Anatomy Physiology of The Brain
Anatomy Physiology of The Brain
Anatomy Physiology of The Brain
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© Johnson & Johnson Services Inc. 2018 All rights reserved. 092892-181219 1
SAY: Welcome to Module 1: Anatomy & Physiology of the Brain. This module will
strengthen your understanding of basic neuroanatomy, neurovasculature, and functional
roles of specific brain regions.
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SAY: The brain is a dense organ with various functional units. Understanding the
anatomy of the brain can be aided by looking at it from different organizational layers.
(Purves 2012/p717/para1)
In this lesson, we’ll explore these organizational layers by discussing the principle brain
regions, layers of the brain, and lobes of the brain. We’ll also discuss the terms used by
scientists and healthcare providers to orient neuroanatomical discussions.
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• Match each of the 4 lobes of the brain with their respective functions
SAY: Please take a moment to review the learning objectives for this lesson.
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Directional Terms
Used in Anatomy
SAY: Specific directional terms are used when specifying the location of a structure or
area of the brain.
Note that the terms anterior, posterior, superior, and inferior refer to the long axis of the
body (which is straight), and doesn’t change. (Purves 2012/p718/Figure A1/caption)
However, the terms dorsal, ventral, rostral, and caudal are relative to the nervous
system axis they are describing,
which bends at the brainstem. (Purves 2012/p718/Figure A1/caption)
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SAY: When studying the internal anatomy of the brain, you may notice different sectional
planes. (Purves 2012/p718/c2/para1)
The terms used to describe these planes help provide a common frame of reference when
discussing the locations of brain structures. (Purves 2012/p718/c2/para1)
There are 3 key planes to note, the coronal plane, the sagittal plane, and the horizontal, or axial
transverse plane.
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• Cerebrum
• Cerebellum
• Diencephalon
• Brainstem
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SAY: There are 4 principal regions of the adult brain, which are shown here. Let’s begin
reviewing these regions starting with the cerebrum.
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SAY: The cerebrum is the largest portion of our brain, accounting for 83% of the total
brain mass. (Marieb 2016/p434/c2/para1)
It is responsible for complex aspects of our consciousness, such as memory,
personality, and intelligence. (Tortora 2009/p508/Table 14.2/c2/last para)
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• 2-4 mm thick
• Billions of neurons
SAY: The cerebral cortex is 2 to 4 millimeters thick, contains billions of neurons, and has
folds that nearly triple its surface area (Marieb 2016/p435/c2/para3). The folds on the
surfaces of the cerebral hemispheres are comprised of ridges of tissue, called gyri,
separated by shallow grooves, called sulci (Marieb 2016/p435/c1/para 3)
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Each hemisphere predominately controls the opposite side of the body; however, no one
functional area of the cortex acts entirely alone—conscious behavior requires the entire
cortex to play a role. (Marieb 2016/p437/c1/para 1)
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• Functions
1. Coordinates skeletal muscle contractions
2. Regulates balance and posture
3. May have a role in language processing and recognition
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SAY: The cerebellum sits in the inferior and posterior part of the cranial cavity (Tortora
2009/p507/c2/para4). It is also known as the “little brain” and is the second largest part
of the brain, accounting for 11% of total brain mass (Tortora 2009/p496/c2/para1)
(Marieb 2016/p434/c2/para1’450/c1/para8).
Similar to the cerebrum, the cerebellum has folds that increase surface area and allow
for a greater number of neurons. (Tortora 2009/p507/c2/para4). The cerebellum
coordinates skeletal muscle contractions, regulates balance and posture, and may have
a role in language processing and cognition. (Tortora 2009/p508/Table 14.2/c1/last
para)
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1. Midbrain
2. Pons
3. Medulla Oblongata
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SAY: The brainstem is located between the diencephalon and the spinal cord. It is
composed of 3 parts. (Tortora 2009/p504/c1/para1)
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Brainstem: Midbrain
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SAY: The midbrain contains tracks for nerve impulses between motor areas of the
cerebral cortex to the spinal cord. (Tortora 2009/p507/c1/para1) Some of the other
functions that relay through the midbrain include reflexes for the head, eyes, and trunk
in response to visual stimuli, and impulses for auditory stimuli (e.g., the startle reflex).
