Meninges, Dural Folds, and Venous Sinuses Flashcards
What are the Cranial Meninges?
Dura Mater (dense irregular CT)
Arachnoid Mater (Loose CT)
Pia Mater (loose CT with direct contact with brain)
What are the Layers of the Dura Mater?
Periosteal Dura: inner periosteum of the cranial bones (cannot be separated from the bones)
Meningeal Dura: Forms Dural “Reflections” or “Folds” but also Dural Venous Sinuses
What do dural venous sinuses do?
Carry venous blood and cerebrospinal fluid
What is the pathway of sinus drainage?
Inferior Sagittal sinus drains into straight sinus to form confluence of sinus with the Superior sagittal sinus
Transverse sinuses drain the confluence into the sigmoid sinus before entering internal jugular veins
*cavernous sinus is also drains into this network via inferior/superior petrosal sinus
How are Dural Venous Sinuses different than veins?
They do not have wall layers (only tunica intima) and no valves
Where does the ophtalmic veins drain?
cavernous sinus
What structures are found within the cavernous sinus?
Internal carotid a.
CN III, IV, V1, V2, VI
What is cavernous sinus syndrome?
Inflammation of the cavernous sinus causing ophthalmoplegia (paralysis of eye muscles) and proptosis (protrusion of the eyes)
Trigeminal sensory loss
Where does CSF flow?
Subarachnoid space
What is the blood supply to the brain (percentages)?
Internal Carotid Artery: 75%
Vertebral Artery: 25%
What are the embryological derivatives of the ventricles of the brain?
Telencephalon: Lateral Ventricle
Diencephalon: Third Ventricle
Mesencephalon: Cerebral Aqueduct
Metencephalon: Anterior part of the fourth ventricle
Myelencephalon: Posterior part of the fourth ventricle
What are Choroid Plexus?
Structures that form CSF as blood filtrate
-found in walls of ventricles and supplied by cerebral arteries
What is the pathway of CSF circulation?
Lateral Ventricles -> third ventricle -> Cerebral aqueduct -> fourth ventricle -> central canal or median/lateral apertures -> subarachnoid space -> arachnoid villi -> superior sagittal sinus
Describe what an epidural hematoma is
Bleeding in the epidural space (convex)
Rupture of middle meningeal artery near the pterion is common cause
Describe a Subdural hematoma
Bleeding in the subdural space. (concave)
Often caused by tearing of bridging veins
What is a subarachnoid hemorrhage?
Artery of the circle of Willis ruptures
Describe the pathway of Sympathetic Nerves of the head and neck
Preganglionic neurons bodies found in lateral horn of T1-T3
Synapse occurs at cervical sympathetic ganglia
Postganglionic fibers form plexuses around branches of carotid arteries
What are the general patterns (levels) of sympathetic nerves of the head?
Superior cervical ganglion (levels C1 - C2)
Middle cervical ganglion (levels C6)
Inferior cervical ganglion (C7)
What structures of the head get sympathetic innervation?
Dilator pupillae muscle: pupillary dilation
Superior tarsal muscle: elevation of upper eyelid
Blood vessels: vasoconstriction
Sweat glands: diaphoresis (sweating)
What is Horner’s Syndrome?
Lesion of the sympathetic pathway to the head
-causes vasodilation, miosis, ptosis, anhidrosis
Where does the oral cavity drain (lymph)?
Submandibular nodes
What does the Anterior cervical nodes drain?
Larynx, tongue, oropharynx, and anterior neck
Where structures drain into the supraclavicular nodes?
gastrointestinal tract, genitourinary tract, pulmonary
What structures drain into the preauricular nodes?
Scalp and skin
What structures drain into the posterior cervical nodes?
scalp, neck, upper thoracic skin
