ANATOMY AND PHYSIOLOGY OF REPRODUCTIVE SYSTEM.pptx
Blood supply of the brain
1. BLOOD SUPPLY OF THE BRAIN
By Dr Pooja Dhabhai
(Assistant Professor Anatomy
R.N.T. Medical College, Udaipur)
2. • Our brains are absolutely dependent on a continuous
supply of well oxygenated blood. After just 10 seconds
of brain ischemia, we lose consciousness. After 20
seconds, electrical activity ceases, and after just a few
minutes, irreversible damage usually begins.
• Corresponding to this metabolic dependence, blood
vessels in the central nervous system(CNS), particularly
in gray matter, are arranged in a dense meshwork.
• An understanding of the brain’s blood supply is
essential to an understanding of its normal function
and of the consequences of cerebrovascular disease.
4. • The arterial supply of the brain and
much of the spinal cord is derived
from two pairs of vessels: The arteries
are directed in essence to the grey
matter, which needs more blood than
the white matter. Superficial cortical
arteries supply the grey matter on the
surface, perforating arteries supply
the subcortical nuclei. Both sets of
arteries send branches to the adjacent
white matter
• THE INTERNAL CAROTID ARTERIES
and
• THE VERTEBRAL ARTERIES
• The internal carotid arteries provide
about 80%, supplying most of the
telencephalon and much of the
diencephalon. The vertebral system
provides the remaining 20%,
supplying the brainstem and
cerebellum, as well as parts of the
diencephalon, spinal cord, and
occipital and temporal lobes.
5. THE INTERNAL
CAROTID ARTERIES
• The internal carotid artery is
a major paired artery, one
on each side of the head
and neck.
• They arise from the
common carotid arteries
where these bifurcate into
the internal and external
carotid arteries at cervical
vertebral level 3 or 4.
• Internal carotid artery lies in
close relation of the optic
nerve.
6. • Along its course the
artery is divided into 4
parts
• Cervical part in the neck
• Petrous part in the
petrous temporal bone
• Cavernous part in the
cavernous sinus
• Cerebral part in the
relation to base of brain
(On angiogram internal
carotid show ‘S’ shaped
figure (carotid siphon).
7. Cerebral part
• It gives rise to the
opthalmic artery,
which travels along
the optic nerve to the
orbit, where it
supplies the eye, other
orbital contents, and
some near by
structures.
• The internal carotid
artery then proceeds
superiorly alongside
the optic chiasm and
bifurcates into the
middle and anterior
cerebral arteries.
Before bifurcating, it
gives rise to two
smaller branches, the
anterior choroidal
artery and the
posterior
communicating
artery.
8. • The anterior choroidal
artery is a long, thin artery
that can be significant
clinically in that it supplies
a number of different
structures and is
frequently involved in
cerebrovascular accidents.
Along its course it supplies
the optic tract; the choroid
plexus of the inferior horn
of the lateral ventricle:
and some deep brain
structure such as portions
of the internal capsule,
basal ganglia, thalamus,
and hippocampus.
• The posterior
communicating artery
passes posteriorly, inferior
to the optic tract and
toward the cerebral
peduncle, and joins the
posterior cerebral
artery(part of the vertebral
artery system).
9. The anterior
cerebral artery
• The anterior cerebral artery
runs medially, superior to
the optic nerve, and enters
the longitudinal fissure.
• The two anterior cerebral
arteries, near their entrance
into the longitudinal fissure,
are connected by the
anterior communicating
artery.
• The anterior cerebral
arteries then arch
posteriorly, following the
corpus callosum, to supply
medial parts of the frontal
and parietal lobes.
10. • Distal to
the anterior
communica
ting artery,
the anterior
cerebral
artery gives
2 branches:
• medial
striate and
recurrent
artery of
huebner
suppling
the basal
ganglia and
internal
capsule
11. • Distal to the
anterior
communicating
artery, the anterior
cerebral artery gives
2 branches:
• medial striate and
recurrent artery of
huebner suppling
the basal ganglia
and internal
capsule then
continues as the
pericallosal artery,
which stays
immediately
adjacent to the
corpus callosum.
• Near the genu of
the corpus
callosum, the
calloso marginal
artery typically
branches off from
the pericallosal
artery and follows
the cingulate sulcus.
• Occlusion of an
anterior cerebral
artery causes
restricted
contralateral motor
and somatosensory
re than other
deficits(affecting
the leg more than
other parts of the
body, because of
the somatotopic
arrangement.
