Cerebral circulation and CSF

1. ANATOMY AND
PHYSIOLOGY OF
CEREBRAL CIRCULATION
AND CSF.
NAME OF THE TEACHER NAME OF THE STUDENT
Dr.(Ms) Sucheta Yangad Miss Seri Lollen
Associate professor MSc.(N) 1st year
Dr. DYCON , PUNE Dr. DYCON,PUNE

2. The brain :-
 The brain is contained in skull & weighs 1300-1400 g
 Made up of about 1000 billion neurons, 7 each neuron is surrounded by about
10 glial cells (neuroglia).
 Brain is also covered by "Meninges" like spinal cord ,outer duramater, middle
arachnoid mater & inner piamater.
 It is one of the largest organs in the body, and coordinates most body activities.
 It is the center for all thought, memory, judgment, and emotion.
 Each part of the brain is responsible for controlling different body functions,
such as temperature regulation and breathing.

3. Anatomy and physiology of brain

4. Ventricles of the brain
There are certain cavities in the brain
called as "ventricles"
These ventricles are filled with CSF.
There are 4 ventricles of brain:-
1) 2 lateral ventricles in two hemisphere of
the brain
2) 3 lies between hypothalamus & thalamus
3) 4th between brain stem & cerebellum
& is continuous with the central cavity of
spinal cord

5. Parts of brain
Cerebrum Cerebellum Brain steam Diencephelon
1)Right cerebral 1) Medulla 1)Thalamus
hemisphere 2) Pons 2)hypothalamus
2) Left cerebral
hemisphere 3)Mid brain 3)Epithalamus&
pineal gland

6. CEREBRAL CIRCULATION :-
 Cerebral circulation is the movement of blood through the network
of blood vessels to supply the brain.
 The arteries carry oxygenated blood and other nutrients to the brain.
 The veins carry deoxygenated blood back to the heart removing
carbon dioxide and other metabolic products.
 The movement of blood in the cerebral circulation is called cerebral
blood flow.

7. Blood supply
Blood supply to the brain is normally divided into anterior and posterior
segments.
 The two main pairs of arteries are :-
1)The Internal carotid arteries (supply the anterior brain)
2) Vertebral arteries (supplying the brainstem and posterior brain).

8. The anterior and posterior cerebral circulations are
interconnected via bilateral posterior
communicating arteries.
They are part of the Circle of Willis, which
provides backup circulation to the brain.

9. 1)Anterior cerebral circulation
 The anterior cerebral circulation is the blood supply to the
anterior portion of the brain including eyes. It is supplied by
the following arteries:
 The internal carotid artery is located in the inner side of the
neck in contrast to the external carotid artery. In human
anatomy, they arise from the common carotid arteries,
where these bifurcate into the internal and external carotid
arteries at cervical vertebral level 3 or 4; the internal carotid
artery supplies the brain, including the eyes, while the
external carotid nourishes other portions of the head, such
as the face, the scalp, the skull, and the meninges.

10. Anterior cerebral artery (ACA)
The anterior cerebral artery (ACA) is one of a pair of arteries on the brain that
supplies oxygenated blood to most midline portions of the frontal
lobes and superior medial parietal lobes. The two anterior cerebral arteries arise
from the internal carotid artery and are part of the circle of Willis. The left and right
anterior cerebral arteries are connected by the anterior communicating artery.
Medial surface of cerebral hemisphere, showing areas
supplied by cerebral arteries. blue

11. Anterior communicating artery:
 The anterior communicating artery is a blood vessel of the brain that connects the left and
right anterior cerebral arteries. the two arteries joining together to form a single trunk, which afterward
divides.
 Normally, the anterior communicating artery does not significantly contribute to cerebral blood
supply, as there is negligible net blood flow within it, and some of its anteromedial branches seem to
be specially adapted to ease forebrain sodium sensing, rather than to supply the brain with blood.

12. Middle cerebral artery
 The middle cerebral artery (MCA) is one of the three major paired arteries that
supply blood to the cerebrum. The MCA arises from the internal carotid and continues into
the lateral sulcus where it then branches and projects to many parts of the lateral cerebral
cortex. It also supplies blood to the anterior temporal lobes and the insular cortices.

13. 2) Posterior cerebral circulation
 The posterior cerebral circulation is the blood supply to the posterior
portion of the brain, including the occipital
lobes, cerebellum and brainstem. It is supplied by the following
arteries:-
Vertebral arteries:
 These smaller arteries branch from the subclavian arteries which
primarily supply the shoulders, lateral chest, and arms. Within
the cranium the two vertebral arteries fuse into the basilar artery.
 As the supplying component of the vertebrobasilar vascular
system, the vertebral arteries supply blood to the upper spinal
cord, brainstem, cerebellum, and posterior part of brain.

