Anatomy [Week 2] Flashcards
What are the 3 CT layers of the meninges?
dura mater, arachnoid mater, pia mater
Where does the majority of venous blood flow in the brain?
dural venous sinuses (into the IJV)
What filters blood plasma to form CSF? Where is it located?
CHOROID PLEXUS; lining walls of all 4 VENTRICLES {flows out of 4th ventricle via apertures)
Where does CSF go from the APERTURES of the 4th VENTRICLE?
out of the median/lateral apertures into SUBARACHNOID SPACE between the arachnoid mater and pia mater
How does CSF get from the SUBARACHNOID MATER back into the VENOUS SINUSES?
via the ARACHNOID VILLI and capillary absorption
What composes the DURA MATER?
PERIOSTEAL and MENINGEAL layers
Where are the 2 layers of the DURA MATER separate?
inseparably bound through most of internal lining but separate at some locations to for DURAL SEPTAE and DURAL VENOUS SINUSES
To what is the PERIOSTEAL layer of the brain attached?
internal surface of the skull via SHARPEY FIBERS; strongly anchored to sutures
What is the MENINGEAL LAYER of dura mater? What special structures does it line?
continuous with dura mater lining internal surface of vertebral canal; envelopes CRANIAL NERVES
What are the DURAL SEPTAE?
folds of MENINGEAL LAYER of dural mater that restrict movement of brain within cranial vault
What is the FALX CEREBRI and where is it located?
layer of MENINGEAL dural mater vertically within longitudinal cerebral fissure; attaches to CRISTA GALLI anteriorly and to TENTORIUM CEREBELLI posteriorly
What is the TENTORIUM CEREBELLI and where is it located?
courses horizontally between PETROUS parts of temporal bone and internal lining of OCCIPITAL bone; separates occipital loves of cerebrum from cerebellum
What does the TENTORIUM CEREBELLI enclose?
TRANSVERSE and SUPERIOR PETROSAL sinuses
What is the DIAPHRAGMA SELLAE?
horizontal hood of DURA MATER that covers the PITUITARY GLAND over the SELLA TURCICA
What is the EPIDURAL SPACE?
potential space between CRANIUM and PERIOSTEAL LAYER of dura mater
When does an EPIDURAL SPACE appear?
pathology; ex. blood hemorrhaging from torn MIDDLE MENINGEAL ARTERY that separates dural mater from skull
Where does the PERIOSTEAL LAYER of the dura mater end and what does that mean for the EPIDURAL SPACE?
it ends at the FORAMEN MAGNUM, which means that it is separate from spinal epidural space
What is SUBDURAL SPACE?
not a natural space; seen during pathology-ex. rupture of cerebral-bridging vein where blood separates dura and arachnoid mater interface
What space is seen when there is a rupture of the CEREBRAL-BRIDGING VEIN?
SUBDURAL SPACE (between dura and arachnoid maters)
What is the LEPTOMENINGES and what is contained in in?
aka SUBARACHNOID SPACE; contains CSF, thin, CELLULAR TRABECULAE of arachnoid mater and many CEREBRAL VESSELS
Which type of cells and cell junctions primarily make up the ARACHNOID MATER?
squamous and cuboidal cells, desmosome cell junctions
What are ARACHNOID VILLI (granulations) and where are they located?
highly folded arachnoid mater projecting into the superior sagittal sinus (often produce indentations in inner surface of calvaria)
What is the purpose of ARACHNOID VILLI?
they are sites where CSF diffuses into blood of SUPERIOR SAGITTAL SINUS
What is the PIA MATER and where is it located?
a 1-2 cell thick layer following the traversing brain and covering blood vessels as they course into the fissures and sulci
What is the relationship to the PIA MATER and CHOROID PLEXUS?
pia mater joins with EPENDYMAL CELLS that line ventricles of brain to form choroid plexus
What is the function of the PIA MATER?
to protect brain and serve as an essential regulatory layer between the subarachnoid space and brain
What does the VENTRICULAR SYSTEM OF THE BRAIN consist of?
2 paired lateral ventricles, and a 3RD and 4TH midline ventricle connected via the CEREBRAL AQUEDUCT; 4th ventricle continuous with central canal of spinal cord
What is the CEREBRAL AQUEDUCT?
connected the 3RD and 4TH VENTRICLES; allows movement of CSF between them
What do the LATERAL VENTRICLES communicate with? Through which opening?
with the 3RD VENTRICLE via the INTERVENTRICULAR FORAMEN
Where is the 3RD VENTRICLE located?
space between the right and left halves of the DIENCEPHALON
What is the 4TH VENTRICLE and where is it located?
diamond-shaped fossa posterior to PONS and MEDULLA and anterior to CEREBELLUM; tapers infeciorly into narrow channel that continues inferiorly as the CENTRAL CANAL
What is CSF composed of and where does it come from?
clear, watery fluid with some electrolytes/protein that arises as ultrafiltrate and secretory product of CHOROID PLUSES of ventricles; receives minor contributions from capillaries in brain and EPENDYMAL lining of ventricles
What is the CEREBRAL AQUEDUCT OF SYLVIUS?
narrow channel within MIDBRAIN that connects 3RD/4TH VENTRICLES; DOES NOT CONTAIN CHOROID PLEXUS
Does the CEREBRAL AQUEDUCT contain choroid plexus?
