muscle) 

Hypoglossal canal: transmits hypoglossal nerve and innervates the muscles of the tongue: when you move your tongue to the left or right when you stick out your tongue 

Foreman magnum: the spinal cord goes through  

Carotid canal: transmits the internal carotid artery  

• Finds its way through the foreman lacerum  

• Opening is known as the internal carotid artery  

External acoustic meatus: within the temporal bone  

Occipital condyle: sit on superior aspects of the first vertebrae, c1 your first vertebra  

Hard palate is actually made up of two bones, the maxilla and palatine bone (come together to make the hard palate which is described as the palatine process of the maxilla and horizontal plate of the palatine bone 

External occipital perturbance: for the attachment of the trapezius muscle  

Superior nuchal line that the nuchal ligament attaches  

Inferior nuchal line  

Stylomastoid foreman: between the styloid process and mastoid process  

*on the inferior view, we cannot see foreman rotundum because It does not open up to the outside of the skull, it opens to another "room" called the pterygopalatine fossa 

Air cells and sinuses make the skull a little lighter and helps resonate your sound and voice as you talk  

Maxillary sinus 

White: filling of teeth