Blood supply Flashcards
Two paired arteries which are responsible for the blood supply to the brain
Vertebral arteries
Internal carotid arteries.
What proportion and area do the vertebral arteries supply?
20% of the total, and supply the posterior part of the cerebrum and the contents of the posterior cranial fossa
What proportion and area do the internal carotid arteries supply?
Supply the remaining 80% and distribute to the anterior and middle parts of the cerebrum and the diencephalon.
Where is the circle of willis located?
The ‘Circle of Willis’ is located in the interpeduncular cistern and enclosing the optic chiasm
Where do the internal carotid arteries arise?
Bifurcation of the left and right common carotid arteries, at the level of the fourth cervical vertebrae (C4)
How do the internal carotid arteries enter the skull?
Carotid canal of the temporal bone.
Initial branches of the ICA?
Anterior cerebral artery and middle cerebral artery
Anterior cerebral artery branches and anastomoses
Gives off the short anterior communicating artery (connects with opposite anterior cerebral, circle of willis)
Posteriorly it anastomoses with branches of the posterior cerebral artery.
Middle cerebral artery supplies mainly
Lateral surface of the cerebral hemisphere
Internal carotid artery branches and anastomoses
A posterior communicating artery - which joins the posterior cerebral artery - ‘connecting vessel’ in the Circle of Willis
A small artery to the choroid plexus of the lateral ventricle.
The ophthalmic artery - supplies the structures of the orbit
Anterior choroidal artery - supplies structures in the brain important for motor control and vision.
Superior hypophyseal arteries - branch from the internal carotid arteries to supply the hypothalamus.
What is the ophthalmic artery a branch of?
ICA
Where does the ophthalmic artery arise?
First branch distal to cavernous sinus
Where do the superior hypophyseal arteries arise from?
ICA
Where does posterior communicating artery arise from?
MCA
What do the vertebral arteries arise from?
Subclavian arteries
How do vertebral arteries ascend?
Ascend the posterior aspect of the neck, through holes in the transverse processes of the cervical vertebrae, known as foramen transversum.
How do vertebral arteries enter the cranial cavity?
Foramen magnum
Branches of the vertebral arteries prior to basilar convergence
Meningeal branch – supplies the falx cerebelli, a sheet of dura mater.
Anterior and posterior spinal arteries – supplies the spinal cord, spanning its entire length.
Posterior inferior cerebellar artery – supplies the cerebellum.
Anterior inferior cerebellar artery - supplies cerebellum
Superior cerebellar artery - supplies cerebellum
What happens to the vertebral arteries at the lower border of the pons?
Vertebral arteries converge to form the basilar artery.
Where does the basilar artery travel initially?
Passes rostrally within the pontine cistern, lying in a shallow groove, the anterior median fissure, or basilar groove, of the pons.
How does the basilar artery terminate?
By bifurcating into the posterior cerebral arteries.
Where do the posterior cerebral arteries lie?
They can be seen at the rostral border of the pons, and can be traced some distance laterally around the cerebral peduncles towards the posterior surface of the cerebrum.
What do the posterior cerebral arteries supply?
The main terminal portions of the posterior cerebral arteries distribute to the occipital and temporal cortex.
Three main (paired) constituents of the Circle of Willis and two connecting vessels
Anterior cerebral arteries – terminal branches of the internal carotid arteries.
Internal carotid arteries – located immediately proximal to the origin of the middle cerebral arteries.
Posterior cerebral arteries – terminal branches of the basilar artery
Anterior communicating artery – connects the two anterior cerebral arteries.
Posterior communicating artery – branch of the internal carotid, this artery connects the ICA to the posterior cerebral artery.
Anterior cerebral arteries mainly supply
Anteromedial cerebrum
Posterior cerebral arteries mainly supply
Medial and lateral posterior brain
What are the three longitudinal arteries, that primarily supply the spinal cord as it descends from the brainstem to the conus medullaris?
Anterior spinal artery – formed from branches of the vertebral arteries, travelling in the anterior median fissure.
Gives rise to the sulcal arteries, which enter the spinal cord.
Two posterior spinal arteries – originate from the vertebral artery or the posteroinferior cerebellar artery,
Where do the two posterior spinal arteries anastomose
Pia mater
What arteries support the spinal cord supply from cervical level down?
Segmental medullary and radicular arteries.
Describe origin and passage of the anterior and posterior medullary arteries
The anterior and posterior segmental medullary arteries are derived from spinal branches of a number of arteries, before entering the vertebral canal through the intervertebral foramina.
The great anterior segmental artery of Adamkiewicz reinforces circulation to the inferior 2/3 of the spinal cord, and is found on the left in the majority of individuals.
Where does the great anterior segmental artery of Adamkiewicz reinforce circulation? t
Inferior 2/3 of the spinal cord
What is the path of the radicular arteries?
The radicular arteries supply (and follow the path of) the anterior and posterior nerve roots. Some radicular arteries may also contribute to supplying the spinal cord.
Does CNS venous drainage follow arterial supply?
No
Where do the veins from the brainstem, cerebellum and cerebrum drain?