14. Posterior inferior cerebellar artery (PICA):
 The posterior inferior cerebellar artery (PICA) is the largest branch
of the vertebral artery. It is one of the three main arteries that supply
blood to the cerebellum, a part of the brain.
 Blockage of the posterior inferior cerebellar artery can result in a
type of stroke called lateral medullary syndrome.
Basilar artery:
 Supplies the midbrain, cerebellum, and usually branches into
the posterior cerebral artery.
Anterior inferior cerebellar artery (AICA)
 Is one of three pairs of arteries that supplies blood to
the cerebellum.

15. Pontine arteries
 The pontine arteries are a number of small vessels which come off at right
angles from either side of the basilar artery and supply the pons and adjacent
parts of the brain.
Superior cerebellar artery (SCA)
 The superior cerebellar artery (SCA) arises near the termination of
the basilar artery.
 The artery supplies:
 Superior half of the cerebellum
 Parts of the midbrain

16. Posterior cerebral artery (PCA)
 The posterior cerebral artery (PCA) is one of a pair of arteries that supply
oxygenated blood to the occipital lobe, part of the back of the human brain.
Posterior communicating artery
 The left and right posterior communicating arteries are arteries at the base
of the brain that form part of the circle of Willis. Each posterior
communicating artery connects the three cerebral arteries of the same side.
Anteriorly, it connects to the internal carotid artery (ICA) prior to the
terminal bifurcation of the ICA into the anterior cerebral artery and middle
cerebral artery. Posteriorly, it communicates with the posterior cerebral
artery.

17. Circulus arteriosus (circle of Willis)
 The greater part of the brain is supplied with arterial blood by an
arrangement of arteries called the circulus arteriosus or the circle of
Willis .
 Four large arteries contribute to its formation: the two internal carotid
arteries and the two vertebral arteries .
 The vertebral arteries arise from the subclavian arteries, pass upwards
through the foramina in the transverse processes of the cervical vertebrae,
enter the skull through the fora men magnum, then join to form the
basilar artery.
 The arrangement in the circulus arteriosus is such that the brain as a
whole receives an adequate blood supply when a contributing artery is
damaged and during extreme movements of the head and neck.
 Anteriorly, the two anterior cerebral arteries arise from the internal
carotid arteries and are joined by the anterior communicating artery.

20.  Posteriorly, the two vertebral arteries join to form the basilar artery. After
travelling for a short distance the basilar artery divides to form two posterior
cerebral arteries, each of which is joined to the corresponding internal carotid
artery by a posterior communicating artery, completing the circle.
 The circulus arteriosus is therefore formed by:
 2 anterior cerebral arteries
 2 internal carotid arteries
 1 anterior communicating artery
 2 posterior communicating arteries
 2 posterior cerebral arteries
 1 basilar artery.
 From this circle, the anterior cerebral arteries pass forward to supply the
anterior part of the brain, the middle cerebral arteries pass laterally to supply the
sides of the brain, and the posterior cerebral arteries supply the posterior part of the
brain. Branches of the basilar artery supply parts of the brain.

21. venous drainage of brain:
 The venous blood from the head is returned by deep and superficial veins.
 Superficial veins with the same names as the branches of the external
carotid artery return venous blood from the superficial structures of the face
and scalp and unite to form the external jugular veins.
 The external jugular vein beings in the neck at the level of the angle of the
jaw. It passes downwards in fornt of the sternocleidomastoid muscles , then
behind the clavicle before entering the subclavian vein.
 The venous blood from the deep areas of the brain is collected into
channels called the dural venous sinuses.
 The dural venous sinuses of the brain are formed by layers of the dura
matar lined with endothelium . the dura matar is the outer protective covering
of the brain .

22. The main venous sinuses are listed below:
1) The superine sagittal sinus carries the venous blood from the superior part of the brain,
It begins in the frontal region and passes directly backwards in the midline of the skull
to the occipital it turns to the right side and continue as the right transverse sinus.
2) The inferior sagittal sinus lies deep within the brain and passes backwards to form the
straight sinus
3) The straight sinus runs backwards and downwards to become the left transverse sinus.
4) The transverse sinuses begin in the occipital region. They run forward and medially in a
curved groove f the skull, to become continuous with the sigmoid sinuses.
5) The sigmoid sinuses are a continuation of the transverse sinuses. Each curves downward
and mediality and lies in a groove in the mastoid process of the temporal bone.
Anteriorly only a thin plate of bone separate the sinus from the air cells in the mastold
process of the temporal bone. Inferiorly it continues as the Internal jugular vein.

