Intercranial Structures and Blood Vessels of the Head and Neck Flashcards
1
Q
Cranial Bones
A
• Have a unique structure consisting of an outer and inner cortical table surrounding the diploe
- Superior Cortical Layer – Outer Cortical Table
- Deeper Cortical Layer – Inner cortical table
2
Q
Meninges of the Brain
A
Dura Mater, Arachnoid Mater, Pia Mater
• Form a protective membranous layer
3
Q
What does the Dura Mater form
A
• Dura mater forms passageways for venous blood to flow
4
Q
Arachnoid Mater
A
o Consists of two differing parts
o Has protrusions called arachnoid villi that pass through the dura mater to enter the dural venous sinus (known as arachnoid granulation when calcified in older individuals)
o Does not go deep into all the sulci but rather forms a roof over each sulcus
5
Q
Role of the Arachnoid Vili
A
o Arachnoid villi allows CSF to drain from the subarachnoid d space into the venous blood to be recycled
6
Q
Pia Mater
A
o One cell layer thick and is invisible to the naked eye
o Attaches to the superficial surface of the brain and travels into all cerebral sulci
7
Q
What are the Dural Reflections?
A
- Falx Cerebri
- Tentorium Cerebelli
- Diaphragma Sellae
- Falx Cerebelli
8
Q
Falx Cerebri
A
o Located in the longitudinal fissure of the brain
o Separates the right and left cerebral hemispheres
9
Q
Tentorium Cerebelli
A
o Separates cerebellum from occipital lobes of the cerebrum
o Forms a tent like structure over the cerebellum
10
Q
Diaphragma Sellae
A
o Roof of sella turcicia
o Protects pituitary gland
o Fold of the dura mater
11
Q
Falx Cerebelli
A
o Short reflection between cerebellar hemispheres
12
Q
Significance of Dural Reflections
A
o Form passageways for venous blood to travel back to the heart
13
Q
Superior Sagittal Sinus
A
o Travels within the longitudinal fissure to reach the confluence of the sinuses posterior to the brain
o Dural venous sinus
o Located within the superior border of the falx cerebri
14
Q
Inferior Sagittal Sinus
A
o Located within the Falx Cerebri
o Joins with the Great Cerebral Vein to become the Straight sinus
15
Q
Straight Sinus
A
o Travels within the falx cerebri and the tentorium cerebelli until it drains into the confluence of sinuses
16
Q
Central Sulcus
A
o Indicates the central sulcus which separates the frontal and parietal lobes of the cerebrum
17
Q
Lateral Fissure
A
o Separates the temporal lobe from the frontal and parietal lobes
o T-shaped appearance
o Deep to the lateral fissure is the 5th lobe of the cerebrum – the insular lobe
18
Q
Parieto-occipital Sulcus
A
o Separates the parietal and occipital lobes
19
Q
What does the Substantia Nigra Produce?
A
• Dopamine is produced and is associated with the function of the basal nuclei
20
Q
Vermis
A
• The median segment of the cerebellum
21
Q
Cerebellum
A
- Consists of two cerebellar hemispheres
- Surface is arranged into folia and fissures
- Each side of the brainstem is attached to the ipsilateral cerebellar hemisphere and vermis by three paired cerebellar peduncles
22
Q
Three Paired Cerebellar Peduncles
A
o Superior – connects midbrain and cerebellum
o Middle – connects pons and cerebrum
o Inferior – connects medulla oblongata and cerebellum
23
Q
Function of the Cerebellar Peduncles
A
• Cerebellar peduncles allow information transfer between brainstem and cerebellum
24
Q
What are ventricles?
A
• Ventricles are spaces within the brain
25
Where is CSF produced?
• CSF is produced within the choroid plexus of the ventricles of the brain
26
Ventricles within the Brain
Lateral Ventricle, 3rd Ventricle, Cerebral Aqueduct, 4th Ventricle
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Location of the differing parts of the Lateral Ventricles
* Anterior horn of the lateral ventricle – frontal lobe of cerebral hemisphere
* Body of lateral ventricle – parietal lobe of cerebral hemispheres
* Inferior horn of lateral ventricle – temporal lobe of cerebral hemisphere
* Posterior horn of lateral ventricle – occipital lobe of cerebral hemisphere
28
Location of the 3rd Ventricle
Diencephalon
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Location of the 4th Ventricle
Pons, medulla oblongata and cerebellum
30
Location of the Cerebral Aqueduct
Midbrain of Brainstem
31
Function of CSF
* Protects brain from trauma
| * Allows means of transport for nutrients and waste material
32
Choroid Plexus Location
• Choroid plexus located within the floor of the lateral ventricle, roof of the third ventricle and roof of the fourth ventricle
33
How much CSF is produced in a day?
