Cranial Cavity, Venous Sinuses, and Brain Flashcards
What are the boundaries of the anterior cranial fossa?
Anterior: frontal bone posterior: lesser wing of sphenoid
What are the boundaries of the middle cranial fossa?
Anterior: lesser wing of sphenoid posterior: Apex of petrous part of temporal bone
What are the boundaries of the posterior cranial fossa?
Anterior: Apex of petrous part of temporal bone posterior: occipital bone
What are the major foramina of the anterior cranial fossa?
Cribriform foramina Anterior ethmoidal foramina Posterior ethmoidal foramina
What are the contents transmitted in the cribriform foramina?
Axons of olfactory nn.
What are the contents transmitted in the anterior ethmoidal foramina?
Anterior ethmoidal neurovasculature
What are the contents transmitted in the posterior ethmoidal foramina?
Posterior ethmoidal neurovasculature
What are the major foramina of the middle cranial fossa?
Optic canals superior orbital fissure foramen rotundum Foramen ovale foramen spinosum
What contents are transmitted through the optic canals?
ophthalmic aa. and optic nn. (CN II)
What contents are transmitted through the superior orbital fissure?
Oculomotor n. (CN III); Trochlear n. (CN IV); Ophthalmic n. (V1); Abducens n. (CN VI); Ophthalmic vv., and sympathetic fibers
What contents are transmitted through the foramen rotundum?
Maxillary n. (V2)
What contents are transmitted through the foramen ovale?
Mandibular n. (V3), and accessory meningeal artery
What contents are transmitted through the foramen spinosum?
Middle meningeal a. and v., and meningeal branch of Mandibular n. V3
What are the major foramina of the posterior cranial fossa?
Jugular foramen foramen magnum hypoglossal canal
What contents are transmitted through the jugular foramen?
Glossopharyngeal n. (CN IX); Vagus n. (CN X); Accessory n. (CN XI); Internal jugular v. (IJV)
What contents are transmitted through the foramen magnum?
Accessory n. (CN XI); transition from medulla oblongata to spinal cord; Vertebral aa.; Anterior & posterior spinal aa.
What contents are transmitted through the hypoglossal canal?
Hypoglossal n. (CN XII)
What are the major parts of the brain?
Cerebrum Brainstem Cerebellum Hypophysis
What is the cerebrum?
The largest component of the brain; consists of the R & L cerebral hemispheres and basal ganglia. The cerebral lobes (frontal, parietal, temporal, and occipital) do not correspond precisely with the similarly named bone.
What separates the R and L cerebral hemispheres of the cerebrum?
the longitudinal cerebral fissure
What are the proximal, intermediate, and distal portions of the brainstem?
the midbrain, pons, and medulla oblongata
Where is the cerebellum located?
The cerebellum is inferior to the cerebrum and posterior to the brainstem.
What connects the two hemispheres of the cerebellum?
the vermis
What gland is known as the hypophysis?
the pituitary gland
Where is the hypophysis located?
Hypophysis is located within the hypophyseal fossa of the sphenoid bone.
What is the pituitary gland (hypophysis) continuous with?
the infundibulum, a component of the hypothalamus.
What are the three types of cranial meninges?
pia mater, arachnoid mater, dura mater
What is the pia mater of the brain?
“delicate mother”. It is closely associated with the brain (even dipping into fissures and sulk). Also, it enmeshes blood vessels on the surface of the brain.
What is the filmy, transparent layer that is connected to the pia mater?
arachnoid mater
How is the arachnoid mater connected to the pia mater?
via trabeculae.
What space separates the pia and arachnoid mater? What fills that space?
the subarachnoid space : cerebrospinal fluid
If you hemorrhage a cerebral artery, where might the blood be contained?
in the subarachnoid space (subarachnoid hematoma)
____________ serve as sites where CSF trains into the blood.
arachnoid villi (projection of the arachnoid mater into the superior sagittal sinus)
What are arachnoid granulations?
tuft-like collections of highly folded arachnoid that project into the superior sagittal sinus and its lateral lacunae (lateral extensions of the superior sagittal sinus).
What do arachnoid granulations do?
release CSF into the superior sagittal sinus and often produce erosion or pitting (granular foveolae) of the inner surface of the calvaria.
What is the outer most layer of the cranial meninges?
Dura mater
What is the difference between the cranial dura mater, and the spinal dura mater?
there are two layers to the cranial dura mater.