24. CEREBROSPINAL FLUID :

25. CEREBROSPINAL FLUID :
Introduction
 CSF is clear, colorless and transparent circulates through cavity of the :-
 -Brain
 -Subarachnoid space
 -Central canal of spinal cord
 -Part of Extracellular fluid (ECF)
Definition :-
 Cerebrospinal fluid (CSF) cushions the brain and along with blood-brain
barrier, the buffering function of neuroglia, and regulation of CNS circulation
controls extracellular environment of neurons. Within the substance of brain in
the ventricular system, there are series of spaces filled with CSF.

27. Composition, Volume and pressure of CSF:-
Composition of CSF:-
 The extracellular fluid within the CNS communicates directly with the CSF.
Thus, the composition of CSF indicates the composition of the extracellular
environment of the neurons in the brain and spinal cord.
 The CSF differs from blood in having a lower concentration of K. glucose,
and protein and a higher concentration of Na' and C.
 CSF normally lacks blood cells.
 The increased concentration of Na' and Cl- enables the CSF to be isotonic to
blood, despite the much lower concentration of proteins in the CSF.

28.  CEREBROSPINAL FLUID
 Water -99.13%
 Solids- 0.87%
 Solid is divided into :-
1)Organic substances
Protein
Amino acids
Sugar
Urea
Uric acid creatinine
Lactic acid
2)Inorganic substances
Sodium
Calcium
Potassium
Magnesium
Sulfates

29. The total volume of human CSF is between
150 and 160 mL .
To maintain this volume, CSF secretion
and drainage must be equal; imbalances to
this equilibrium will produce an increase in
the total fluid content of the brain,
subsequently causing an elevation in
pressure.

30.  PROPERTIES
 Volume: approximately 150 mL
 Rate of formation: approximately 0.3 mL/min
 Specific gravity: 1.005
 Reaction: Alkalin
Formation of CSF
 Formed by the choroid plexus situated within the ventricles.
 The choroid plexus are tuft of capillary projections present inside ventricles
and covered by:
 Pia mater
 Ependymal covering.

31. Substances affecting the formation of CSF
 Pilocarpine, ether and extracts of pituitary gland stimulates the secretion of
CSF by stimulating choroid plexus.
 Injection of isotonic saline also stimulates CSF formation.
 Injection of hypotonic saline
 -Causes greater rise in capillary pressure and intracranial
pressure,
 -Fall in osmotic pressure leading to increase in CSF
formation.
 Hypertonic saline
 -Decreases CSF formation
 -Decreases CSF pressure

32. Circulation of CSF
 CSF formed in the lateral ventricles passes through the interventricular
foramina into the third ventricle. Thence the fluid flows trough the cerebral
aqueduct (of Sylvius) into the fourth ventricle. From fourth ventricle, some
CSF passes into the central canal of spinal cord, but most escapes into the
subarachnoid space (surrounding the brain and spinal cord) through the
median aperture (foramen of Magendie) of fourth ventricle and the two lateral
apertures of fourth ventricle (foramina of Luschka). Subarachnoid cistern
refers to the regions where subarachnoid space is distended to form pools of
CSF. An example as the lumbar cistern which surrounds the lumbar and sacral
spinal root belows the level of termination of spinal cord. The lumber cistern is
the targeted for lumber puncture. A procedure used clinically to sample the csf.

34. Absorption of CSF
 Mostly absorbed by the Arachnoid villi into Dural sinuses and Spinal veins.
 Small amount is absorbed along the perineural spaces into cervical
lymphatics and in to the perivascular spaces.
 Normally, 500 mL of CF is formed everyday and equal amount is absorbed.
Functions of CSF .
 Protection to CNS by acting as water-jacket, as it absorbs shock in the
event of blow .
 Removal of Waste products of brain metabolism.
 Regulates extracellular environment for the neurons of central nervous
system.
 Transports hormones and hormone-releasing factors.

35. BLOOD -CSF BARRIER
 The capillaries that travers the choroidal plexuses are freely permeable
to plasma solutes. However , a barrier exists at the level of epithelial calls
that make up the choroid plexuses. This barrier is responsible for carrier
mediated active transport.

36. Thank you