Skull And Orbit Flashcards
(28 cards)
Skull - bones
Skull is comprised of 22 separate bones grouped into 4 regions: cranium, facial skeleton, lower jaw and hyoid bone
Cranial bones x8
Frontal
Temporal R&L
Parietal R&L
Occipital R&L
Ethmoid
Sphenoid
Facial bones x14
Zygomatic R&L
Maxilla R&L
Nasal R&L
Lacrimal R&L
Palatine R&L
Inferior nasal conchae R&L
Vomer
Mandible
General features of skull
Suture
Fissure
Fossa
Foramen
Canal
Sinus
Periosteum
Suture - fused join between 2 bones of skull
Fissure - gap between 2 bones or between 2 wings of same bone
Fossa - depression in surface of bone, usually housing a structure
Foramen - opening in the surface of bone, usually carrying nerves or blood vessels
Canal - passage through bone, carrying nerves or blood supply
Sinus - hollow cavity with a bone / structure
Periosteum - connective tissue covering on surface of bone, firmly attached to bone at sutures
Frontal bone x4
- forms forehead, floor of anterior cranial fossa and orbit roof
- where the bone forms part of the external wall of the skull
- sinuses help reduce overall weight
- where this bone firms an internal structure (such as orbit ceiling) it’s much thinner and not as strong
Sphenoid x5
- extends across cranial cavity forming most of the floor and anterior wall of middle of cranial fossa.
- greater and lesser wings, separated by superior orbital fissure
- lesser wings form part of anterior cranial fossa and roof of orbit
- has the pituitary fossa on upper surface
- contains:
- foramen rotundum which carries maxillary nerve
- optic canal - carries optic nerve and ophthalmic artery
Maxillary bones x4
- all facial bones (except mandible) articulate with the maxilla.
- forms majority of the orbit floor
- maxillary sinus lies above teeth and below orbit floor - carries nerves and blood vessels to & from teeth to upper jaw
- contains infra-orbital canal and infra-orbital foramen which carry branches of maxillary nerve
Temporal bones x4
- form the lower and lateral surface of the skull and part of the cranial floor
- contains carotid canal
- has 4 areas: petrous, squamous, tympanic, mastoid
- mastoid processes sit behind the ears
Occipital bones x3
- forms part of posterior wall of skull and most of floor of posterior cranial fossa
- protects occipital lobe of brain which contains visual cortex
- contains:
•foramen magnum - large opening for passage of lower end of brain stem, canals for hypoglossal nerves.
• jugular foramen and occipital condyles which articulate with top of spinal column
Blood supply x5
- supplied to structures within skull via common carotid artery and vertebral artery
- common carotid divides into internal carotid artery and external carotid artery
- internal enters skull through carotid foramen and canal in temporal bones
- external serves superficial areas of skull and face
- vertebral artery enters skull through foramen magnum in occipital bone
The orbit x5
- structure of skull that houses and protects the eyeball
- lies between the face and brain
- contains eyeball, EOMs, nerves and blood vessels that serve the globe and most of lacrimal apparatus
- posterior to globe is cushion of fatty tissue for protection and support
- lined with periorbita
Bones that make up orbit x7
Frontal
Zygomatic
Maxilla
Lacrimal
Ethmoid
Palatine
Sphenoid
Orbital shape and dimensions x4
- orbit margin made up of frontal, maxilla and zygomatic
- protecting ridge of bone provides clearance and protects globe from impact related trauma
- orbit is shaped approx. As a quadrilateral pyramid with rounded sides
- apex of this pyramid is directed posteriorly, towards optic canal
Orbit dimensions x8
- medial walls roughly parallel to each other
- lateral walls make angle 90° to one another
- lateral and medial walls make angle of 45°
- average adult skull, medial walls are about 2.5cm apart
- front to back of orbit is approx 40mm
- anterior opening is wider than it is tall
- widest part is approx 1.5mm behind margin
- floor slopes nasally upwards at approx 12°
Orbit ceiling / superior wall
Feature
Location
Function
Formed by:
Feature: Supra-orbital notch / foramina
Location: upper margin / frontal bone
