Lecture 5: Dural Sinuses, Meninges, and Vasculature Flashcards
What are the three layers of the cranial meninges from superficial to deep?
Dura Mater, Arachnoid Mater & Pia Mater
What are the two layers of dura mater?
Periosteal Layer: attached to cranial bones
Meningeal Layer
What is the space called between the two layers of the dura mater?
Dural Septa
What are emissary veins?
Veins that drain the scalp into the dural venous sinuses
What are the structures that collect pools of blood in the brain and drain the central NS, face and scalp?
Where do they ultimately drain to?
Dural Venous Sinuses
Internal Jugular Vein
What can infections of the scalp lead to?
Meningitis
What are bridging veins?
Veins that drain cerebral cortex into the dural venous sinuses
What is the subdural space?
Potential space between arachnoid and dura mater. In theory, this space should not exist.
What can form a subdural space?
- Bleeding of Bridging Veins
- Lumbar Punctures
What is found in the subarachnoid space?
CSF & Branches of the Internal Carotid A.
How can aneurysms form in the subarachnoid space?
Low collagen can cause weaker blood vessels, which can lead to higher potential of aneurysms from the Internal Carotid A. branches in the subarachnoid space.
Where is pia mater found?
Tightly adheres to brain and follows every contour of the brain surface
What is the cranial dural septa? What is their purpose?
Meningeal layer of Dura Mater extends as flat partitions deep into the cranial cavity. The septa provides stabilization and support for the brain. It also separates specific parts of the brain.
What does the falx cerebri separate?
The two hemispheres of the cerebrum
What does the tentorium cerebelli separate?
Cerebellum from Cerebrum
What does the falx cerebelli separate?
The two hemispheres of the cerebellum
What is the diaphragma sellae?
Dura Septa that covers the Pituitary Gland
What plane is the falx cerebri and falx cerebelli found in?
Sagittal Plane
What plane is the tentorium cerebelli found in?
Transverse/Horizontal Plane
What are the dural venous sinuses that are found in the cranial dural septa?
- Superior Sagittal Sinus
- Inferior Sagittal Sinus
- Straight Sinus
- Transverse Sinus
- Sigmoid Sinus
- Cavernous Sinus
- Superior Petrosal Sinus
- Inferior Petrosal Sinus
- Confluence of Sinuses
What is the main artery that supplies the three layers of the cranial meninges? Where does it branch from?
Middle Meningeal Artery
ECA –> Maxillary Artery –> MMA
What are the two branches of the Middle Meningeal Artery?
How does it enter the cranium
Anterior and Posterior Branch
Foramen Spinosum
What cranial nerve provides sensory afferent information to the meninges?
All branches of Cranial Nerve V (Trigeminal Nerve)
What causes an epidural hematoma? What does it look like on an x-ray?
Ruptured Middle Meningeal Artery - can be caused if hit at the pterion. Lens shaped hematoma on side of brain
Epidural hematoma is when bleeding occurs between the tough outer membrane covering the brain (dura mater) and the skull
What is a pterion?
Point where temporal bone, parietal bone, sphenoid bone, and frontal bone meet. Middle Meningeal lies deep to it.
What causes a subdural hematoma? What does it look like on an x-ray?
Bleeding of bridging veins froms blow to head that jerks brain inside cranium (i.e. hitting windshield in car accident). Crescent shaped hematoma on side of brain
gathers between the inner layer of the dura mater and the arachnoid mater of the meninges surrounding the brain. It usually results from tears in bridging veins that cross the subdural space.
What causes a subarachnoid hemmorrhage? What does it look like on an x-ray?
Ruptured cerebral arteries or anuerysm leading to extravasation of arterial blood into subarachnoid space. Can also be caused by head trauama or a bad lumbar puncture. Spiderweb shape
Predipositions: pregnancy and people with hypertension.
Where can the supra-orbital vein, superior ophthalmic vein, and inferior ophthalmic vein drain into?
- Facial Vein
- Dural Venous Sinuses via the orbit
What does the Sigmoid sinus drain into?
Jugular Vein
What structures are in the cavernous sinus?
