Skull Overview And Meninges Flashcards
Cranium components
Neurocranium and viscerocranium
Neurocranium
. Cranial vault
. Bony case surrounding brain and its meninges
. Calvarium: sup. Braincase (skull cap, membranous neurocranium)
. Basicranium: cranial base, cartilaginous neurocranium, chondrocranium (floor of braincase)
Viscerocranium
. Facial skeleton surrounds the openings of oral cavity, nasal cavity, and much of the orbits
.forms primarily in pharyngeal arches from neural crest cells
.
Bones in neurocranium
. 2 parietal . 2 temporal . Frontal . Sphenoid . Ethmoid . Occipital
Viscerocranium
. 2 maxillae . Zygomatics . 2 each palatines, lacrimals, nasals . 2 inf. Nasal conchae . Vomer . Mandible
Structure of cranial bones
. Bones of skull have inner and outer plates of compact bone
. Spongy bone (diploe) lies btw 2 plates of compact bone that contains marrow
. Compact bone provides strength
. Spongy bone make skull lighter
Cranial sutures
. Fibrous joint
. Margins of articulating bones interlock along wavy line
. Fuse by adulthood
Fontanelles
. Fibrous joints
. Wide area of fibrous tissue located btw bones in fetal and newborn skulls
.bones grow toward one another and they close by 18 months old
Synchondroses
. Articulating bones united by hyaline or fibrous cartilage
. Limited movements are permitted
. Form btw bones that have cartilaginous origin
Synovial joints of cranium
. Articular surfaces covered w/ articular hyaline cartilage
. Bone surfaces separated from one another by joint cavity
. Temporomandibular joint: modified hinge joint w/ movement in 2 planes
. Joints btw auditory ossicles
Cranial cavities
. Neurocranium . Nasal . Oral . Orbital . Middle ear (tympanic)
Paranasal sinuses
. Bony-air filled spaces lined w/ mucous membranes . Secretions drain into nasal cavity . Frontal . Maxillary . Ethmoid air cells . Sphenoid
Frontal bone
. Supraorbital foramen transmits supraorbital n. (CN V1) a., and v.
. Orbital plate
. Metopic suture
. Temporal lines continue onto parietal bones, attachment of temporal fascia and temporalis m.
Parietal bones characteristics
. Sup. Sagittal sinus groove
. Depression for arachnoid granulation located w/in sup. Sagittal sinus groove
. Middle meningeal grooves
Maxillae characteristics
. Alveolar process
. Infraorbital groove, infraorbital canal, and infraorbital foramen transmit the infraorbital n. (CV V2), a., and v.
. Palatine process
Hard palate
. Separates oral and nasal cavities
. Forms roof of the oral cavity and floor of nasal cavity
. Formed by palatine processes of maxillae and horizontal plates of palatine bones
. Includes greater and lesser palatine foramina
Zygomatic bone
. Orbital process
. Malar surface
. Temporal surface
. Temporal process articulates w/ zygomatic process of temporal bone to form zygomatic arch
Orbital cavities
. Paired orbital cavities house orbits
. Formed by frontal, greater/lesser wings, orbital plate of ethmoid, maxillae, zygomatic, lacrimal, and palatine
Superior orbital fissure
. Connects cranial and orbital cavities
. Transmits oculomotor n. (CN III), trochlear n. (CN IV), abducens n. (CNVI), branches of ophthalmic n. (CN V1) and sup. Ophthalmic v.
Inferior orbital fissure
. Connects orbital cavity w/ pterygopalatine fossa, infratemporal and temporal regions
. Transmits maxillary n., infraorbital vessels, branches from pterygopalatine ganglion
Optic foramen
. Connects orbital and cranial cavities
. Transmits optic n. (CN II) and ophthalmic a.
Opening of nasolacrimal duct
. Connects orbital cavity and the nasal cavity
. Transmits nasolacrimal duct
Piriform (nasal) aperture
. External opening into nasal cavities
. Aperture formed by nasal bones and maxillae
. Bony and caritlaginous nasal septum divides nasal cavity into R and L sides
. Nasal conchae: visible as curved bony plates on lat. walls of nasal cavity, covered in nasal mucosa
Mandible characteristics
. Ramos, body, and angle of mandible
. Alveolar process
. Mental protuberance
. Head (condyle) of mandible: forms part of temporomandibular joint (TMJ)
. Mandibular foramen: transmits inf. Alveolar n. (CN V3), a., and v.
. Mental foramen: transmits mental n. (CN V3), a., and v.