12. MIDDLE CEREBRAL ARTERY
• The large middle
cerebral artery proceeds
laterally into the lateral
sulcus. It divides into a
number of branches that
supply the insula,
emerge from the lateral
sulcus, and spread out to
supply most of the
lateral surface of the
cerebral hemisphere.
Most of the precentral
and postcentral gyri are
within this area of
supply, so occlusion of a
middle cerebral artery
causes major motor and
somatosensory deficts.
• In addition, if the left
hemisphere is the one
involved, language
deficits are almost
invariably found.
13. • Along its course
toward the lateral
sulcus, the middle
cerebral artery
gives rise to as
many as a dozen
very small
branches that
penetrate the
brain near their
origin and supply
deep structures of
the diencephalon
and
telencephalon.
The particular
arteries are called
the
lenticulostriate
arteries,.
14. • Perforating arteries are
particularly numerous in the
area adjacent to the optic
chiasm and in the area
between the cerebral
peduncles; for this reason they
are called the anterior and
posterior perforated
substances, respectively. The
narrow, thin walled vessels of
the anterior perforated
substance are involved
frequently in strokes. The deep
cerebral structures they supply
are such that damage to these
small vessels can cause
neurological deficits out of
proportion to their size. For
example, the somatosensory
projection from the thalamus to
the postcentral gyrus must pass
through the internal capsule;
damage to a small part of the
internal capsule from rupture
or occlusion of a perforating
artery can cause deficits similar
to those resulting from damage
to a large expanse of cortex.
15.
16.
17. VERTEBRO BASILAR
SYSTEM
• The two Vertebral
arteries ( from
Subclavian artery)
unite to form Basilar
artery.
• It divides at the upper
border of the pons into
two Posterior Cerebral
arteries.
18. The Vertebral –
Basilar System
• The vertebral arteries arise from the
subclavian arteries, one on each side
of the body, then enter the foramen
transversarium at the level of the 6th
cervical vertebrae(C6), or occasionally
(in 7.5% of cases) at the level of C7.
They then proceed superiorly, in the
transverse foramen of each cervical
vertebra. Once they have passed
through the transverse foramen of C1,
the vertebral arteries travel across the
posterior arch of C1 and through the
suboccipital triangle before entering
the foramen magnum, it then run
rostrally alongside the medulla and
fuse at the junction between the
medulla and pons to form the midline
basilar artery, which proceeds
rostrally along the anterior surface of
the pons.
19.
20. • Before joining the basilar
artery, each vertebral artery
gives rise to three branches:
the posterior spinal artery,
anterior spinal artery, and
posterior inferior cerebellar
artery.
• The posterior spinal artery
runs caudally along the
postero lateral aspect of the
spinal cord and supplies the
posterior third of the cord.
• The anterior spinal arteries
join together forming a single
anterior spinal artery that runs
caudally along the anterior
midline of the spinal cord,
supplying the anterior two
thirds of the cords.
• The posterior inferior
cerebellar artery (often
referred to by the acronym
PICA), as its name implies,
supplies much of the inferior
surface of the cerebellar
hemisphere.
21. THE BASILAR ARTERY
• The basilar artery proceeds rostrally and,
at the level of the midbrain, bifurcates
into the two posterior cerebral arteries.
Before this bifurcation, it gives rise to
numerous unnamed branches and two
named branches,the anterior inferior
cerebellar artery and the superior
cerebellar artery.
• The anterior inferior cerebellar artery
(or AICA) arises just rostral to the origin
of the basilar artery and supplies the
more anterior portions of the inferior
surface of the cerebellum(e.g.,the
flocculus), as well as parts of the caudal
pons.
• The superior cerebellar artery arises just
caudal to the bifurcation of the basilar
artery and supplies the superior surface
of the cerebellum and much of the
caudal midbrain and rostral pons. The
many smaller branches of the basilar
artery, collectively called pontine
arteries ,supply the remainder of the
pons.
• The internal auditory or labyrinthine
artery (which is often a branch of the
AICA), although hard to distinguish from
the others by appearance, is functionally
important because it also supplies the
inner ear. Its occlusion can lead to vertigo
and ipsilateral deafness.