Function: carries supra-orbital nerves and vessels in & out orbit
Feature: lacrimal gland fossa
Location: upper temporal / frontal bone
Function: houses lacrimal gland
Feature: trochlear fossa
Location: upper nasal / frontal bone Function: houses trochlea
Feature: optic foramen
Location: apex of orbit / sphenoid bone
Function: carries optic nerve about the orbit
Formed by: frontal bone, lesser wing of sphenoid
Orbit floor / inferior wall
Feature
Location
Function
Formed:
Feature: inferior orbital fissure
Location: between maxilla and palatine and greater wing
Function: carries maxillary and zygomatic nerve branches of infraorbital vein out of orbit
Feature: infra-orbital groove
Location: orbit floor - upper surface of maxilla
Function: carries infraorbital nerve into orbit to join maxillary. Carries infraorbital vessels
Feature: infraorbital canal
Location: through maxilla
Feature: carries infraorbital nerve into orbit to join maxillary. Carries infraorbital vessels
Feature: infraorbital foramen
Location: maxilla - below margin on face
Feature: carries infraorbital nerve into orbit to join maxillary. Carries infraorbital vessels
Formed by: maxilla, palatine, lesser wing of sphenoid
Medial wall / nasal wall
Feature
Location
Function
Formed by
Feature: lacrimal fossa
Location: anterior region of nasal wall in surface of lacrimal bone
Feature: houses lacrimal sac
Feature: lacrimal foramen
Location: base of lacrimal bone
Function: drains lacrimal sac into nasal meatus
Feature: ethmoid foramina
Location: at suture between ethmoid and frontal bone
Function: carries nerve and vessels to anterior cranial fossa
Formed by: frontal, sphenoid, ethmoid, lacrimal, maxilla
Lateral wall / temporal wall
Feature
Location
Function
Formed
Feature: zygomatic foramen
Location: interior wall of zygomatic bone within orbit
Function: carries zygomatic nerve into orbit from side of face.
Feature: supra orbital fissure
Location: separated greater and lesser wing of sphenoid
Function: carries CN3,4&6. Branches of cranial nerve 5 out to form ophthalmic nerve
The orbit x5
- structure of the skull that houses and protects the eyeball
- lies between the face and the brain
- contains eyeball, EOMs, nerves and blood vessels that serve the globe and most of the lacrimal apparatus
- posterior to the globe is cushion of fatty tissue for protection and support
- lined with the periorbita
Bones that make up the orbit x7
Frontal
Zygomatic
Maxilla
Lacrimal
Ethmoid
Palatine
Sphenoid
Orbital shape and dimensions x4
- orbit margin made up of frontal, maxilla and zygomatic
- protecting ridge of bone provides clearance and protects globe from impact trauma
- orbit is shaped approx as a quadrilateral pyramid with round edges
- apex of the pyramid is directed posteriorly towards optic canal
Orbit dimensions x8
- medial walls roughly parallel to each other
- lateral walls make angle 90° to each other
- lateral and medial walls make angle 45°
- average adult skull, medial walls about 2.5cm apart
- front to back orbit is approx 40mm
- anterior opening wider than it is tall
- widest part is approx 1.5mm behind margin
- floor slopes nasally upwards at 12°
Orbit ceiling / superior wall
Formed by: frontal bone and lesser wing of sphenoid
Supra-orbital notch / foramina
Frontal bone
Carries supra-orbital nerves and vessels in and out of orbit
Lacrimal gland fossa
Frontal bone
Houses lacrimal gland
Trochlear fossa
Frontal bone
Houses trochlea
Optical foramen
Sphenoid bone
Carries optic nerve out of orbit
Orbit floor / inferior wall
Formed by: maxilla, Paletine, lesser wing of sphenoid
Inferior orbital fissure
Between maxilla and palatine and greater wing
Carries maxillary and zygo nerves and branches of infraorbital vein out of orbit
Infraorbital groove
Upper surface of maxilla
Carries infraorbital nerve into orbit to join maxillary. Carries infraorbital vessels
Infraorbital canal
Through maxilla
Carries infraorbital nerve into orbit to join maxillary. Carries infraorbital vessels
Infraorbital foramen
Maxilla - below the margin of the face
Carries infraorbital nerve into orbit to join maxillary. Carries infraorbital vessels