Empty into the dural venous sinuses.
Where do the spinal veins drain?
Internal and external vertebral plexuses.
Where do the dural venous sinuses lie?
Between the periosteal and meningeal layers of the dura mater.
All the dural venous sinuses ultimately drain into the
Internal jugular vein.
Do dural venous sinuses have valves?
No
How many dural venous sinuses?
11
What sinuses converge at the confluence of sinuses?
Straight, superior and inferior
How does blood drain out from the confluence of sinuses?
Out transverse sinus, down sigmoid, into internal jugular vein
Upon exiting the cerebral parenchyma, where do the veins run?
In the subarachnoid space and pierce the meninges to drain into the dural venous sinuses.
Superficial System of veins is largely responsible for
Draining the cerebral cortex
Superficial veins (3 main ones)
Superior cerebral veins: Drain the superior surface, carrying blood to the superior sagittal sinus.
Superficial middle cerebral vein: Drains the lateral surface of each hemisphere, carrying blood to the cavernous or sphenopalatine sinuses.
Inferior cerebral veins: Drain the inferior aspect of each cerebral hemisphere, depositing blood into cavernous and transverse sinuses.
Connects the superficial middle cerebral vein to the superior sagittal sinus.
Superior anastomotic vein (Trolard)
Connects the superficial middle cerebral vein to the transverse sinus.
Inferior anastomotic vein (Labbé)
Deep veins
Subependymal veins receive blood from the medullary veins and carry it to the dural venous sinuses.
The great cerebral vein (vein of Galen) is formed by the union of two of the deep veins, and drains into the straight sinus.
Medullary veins: Originate 1-2cm below the cortical grey matter, and drain into subependymal veins. These drain the deep areas of the brain.
What veins are responsible for the venous drainage of the cerebellum?
The superior and inferior cerebellar veins.
They empty into the superior petrosal, transverse and straight dural venous sinuses.
Spinal cord venous drainage
The spinal cord is supplied by three anterior and three posterior spinal veins.
These veins are valveless, and form an anastamotic network along the surface of the spinal cord.
They also receive venous blood from the radicular veins.
Where do spinal cord veins drain?
The spinal veins drain into the internal and external vertebral plexuses, which in turn empty into the systemic segmental veins.
The internal vertebral plexus also empties into the dural venous sinuses superiorly.
A skull fracture at the pterion is likely to cause - and why?
Epidural haemotoma (by rupture of middle meningeal artery)/ extra dural haemorrhage
State the expected consequence of a lesion resulting from occlusion of anterior cerebral artery.
Contralateral loss of motor and sensory function of the lower limb
State expected consequence of a lesion resulting from occlusion of middle cerebral artery
Contralateral loss of motor and sensory function in upper limb
State expected consequence of a lesion resulting from occlusion of posterior cerebral artery
Contralateral loss of hemifield vision (homonymous hemianopsia)
State expected consequence of a lesion resulting from occlusion of anterior spinal artery branches to medial medulla
Medial medullary syndrome
A deviation of the tongue to the side of the infarct caused by ipsilateral muscle weakness.
Limb weakness on the contralateral side of the infarct and a loss of discriminative touch, conscious proprioception, and vibration sense on the contralateral side of the infarct
State expected consequence of a lesion resulting from occlusion of hypothalamo-hypophysial portal veins
Pickardt syndrome - a type of hypothyroidism
The pterion is found at the junction of which four bones?
Frontal, Parietal, Temporal and Sphenoid
The main artery that supplies the visual cortex bordering the calcarine sulcus?
Posterior cerebral
The artery from which the labyrinthine artery to the inner ear branches?
Anterior inferior cerebellar/Basilar
Rupture of a berry aneurysm on the posterior communicating artery will cause
Oculomotor nerve palsy
Lesions of the posterior parietal cortex cause
Neglect syndromes
When does the common carotid artery divide?
C4
Branches of the external carotid artery?
Superior thyroid, ascending pharyngeal, lingual, facial, then it terminates into the maxillary and the superficial temporal
What does the superior thyroid branch of external carotid supply?
Superior thyroid and the larynx
What supplies the tonsils?
Ascending pharyngeal branch of the external carotid
What does the maxillary artery supply
Deep structures
What supplies the tongue?
Lingual
What does the superficial temporal artery lie behind?
Masseter
What drains the head and neck?
Many veins which drain into both the internal and external jugular
What veins are notably valveless why is this significant?
Emissary veins drain into the cavernous sinus, likely to pass infection into the brain from regions around the nose and upper lip
What joins to form the external jugular?
Retromandibular and posterior auricle vein
Lymphatic drainage of head and neck
Lymph from the head, face and neck drains to the submental, submandibular, parotid, mastoid and occipital nodes
Then ultimately into deep cervical nodes then jugular lymphatic trunk then thoracic duct on left and IJV ON RIGHT
What does anterior jugular drain?
Subligual region
What drains lymph from the tongue?
Submental and submandibular
What drains lymph from nasopharynx and auditory meati?
Retropharnygeal