(Tortora 2009/p503/c2/para2)
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Brainstem: Pons
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SAY: The pons serves as a bridge to connect areas of the brain to one another. The
pons contains areas that relay signals for voluntary movements, equilibrium information
from the inner ear, and areas that (together with the medulla oblongata) help control
breathing. (Tortora 2009/p505/c2/para2)
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SAY: The medulla oblongata (also called medulla) contains areas that control key vital
body functions. For example, the medulla contains the cardiovascular center, which
regulates the rate and force of the heartbeat and the diameter of blood vessels. The
medulla also contains the respiratory center, which adjusts the basic rhythm of
breathing. (Tortora 2009/p503/c2/para2) Other sections of the medulla control reflexes
for swallowing, sneezing, vomiting, hiccupping, and coughing. (Tortora
2009/p503/c2/para3)
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• Connective tissue
• 3 layers:
– Dura Mater
– Arachnoid Mater
– Pia Mater
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SAY: Now that we have discussed the principle parts of the brain, let’s look at the layers
of the brain from the outside moving in. The brain is surrounded by 3 layers of
connective tissue membrane called meninges. These layers cover and protect the brain
and blood vessels, contain cerebrospinal fluid, and create partitions in the skull. (Marieb
2016/p460/c2/para1)
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• Outermost layer
• 2-layered sheet
1. Marieb 2016/p460/c2/para1
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SAY: The outermost layer of the meninges, the dura mater, is the strongest of the 3
meninges. The dura mater is a 2-layered sheet, the most superficial of which is attached
to the inner surface of the skull. (Marieb 2017/p460/c2/para3) In some places, the folds
of the dura mater extend into the cerebral hemispheres to limit excessive movement of
the brain within the cranium. (Marieb 2017/p460/c2/para3)
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• Middle layer
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SAY: The middle layer of the meninges is the arachnoid mater. This layer forms a loose
brain covering that is separated from the dura mater by a narrow cavity. Beneath the
arachnoid membrane is the subarachnoid space, which contains web-like extensions
that secure the arachnoid mater to the pia mater below it. (Marieb 2017/p461/c1/para4)
The term arachnoid comes from the word arachnida, meaning spider. The arachnoid
mater is named for its web-like extensions. (Marieb 2017/p461/c1/para4)
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• Innermost layer
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SAY: The pia mater is the innermost layer of the meninges and closely adheres to the
shape of the brain. (Marieb 2017/p461/c1/para5-c2/para1) The pia mater is composed
of delicate connective tissue and many small blood vessels. (Marieb
2017/p461/c1/para4) As blood vessels pass along the surface of the brain and turn
inward, they are covered by a loose-fitting sleeve of pia mater. (Tortora
2009/p496/c2/para2)
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SAY: Let’s shift our attention to another form of anatomical subdivision, the lobes of the
brain.
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• Frontal
• Parietal
• Occipital
• Temporal
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SAY: There are 4 lobes of the brain. Specific gyri and sulci on the surface of the
cerebrum serve as anatomical landmarks to divide the brain into 4 lobes: frontal,
parietal, occipital, and temporal. (Purves 2012/p720/c1/para3)
Landmarks that divide the brain into lobes include the central sulcus that divides the
frontal lobe from the parietal lobe. Additionally note the lateral fissure, also known as the
Sylvian fissure, dividing the temporal lobe from the frontal and parietal lobes. (Purves
2012/p720/c1/para1)
Looking at the brain from the hemisected view allows us to note the parieto-occipital
sulcus separates the parietal and occipital lobes.
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• Prefrontal Cortex:
– Executive functions (e.g., personality & recognizing
consequence)
• Broca’s area:
– Production of language
– Damage causes Broca’s aphasia, a condition in
which the patient understands many written and
spoken words, but has difficulty speaking them
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SAY: The frontal lobe is associated with executive functions, motor performance, and
production of language. (Vanderah 2016/p61/c2/last para-p62/c2/para1)
The first of these functions occupies a large portion of the frontal lobe and is called the
prefrontal cortex. This area is involved with executive functions, which include
personality, and recognizing future consequences of current actions. (Vanderah
2016/p62/c1/para2)
Areas of the frontal lobe associated with motor performance include the primary motor
cortex, which is involved in the initiation of voluntary movement, as well as the premotor
and supplementary motor areas, which coordinate the planning and initiation of
voluntary movement.
The motor aspects of language (ie, the production of language) are controlled by an
area in 1 hemisphere (typically the left) of the frontal lobe called Broca’s area.
