Osteology (2)

Question 1

How many bones comprise the adult skull?

Answer 1

• 22 - 21 immovable + mandible

Question 2

21 bones are connected by what?

Answer 2

• immovable sutures that ossify during adulthood

Question 3

what are the divisions of the adult skull?

Answer 3

• neurocranium - viscerocranium

Question 4

Neurocranium

Answer 4

• calvarium: skullcap, protects brain - cranial base: skull floor, supports weight of the brain

Question 5

Neurocranium (8 bones)

Answer 5

• frontal - ethmoid - sphenoid - occipital - parietal (2) - temporal (2)

Question 6

Viscerocranium (14 bones)

Answer 6

• maxilla (2) - zygomatic (2) - nasal (2) - lacrimal (2) - palatine (2) - inferior nasal concha (2) - vomer - mandible

Question 7

Neurocranium: Frontal Bone (external features)

Answer 7

• supraorbital notch/foramen - orbital plate - lacrimal fossa - trochlear fovea

Question 8

Neurocranium: Frontal Bone (internal features)

Answer 8

• frontal crest: anchors dura mater - foramen cecum: pathway for emissary vein to pass between superior sagittal sinus and the nasal cavity (potential route for spread of infections intracranially) - orbital plate: roof of the orbit, supports frontal lobes of the brain (external & internal) - frontal sinus: air cavity within frontal bone that is lined with mucus membrane and drains into the nasal cavity via the frontonasal duct

Question 9

Neurocranium: Frontal Bone (cranial landmarks)

Answer 9

• glabella: anterior-most point of the frontal bone - nasion: point of intersection of frontal bone and inter-nasal suture

Question 10

Neurocranium: Frontal Bone (frontal suture)

Answer 10

• only present in infants; not in adult skull

Question 11

Neurocranium: Frontal Bone (articulations -12)

Answer 11

• nasal (2) - zygomatic (2) - Lacrimal (2) - Maxillae (2) - Parietal (2) - Sphenoid - Ethmoid

Question 12

Neurocranium: Parietal Bone (internal features)

Answer 12

• middle meningeal sulcus: impression on internal surface of parietal bone caused by the middle memingeal artery (vascular transmission) - sagittal sulcus: runs along the length of the sagittal surface of the cranial cavity - pacchionian pits (arachnoid pits): impressions on the bone where the cerebrispinal fluid pools within arachnoid granulations

Question 13

Neurocranium: Parietal Bone (sutures)

Answer 13

• coronal: articulation with frontal bone - sagittal: articulation with opposite parietal bone - lambdoidal: articulation with occipital bone

Question 14

Neurocranium: Parietal Bone (articulations-5)

Answer 14

• parietal - frontal - sphenoid - occipital - temporal

Question 15

Neurocranium: Occipital Bone (external features 4)

Answer 15

• external occipital protruberance: protrusion on posterior aspect of the occipital bone at the site of the CONFLUENCE OF SINUSES - occipital condyles: curved and smooth projections that articulate with the cervical vertebra - foramen magnum: large opening for neurovascular structure - jugalr notch: small indentation in the occipital bone that makes up the jugular foramen with the jugular notch of the temporal bone

Question 16

Neurocranium: Occipital Bone (internal features 7)

Answer 16

• internal occipital protuberance: small protrusion on internal surface of the occipital bone - cruciform eminence: cross-like feature where the two transverse sulci and sagittal sulcus meet - hypoglossal canal: exit for hypoglossa nerve from cranial cavity - sigmoid sulcus: groove that transmits the sigmoid sinus - cerebral fossa: indentation in occipital bone where the occipital lobe lies - cerebellar fossa: indentation in the occipital bone where the cerebellar lob lies - basilar part: four-sided plate anterior to foramen magnum that articulates with the sphenoid bone

Question 17

Neurocranium: Occipital Bone (articulations 6)

Answer 17

• parietal (2) vis lambdoidal suture - temporal (2) - sphenoid - C1 (atlas): articulates with occipital condyle

Question 18

Neurocranium: Temporal Bone (critical features & distinct part)

Answer 18

• contains critical features necessary for mastication, taste, hearing, and balance - distinct parts: ~ squamous portion (body): fan-shaped and flat ~ petrous portion: houses inner ear and is one of the thickest and strongest parts of the cranium (helps form cranial floor) ~ tympanic part: associated with ear canal

Question 19

Neurocranium: Temporal Bone (external view 5)

Answer 19

• mastoid process: air filled projection of bone (helps equalize pressure in the ear); projects downward behind the external acoustic foramen / meatus - jugular notch: indentation/gap in temporal bone that forms jugular foramen when paired with jugular notch of occipital bone - carotid foramen: medial and anterior to the jugular notch; opening for the carotid canal - styloid process: downward-projecting fingerlike extension - stylomastoid foramen: exit for motor branch of the facial nerve

Question 20

Neurocranium: Temporal Bone (internal view 5)

Answer 20

• internal acoustic/auditory meatus: opening within petrous part of temporal bone that transmits the facial and vestibulocochlear nerves - jugular notch: meets with jugular notch of the occipital bone to form the jugular foramen that transmits the glossopharyngeal, vagus, and spinal accessory nerves - carotid foramen: opening for internal carotid artery - trigrminal depression: area where the trigeminal ganglion rests on the temporal bone - petrous portion of temporal bone: onr the strongest parts of the skull that houses the inner ear structure

Question 21

Auditory Ossicle (location - bones - articulation)

Answer 21

location: ~Tempanic cavity - air filled space within temporal bone that extends from the tympanic membrane (eardrum) to the lateral wall of the inner ear ( located within petrous part of temporal bone bones: ~ malleus “hammer” ~ incus “anvil” ~ stapes “stirrup” -attaches to oval window

Question 22

Answer 22

• malleus
• incus
• stapes

Question 23

Answer 23

Question 24

Answer 24

Question 25

Answer 25

Question 26

Answer 26

Question 27

Question 28

Answer 28

Question 29

Answer 29

Question 30

Answer 30

Question 31

Answer 31

Question 32

Answer 32

Question 33

Answer 33

Question 34

Answer 34

Question 35

trochlear fovea

Answer 35

a small depression in the medial wall where trochlea of the superior oblique muscle attaches to frontal bone