Lecture 12 - Osteology of the Skull Flashcards
Bones of the base of the skull
- Underlie the brainstem
* Endochondral
Bones forming the sides and roof of the skull
- Dermal bones
* Make up the bones of the face
The skull forms the other part of the ____ skeleton.
what is it made of?
Axial
•It may be a combination of cartilage, dermal bone, and/or endochondral bone.
Vertebrate Skull Organization/Components
Chondrocranium: •Neurocranium: •Cartilage and/or endochondral bone •Splanchnocranium: •Also referred to as the viscerocranium •Cartilage and/or endochondral bone
Dermatocranium: •Dermal bone
Chondrocranium
The cartilaginous embryonic skull is the chondrocranium; it consists of:
•The braincase, or neurocranium:
•Makes up the mass up the mass of cartilage that condenses beneath the embryonic brain and the bones that replace this cartilage.
•Collectively referred to as basicranium
•Includes three pairs of cartilaginous capsules housing special sensory organs:
•Olfactory (most anterior)
•Optic
•Otic(most posterior)
•The pharyngeal (gill) arches) or splanchnocranium
Neurocranium
Floor forms from two pairs of cartilaginous plates:
- prechordals
- parachrodals
posterior wall- foramen magnum
roof- usually open, closed in chondrichthyes
Bones of basicranium: •These represent the primitive vertebrate braincase Five bones: •Ethmoid •Sphenoid •Left and right temporals •Occipital bone
Ethmoid
Only basicranialbone 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
Sphenoid
Formed from both cartilage and dermal elements
Components:
•Pterygoid plates
-body
-greater wings
Temporal bones
petrous part mastoid process styloid process squamous part tympanic part
Petrous Part
- Surrounds ear apparatus
- First pharyngeal pouch grows underneath this part and expands to form the middle ear chamber.
- Cavity’s connection with pharynx forms eustachian (auditory) tube.
- Forms carotid canal for the internal carotid canal
Mastoid Process
Mass of air-filled outpocketings(air cells) from petrous part
Styloid Process
- Derived from second gill arch
- Fuses to petrous portion in front of mastoid
- Attachment site for muscles and ligaments
Squamous Part (Temporal)
Thin sheet of dermal bone forming lateral wall of braincase above auditory meatus
Tympanic Part
- Part of temporal bone that forms a ring of dermal bone around the eardrum
- Expands after birth to become the external auditory meatus (bony tube leading to ear drum from the outside
Occipital Bone
Squamous Part and Basilar Part
Squamous Part (Occipital)
Large dermal bone that forms the lower back of the head
Basilar Part
- Cartilage-replacement bone formed from anterior vertebral elements
- Forms from 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 XI
Frontal Bone
- paired in fetus
- fused in adult (metopic suture)
- supraorbital foramina (notches)
Maxillary Bones
- alveolar process
- infraorbital foramina
zygomatic bones
nasal bones
Parietal Bones
superior and inferior temporal lines
Anterior Skill
- Sphenoid (greater wing and lesser wing)
- Ethmoid
- Lacrimal
- Vomer
Base of Skull
Occipitals •Occipital condyles •Foramen magnum •Supreme, superior, inferior nuchal lines •External occipital protuberance •Pharyngeal protuberance
Mandible
Ramus: •For muscle attachment •Lingula •Condylar process •Mandibular notch •Coronoid process Angle Body: •Mental protuberance •Mental foramen
Anterior Cranial Fossa
Mostly formed by frontal bone Located superior to orbits Features: •Crista galli •Cribriform plate and olfactory foramina Contains: •Frontal lobes of cerebrum
Middle Cranial Fossa
Formed mostly by body and greater wings of sphenoid
Features: •Attachment for diaphragma sellae •Dorsum sellae •Posterior clinoid processes •Chiasmatic sulcus •Optic canal •Superior orbital fissure •Foramen rotundum •Foramen ovale •Foramen spinosum •Foramen lacerum
Contains: •Temporal lobes of cerebrum
Posterior Cranial Fossa
Formed mostly by occipital bone Features: •Clivus •Foramen magnum •Jugular foramen •Hypoglossal canal •Condylar canal •Mastoid canal •Roofed over by tentorium cerebelli •Tentorium incisure
Contains: •Cerebellum, pons, medulla
Sutures
Sagittal
Lamboidal
Coronal
Frontal
Fontanelles
Anterior
Posterior
Posterolateral
Anterolateral
Landmarks of Skull
Nasion Pterion Inion Asterion Glabella