What are the two layers to the cranial dura mater?
periosteal dura - lines the cranial cavity : meningeal layer - inner layer that is sometimes separated from the periosteal layer, forming dural venous sinuses and partitions
What are dural partitions?
elaborations of the meningeal layer of cranial dura mater. They project into fissures of the brain.
What are the 4 cerebral partitions?
falx cerebri falx cerebelli tentorium cerebelli diaphragma sellae
Location of the falx cerebri.
Location: in the longitudinal fissure between the cerebral hemispheres.
What are the attachments of the falx cerebri?
Anterior: crista galli - Posterior: tentorium cerebelli and internal occipital protuberance
Describe the falx cerebri.
Sickle-shaped; inferior concave border is free and contains inferior sagittal sinus; attachment to frontal and parietal bones at the sagittal suture encloses the superior sagittal sinus
Location of the falx cerebelli.
Positioned between cerebellar hemispheres
Describe the falx cerebelli.
Small sickle-shaped projection; Contains the occipital sinus in its attachment to the occipital bone
Where is the tentorium cerebelli?
Between the occipital lobe of the cerebrum and cerebellum; separates forebrain from hindbrain
Describe the tentorium cerebelli.
Crescentic fold; supports the occipital lobe of the cerebral hemisphere; internal concave border is free and defines the tentorial notch; its attachments to the occipital & temporal bones enclose the transverse sinus posteriorly & superior petrosal sinus anteriorly
Where is the Diaphragma sellae?
Covers the sella turcica of the sphenoid bone and pituitary gland.
Describe the diaphragma sellae.
Circular, horizontal fold; has a central aperture for the hypophysial stalk or infundibulum
What is the tectorial notch?
a distinct notch in the tentorium cerebelli. It separates the tentorium cerebelli from the diaphragma sellae.
What is cerebrospinal fluid and where is it formed?
is formed in the brain from arterial blood supplying the choroid plexuses of the ventricles.
How does cerebrospinal fluid drain?
It drains via arachnoid granulations projecting into the superior sagittal sinus.
What are the major parts of the ventricular system of the brain, and how are they connected?
Cerebral hemispheres are hollow and each contain a lateral ventricle. The lateral ventricles communicate with the third ventricle (shared by both hemispheres) by way of the interventricular foramen. The third ventricle is then connected to the fourth ventricle by the narrow cerebral aqueduct.
What is the secretory tissue contained by each lateral ventricle?
the choroid plexuses. they convert arterial blood into cerebrospinal fluid.
What provides a roof to the third and fourth ventricles?
thin membranes with attached choroid plexuses.
Where does the fourth ventricle lie?
between the pons, cerebellum, and the medulla
What does the fourth ventricle communicate with?
cerebral aqueduct, the central canal of the spinal cord, and the subarachnoid space.
What makes the membrane above the fourth ventricle different from the third?
it is perforated by a small median aperture and two lateral apertures that allow cerebrospinal fluid to exit the ventricular system and bathe the brain and spinal cord.
Explain how cerebrospinal fluid is produced.
CSF is secreted (produced) by the choroidal epithelial cells of the choroid plexuses in the lateral, third, and fourth ventricles. It leaves the lateral ventricles through the interventricular foramen and enters the third ventricle. CSF then passes through the cerebral aqueduct into the fourth ventricle. CSF leaves this ventricle through its median and lateral apertures and enters the subarachnoid space, which is continuous around the spinal cord and brain. The arachnoid forms borders of cisterns (spaces around the brain), filled with CSF.
How is cerebrospinal fluid reabsorbed?
The main site for reabsorption of CSF back into the venous system is at the arachnoid granulations. The subarachnoid space containing CSF extends into the arachnoid granulations, which in turn project upward through the dura into the superior sagittal sinus and lateral projections from it called lateral lacunae.
Map out the dural venous system.
Internal carotid a. with cranial branches in order:
Internal carotid > ophthalmic a. > posterior communicating a. > middle cerebral a./anterior cerebral a.
What are the main arterial supplies of the brain?
the internal carotid a., the vertebral a., and circle of willis
Visualize/name each branch in the Cerebral Arterial Circle (Circle of Willis).
Actual circle is Anterior communicating/anterior cerebral/posterior communicating/posterior cerebral
Vertebral a. with cranial branches in order:
Vertebral a. > posterior inferior cerebellar a. (posterior spinal a.) > anterior spinal a. >> (combines to make) basillar a. > anterior inferior cerebellar a. > superior cerebellar a. > posterior ceberal a. (posterior communicating a.)