22. THE POSTERIOR
CEREBRAL ARTERY
• The posterior cerebral
artery curves around the
midbrain and passes
through the superior
cistern: its branches
spread out to supply the
medial and inferior
surfaces of the occipital
and temporal lobes.
Along the way, it sends
branches to the rostral
midbrain and posterior
parts of the
diencephalon including
the thalamus. It also
gives rise to several
posterior choroidal
arteries, which supply
the choroid plexus of the
third ventricle and the
body of the lateral
ventricle. The anterior
and posterior choroidal
arteries form
anastomoses
23. THE POSTERIOR
CEREBRAL ARTERY
• The primary visual cortex is
located in the occipital
lobe, so occlusion of a
posterior cerebral artery at
its origin leads to visual
field losses in addition to
other deficits referable to
the midbraiin and
diencephalon.
24. The Cerebral Arterial
Circle(Circle of Willis)
• The circle of Willis is a part of the
cerebral circulation and is composed of
the following arteries:
• Anterior cerebral artery(left and right)
• Anterior communicating artery
• Internal carotid artery(left and right)
• Posterior cerebral artery(left and right)
• Posterior communicating artery(left and
right)
• The middle cerebral arteries, supplying
the brain, are not considered part of the
circle of Willis.
• The posterior cerebral artery is
connected to the internal carotid artery
by the posterior communicating artery.
• This completes an arterial polygon called
the cerebral arterial circle(circle of
willis), (the French call it, more
accurately, the polygon of Willis) through
which the anterior cerebral, internal
carotid, and posterior cerebral arteries
of both sides are interconnected. It is
named after Thomas Willis, an English
physician.
25. Arterial supply of the other parts of
the Brain
• The corpus striatum and internal
capsule are supplied mainly by central
branches(medial and lateral striate
arteries) of middle cerebral artery and
to some extent by central branches of
anterior cerebral artery
• The thalamus is supplied mainly by
central branches of posterior
communicating, posterior cerebral and
basilar arteries.
• The midbrain is supplied by posterior
cerebral, superior cerebellar and basilar
arteries.
• The pons is supplied by basilar, superior
cerebellar and anterior inferior
cerebellar arteries.
• The medulla is supplied by:
a) The medullary branches of the
vertebral artery.
b) Branches from the posterior inferior
cerebellar artery.
26. Blood Supply to Cerebellum
• Superior cerebellar
artery (SCA) from
basilar artery
• Anterior inferior
cerebellar artery (AICA)
from basilar artery
• Posterior inferior
cerebellar artery (PICA)
from vertebral artery
27. Blood Supply to Spinal Cord
• The spinal cord is supplied with blood by three arteries that
run along its length starting in the brain, and many arteries
that approach it through the sides of the spinal column
• The three longitudinal arteries are called the anterior
spinal artery, and the right and left posterior spinal
arteries
• These travel in the subarachnoid space and send branches
into the spinal cord
• They form anastamoses via the anterior and posterior
segmental medullary arteries, which enter the spinal cord
at various points along its length
• Supply blood upto cervical segments
28. Blood Supply to Spinal Cord
• Arterial blood supply below the cervical region comes from the
radially arranged posterior and anterior radicular arteries, which
run into spinal cord alongside the dorsal and ventral nerve roots
• These intercostal and lumbar radicular arteries arise from the aorta,
provide major anastomoses and supplement the blood flow to the
spinal cord
• Largest of the anterior radicular arteries is known as the artery of
Adamkiewicz, which usually arises between L1 and L2
• Impaired blood flow through these critical radicular arteries,
especially during surgical procedures that involve abrupt disruption
of blood flow through the aorta for example during aortic aneursym
repair, can result in spinal cord infarction and paraplegia
29.
30. Venous Drainage of Brain
• The veins of the brain drain into the intracranial dural venous sinuses,
which eventually open into the internal jugular veins of the neck. The
veins emerge from the brain, traverse the subarachnoid space’ pierce the
arachnoid mater and meningeal layer of dura mater to drain into venous
sinuses.
• Characteristic features:
1. Venous return in the brain does not follow the arterial pattern.
2. The veins of the brain are extremely thin- walled due to absence of
muscular tissue in their walls.
3. Possess no valves.
4. Run mainly in subarachnoid space.
5. The cerebral veins, generally enter obliquely into dural venous sinuses
against the flow of blood in the sinuses to avoid their possible collapse
following an increased intracranial pressure as they are thin walled.