Pituitary Gland - sits in hypohysial fissure
Internal Carotid Artery
CN III (Oculomotor Nerve)
CN IV (Trochlear Nerve)
CN VI (Abducens Nerve)
CN V1 (Ophthalmic Nerve),
CN V2 (Maxillary Nerve)
What type of blood surrounds cavernous sinus?
Venous Blood
What structures sit inside the cavernous sinus and not the wall
Internal Carotid A. & Abducens Nerve (CN VI)
What structures sit in the wall of the cavernous sinus (Dura Mater)
Occulomotor N
Trochlear N
Opthalmic N (CN V1)
Maxillary N (CN V2)
What causes a cavernous sinus thrombosis and what are the symptoms?
Infection of face that can spread through Facial V. (ophthalmic vein) and reach cavernous sinus.
Symptoms: Edema & chemosis of the eyes (puffiness and redness)
Cranial nerve VI (abducens N) palsy = Eyes can’t move laterally.
HINT THAT IT’S VEIN NOT ARTERY: Veins are bidirectional in the head and neck
Where is cerebrospinal fluid (CSF) found?
Subarachnoid Space - space between the Arachnoid Mater and Pia Mater
What makes CSF?
Choroid plexus in ventricles
What is the difference between CSF and blood plasma composition?
CSF: Greater sodium, hydrogen and calcium but less potassium
What structure drains CSF into dural venous sinuses?
Arachnoid Granulations
What happens if there is a problem with pressure gradient with dural venous sinuses or an obstruction in CSF to the Dural Venous Sinuses?
Hydrocephalus (brain has enlarged ventricles)
What is unique about the venous structures in the head and neck
They are bi-directional. Don’t have valves pushing them in one direction. Move through pressure gradient.
What is the main artery that supplies the neck and face and what are it’s main branches?
Common Carotid A.
External Carotid A. & Internal Carotid A.
What is the Carotid Sinus & where is it found?
reflex area of the carotid artery, consisting of baroreceptors which monitor blood pressure.
Found superior to bifurcation on internal carotid A.
What are the branches of the External Carotid A.
Superior Thyroid
Ascending Pharyngeal A
Lingual A.
Facial A.
Occipital A.
Posterior Auricular A.
Maxillary A.
Superficial Temporal A.
Some Anatomist Like Freaking Out Poor Medical Students
What is the terminal branch of the Facial A.
Angular A.
located in the medial angle of the eye
What are the divisions of the Maxillary A.
Mandibular Part
Pterygoid Part
Pterygopalatine Part
List the Maxillary A branches you should know for lab
Mandibular Part: Middle Meningeal, Inferior Alveolar,
Pterygoid Part: Buccal, Anterior and Posterior Deep Temporal
Pterygopalatine Part: Posterior Superior Alveolar, Infraorbital, Descending Palatine, Greater Palatine, Lesser Palatine, Sphenopalatine
Route of Internal Carotid A
Doesn’t branch in neck. Enters cranium via carotid canal in temporal bone. Courses through cavernous sinus then branches.
Branches of Internal Carotid A
Opthalmic A.
Anterior Cerebral A.
Middle Cerebral A.
What are the branches of the Opthalmic A for lab
Lacrimal A.
Supraorbital A.
Supratrochlear A.
Anterior Ethmoidal A.
Posterior Ethmoidal A.
Note: opthalmic means relating to eye (LSA - Looking Superior w/ Eyes
What is the Circle of Willis
The Circle of Willis is the joining area of several arteries at the bottom (inferior) side of the brain
What structures make up the circle in the Circle of Willis
Hint: list from top to bottom
Anterior cerebral artery (2)
Anterior communicating artery
Internal Carotid A. (2)
Middle cerebral A. (2)
Posterior communicating artery (2)
Posterior cerebral A. (2)
Basilar A.
What is Subclavian Steal Syndrome
Occlusion of the subclavian artery. Blockage causes reverse flow through the verterbral artery of the affected side to supply blood to upper extremity, decreasing blood flow to the brain.
What is the Danger Zone
Triangle area from upper lip and bridge of nose where an infection can lead to cavernous thrombosis.