Temporal bone characteristic
Squamous portion
. Petrous portion
. Tympanic portion
. Zygomatic process
. Mastoid and styloid processes: attachment sites for muscles and ligaments
. External auditory meatus: a bony canal from the outer ear to the tympanic membrane
. Articular eminence
. Mandibular (glenoid) fossa; forms part of TMJ
. Carotid canals: Passage of the internal carotid arteries into the head
Occipital bone characteristics
Superior nuchal line . External occipital protuberance . Spheno-occipital synchondrosis . Foramen magnum . Occipital condyle: Convex, joint surfaces for articulation with the C1 vertebra . Hypoglossal canals (transmit CN XII) . Jugular foramina: Passage of the internal jugular veins and some cranial nerves out of the head
Sphenoid bone characteristics
. Greater wings form parts of the orbit, basicranium, and sides of the skull
. Lesser wings form parts of the orbit and basicranium
. Optic canal
. Body of
. Med. and lat. pterygoid plates: Paired inf. projections that serve as muscle attachment sites
. Foramen ovale (transmits CN V3)
. Foramen spinosum
. Sphenoid sinus
. Sella turcica
. Hypophyseal fossa holds the pituitary gland
. Dorsum sellae
Ethmoid bone characteristics
. Cribriform plate with foramina . Crista galli . Ethmoid air cells . Orbital plates of . Perpendicular plate of . Middle nasal concha
Anterior cranial fossa (ACF)
. Supports frontal lobes of brain and forms roof of the orbits
. Composed of the orbital plates of the frontal bone, the lesser wings of the sphenoid, and the cribiform plate
Middle cranial fossa (MCF)
. Supports temporal lobes of the brain
. Midline part: sella turcica that includes hypophyseal fossa which houses pituitary gland
. Composed of greater wings and body of sphenoid, squamous and petrous portions of temporal bones, and parietal bones
Posterior cranial fossa (PCF)
. Supports cerebellum, pons, and medulla oblongata of the brain
. Composed of petrous portions of the temporal bones, dorsum sellae of the sphenoid, and basal portion of the occipital bone
. Sloping surface of sphenoid and occipital bone leading to foramen magnum (Clivus)
. Contains internal acoustic meats, jugular foramen, and foramen magnum
pia mater
. Innermost layer directly adhered to surface of brain
Arachnoid mater
. Transparent membrane separated from pia mater by subarachnoid space
. Subarachnoid space contains CSF
. Arachnoid trabeculae: thin strands of arachnoid mater that attach to the pia mater
. Arachnoid granulations: tuft-like projections of arachnoid mater that protrude through inner layer of dura and drain CSF into dural venous system
Dura mater
. Outermost, fibrous layer
. Inner meningeal layer and outer endosteal layer that adheres to inner surface of the skull and forms internal layer of periosteum
. Sensory innervation via trigeminal n., vagus n., and upper cervical spinal nn.
. Blood supply: L/R middle meningeal aa. Arising in the infratemporal fossae and enter the skull through foramina spinosum
Dural folds
. Inner layer of dura projects into neurocranium cavity forming 4 folds that help support and separate parts of brain
Falx cerebri
. Sickle-shaped vertical partition that separates cerebral hemispheres in the midline
. Attaches to crista galli ant. And the internal occipital protuberance post.
. Inf. Margin is unattached except post. Where it attaches to tentorium cerebelli
Tentorium cerebelli
. Wide arched fold that lies in horizontal plane and separates the occipital lobes in the middle cranial fossa from the cerebellum in post. Cranial fossa
. Attaches anterolat. To sphenoid bone, post. To occipital bone along groove for transverse sinuses and in midline to falx cerebri
. Anteromedial. Concave border is unattached, opening btw free edges of tentorium cerebelli is tentorial notch
Falx cerebelli
. Vertical projection that lies in post. Cranial fossa and separates cerebellar hemispheres
. Attaches to internal occipital protuberance and foramen magnum
Diaphragma sellae
. Circular horizontal fold located over hypophyseal fossa in the sella turcica
. Central aperture for the stalk of pituitary gland
Dural venous sinuses
. Endothelium-lined spaces btw layers of cranial dura mater
. Lie btw inner and outer dural layers or btw folded inner layers of dura
. Function as veins enclosed w/in dura
. Carry venous blood from brain and meninges as well as CSF drained from arachnoid granulations
. All dural venous sinuses ultimately drain their contents into internal jugular v. At the jugular foramen
Superior sagittal sinus
. Lies in midline
. Superior edge of the falx cerebri
. Courses ost. To internal occipital protuberance and then bends to the right to form the right transverse sinus
Inferior sagittal sinus
. Lies in midline
. Inf. Free margin of falx cerebri
. Courses post. To the junction of the falx cerebri and tentorium cerebelli and drains into straight sinus
Straight sinus
. Occupies area where tentorium cerebelli and falx cerebri meet
. Courses post. To the internal occipital protuberance where it bends left to form left transverse sinus
Paired transverse sinuses
. Begin as continuations of the straight and sup. Sagittal sinuses
. Course along post. Attachment of the tentorium cerebelli
. As they leave plane of tentorium cerebelli lat. they curve inf. Along the occipital bone as sigmoid sinuses
Paired sigmoid sinuses
. Course inferomedially in the post. Cranial fossa to jugular foramina where they form the start of the internal jugular vv.
Confluence of sinuses
. Dilation near internal occipital protuberance that represents junction of the straight, sup. Sagittal, occipital, and transverse sinuses
Paired cavernous sinuses
. Lie on either side of the sphenoid body in the middle cranial fossa btw inner and outer layers of dura
. CN III, IV, V1, and V2 course w/in lat. wall of cavernous sinus
. Internal carotid a. And CN VI course w/in the sinus itself
. Sinus receives drainage from various sources including ophthalmic vv.
. Epidural hematoma
. Lie btw skull and outer layer of dura
. Due to tear in middle meningeal a. Resulting in a slow, localized accumulation of blood that may compress the brain and require aspiration or craniotomy to remove the hematoma
Sub dural hematoma
. Located in subdural space (potential space)
Subdural hematoma
. In subdural space, a potential space btw inner layer of dura and arachnoid mater
Subarachnoid hemorrhages
. Bleed into subarachnoid space
. Common following cerebrovascular accident (stroke)