600-700mL
34
Cilia role in CSF production
Cilia allow beating movement to move the CSF into the subarachnoid space
35
Flow of the CSF
* CSF leaves the subarachnoid space via the arachnoid villi to the dural venous system for cycling
* Lateral Ventricle -> flows through interventricular foramen (connect right and left lateral ventricles) -> flows the cerebral aqueduct and is located within the midbrain -> apertures allow CSF to flow out the ventricular system and into the subarachnoid space -> fills all the sulci covering the brain -> drains into the arachnoid villi (only lie within the midsagittal plane as they drain into the superior sagittal sinus)
36
Apertures
• Located at the inferior portion of the fourth ventricle
3 individual apertures
o Single median and two lateral apertures
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What is a Cistern
• Regions in which there is dilation and CSF begins to pool
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Cisterna Magna
o Largest Cistern
| o Between the medulla oblongata and the inferior part of the cerebellum
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Cistern of the Great Cerebral Vein
o Located superior to the cerebellum and posterior to the diencephalon
40
Prepontine (or pontine) Cistern
o Passageway anterior to the Pons
| o Basilar artery lies here
41
Interpeduncular Cistern
o Lies anterior to the midbrain
| o Space located between the two cerebral peduncles and the anterior parts of the midbrain
42
Chiasmatic Cistern
o Located around the optic chiasm
43
Paracallosal Cistern
o Located in the longitudinal fissure
o Between the boundary of the falx cerebri and the corpus callosum
o Parallel to the corpus callosum
44
Gray Matter of the Brain
* Nervous tissue contained cell bodies and synapses of the neurons
* Grey is due to unmyelinated cell bodies
45
Cerebral Cortex
o Forms superficial boundary of the cerebral hemisphere
o Follows all the sulci and gyri of the cerebral hemispheres
o Gyri and Sulci create convolutions in the brain to increase surface area of the cerebral cortex increased number of neuronal cell bodies within the brain
46
Basal Ganglia
Basal nuclei consist of a number of differing centres
Lentiform nucleus - Lateral
Caudate nucleus – Anterior
Important role in motor control
47
Caudate Nucleus
* Comma shaped, curls around lentiform nucleus
* Shape is the same at the lateral ventricle and lies within the floor
* Head is anterior, Tail is posterior
48
Thalamus
o Located medially in the diencephalon of the brain
o Medial to the lentiform nucleus
o Divided into a right and a left
Interthalamic Adhesion (joins the right and left thalami)
o 20% of the population is missing this (more prominent in males)
49
Hypothalamus
o Hypothalamic sulcus
| o Separates the hypothalamus and the thalamus
50
Epithalamus
Pineal Gland - Produces melatonin
51
Internal Capsule
• An area of white matter located between the lentiform nucleus and caudate nucleus (anterior limb) and the lentiform nucleus and thalamus
52
Corpus Callosum: Four Parts
o Rostrum – connection between frontal lobes
o Genu – connection between frontal lobes
o Body – connection between parietal lobes
o Splenium – connection between occipital lobes
53
What is the Corticospinal Tract
• A bundle of motor neurons that course from the cerebral cortex of the precentral gyrus of the frontal lobe to the spinal cord to extend into the periphery
o Innervates skeletal muscles for voluntary muscle contraction
54
• Pathway of Motor Neuron Cell Bodies and Axons
1) Cerebral cortex of right frontal lobe
2) Corona Radiata
3) Internal Capsule
4) Cerebral Peduncles
5) Pons
6) Decussation of Motor Fibres
55
o Cerebral cortex of right frontal lobe
Cell bodies of the motor neurons of the corticospinal tract arise here in the precentral gyrus of the frontal lobe of the brain
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o Corona Radiata
White matter zone
| Myelinated axons of neurons course to and from the cerebral cortex
57
o Cerebral peduncles
Anterior columns of midbrain containing white matter
58
o Decussation of Motor Fibres
Motor neurons cross from the right side of the cerebrum to the left side of the spinal cord and vice versa here in the medulla oblongata
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Right Common Carotid Origin
arises as a terminal branch of the brachiocephalic trunk at the right sternoclavicular joint
60
Left Common Carotid Origin
arises as a collateral branch of the aortic arch
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Left and Right Common Carotid Arteries Course and Termination
Ascend posterolateral to the trachea and larynx and terminally divide into the external and internal carotid arteries at the superior border of the thyroid cartilage.