NO!!!!!
What do the cells of the CHOROID PLEXUS serve as?
a blood-CSF barrier (BBB)
What is the volume of the CSF within VENTRICLES and SUBARACHNOID SPACE?
about 125-150 mL
Of the CSF in ventricles/subarachnoid space, how much is intracranial and how much in spinal cord?
intracranial=125 mL; 25 mL in ventricles and 100 in subarachnoid space
spinal cord=25 mL
What is the function of CSF?
to provide a hydraulic cushion to buoy and protect brain and spinal cord within bony encasements; also prevents weight of brain from compressing CRANIAL NERVES and blood vessels
Describe the circulation of CSF from the CHOROID PLEXUS to the SUBARACHNOID SPACE.
about 450 mL/day CSF produced from choroid plexus–>leaves lateral ventricles, down intraventricular foramen to 3rd ventricle then through cerebral aqueduct to 4th ventricle–>CSF enters subarachnoid space via:
(1) MEDIAN APERTURE OF MAGENDIE
(2) LATERAL APERTURE OF LUSCHKA
What is the MEDIAN APERTURE OF MAGENDIE?
UNPAIRED opening that drains CSF from 4th ventricle into CISTERNA MAGNA of subarachnoid space
What is the CISTERNA MAGNA?
type of subarachnoid space; posterior to pons and anterior to cerebellum; MEDIAN APERTURE drains to here
What is the LATERAL APERTURE OF LUSCHKA?
PAIRED openings that drain CSF from 4th ventricle into CEREBELLOPONTINE ANGLE CISTERN of subarachnoid space
What is the CEREBELLOPONTINE ANGLE CISTERN?
type of subarachnoid space; LATERAL APERTURE of 4th ventricle drains here
Why can increased CSF volume result in vision deficit?
CSF surrounds CRANIAL NERVES as it exits the 4th ventricle into the subarachnoid space; the optic nerve, CN II, is particularly vulnerable
How is CSF ultimately absorbed back into systemic blood stream?
via MENINGEAL CAPILLARIES, EXTRACRANIAL LYMPHATICS and ARACHNOID VILLI
From which 3 arteries do the DURA MATER and overlying SKULL BONES receive their arterial supply?
ANTERIOR MENINGEAL ARTERY (AMA)
MIDDLE MENINGEAL ARTERY (MMA)
POSTERIOR MENINGEAL ARTERY (PMA)
From where does the ANTERIOR MENINGEAL ARTERY originate and what does it supply?
originates from the ANTERIOR and POSTERIOR ETHMOIDAL ARTERIES; supplies DURA MATER in anterior cranial fossa
From where does the MIDDLE MENINGEAL ARTERY ORIGINATE and what does it supply?
originates from the MAXILLARY ARTERY (infratemporal fossa) and traverses the FORAMEN SPINOSUM and courses along the SQUAMOUS part of temporal bone–>bifurcates into FRONTAL and PARIETAL branches; supplies dura mater and overlying skull
What is an important relationship between the MMA and AURICULOTEMPORAL NERVE?
auriculotemporal nerve SPLITS and courses around both sides of the MMA prior to joining together again adjacent to TEMPOROMANDIBULAR joint
From where does the POSTERIOR MENINGEAL ARTERY ORIGINATE and what does it supply?
PMA originates from OCCIPITAL ARTERY and supplies dura mater in POSTERIOR cranial fossa
Where are the DURAL VENOUS SINUSES located?
between periosteal and meningeal layers of dura mater
What are a few characteristics of the DURAL VENOUS SINUSES?
lined with endothelium, LACK VALVES, serve as vessels for blood from the cerebral veins, diploic veins and emissary veins, receive CSF drained by arachnoid granulations
Where does the blood from the DURAL VENOUS SINUSES primarily drain? How about secondarily? Why?
primary=INTERNAL JUGULAR VEINS
secondarily=SUPERIOR OPHTHALMIC VEINS or PTERYGOMAXILLARY PLEXUS (because no valves)
Where does the SUPERIOR SAGITTAL SINUS course?
