Blood Supply of the Brain and Spinal Cord and Meninges

two Internal Carotid and the two Vertebral Arteries

The brain is supplied by?

Subarachnoid Space

The four arteries lie within the?

Circle of Willis

Their branches anastomose on the inferior surface of the brain to form the

Internal Carotid Artery

 Begins at the bifurcation of the common carotid artery

 Ascends the neck and perforates the base of the skull by passing through the carotid canal of the temporal bone

 Enters the Subarachnoid space and divides into Anterior and Middle Cerebral Arteries

Choroidal Artery, Anterior Cerebral Artery, Middle Cerebral Artery, Posterior Communicating Artery, Ophthalmic Artery

Branches of the Cerebral Portion

Choroidal Artery

 A small branch originates from the Internal Carotid Artery

 Passes posteriorly close to the optic tract

 Enters the inferior horn of the lateral ventricle and end in the choroid plexus

 carries blood to the choroid plexus of the lateral ventricles as well as to adjacent brain structures

Anterior Cerebral Artery

 Is the smaller terminal branch of the Internal Carotid Artery

 Joined to the Anterior Cerebral Artery of the opposite side by the Anterior Communicating Artery

 The cortical branches supply all the medial surface of the cerebral cortex

 Supplies the “leg area” of the precentral gyrus

 Also supply the genu of corpus callosum

Middle Cerebral Artery

 The largest branch of the Internal Carotid Artery

 The cortical branches supply the entire lateral surface of hemisphere

 The left middle cerebral artery is sometimes called the "artery of speech“

Posterior Communicating Artery

 Is a small vessel that originates from the Internal Carotid Artery

 It runs posteriorly above the oculomotor nerve to join the Posterior Cerebral Artery, forming part of the Circle of Willis

Ophthalmic Artery

 Arises as the Internal Carotid artery emerges from the cavernous sinus

 Enters the orbit through the Optic Canal

 It supplies the eye and other orbital structures

Vertebral Artery

 Branch of subclavian artery

 Ascends the neck by passing through the foramina in the transverse process of C1-C6 vertebra

 Enters the skull through the foramen magnum

 At the lower border of the pons, it joins the vessels of the opposite side to form the BASILAR ARTERY

Meningeal Branches, Medullary Arteries, Anterior Spinal Artery, Posterior Spinal Artery, Posterior Inferior Cerebellar artery

Branches of the Cranial Portion

Meningeal Branches

Supply the bone and dura in the posterior cranial fossa

Medullary Arteries

Very small branches that are distributed to the medulla oblongata

Anterior Spinal Artery

 Is formed from a contributory branch from each vertebral artery

 Descends on the anterior surface of the medulla oblongata and spinal cord

 Reinforced by radicular arteries that enter the vertebral canal through intervertebral foramina

Posterior Spinal Artery

 Arise from the Vertebral artery or the Posterior Inferior Cerebellar Artery

 Descends on the posterior surface of the spinal cord

 Supplies the Posterior 1/3rd of the Spinal Cord

 The posterior spinal arteries supply the dorsal white columns and the posterior portion of the dorsal gray columns.

 they branch at various levels to form the posterolateral arterial plexus.

Posterior Inferior Cerebellar artery

 The largest branch of vertebral artery

 Supplies the inferior surface of the vermis, the cerebellar hemisphere

 It also supplies the medulla oblongata and the choroid plexus of the fourth ventricle

Basilar Artery

 Formed by the union of the two vertebral arteries

 Ascends on in a groove on the anterior surface of the pons

 The upper border of the pons it divides into two posterior cerebral arteries

Pontine Arteries, Labyrinthine Artery, Anterior Inferior Cerebellar Artery, Superior Cerebellar Artery, Posterior Cerebral Artery

Branches of Basilar Artery

Pontine Arteries

Are numerous small vessels that enter the substance of the pons

Labyrinthine Artery

 Is a long, narrow artery that accompanies the facial and the vestibulocochlear nerves into the internal acoustic meatus and supplies the inner ear

 Arise as branch of the Anterior Inferior Cerebellar Artery

Anterior Inferior Cerebellar Artery

Supplies the anterior and inferior parts of the cerebellum

Superior Cerebellar Artery

 Supplies the superior surface of the cerebellum

 It also supplies the pons, pineal gland

Posterior Cerebral Artery

 Joined by the Posterior Communicating Artery branch of Internal Carotid Artery

 Cortical Branches supply the Inferolateral and Medial surfaces of temporal lobe and the lateral and medial surface of the occipital lobe

