Cranial Fossa:Brain and Spinal Cord

PA 481 A&P

Tony Serino, Ph.D.

Biology Dept.

Misericordia Univ.

Central Nervous System (CNS)

• Gray vs. White matter• Protection of CNS

– Meninges– CSF flow

• Brain– Development– Selected structures

• Spinal cord– Selected structures

Cranial Fossa

Anterior

Middle

Posterior

CNS (Central Nervous System)

• Brian and spinal cord

• Displays gray and white matter– Gray matter are areas of CNS with many cell

bodies of neurons present (little myelinated nerve fibers)

– White matter are area of CNS with few cell bodies but many myelinated nerve fibers

• Protected by bone and membranes

Gray and White Matter

• Since the cerebrum and cerebellum outgrow their cores, gray matter ends up on outside of both structures.

Meninges• Dura Mater –outermost; tough, fibrous CT

– In brain, divided into two layers (periosteal and meningeal)

– In spine, only one layer with fat filled space above the layer called the epidural space

• Arachnoid –middle; web-like appearance– Potential space between Dura and arachnoid is

the subdural space

• Pia Mater –innermost, delicate membrane fused with CNS surface– Space between Pia and Arachnoid is the

subarachnoid space

Meninges of the Spinal Cord

Pia materArachnoid

Dura mater Meninges

Centrum

Epidural space

Subdural space

Subarachnoid space

Dorsal Root Ganglion

Brain Meninges

Extensions of Dura Materhold brain in cavity

Sellar diaphragm (not shown)

Venous Sinuses of Cranium

Superior Sagittal

Inf. Sagittal

Straight

Cavernous

Sigmoid

Transverse

Lateral Venous Lacunae

Arachnoid villi

Maxillary A.

Middle Meningeal A.

Middle Meningeal Artery

Brain Ventricles

Choroid Plexus

CSF (cerebral-spinal fluid) Flow

Hydrocephalus

• Blockage of CSF flow can lead to severe brain and/or head enlargement.

• In an adult, such swelling would be fatal.

Brain

• Development• Structures• Functional Areas

Neural Tube

forming

Neural Tube

Brain Vesicles

Flexures and Cerebral Cortex Growth

Major Divisions of Brain

Brain Stem = midbrain + pons + medulla

Brain Anatomy (req’d)

Projections vs. Commissures

Functional Anatomy of Brain

Functional Areas of Cerebrum

Primary Motor and Somatosensory Gyri

Basal Nuclei: cerebral nuclei

Putamen and Globus Pallidus

Subthalamic nuclei andthe Substantia nigra are usually included

Reticular FormationExtends along length of brain stem; used in maintaining alertnesswhile awake; also includes motor nuclei such as centers for Cardiac,Respiratory and Vasomotor control.

RAS receives inputs from eye, ear and genral sensation to maintain alertness

Limbic System: functional system; responsible for emotion and memory

Cingulate Gyrus

Fornix

Mammillary body

Hypothalamus Control of Pituitary

Posterior Pituitary

Anterior Pituitary

Pineal Gland• Plays a major role in

circadian rhythm control through its sympathetic connection to the hypothalamus

• Melatonin increases at night and decreases during daylight

• Implicated in the control of major life changes (such as the onset of puberty and adulthood

Internal Carotid Artery

Blood Supply(Circle of Willis)

Vertebral A.

Internal Carotid A.

Ant. Communicating

Post. Communicating

Ant. Cerebral

Post. Cerebral

Middle Cerebral

Basilar A.

Cranial Nerves

CN I: Olfactory Nerve• covered by meninges and contain glial cells•Cribiform plate damage after trauma could lead to CSF leakage (runny nose after head trauma)

Pathway: Bulbtract med and lat. stria prepiriform and amygdala

CN II: Optic Nerve•Covered by meninges•Leaves by optic canal•Pathway: nervechiasma tracts lat. geniculate and sup. colliculus optic radiation to occipital lobe

Superior Orbital Fissure Midbrain

PonsOculomotor N. (III)

Ciliaryganglion

InferiorRectus muscle

InferiorOblique muscle

Superior Rectusmuscle

Medial Rectusmuscle

Levator Palpabraemuscle

ParasympatheticMotor fibers

•Originates from brain stem: midbrain•Leaves via sup. orbital fissure•Path: occulomotor nucleus muscles : levator palpebrae, sup., medial, inf. rectus, and inf. oblique. Separate branch from Edinger-Westphal nuclues ciliary ganglion parasym innervation to iris sphincter and ciliary muscle.

Palsy –leads to ptosis, diplopia, dilated pupil; gaze is “down and out”; pupil involvement usually due to increase cranial pressure due to surface location of fibers in nerve

CN III: Occulomotor Nerve

CN IV: Trochlear Nerve•Originates from brain stem: midbrain•Complete decussation in midbrain•Nucleus to Sup. oblique, runs the longest distance in cranial vault•Passes through sup. orbital fissure•In injury, affected eye is higher and deviated medially, head tilts away from lesion; hardest to diagnose

CN V: Trigeminal Nerve

CN VI: Abducens Nerve

•Originates from brain stem: pons goes to lateral rectus m.•Passes through sup. orbital fissure•Injury: affected eye deviates medially (crosseyed look) patient may turn head to compensate

CN VII: Facial Nerve

CN VIII: Vestibulocochlear Nerve

CN IX: Glossopharyngeal Nerve

CN X: Vagus Nerve

CN XI: Accessory Nerve

CN XII: Hypoglossal Nerve