The veins of the brain comprise, cerebral veins, cerebellar veins, and
veins of brainstem.
31. Cerebral veins
• Divided into external and internal cerebral veins which
drain the external surfaces and the internal regions of
the cerebral hemisphere respectively.
• External (superficial) cerebral veins: drains the
surface of the hemisphere and are divided into three
groups a)superior b)middle c) inferior.
1. Superior cerebral vein: 8 to 12 in number, drain the
upper parts of the superolateral and medial
surfaces of hemisphere, enters the superior sagittal
sinus.
1. Middle cerebral vein: 4 in number
a) superficial middle cerebral vein: lies superficially in
the lateral sulcus. Anteriorly it runs forwards to
drain into the cavernous sinus while posteriorly it
communicates with the superior saggittal sinus via
superior anastomotic vein (of Trolard) and with the
transverse sinus via inferior anastomotic vein (of
Labbe)
b) Deep middle cerebral vein: lies deep in the lateral
sulcus on the insula along with middle cerebral
artery. It runs downwards and forwards and joins
the anterior cerebral vein to form the basal vein.
3. Inferior cerebral veins :many in number. They
drain the inferior surface and lower parts of medial
and superolateral surfaces of the cerebral
hemisphere into nearby intracranial dural venous
sinuses, eg transverse sinus.
32. Other veins
• Anterior cerebral vein: it
accompanies the
anterior cerebral artery
around the corpus
callosum and drains the
parts of medial surface
which cannot be drained
into the superior and
inferior sagittal
sinuses.(the anterior
cerebral vein is the only
large vein of the brain
which has a similar
name and course as its
companion
artery(anterior cerebral
artery)
33. • Basal vein (of Rosenthal) It is
formed at the base of brain in the
region of anterior perforated
substance by the union of three
veins: anterior cerebral, deep middle
cerebral and striate veins. The
striate veins emerge from the
anterior perforated substance.
• The basal vein runs posteriorly
around the midbrain, medial to the
uncus and parahippocampus and
terminate into the great cerebral
vein (of Galen) below the splenium
of corpus callosum.
• Tributaries
Besides the formative three veins,
the basal vein receives the
tributaries from:
• Cerebral peduncle
• Uncus and parahippocampus
• Structures of interpeduncular fossa
• Optic tract and olfactory trigone
• Inferior horn of the lateral ventricle.
34. Internal cerebral veins
• There are two internal cerebral veins located one on
either side of midline in the tela choroidea of the third
ventricle.
• Each internal cerebral vein is formed at the
interventricular foramen( of Monro) by the union of
three veins: thalamostrite, septal and choroidal. The
two internal cerebral veins run posteriorly one on either
side of midline, between the two layers of tela
choroidea of third ventricle and unite together beneath
the splenium of corpus callosum to form the great
cerebral vein( of Galen) which empties into the straight
sinus.
• The thalamostriate, septal and choroidal veins are the
most important deep veins of the cerebrum. As their
names imply, the thalamostriate( striothalamic) vein
drains the thalamus and basal ganglia; the septal vein
drains the septum pellucidum, and the choroidal vein
drains the choroid plexus.
• Great cerebral vein (of Galen):
formed by union of two internal cerebral veins ,receives
two basal veins and joins inferior sagittal sinus to form
the straight sinus.
Tributaries
• Internal cerebral veins
• Basal vein
• Veins from colliculi
• Veins from cerebellum, cerebrum
35. CLINICAL ANATOMY
• Imaging Techniques allow arteries and veins to
be visualized.
• Blood vessels can be visualized with most
imaging techniques by finding a way to make
the blood contained within them differ in
some way from surrounding structures.
36. Cerebral angiography
• The cerebral angiography is a radiological technique to visualize the
vessels of the brain.
• A radiopaque solution is injected into one of the major arteries
supplying the brain, and serial radiographs of skull are taken at
approximately 1 second intervals.
• The injections into the common carotid artery or the internal
carotid artery( carotid angiogram) shows the distribution of middle
and anterior cerebral arteries;
• whereas the injection into the vertebral artery permits the
visualization of vertebral, basilar and posterior cerebral arteries
together with their branches. The cerebral angiography is valuable
in identifying vascular malformations and aneurysms. It is also
provides useful information about occlusive vascular disease and
space occupying lesions.
37. • Thrombosis of lateral striate branches of
middle cerebral artery causes motor and
sensory loss to most of the opposite side of
body except lower limb.