Have no collateral branches
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Subclavian Artery Branches
o Major collateral branches include the vertebral and internal thoracic arteries
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Subclavian Artery Termination
o Terminate at the external margin of the 1st rib to become continuous with axillary arteries
o Major collateral branches include the vertebral and internal thoracic arteries
64
Vertebral Artery Origin and Terminaton
o Arises as a collateral branch of the subclavian artery and terminates at the pontomedullary junction by uniting with the contralateral vertebral artery to form the basilar artery (supplying the brain)
65
Course of the Vertebral Artery
o Travels through the transverse foramina of cervical vertebra C6 to C1
66
Differing Parts of the Vertebral Artery
Cervical Part
Before entering the small passageways within the vertebral column
Vertebral Part
Enters passageways in the vertebrae from C6 to C1
Small holes are known as transverse foramina (holes within the transverse processes)
Sub-occipital Part
Lies directly underneath occipital bone before entering the foramen magnum
Intracranial Part
Passes through the foramen magnum and enters the cranial space
67
Internal Carotid Artery Origin and Termination
o Arises as a terminal branch of the common carotid artery at C3/C4 at the superior border of the thyroid cartilage and terminates by terminally branching into the anterior cerebral, middle cerebral and posterior communicating arteries (supplying the brain)
68
Internal Carotid Artery Branch
o Has a single collateral branch in the head, the ophthalmic artery
69
Internal Carotid Artery Differing Parts
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Neck Region (Cervical Part)
Petrous Part
Cavernous Part
Cerebral Part
U-Bend
```
70
Petrous Part of the Internal Carotid Artery
Passes through the petrous part of the temporal bone
Passes through a passageway known as the carotid canal
71
Neck region of the internal carotid artery
Travels with the Internal Jugular Vein in the carotid sheath
72
Cavernous part of the internal carotid artery
Following the carotid canal
Passes through the cavernous venous sinus
Continues passing through to the anterior part of the head
73
Cerebral Part of the Internal Carotid Artery
Terminal part which lies on the inferior surface of the brain with the terminal branches contributing to the blood supply of the brain
74
U-Bend of the Internal Carotid Artery
Formed by the distal part of the cavernous part and the proximal part of the cerebral part is called the carotid siphon
75
Opthalmic Artery
o Arises from the carotid siphon in the cranial cavity and courses into the orbital cavity to supply blood to the eyeball
o Branches off between the cavernous and cerebral regions at the U bend
76
Internal Jugular Vein Origin
o Arises as a continuation with the sigmoid sinus at the jugular foramen and terminates as a confluence with the subclavian vein to form the brachiocephalic vein
77
Internal Jugualr Vein Location
o Lies superficial to the internal and common carotid arteries
78
Subclavian Vein Course
o Continuous with the axillary vein at the lateral border of the 1st rib
79
External Carotid Artery
o Lies anterior and superficial to the internal carotid artery, supplying blood to the face and extracranial structures
o Has many collateral branches in the neck (supplying the thyroid gland and all parts of the head except the brain and eyes
80
Internal Carotid Artery Branches
o Has no branches within the neck (only a single collateral branch in the head – the ophthalmic artery
81
Carotid Sinus
o Located in the most proximal part of the cervical part of the internal carotid artery
o Is a dilation containing baroreceptors in its walls to measure blood pressure
82
Aortic Arch Variation
* Variation in the aortic arch can occur during the development of the aorta
* Typically, the arch consists of three collateral branches (brachiocephalic trunk, left common carotid, left subclavian arteries)
83
Bovine Arch
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Bovine Arch (8-25%)
o One of the most common variations
o Brachiocephalic trunk and left common carotid share the same origin
```
84
Middle Meningeal Arteries Origin
• Middle meningeal artery is a collateral branch of the maxillary artery of the external carotid artery
85
Middle Meningeal Artery Course
• Enters the cranial cavity through the foramen spinosum
86
Middle Meningeal Artery Branches
• At the pterion (cranial landmark), it divides into the anterior and posterior branches and supplies the cranial bones and dura
87
Variation in Cerebral Arterial Circle
Only 20-30% of the population have a complete Cerebral arterial circle
Hypoplastic - small diameter or absence of the posterior communicating artery
Absence or small diameter of the anterior cerebral artery
Anterior communicating artery absent or narrowed
Most common - underdeveloped or absent posterior cerebral artery.