What is clinically important about the circle of willis?
it forms a means of colateral circulation in case of obstruction
What are the cranial nerves in order from I - XII
Olfactory (CN I), Optic (CN II), Oculomotor (CN III), Trochlear (CN IV), Trigeminal (CN V), Abucens (CN VI), Facial (CN VII), Vestibulocochlear (CN VIII), Glossopharyngeal (CN IX), Vagus (CN X), Accessory (CN XI), Hypoglossal (CN XII)
Olfactory (CN I): Sensory/Motor and Innervation
Sensory / Mucosa of nasal cavity
Optic (CN II): Sensory/Motor and Innervation
Sensory / Retina
Oculomotor (CN III): Sensory/Motor and Innervation
Motor / 4 extra-ocular eye muscles; parasympathetic: ciliary and sphincter pupillae mm.
Trochlear (CN IV): Sensory/Motor and Innervation
Motor / Superior oblique m. (extra-ocular)
What nerves make up the trigeminal n. (CN V)?
(V1) Ophthalmic n. (sensory)
(V2) Maxillary n. (sensory)
(V3) Mandibular n. (both)
Ophthalmic n. (V1): sensory/motor and innervation
sensory / cutaneous sensation from superior face, and mucosa of superior nasal cavity
maxillary n. (V2): sensory/motor and innervation
sensory / cutaneous sensation from midface, maxillary teeth, and mucosa of maxillary sinuses, palate, inferior nasal cavity
mandibular n. (V3): sensory/motor and innervation
Motor - muscles of mastication, tensor veli palatini, tensor tympani, digastric m. (anterior belly), mylohyoid
Sensory - cutaneous sensation from lower face, mandibular teeth, TMJ, anterior 2/3rds of tongue
Abducens n. (CN VI): sensory/motor and innervations
Motor - Lateral rectus m. (extra oricular)
Facial n. (CN VII): sensory/motor and innervations
Sensory: taste, anterior 2/3rds of tongue
Parasympathetic: lacrimal, sublingual, submandibular, and nose/palate glands
Motor: muscles of facial expression, digastric m. (posterior belly), stylohyoid m., and stapedius
Vestibulocochlear n. (CN VIII): sensory/motor and innervations
Inner ear (hearing and equilibrium)
Glossopharyngeal n. (CN IX): sensory/motor and innervation
Sensory: taste, posterior 1/3rd of tongue; carotid body & sinus, middle ear, pharynx, external ear (cutaneous), and parotid gland
Parasympathetic: Parotid gland
Motor: Stylopharyngeus
Vagus (CN X): sensory/motor and innervations
Sensory: Cutaneous sensation from auricle, dura mater of posterior cranial fossa, and external acoustic meatus; taste from palate and epiglottis; visceral sensation from base of tongue to L. colic flexure
Parasympathetic: digestive tract, trachea, bronchi, coronary aa., and conduction system of heart
Motor: intrinsic mm. of larynx, mm. of pharynx, palate mm.
Accessory n. (CN XI): sensory/motor and innervations
motor to SCM and trapezius
Hypoglossal n. (CN XII): sensory/motor and innervations
extrinsic/intrinsic mm. of the tongue
What is a common cause of an epidural hemmorhage, what tissue does it involve, and what would a likely vascular origin be?
Trauma to the pterion : Between the calvaria and periosteal dura : Arterial (middle maningeal a.)
What is a common cause of an subdural (Dural border) hemmorhage, what tissue does it involve, and what would a likely vascular origin be?
Trauma pushing brain violently against cranium : Creates a space between the meningeal dura mater and the arachnoid mater : Venous , superior sagital sinus or superior cerebral v.
What is a common cause of an subarachnoid hemmorhage, what tissue does it involve, and what would a likely vascular origin be?
Rupture of aneurysm : subarachnoid space : Arterial
What is a brain infarction?
an area of dead (necrotic) tissue in the brain, often areas of the cerebrum. This is typically caused by stenosis of an artery (such as the common carotid aa., internal carotid aa., or vertebral aa.), usually by an accumulation of plaque within the artery. A portion of the plaque (an embolus) may dislodge and travel in the bloodstream until it cannot pass (gets stuck) in a smaller, intracranial branch, typically causing insufficient arterial supply to that region of the brain (acute cortical infarction).