from FALX CEREBRI at FORAMEN CECUM where it communicates with nasal cavity [*danger triangle]; courses along superior border and drains into confluence of sinuses where deviates to RIGHT side (usually) as TRANSVERSE SINUS
What is the course of BRIDGING VEINS?
from brain, pierce ARACHNOID and DURA maters and drain directly into SUPERIOR SAGITTAL SINUS
What is the course of the INFERIOR SAGITTAL SINUS?
in midline along inferior forder of FALX CEREBRI along CORPUS CALLOSUM; receives veins from medial surface of cerebrum and joins with GREAT CEREBRAL VEIN OF GALEN to form STRAIGHT SINUS
What is the course of the STRAIGHT SINUS?
along line of attachment of FLAX CEREBRI to TENTORIUM CEREBELLI; continuation of INFERIOR SAGITTAL SINUS and drains into TRANSVERSE SINUS
What is the course of the OCCIPITAL SINUS?
within FLAX CEREBELLI from confluence of sinuses and terminates at FORAMEN MAGNUM with the INTERNAL VERTEBRAL VENOUS PLEXUS (smallest of dural venous sinuses)
What is the CONFLUENCE OF SINUSES?
the union of: -SUPERIOR SAGITTAL SINUS -STRAIGHT SINUS -OCCIPITAL SINUS at internal occipital protuberance
What is the course of the TRANSVERSE SINUS?
laterally from CONFLUENCE OF SINUSES within tentorium cerebelli inferiorly as SIGMOID SINUS; receives INFERIOR CEREBRAL and INFERIOR CEREBELLAR VEINS
Why is the RIGHT transverse sinus usually larger than the left?
because it is a continuation of the SUPERIOR SAGITTAL SINUS!
What is the course of the SIGMOID SINUS?
continuation of TRANSVERSE SINUS; descending S-shaped groove; unites with SUPERIOR PETROSAL SINUS at the JUGULAR FORAMEN to form the IJV
Where is the CAVERNOUS SINUS located?
on each side of the SELLA TURCICA, extending from the superior orbital fissure to the petrous part of temporal bone
What courses through the middle of the CAVERNOUS SINUS? What courses anteriorly through its lateral walls?
in middle= INTERNAL CAROTID ARTERY and CN VI
anteriorly=CN III, CN IV, CN VI, CN V2
How does the CAVERNOUS SINUS communicate with the PTERYGOID VENOUS PLEXUS?
via EMISSARY VEINS and SUPERIOR/INFERIOR OPTHALMIC VEINS (in orbit)
How does the CAVERNOUS SINUS communicate with the TRANSVERSE SINUS?
via SUPERIOR PETROSAL SINUS
How does the CAVERNOUS SINUS communicate with the INTERNAL JUGULAR VEIN?
via SUPERIOR/INFERIOR PETROSAL SINUS
What is the course of the SUPERIOR PETROSAL SINUS?
along superior portion of PETROUS part of temporal bone from CAVERNOUS SINUS to TRANSVERSE SINUS
What is the course of the INFERIOR PETROSAL SINUS?
along inferior portion of PETROUS part of temporal bone from CAVERNOUS SINUS to IJV
What is the SPHENOPARIETAL SINUS?
variable sinus that is more likely combination of sinus of LESSER WING of sphenoid bone and MIDDLE MENINGEAL VEIN; joins CAVERNOUS SINUS
What is the course of DIPLOIC VEINS?
within SPONGY portion of cranial bones and drain into most of DURAL VENOUS SINIUSES
What is the course of EMISSARY VEINS?
EXTRACRANIALLY from scalp into DURAL VENOUS SINUSES intracranially
Describe LYMPHATICS in the context of the brain and spinal cord.
lymphatic vessels DO NOT EXIST within parenchyma of brain/spinal cord
What gives the DURA MATER general SENSORY and SYMPATHETIC INNERVATION (to blood vessel smooth muscle)?
MENINGEAL BRANCHES of 3 divisions of CN V and C2-C3 spinal nerves
Where is pain from the dura mater usually referred? What nerves are responsible for this?
to the head; it is perceived as a headache; from mucosal regions supplied by CN V or C2-C3 dermatomes
How is GRAY and WHITE matter arranged in the spinal cord?
gray=inside
white=outside
A patient comes to the ER after getting hit in the side of the head with a softball during an intramural game. He passed out at the scene then regained consciousness, so his teammates thought he was okay. Later, however, he lost consciousness again. In the ER you notice swelling of the patient’s head that stops abruptly as a “lensticular” shape. What would be in your differential diagnosis and what structures would be involved? What is the worst outcome anatomically?
