Transcript Meninges (singular Meninx)

Meninges, CSF
and Blood Supply
of the Head and
Neck
Ruhaizan, Diyana, Fatimah, Fadhila,
Marshitah, Marzura, Sakinah
Meninges (singular: Meninx)
• Def: 3 membranous
envelopes; Dura mater,
Arachnoid and Pia Mater surrounding brain and spinal
cord
• Functions:
1. Protecting the brain and
spinal cord from mechanical
injury
2. Providing blood supply to skull
& hemispheres
3. Providing a space for the flow
of CSF
Meninges
Dura mater
-most superior
-toughest & inflexible
-”Tough mother”
(latin name)
Arachnoid
-middle layer
-Spider web-like of
blood supply
Pia mater
-innermost layer
-”tender mother”
(latin name)
Production of CSF
• Cerebrospinal Fliud (CSF) is a clear fluid produced by
dialysis of blood in the choroid plexus.
• Further production also comes from the ependymal
cell linings and vessels within the pia mater.
• Edendymal cell production of CSF is via ultrafiltration of
blood plasma and active transport across the
ependymal cells.
Production of CSF
• Of the total CSF
production, 35% is
produced within the
third ventricle of the
brain, 23% via the
fourth ventricle and
42% from general
ependymal cell
filtration.
Function of CSF
• Cerebrospinal fluid (CSF) surrounds the brain as well
as the central canal of the spinal cord.
• It helps cushion the central nervous system (CNS),
acting in a similar manner to a shock absorber.
• It also acts as a chemical buffer providing
immunological protection and a transport system for
waste products and nutrients.
Function of CSF
• The CSF also provides buoyancy to the soft neural
tissues which effectively allows the neural tissue to
"float" in the CSF  prevents the brain tissue from
becoming deformed under its own weight.
• It acts as a diffusion medium for the transport of
neurotransmitters and neuroendocrine substances.
Flow of CSF
CSF
(from choroid plexus)
Hydrostatic
pressure
Interventricular
Foramina
3rd Ventricle
(located in diechephalon)
Through cerebral
aqueduct
4th Ventricle
(located in hindbrain)
Central canal of spinal
cord
Subarachnoid Space
Cerebromedullary
cistern
Circulate over the
cerebral hemisphere
Flows down the length
of spinal cord in the
subarachnoid space
Dura & Arachnoid
Meninges
Drained into venous
sinuses
(through arachnoid
granulation in dorsal
sagittal sinus)
MAJOR
ARTERIES
SUPPLYING
HEAD AND
NECK
Arteries supplying
Head & Neck
The major arteries supplying head and neck derived
from :
1. Common carotid
i. internal carotid artery
ii. External carotid artery
2. Subclavian arteries
3. Vertebral artery
(branched from 1st part of subclavian a.)
Common Carotid Artery
• CCA runs
upwards to
the sup.
border of
thyroid
cartilage at
C3
• Bifurcates
into external
and internal
carotid a.
Blood supply- Arteries
 The external carotid artery: provides the major blood
supply for the face and mouth.
•
The two major terminal branches of the external
carotid artery:

the maxillary arteries

facial arteries
Blood supply- Arteries
Blood supply- Arteries
•
The maxillary artery is the large of the two terminal branches
of the external carotid artery.
 It arises behind the angle of the mandible and supplies
the deep structures of the face.
Blood supply- Arteries
Major branches of the maxillary artery:
1. Infraorbital artery
2. Posterior superior alveolar artery
3. Inferior alveolar artery
1
2
3
Blood supply- Arteries
1. Infraorbital artery gives branches to anterior and middle superior
alveolar arteries. Their distribution to the maxillary incisors and canine
teeth and to the maxillary sinuses.
2. Posterior superior alveolar artery. Its distribution is to the maxillary
molar and premolar teeth and gingiva.
3. Inferior alveolar artery. It descends close to the medial surface of the
mandibular ramus to the mandibular foramen. Before entering the
foramen, it gives off the mylohyoid branch which supplies tissues in the
floor of the mouth.
Blood supply- Arteries
• The facial artery is the
other major branch of the
external carotid artery.
 It enters the face at
the inferior border of
the mandible. It
passes forward and
upward across the
cheek towards the
angle of the mouth.
 It continues upward
along the side of the
nose and ends at the
medial canthus (inner
corner) of the eye.
Blood supply- Arteries
• The lingual artery also is a branch of the external carotid artery.
 Its distribution is along the surface of the tongue.
Internal Carotid Artery
• There are no branches of ICA in the neck;
passes superiorly in the neck within carotid sheath
anterior to transverse process of upper cervical
vertebrae and enters skull through carotid canal
• At its root, ICA has a dilatation
area a.k.a carotid sinus
• Inside skull, gives off to
opthalmic a. (supplies optic nerve,
eye, orbit an scalp)
Arterial supply of the
brain
• Normally divided into anterior and posterior
cerebral circulation
• Two main pair of artery supplying cerebral artery
and cerebrum:
i. Internal carotid artery
ii. Vertebral artery
Venous Drainage of the
Head and Neck
• The veins of the head and neck collect
deoxygenated blood and return it to the heart.
• Anatomically, the venous drainage can be divided
into three parts:
1.
2.
3.
Venous drainage of the brain and meninges: Supplied by
the dural venous sinuses
Venous drainage of the scalp and face: Drained
by veins synonymous with the arteries of the face and
scalp. These drain into the internal and external jugular
veins.
Venous drainage of the neck: Carried out by the anterior
jugular veins.
External Jugular Vein
• The external jugular vein and its tributaries supply the
majority of the external face.
• It is formed by the union of two veins:
o Posterior auricular vein - drains the area of scalp superior
and posterior to the outer ear.
o Retromandibular vein (anterior branch) – itself formed by
the maxillary and superficial temporal veins, which drain the
face.
External Jugular Vein
Anterior Jugular Veins
• The anterior jugular veins vary from person to
person.
• They are paired veins, which drain the anterior
aspect of the neck.
• Often they will communicate via a jugular venous
arch.
• The anterior jugular veins descend down the midline
of the neck, emptying into the subclavian vein.
Anterior Jugular Veins
Internal Jugular Vein
• The internal jugular vein
(IJV) begins in the
cranial cavity, as a
continuation of the
sigmoid sinus
• The initial part of the IJV
is dilated, and is known
as the superior bulb.
• The vein exits the skull
via the jugular
foramen.
Internal Jugular Vein
• In the neck, the internal jugular vein descends
within the carotid sheath, deep to the
sternocleidomastoid, and lateral to the common
carotid artery.
• At the bottom of the neck, posteriorly to the sternal
end of the clavicle, the IVJ combines with the
subclavian vein to form the brachiocephalic vein.
• Immediately before its termination, the inferior end
of internal jugular vein dilates, to form the inferior
bulb of the IJV.
Internal Jugular Vein
Dural Venous Sinuses
• The dural venous sinuses are spaces between the
periosteal and meningeal layers of dura mater,
which are lined by endothelial cells.
• They collect venous blood from the veins that drain
the brain and bony skull, and ultimately drain into
the internal jugular vein.
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