Introduction to brain structure and function

Layers of the head

1. Scalp

2. Bone

3. Dura mater

4. Arachnoid mater

5. Pia mater

What are the 3 meninges?

Dura mater

Arachnoid mater

Pia mater

3 folds/reflections of the dura mater

Falx cerebri

Tentorium cerebelli

Falx cerebelli

Types of tensorial tumours

Infratentorial

Supratentorial

3 types of meningeal haematomas

1. subarachnoid

2. subdural

3. epidural

Which meningeal layer has blood vessels and cerebral spinal fluid?

Arachnoid mater

Which meningeal layer protects the brain?

Dura mater

Contents of the arachnoid mater

blood vessels, cerebral spinal fluid (CSF), and granulations to drain CSF back into the venous system

Sulcus on outside of brain

Sulcus on inside of brain

What is the cortical gyri?

Area including precentral gyrus - associated with motor complex (movement) and post central gyrus (sensation)

• Separated by central sulcus

Cortical lobes (4)

Frontal - voluntary movement personality.

Parietal - senses

Occipital - vision

Temporal - memory, speech

Hindbrain structural development (rhombencephalon)

Metencephalon → Pons + Cerebellum

Myelencephalon → Medulla oblongata

Midbrain structural development (mesencephalon)

Mesencephalon → Tectum (colliculi), Tegmentum + Cerebral peduncles

Forebrain structural development (prosencephalon)

Diencephalon → Thalamus + Hypothalamus

Telencephalon → Basal ganglia and cortex

Centre of brain structures

Structures found from the top of the head to the bottom of spinal cord

Structures of the mid brain

• Cerebral peduncles

• Tectum: superior(vision)and inferior colliculi (hearing)

• Superior colliculi is closer to the middle

Transverse midbrain

Tectum

Cerebral aqueduct

Periaqueductal gray

Substantia nigra (motor function, Parkinson’s)

Red nucleus (3rd cranial nerve for the eyes)

Cerebral peduncles

What is this structure?

Putamen

What is this structure?

Cerebral peduncles

What is this?

Hind brain

Summary

Ventricular system

Function of cerebral spinal fluid

Fills ventricles, colour-less liquid that baths the brain, assists in circulating substances, it provides cushioning and absorbs shock

What is the choroid plexus?

Group of cells that line the ventricles

• produces CSF

• induces CSF circulation

• acts as a medium of exchange between extra cellular fluid and blood stream

Structures involved in CSF circulation

CSF circulation (midbrain)

Vertebral level for safe CSF sampling, adult vs infants

Adults: L3-L4/ L4-L5

Infants: at or below L4-L5

What is this structure?

Ventricular system - 3rd ventricle

CSF summary

Describe the blood supply to the brain

• Dual supply - internal carotid arteries and vertebral arteries

• Internal carotid - Anterior and middle cerebral arteries (terminal)

• Vertebral - unite to form basilar artery→ posterior cerebral arteries

Circle of Willis

Arterial territories

Subcortical blood supply

What are these arteries?

Posterior and basilar

How can you visualise arteries?

Angiograms

Arterial supply summary

Venous drainage of brain

What are these veins?

Superior sagittal and sigmoid sinuses

Venous drainage summary

What is the blood brain barrier?

an interface that ensures the circulatory system (blood) is kept separate from the extracellular fluid/CSF

Maintained by pericytes and astrocytes

Which molecules can cross the BBB?

Small molecules - oxygen, carbon dioxide, glucose, select amino acids

BBB summary