Osteology of the Skull Flashcards
What is the difference between endochondral and dermal bones?
Endochondral- Bones of the base of the skull
Dermal- Bones forming the sides and roof of the skull
What are the 5 major bones of the skull?
Ethmoid
Sphenoid
Left and Right Temporals
Occipital Bone
Describe the Ethmoid bone and its 5 components
The only basicranial bone that is entirely preformed in cartilage
Components:
Cribriform plate
Crista Galli- Attachment for falx cerebri
Perpendicular plate
Labyrinth- Superior and middle nasal conchae
Ethmoid air cells
Describe the Sphenoid bone. What is it formed from? What are its 2 main components?
Formed from both cartilage and dermal elements
Components:
Pterygoid plates:
-Medial and lateral plates hanging down
-Dermal components attached to the endochondral portion of the sphenoid base
Body:
- Hypophyseal fossa
- 4 clinoid processes joined anteriorly by dorsum sellae
Describe the Greater Wings of the Saphenoid bone. What does it contribute to?- What is that the location of?
Describe the 3 foramina of the lower flaps and 2 from the upper flaps.
Contribute to the floor of the middle cranial fossa- the location of temporal lobes
Foraminae of the lower flaps: ROS
- Foramen Rotundum- V2 (Maxillary Nerve)
- Foramen Ovale- V3 (Mandibular Nerve)
- Foramen Spinosum- Middle meningeal vessels
Foraminae of the upper flaps:
- Optic canal
- Anterior clinoid process
Describe the 5 Temporal bones parts/processes
Petrous Part Squamous Part Tympanic Part Mastoid Process Styloid Process
PST MS
Describe the 4 facts about the Petrous part of the temporal bone. What does it surround? What develops underneath this? What does this form when it connects with the pharynx?
Surrounds ear apparatus.
Middle ear chamber develops underneath this from the pharynx.
The Cavity’s connection with the pharynx forms the eustachian (auditory) tube.
Forms the Carotid canal for the internal carotid canal
Describe the Squamous part of the temporal bone. What does it form and is above what?
Thin dermal bone forming the lateral wall of the braincase above the auditory meatus
Describe the Tympanic part of the temporal bone. What does it form around the eardrum? When it expands after birth, what does it become?
Forms a ring of the dermal bone around the eardrum
Expands after birth to become the external auditory meatus (bony tube leading to the eardrum from the outside)
Describe the Mastoid Process of the temporal bone
Mass of air-filled outpocketings (air cells) from the petrous part
Describe the Styloid Process of the temporal bone. What attaches here?
Fuses to form the petrous portion in front of mastoid
Attachment site for muscles and ligaments
Describe the 2 Occipital bones parts. It also forms 4 separate bones that fuse around the spinal cord to form what? What 3 structures pass through this?
Squamous part- Large dermal bone that forms the lower back of the head
Basilar part:
-Cartilage replacement bone formed from anterior vertebral elements
-Forms four separate bones that fuse around the spinal cord to form the foramen magnum–> For passage of spinal cord, vertebral arteries, and spinal root of CN XI
What are the 5 Membrane Bones of the Skull?
Frontal Bone Maxillary Bones Zygomatic Bones Nasal Bones Parietal Bones
Fuck Me Zigi Now Please
Describe the Frontal Bone. When is it paired? When is it fused? What foramina does it contain?
Paired in fetus
Fused in adult-Metopic suture
Supraorbital Foramina (notches)
Describe the Maxillary Bones. What process does it contain? What foramina does it contain?
Alveolar process
Infraorbital foramina