88
Middle Cerebral Artery
* Arises as a terminal branch of the internal carotid artery
* Courses through the lateral fissure to supply blood to the lateral surfaces of the frontal, parietal and temporal lobes
89
Posterior Cerebral Artery
* Arises as a terminal branch of the basilar artery
* Courses posteriorly around the midbrain to supply blood to the inferior surface of the temporal lobe and the entire occipital lobe
90
Anterior Cerebral Artery
* Arises as a terminal branch of the internal carotid artery
* Courses into the longitudinal fissure between the corpus callosum and flax cerebri in the Paracallosal cistern to supply blood to the medial surfaces of the frontal and parietal lobes
91
Dural Venous Sinus
* Allow the drainage of blood from the brain
| * Passageways running through two layers of the dura mater before exiting the cranial cavity
92
Transverse sinus
Becomes continuous with the sigmoid sinus at the petrus part of the temporal bone
93
Sigmoid Sinus
o S-shaped
o Travels more inferiorly across the petrus part of the temporal bone and becomes continuous with the internal jugular vein at the jugular foramen
94
Flow in the Dural Venous Sinuses
* SSS drains blood posteriorly to enter a dilation called the confluence of the sinuses
* ISS drains posteriorly in the inferior border of the Falx Cerebri --> drains into the straight sinus
* Great Cerebral vein forms confluence with ISS to form straight sinus --> Straight sinus joins the SSS at the confluence of the sinuses
* Blood is diverted around the posterior cranial cavity by entering the R and L transverse sinuses which wrap around posteriorly on the occipital bone
95
Cerebral Arterial Circle
* Unique system of arteries located inferior to the brain and provides all blood supply to the brain
* Arises from two major blood vessels – internal carotid arteries and vertebral arteries
96
Cerebral Arterial Circle Flow
* Vertebral arteries unite to form the basilar artery
* Basilar artery terminally divides into the posterior cerebral artery (provides blood to the occipital lobe and the inferior surface of the brain)
* Internal Carotid Arteries terminally divide into the anterior cerebral arteries, middle cerebral arteries and the posterior communicating arteries
* Posterior Communicating Arteries connect to the posterior cerebral arteries to form an anastomoses around the optic chiasm
97
Cerebral Arterial Circle: Anastamoses between PCOMA and Posterior Cerebral Arteries
o Allows for alternate routes of blood flow
o Neurons are postmitotic in adults cannot proliferate death is permanent
98
Pathology in Cerebral Arterial Circle
o Narrowing or occlusion of blood vessel due to clot or plaque
99
Anterior Communication Artery
Connects between two paired anterior cerebral arteries and completes the cerebral arterial circle
100
What is Hydrocephalus?
An abnormal build up of fluid in the ventricles (cavities) deep within the brain
101
What can cause hydrocephalus and what can it lead to?
- Overproduction of CSF, obstruction of flow, interference with absorption --> excess of CSF in the ventricles
- Excess CSF --> dilates ventricles, thinning the surrounding brain. In infants, this can separate the bones of the skull.
102
Obstructive Hydrocephalus
Obstruction of cerebral aqueduct, interventricular foramen, apertures
103
Communicating Hydrocephalus
Obstruction outside the ventricular system (subarachnoid space or arachnoid villi)
104
What are the consequences of increased pressure on the brain?
Atrophy of cells - depends on the age of the individual
Adult - Permanent, lack of mitotic capacity
Neonate - Some regenerative capacity
105
What are the consequences of increase pressure on the skull?
May occlude blood vessels/sinuses
Expansion of sutures in young children --> enlargement of cranial cavity
106
Treatment Options for Hydrocephalus
Shunting of CSF through surgical introduction of shunt - provide an alternative route
(usually from ventricle or subarachnoid space to abdominal cavity or heart)