38. • Hemiplegia is a common
condition. It is an upper motor
neuron type of paralysis of
one half of the body, including
the face.
• It is usually due to an internal
capsule lesion caused by
thrombosis of one of the
lenticulostriate branches of
middle cerebral artery(cerebral
thrombosis)
• one of the lenticulostriate
branches is most frequently
ruptured(cerebral
haemorrhage); it is known as
Charcot’s artery of cerebral
haemorrhage.
• The lesion also produces
hemiplegia with deep coma,
and is ultimately fatal.
39. • Thrombosis of Heubner’s recurrent branch of
the anterior cerebral artery causes
contralateral upper monoplegia.
• Thrombosis of the paracentral artery(terminal
cortical branch of the anterior cerebral artery)
causes contralateral lower limb monoplegia.
40. • Occlusion of anterior
cerebral artery proximal to
the anterior communicating
artery is normally well
tolerated because of the
cross flow
• Distal occlusion of anterior
cerebral artery results in
weakness and cortical
sensory loss in the
contralateral lower limb
with associated
incontinence.
• This artery supplies the
area of lower limb and
perineum.
41. Arterial Disorders
Stroke (Sudden occlusion
of the blood supply):
It can be:
Hemorrhagic
Ischemaic
Aneurysm
42. Occlusion of anterior
cerebral artery(distal to
anterior communicating
artery)
• Contralateral hemiparesis and
hemianaesthesia involving mainly
the leg and foot, due to
involvement of upper parts of
primary motor and sensory areas,
and paracentral lobule.
• Inability to identify the objects
correctly, due to involvement of
superior parietal lobule.
• Apathy and personality changes,
due to involvement of part of
frontal lobe.
43. Occlusion of middle
cerebral artery
• Contralateral hemiparesis
and hemianaesthesia
involving mainly the face
and arm, due to
involvement of most of
the primary motor and
sensory areas.
• Aphasia if left dominant
hemisphere is involved,
due to involvement of
motor and sensory
speech areas.
• Contralateral
homonymous
hemianopia, due to
involvement of optic
radiation
44. Occlusion of posterior
cerebral artery
• Contralateral homonymous
hemianopia, due to
involvement of visual cortex
with some degree of macular
sparing.
• The macular vision is spared
because it is represented in
the occipital pole which
receives a collateral supply
from the middle cerebral
artery
• ( anastomosis exists between
the branches of middle and
posterior cerebral arteries in
the region of the occipital
pole).
45. STROKES
• Strokes result from disruption of the vascular supply.
• Cerebrovascular disease and accidents are the most
common causes of neurological deficits.
• Normally, about 55 ml of blood flows through each 100
g of CNS per minute. This is a little more than the CNS
needs to survive, but any significant reduction of this
perfusion rate rapidly causes malfunction or even death
of neurons.
• Reduction to about 10 mL/ 100 g/ min for more than a
few minutes initiates processes that result in necrosis of
the involved brain tissue.
• A necrotic region of tissue is called an infarct. An abrupt
incident of vascular insufficiency is called a stroke;
bleeding into or immediately adjacent to the brain can
also have stroke- like consequences called a
hemorrhagic stroke.
• Ischemic strokes(those caused by sudden blockage of
blood flow to some part of the CNS) are most commonly
caused by a thrombus (a blood clot formed within a
vessel) or an embolus ( a bit of foreign matter, such as
part of a blood clot or an atherosclerotic plaque, carried
along in the bloodstream)
46. Subarachnoid Hemorrhage
• It results from leakage
or rupture of a
congenital aneurysm on
the circle of Willis
• The sudden symptoms
include severe
headache; stiffness of
the neck and loss of
consciousness
• The diagnosis is
established by
withdrawing heavily
blood- stained CSF
fluid through a lumbar
puncture ( spinal tap )
47. ANEURYSMS
• Aneurysms(Greek for ‘dilation’) are
balloon- like swellings of arterial walls.
• They occur most frequently at or near
arterial branch points.
• Those close to the brain usually occur
in or near the anterior half of the
cerebral arterial circle, although they
are also found at other locations.
• An aneurysm can cause neurological
deficits in two ways. As it grows( some
can become huge), it may push
against and compress brain
structures, much as a growing tumor
would.
• It also can rupture and cause a
subarachnoid hemorrhage that,
depending on its size and location,
can have disastrous consequences