- the ball probably hit the PTERION SUTURE, causing a fracture and laceration of the FRONTAL, MIDDLE MENINGEAL ARTERY, leading to an EPIDURAL HEMATOMA (separation of peritoneal layer of dura mater from skull bone); “lensticular” shape is due to dura mater’s strong attachment to cranial sutures, limiting spread of blood
- worst outcome would be that the brain is compressed down through the FORAMEN MAGNUM
A patient comes to the ER after a car accident during which the patient had to slam on her breaks. In the ER you notice amorphous swelling of the patient’s head. What would be in your differential diagnosis and what structures would be involved?
because the dura matter and arachnoid mater is connected tightly to the skull, the sudden stop would cause the brain to move within its casing, causing sheering of the BRIDGING VEINS (in the SUBARACHNOID SPACE) leading to a SUBARACHNOID HEMATOMA
A patient comes to the ER because he has a terrible headache. He tells the doctor he was playing a drinking game to The Dark Knight where he took a shot every time Christian Bale did his Batman voice. What is the physiological cause of this headache?
alcohol causes you to become dehydrated (it is a diuretic) and so your CSF volume decreases, causing the bath of CSF fluid around the brain to decrease, stimulating CN V sensory nerves due to mechanical forces on the brain (it isn’t suspended anymore)
What groove runs along the anterior portion of the TENTORIUM CEREBELLI attachment?
SUPERIOR PETROSAL groove (contains the venous sinus)
Which 2 canals are part of the JUGULAR FORAMEN and which structures go through the each?
VASCULAR canal=INTERIOR JUGULAR FORAMEN
NERVOUS canal=CN IX, X, XI
What is the path of venous drainage when standing up?
- superior sagittal sinus and confluence of sinuses drain into…
- transverse sinus which drain into…
- [superior transverse sinus and] sigmoid sinus which drains into..
- IJV which track through…
- JUGULAR CANAL
Where does the PTERYGOID VENOUS PLEXUS drain?
directly to CAVERNOUS SINUS
You need to do an emergency procedure to put in a CENTRAL VENOUS CATHETER. Which side and through which structure should you put the catheter?
through the IJV on the RIGHT side by finding SCM and inserting the needle between the insertion of the clavicle and sternum; RIGHT because IJV meets subclavian and goes all the way across the midline on the left side before it dumps into the RIGHT ATRIUM (so would need longer catheter on left side)
What are the tributaries to the DANGER ZONE OF THE FACE?
- ANGULAR (supraorbital=sup/inf. ophthalmic v.; supratrochlear, external nasal)*
- SUPERIOR LABIAL*
- DEEP FACIAL*
- INFERIOR LABIAL*
- TONSILLAR
- SUBMENTAL
- SUBMANDIBULAR
- exposed to surface of face
Why is the DANGER ZONE OF THE FACE dangerous?
a clotting cascade from infection or the infection itself have direct access to the CAVERNOUS SINUS, and therefore to the brain
A teenager picked a pimple two days ago on his nose and now he cannot look laterally (eye stuck medially) with his left eye and he has double vision. What happened and which nerve is affected?
the angular vessels of CN VII drain directly into cavernous sinus which, when an infection gets in, can swell and affect CN VI (innervating the LATERAL RECTUS MUSCLE of the eye)
Which nerves are close in proximity to the CAVERNOUS SINUS? Which is the closest?
- CN III, CN IV, CN V (1 &2), CN VI
- CN VI is the closest
A patient has a cavernous sinus THROMBOSIS. Which nerve is most likely to be affected and how will the patient present?
CN VI (abducens); lateral rectus muscle not working–>eye pointed in medially and patient would have double vision due to venous swelling
A patient has a stabbing pain on the bridge of his nose. Which nerve is the CAVERNOUS SINUS THROMBOSIS affecting?
CN V (1)
A patient has a stabbing pain on his upper lip. Which nerve is the CAVERNOUS SINUS THROMBOSIS affecting?
CN V (2)
From what is the ANTERIOR CRANIAL FOSSA formed?
- orbital plates of frontal bone
- jugum of sphenoid
- lesser wings of sphenoid
- crista galli and cribriform plate of ethmoid
What goes through the OLFACTORY FORAMINA?
olfactory nerve (CN I)
What surrounds the OLFACTORY BULB?
subarachnoid space with CSF
What provides attachment for the FLAX CEREBRI in the ANTERIOR CF?
CRISTA GALLI
What usually goes through the FORAMEN CECUM?
emissary vein
How might a fracture of the floor of the ANTERIOR CF result in leakage of CSF from the nose?
the OLFACTORY BULB is surrounded by CSF and is connected to the nasal opening via cribriform plates; subarachnoid space and nasal cavity are in continuity
What is CSF RHINORRHEA?
when a cribriform fracture causes the CSF surrounding the olfactory bulb to leak out the nose