 Central Branches supply parts of the thalamus, lentiform nucleus, midbrain pineal gland, medial geniculate bodies

 Choroidal Branch supplies the choroid plexus and choroid plexus of the third ventricle

Circle of Willis

 Lies in the INTERPENDICULAR FOSSA at the base of the brain

 It is formed by anastomosis between the two internal carotid arteries and two vertebral arteries

 Allows blood that enters by either internal carotid or vertebral arteries to be distributed to any part of the cerebral hemispheres

Sir Thomas Willis

Circle of Willis is named after an English neuroanatomist named?

Hexagon

Shaoe of Circle of Willis

Anterior Communicating

Anterior Cerebral

Internal Carotid

Posterior Communicating

Posterior Cerebral

Basilar Arteries

The following arteries contribute to the circle of willis:

Corpus striatum and Internal Capsule

 Supplied by Middle Cerebral Artery (Medial and Lateral Central Branches)

 Remainder of the structures supplied by the Anterior Cerebral Artery

Thalamus

Supplied by the Posterior Communicating, Basilar, and Posterior Cerebral Artery

Midbrain

Supplied by Posterior Cerebral, Superior Cerebellar and Basilar arteries

Pons

Supplied by Basilar, Anterior Inferior Cerebellar and Superior Cerebellar arteries

Medulla Oblongata

 Supplied by the Vertebral, Anterior and posterior Spinal, posterior Inferior Cerebellar and Basilar arteries

Cerebellum

Supplied by Superior Cerebellar, Anterior Inferior Cerebellar, and Posterior Inferior

Cerebellar arteries

arterial blood pressure

The most important factor in forcing the blood through the brain is the

50 to 60 ml per 100g of brain per minute

(N) Cerebral Blood Flow?

a. two Posterior Spinal Arteries

b. Anterior Spinal Artery

The spinal cord receives arterial supply from three small arteries

Posterior Spinal Arteries

 Arise either from the vertebral arteries inside the skull or indirectly from the Posterior Inferior Cerebellar Arteries

 Supplies the Posterior 1/3rd of the Spinal Cord

Anterior Spinal Artery

 Is formed by the union of two arteries from vertebral artery

 Arise from the vertebral artery inside the skull

 Supplies the Anterior 2/3rd of the Spinal Cord

Cerebral Ischemia

 Unconciousness occurs in 5-10 seconds if the blood flow to the brain is completely cutoff

 Irreversible brain damage with death of nervous tissue rapidly follows

 Neuronal function ceases after about 1 MINUTE, and irreversible changes start to occur after about 4 minutes

 Cardiac arrest due to coronary thrombosis is the most common cause of this condition

Anterior Cerebral Artery Occlusion, Middle Cerebral Artery Occlusion, Posterior cerebral Artery Occlusion, Vertebrobasilar Artery Occlusion

Cerebral Artery Syndromes

Anterior Cerebral Artery Occlusion

 Occlusion distal to the communicating artery may produce the following signs and symptoms

 (+) Contralateral Hemiparesis (LE>UE)

 (+) Contralateral Hemisensory loss (LE>UE)

 Inability to identify objects correctly, apathy, personality changes (Frontal and Parietal lobes)

Middle Cerebral Artery Occlusion

 (+) Contralateral Hemiparesis (UE>LE)

 (+) Contralateral Hemisensory loss (UE>LE)

 (+) Aphasia if (L) hemisphere is affected (rarely if ® hemisphere is affected)

 (+) Contralateral homonymous hemianopia (damage to optic radiation)

 (+) Anosognosia if the ® Hemisphere is affected (rarely if the (L) hemisphere is affected)

Posterior cerebral Artery Occlusion

 (+) Contralateral Homonymous hemianopia (damage to calcarine cortex)

 (+) Visual Agnosia (Ischemia to the (L) Occipital lobe)

 (+) Impairment of memory (Possible damage to medial aspect of temporal lobe)

Vertebrobasilar Artery Occlusion

 (+) Ipsilateral pain and temperature sensory loss of the face

 (+) Contralateral pain and temperature sensory loss of the body

 (+) Ipsilateral loss of Gag reflex, Dysphagia due to lesion of vagus nerve

 (+) Hoarseness due to lesion of nuclei of glossopharyngeal nerve

 (+) Vertigo, Nystagmus, Nausea and Vomiting

 (+) Ipsilateral Horner’s Syndrome

 (+) Ipsilateral Ataxia

 Unilateral or Bilateral Hemiparesis

 Coma

a. disease that produce alteration of blood pressure

b. diseases of arterial walls

c. diseases that result in blockage of the arterial lumen

“Impairment of Cerebral Blood Flow” Caused by large number of conditions:?

