23: Brain 1

Layers of the meninges

• Dura mater

• Arachnoid mater

• Pia mater

Characteristics of the dura mater

Dense, fibrous CT

Characteristics of the arachnoid mater

Deeper and close to the dura, no ID on our cadavers

Characteristics of the pia mater

Delicate, contains the arteries, sits right on the CNS

Spaces of the meninges

• Subdural space

• Subarachnoid space

Key feature of the subarachnoid space

Contains the CSF

Falx cerebri

Double fold of dura mater between the cerebral hemispheres

Name of the space where the falx cerebri sits

Longitudinal fissure

Tentorium cerebelli

Double fold of dura mater between the cerebrum and cerebellum

Which of the two folds of dura mater is partially ossified in cats (and can be in dogs)

Tentorium cerebelli

Why is there a gap in the tentorium cerebelli

Exit for the brain stem

Spaces where the arachnoid mater and pia mater are wider apart

Subarachnoid cisterns

Clinical significance of the subarachnoid cisterns

Good place for a CSF tap

Common site for a cisternocentesis

Cisterna magna/cerebellomedullary cistern (at atlantooccipital joint)

Arterial structure that supplies the brain

Arterial circle

Arteries that meet to form the arterial circle in dogs

• Internal carotid arteries (R and L)

• Basilar artery (from the caudal aspect)

Arteries that meet to form the arterial circle in cats

• Rete mirable (from maxillary artery)

• Basilar artery

At the level of the brain in cats, what is the internal carotid

A fibrous cord

Where is the arterial circle

Ventral aspect of the brain

Paired branches of the arterial circle (rostral → caudal)

• Rostral cerebral

• Middle cerebral

• Caudal cerebral

• Rostral cerebellar

What pair of arteries supplies the brain but comes off the basilar artery, caudal to the arterial circle

Caudal cerebellar

Function of the rostral cerebral arteries

Supplies the rostromedial parts of the cerebral hemispheres

Function of the middle cerebral arteries

Supplies the lateral parts of the cerebral hemispheres

Function of the caudal cerebral arteries

Supplies the caudomedial parts of the cerebral hemispheres and some of the brain stem

Function of the rostral cerebellar arteries

Supplies rostral cerebellum and parts of the brain stem

Function of the caudal cerebellar arteries

Supplies the caudal cerebellum and parts of the brain stem

How does blood drain from the brain

Venous sinuses, there are no satellite veins!

What is the key venous sinus of the brain that we have to know

Dorsal sagittal sinus

Where is the dorsal sagittal sinus and where does it drain to

Between the dura and skull within the longitudinal fissure; drains into the internal carotid vein

What does the nervous system start as in early embryonic development

Neural tube with a neurocele

What are the three initial embryonic brain segments

Fore, mid, and hindbrain

What are the five embryonic brain divisions

• Telencephalon

• Diencephalon

• Mesencephalon

• Metencephalon

• Myelencephalon

What are the three gross divisions of the brain

• Cerebrum

• Cerebellum

• Brainstem

Lobes of the cerebrum

• Frontal

• Parietal

• Occipital

• Temporal

• Piriform (rostroventral to the midbrain)

Parts of the cerebellum

• Lateral hemispheres (L and R)

• Vermis (central region)

Parts of the brainstem

• Midbrain

• Pons

• Medulla

Parts of the brain associated with the telencephalon

Cerebrum

Parts of the brain associated with the diencephalon

Thalamus and associated structures

Parts of the brain associated with the mesencephalon

Midbrain

Parts of the brain associated with the metencephalon

Cerebellum and pons

Parts of the brain associated with the myelencephalon

Medulla

What groove separates the cerebral hemispheres

Longitudinal fissure

What groove separates the cerebrum and cerebellum

Transverse fissure

Grooves of the brain

Sulci

Ridges of the brain

Gyri

Main function of the frontal lobe

Motor function

Main function of the parietal lobe

• Motor

• Touch/pain

• Proprioception

Main function of the temporal lobe

• Hearing

• Memory

Main function of the occipital lobe

• Visual reception

• Visual interpretation

Main function of the piriformis and olfactory peduncles

Smell

How does the cerebellum attach to the brain stem

Cerebellar peduncles

Name for the white matter in the center of the cerebellum

Arbor vitae

VENTRICULAR SYSTEM: Choroid plexus →

Lateral ventricles

Lateral ventricles →

Interventricular foramina

Interventricular foramina →

III ventricle

III ventricle →

Mesencephalic aqueduct

Mesencephalic aqueduct →

IV ventricle

IV ventricle →

Central canal in spinal cord

Location of the lateral ventricles

In each cerebral hemisphere

Location of the III ventricle

Donut shaped around the thalamus

Location of the IV ventricle

Dorsal side of the brainstem, ventral to the cerebellum

Which of the ventricles is a good site for a CSF tap

IV ventricle

How are the two parts of the thalamus attached to eachother

Interthalamic adhesions

How are the lateral ventricles separated in the brain

Midline membrane

Location of the mesencephalic aqueduct

Midline, traveling on top of the brainstem

What ventricle structure can you see in the same cross section as the III ventricle

Lateral ventricles

What ventricle structure can you NOT see in the same cross section as the III ventricle

Mesencephalic aqueduct

Where is the CSF produced

Choroid plexuses in the ventricular system

Function of CSF

• Maintains intracranial pressure

• Protection

• Nutrients

How does the CSF get to the subarachnoid space

IV ventricle → lateral apertures → subarachnoid space

How is the CSF drained

Arachnoid villi → venous sinuses

Hydrocephalus pathology

Insufficient CSF drainage leading to dilation of ventricles and degradation of brain tissue

Causes of hydrocephalus

• Congenital

• Infectious

Types of neural tissue

• Gray matter: cell bodies

• White matter: myelinated axons

What parts of the cerebrum are gray or white matter

• Gray: cortex

• White: corona radiata

What parts of the cerebellum are gray or white matter

• Gray: cortex

• White: arbor vitae

What parts of the brain stem are gray or white matter

They are a mixed up jumble, good luck

What parts of the spinal cord are gray or white matter

• Gray: dorsal/ventral/lateral horns

• White: Funiculi

White matter connection between the cerebral hemispheres

Corpus callosum