Brain and Meninges Flashcards
Average mass of brain
1300 to 1400 grams
Telencephalon
Cerebrum
Cerebral hemispheres separated by the longitudinal fissure
Gyri and Sulci
Lobes - frontal, parietal, temporal, insula, and occipital
Diencephalon
Thalamus
Epithalamus
Hypothalamus
Mesencephalon
Midbrain
Metencephalon
Pons and Cerebellum
Myelencephalon
Medulla Oblongata
Cerebrum
Frontal
Parietal
Occipital
Temporal
Frontal Lobe
(motor control, personality, judgment, planning, language production)
Parietal Lobe
Sensation, body orientation
Occipital Lobe
Visual perception and interpretation
Temporal Lobe
Audition (hearing), language comprehension and memory
Cerebellum
coordination and control of movement
Brainstem
midbrain, pons, medulla oblongata
Breathing, reticular activation (consciousness) and cardiovascular control
Diencephalon
Relay of sensory info; feeding, emotion, fight or flight response, and sexual behavior
Meninges
Cranial meninges are continuous with the spinal meninges at the foramen magnum
Dura, arachnoid, pia
Cranial dura mater
Two layers
Periosteal
Meningeal
Periosteal Dura Mater
outer layer representing the periosteum of the cranial cavity
contains meningial arteries
NOT continuous with the spinal dura mater
Meningeal Layer of dura mater
Inner layer continuous with the spinal dura mater at the foramen magnum
The two layers separate and form…
- Dural partitions (folds)
2. Venous Sinuses (important for drainage)
Dural Partitions
Falx Cerebri - separates cerebral hemispheres
Tentorum Cerebelli - separates cerebellum from posterior portions of cerebral hemispheres
Falx Cerebelli - short projection btw cerebellar hemispheres
Diaphragma sellae - forms a roof over the sella turcica
Primary arterial supply is from
Middle meningeal arteries (branches of the maxillary arter)
Innervation
Principally by the ophthalmic, maxillary, and mandibular divisions of triggeminal (CN V)
Dura of posterior cranial fossa - upper cervical nerves
Arachnoid Mater
Thin membrane lining the inner meningeal layer of the dura mater
Thin processes extend into the subarachnoid space and are continuous with the pia mater
Pia Mater
Thin, delicate membrane adherent to the surface of the brain
Meningial Spaces
Extradural (Epidural) Space
Subdural Space
Subarachnoid Space
Extradural (Epidural) Space
Potential space btw the skull and periosteal dural layer
Extradural (Epidural) Space Clinical Correlation
Becomes a real space when an extradural hematoma forms from either a rupture of the meningeal artery or a tear in a dural venous sinus
Subdural Space
Potential space btw menngeal dural layer and arachnoid mater
Subdural Space Clinical Correlation
Real space may result when a subdural hematoma forms from the tearing of a vein entering a dural venous sinus
Subarachnoid Space
Real space btw arachnoid mater and pia mater filled with CSF
CSF is formed by specialized vascular structures, the choroid plexuses, in the ventricles and is reabsorbed into the dural venous sinuses via arachnoid villi that form the arachnoid granulations and lateral lacunae
Subarachnoid Space Clinical Correlation
Subarachnoid hemorrhage - most result from ruptures aneurysm
Ventricular System
Cavities filled with CSF secreted by the choroid plexuses
Lateral Ventricles
Each communicates with 3rd ventricle via interventricular foramen (aka foramen of monro)
Third Ventricle
Communicates with 4th ventricle via cerebral aqueduct (of sylvius)
Fourth Ventricle
Communicates with subarachnoid space via the median aperture (foramen of Magendie) and lateral apertures (foramen of Luschka)
Ventricular System - Clinical Correlation
Hydrocephalus - dilation of the ventricular system of the brain due to
1. obstruction of CSF flow (most common)
2. CSF not being adequately reabsorbed (less common)
3. overproducation of CSF (rare)
Not in adults - fused bones
Arterial Supply
Two pairs of arteries supply the brain
- Vertebral
- Internal Carotid Arteries
Vertebral arteries join and form the
Basilar Artery
- it then divides into the posterior cerebral arteries
Internal carotid arteries divide into
Terminal branches
Anterior and middle cerebral arteries
Cerebral Arterial Circle (of Willis)
Internal Carotid Arteries Anterior Cerebral Arteries Anterior Communicating Artery Posterior Communicating Arteries Posterior Cerebral Arteries
Clinical Correlation Arterial Supply
strokes relate to a disruption in blood supply leading to tissue death
A Cerebral Infarction occurs when blood is obstructed, and can lead to an ischemic stroke
A Cerebral Aneurysm is a weak spot in cerebral vessel which can rupture causing a hemorrhagic stroke
Location will affect specific brain structures and thus affect specific functions
Venous Drainage
Small cerebral and other veins drain into dural venous sinuses, which (most) ultimately drain into the internal jugulars
Name Venous Drainage
Superior Sagittal Sinus Inferior Sagittal Sinus Confluence of Sinuses Transverse Sinuses Sigmoid Sinuses Cavernous Sinuses Superior and Inferior Petrosal Sinuses
Confluence of Sinuses
Meeting of superior sgaittal, straight, and occipital
Transverse Sinuses
Drain the confluence and continue distally as the sigmoid sinuses, emptying into the internal jugular veins
Cavernous sinuses
Relation to danger triangle
CN 1
Olfactory - sensory for smell
CN II
Optic - sensory for vision
CN III
Oculomotor - motor to levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, inferior oblique, sphincter pupillae, and ciliary muscles
CN IV
Trochler - motor to superior oblique
CN V
Trigeminal - sesnory from face and dura mater
Motor to muscles of mastication, anterior belly of digastric, and mylohyoid
CN VI
Abducens - motor to lateral rectus
CN VII
Facial - Sensory from external acoustic meatus portion of auricle
Taste from anterior 2/3 tongue
Motor to submandibular, sublingual, and lacrimal glands
Motor to muscles of facial expression, posterior belly of digastric, stylohyoid, and stapedius
CN VIII
Vestibulocochlear - sensory for balance and hearing
CN IX
Glossopharyngeal - sensory from carotid belly and sinus, posterior 1/3 tongue, palatine tonsils, oropharynx, and mucosa of middle ear and pharyngotympanic tube
Taste from posterior 1/3 of tongue
Motor to parotid gland and stylopharyngeus
CN X
Vagus - sensory from larynx, laryngopharynx, parts of auricle and external acoustic meatus, aortic body chemoreceptors and aortic arch baroreceptors, esophagus, bronchi, lungs, heart, and abdominal viscera
Taste from epiglottis and pharynx
Motor to GI viscera, throacic viscera, larynx, pharynx, palatoglossus, and palate
CN XI
Accessory - Motor to trap and SCM
CN XII
Hypoglossal - Motor to intrinsic tongue muscles, hypoglossus, genioglossis, styloglossus