(Vanderah 2016/p62/c1/para3) Damage to this area causes Broca’s aphasia, a
condition in which the patient understands many written and spoken words but has
difficulty speaking them. (Dorland’s/broca’s asphasi)
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Parietal Lobe
Associated with integrating sensory information, contains the spatial orientation
system, and is involved in the comprehension of language
• Parietal Cortex:
– Controls aspects of spatial orientation and directing
attention
• Wernicke’s area:
– Located partially in the parietal lobe
– Involved in recalling, recognizing, and interpreting
words and other sounds in the process of using
language
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SAY: The parietal lobe is associated with integrating sensory information, contains the
spatial orientation system, and is involved in the comprehension of language.
(Vanderah 2016/p64/c1/para2-c2/para3)
An area of the parietal lobe, called the primary somatosensory cortex, is concerned
with the processing of proprioceptive and tactile stimuli. (Vanderah 2016/p64/c1/last
para-c2/para1)
The parietal cortex controls complex aspects of spatial orientation and directing
attention. (Vanderah 2016/p64/c2/para3)
A large portion of the parietal lobe of one of the hemispheres (typically the left) works
with portions of the temporal lobe to comprehend language.
Wernicke’s area is located partially in the parietal lobe and is involved in recalling,
recognizing, and interpreting words and other sounds in the process of using language.
(Dorland’s/Wernicke aphasia) (Taber’s/Wernicke).
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Occipital Lobe
Chiefly responsible for visual functions
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SAY: The occipital lobe is chiefly responsible for visual functions. This lobe contains the
primary visual cortex and the majority of the visual association area, involved in higher
order processing of visual information. (Vanderah 2016/p65/c2/para2)
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Temporal Lobe
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SAY: The temporal lobe contains the primary auditory cortex (involved with auditory
perception (Taber’s/auditory area) and part of Wernicke’s area. (Vanderah
2016/p65/c1/para2) Recall that Wernicke’s area is involved in the comprehension of
language; a patient with damage to Wernicke’s area (Wernicke aphasia) would be
unable to understand written, spoken, or tactile speech symbols. (Dorland’s/Wernicke
aphasia) Medial parts of the temporal lobe are involved in aspects of memory and
learning. (Vanderah 2016/p65/c1/para3)
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a) Occipital lobe
b) Parietal lobe
c) Frontal lobe
d) Temporal lobe
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SAY: Let’s briefly review. Which of the lobe’s primary function is integrating sensory
information?
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a) Occipital lobe
b) Parietal lobe
c) Frontal lobe
d) Temporal lobe
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SAY: That’s correct – the parietal lobe’s primary function is integrating sensory
information
OR
SAY: That’s incorrect – the parietal lobe’s primary function is integrating sensory
information
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a) Occipital lobe
b) Parietal lobe
c) Frontal lobe
d) Temporal lobe
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SAY: Let’s do another review. Which lobe is associated with executive functions, motor
performance, and production of language?
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a) Occipital lobe
b) Parietal lobe
c) Frontal lobe
d) Temporal lobe
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SAY: That’s correct – the frontal lobe is associated with executive functions, motor
performance, and production of language
OR
SAY: That’s incorrect - the frontal lobe is associated with executive functions, motor
performance, and production of language
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Lesson 2:
In this lesson, we’ll discuss the arterial system and the branches of the aorta that
supply our brains with this critical substance.
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SAY: Let’s move on to the next topic: blood supply to the brain. In this lesson, we’ll
discuss the arterial system and the branches of the aorta that supply our brains with this
critical substance.
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• Define the types of arteries in the arterial system, and the flow of blood
through these arteries
• Label the aortic arch, the brachiocephalic artery, and their respective
branches
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SAY: Please take a moment to review the learning objectives for this lesson.
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How quickly do we lose consciousness after losing blood supply to the brain?
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SAY: How quickly do we lose consciousness after losing blood supply to the brain?
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1. Systemic arteries:
– Carry blood from the heart to the whole body
– Direct or indirect branches from the aorta, the main and
largest artery of the body
2. Pulmonary arteries:
– Carry deoxygenated blood from the heart to the lungs.
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SAY: The arterial system is divided into 2 major circulation systems. (SEER
2018/p1/para1)
The first are the systemic arteries that carry blood from the heart to the whole body.