Intracranial Hemorrhage

Results from trauma or cerebral vascular lesions

a. Epidural Hemorrhage

b. Subdural Hemorrhage

c. Subarachnoid Hemorrhage

d. Cerebral Hemorrhage

Types of Intracranial Hemorrhage

Meninges

The brain and spinal cord are separated from bony walls of the cranial cavity and

vertebral canal by three fibrous membranes collectively called the

a. Dura Mater

b. Arachnoid Mater

c. Pia Mater

Three Meninges:

Dura Mater

− Is a strong non-elastic membrane

− Strong, fibrous membrane that encloses the spinal cord and the cauda equine

− Continuous above the foramen magnum with the meningeal layer of the dura mater covering the brain

− Inferiorly, it ends on the Filum Terminale at the level of lower border of S2 vertebra

Pachymeninx

Other term for Dura Mater

a. External Endosteal Layer

b. Internal Meningeal Layer

Two Layers of the Dura Mater:

External Endosteal Layer

• tightly adherent to the inner surface of the cranial vault

• continuous with the Pericranium at the foramen magnum and

cranial nerve foramina

Internal Meningeal Layer

• follows the inner contours of the skull

• tightly joined to the endosteal layer except at the sites of the

venous sinuses

• it reflected inward to form partitions between various portions of the brain called:

a. Falx Cerebri

b. Tentorium Cerebelli

c. Falx Cerebelli

d. Diaphragma Sellae

Falx Cerebri

− Is a sickle-shaped fold of dura mater attached to the entire length of the calvaria

− Lies in the midline between the two cerebral hemispheres

− Rostrally, is attached to the CRISTA GALLI of the ethmoid bone

Tentorium Cerebelli

− Crescent-shaped fold of dura mater that forms the roofs of posterior cranial fossa

− Separates the superior surface of the cerebellum from the occipital lobes of cerebral

hemispheres

Falx Cerebelli

Is a small, sickle-shaped fold of dura mater attached to the internal occipital crest and projects forward between the two cerebellar hemispheres

Diaphragma Sellae

− Quadrangular portion of the meningeal dura

− Allows passage of the Hypophysis Cerebri

Arachnoid Mater

− Is a delicate, impermeable membrane covering the brain

− Lies between the pia mater internally and dura mater externally

− Separated from the dura mater by a space called Subdural Space

o The Subdural Space, filled by a film of fluid

− Separated from the pia mater by a space called Subarachnoid Space

− The Subarachnoid Space, filled with CSF

− Continuous above the foramen magnum with arachnoid covering the brain

− Inferiorly, it ends on the Filum terminale at the level of lower border of S2 vertebra

Subdural Space

Arachnoid Mater is separated from the dura mater by a space called

Subarachnoid Space

Arachnoid is separated from the pia mater by a space called

Cerebrospinal Fluid (CSF)

Produced by the choroid plexuses with the lateral, third and fourth ventricles of the brain

Pia Mater

− Is a vascular membrane covered by flattened mesothelial cells

− Forms the Tela Choroidea of the roof of the third and fourth ventricles of the brain and fuses with the ependyma to form the Choroid Plexuses

− Is thickened on either side between the nerve roots to form the Ligamentum Denticulatum

Epidural Hemorrhage and Subdural Hemorrhage

Two of the Intracranial Hemorrhages

Epidural Hemorrhage

− Results from injuries to the meningeal arteries or veins

− The most commonly to be damaged is the Anterior Division of the Middle Meningeal Artery

− Minor blow to the side of the head, resulting to fracture of the Anterior-Inferior portion of the parietal bone may sever the artery.

Subdural Hemorrhage

− Results from tearing of Superior Cerebral Veins at the Superior Sagittal Sinus

− Due to a blow on the front or back of the head causing excessive Anteroposterior displacement of the brain within the skull

Meningitis

− Inflammation of the meninges

− Causes a severe headache over the entire head and back of the neck