(SEER 2018/p2/para1)
All systemic arteries are either direct or indirect branches from the aorta, (SEER
2018/p2/para3), the main and largest artery of the body. (Patton 2014/p705/aorta) The
second are the pulmonary arteries that carry deoxygenated blood from the heart to the
lungs. (Patton 2014/p399/c1/para2-c2/parra1) (Marieb 2016/p729/c1/para3)
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• Systemic arteries
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SAY: Systemic circulation carries oxygenated and nutrient-rich blood from the left
ventricle of the heart, through systemic arteries to capillaries in the body’s tissues, and
then returns deoxygenated blood back to the heart through systemic veins. (Patton
2014/p399/c1/para2-c2/para1) (Marieb 2016/p729/c1/para3)
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SAY: Pulmonary circulation brings blood from the right ventricle of the heart, through the
left and right pulmonary arteries, to the lungs for gas exchange. (Marieb
2016/p728/c1/para1-2)
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The Aorta
The aorta can be divided into 3 main portions
1. Ascending aorta
2. Aortic arch
3. Descending aorta
– Thoracic part
– Abdominal part
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SAY: The aorta can be divided into 3 main portions. (SEER 2018/p2/para3):
The first portion is the ascending aorta, which begins where the aorta arises from the
left ventricle of the heart. The second part begins as it then bends into the aortic arch.
Finally, the third portion arises as it proceeds downward as the descending aorta
through the upper thoracic part and the lower abdominal part. At that point, it divides into
the 2 common iliac arteries, the internal and external. (Dorlands/aorta)
(Taber’s/artery/p7(external); p10(internal))
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Aortic Arch
• Brachiocephalic trunk/artery
– Brachiocephalic artery or innominate
artery
– First and largest branch
– Ascends beside the trachea
• Subclavian artery
– Vertebral artery
– Internal thoracic artery
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SAY: The brachiocephalic trunk, also called the brachiocephalic artery or the innominate
artery, is the first and largest branch that arises from the aortic arch. (Osborn
1999/p12/c2/para2)
The brachiocephalic artery ascends beside the trachea, and branches into the right
common carotid artery and the right subclavian artery (Osborn 1999/p12/c2/paara2)
Arteries that further branch from the right subclavian artery are the right vertebral artery,
the internal thoracic artery, and the thyrocervical artery. (Osborn 1999/p13/Figure 1-7)
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• Types
– Type I: Distance from origin to top of the
arch is <1 diameter of the left common
carotid artery
– Type II: Distance from origin to top of the
arch is between 1 and 2 diameters of the
left common carotid artery
– Type III: Distance from origin to top of the
arch is >2 diameters of the left common
carotid art
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SAY: Knowledge of the differences in each individual’s aortic arch is important for
surgeons and interventionalists (Demertzis 2010/p588/c1/para1) in designing and
optimizing therapeutic intervention. (Demertizis 2010/p588/c2/para1).
One way the aortic arch can be described is by aortic arch type, which measures the
vertical distance from the origin of the brachiocephalic trunk to the top of the arch.
(Demertzis 2010/p589/c2/para1)
The 3 types are shown here
• First is the type I arch, where the distance from origin to top of the arch is <1 diameter
of the left common carotid artery.
• Next is the Type II arch, where the distance from origin to top of the arch is between 1
and 2 diameters of the left common carotid artery.
• Finally, there is the Type III arch, where the distance from origin to top of the arch is >2
diameters of the left common carotid artery. (Demertzis 2010/p589/c2/para1)
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SAY: The bovine arch refers to anatomical variations in the configuration of the 3 vessels
originating from the aortic arch. (Spacek 2012/p166/para1)
Knowledge of the aortic arch branching variations is important for therapeutic interventions,
especially during stenting of the left internal carotid artery, which is performed by passage
through the bovine arch. (Spacek 2012/p166/para3)
In the less usual variation, or about 7% of the population, the brachiocephalic artery trifurcates
into the left common carotid artery, the right common carotid artery and the right subclavian
artery, shown in Figure A here. (Spacek 2012/p166/para1)
In the more usual variation, or about 20% of the population, the brachiocephalic artery and the
left common carotid artery share a common origin, shown in Figure B here. (Spacek
2012/p166/para1)
Note that the name of the bovine arch is a common misnomer in medical literature. The
anatomical configuration it describes in humans does not have any resemblance with the aortic
arch branching pattern found in cattle. (Layton 2006/p1541/c1/para1).
Instead, it is believed to have been named for the resemblance the pattern has to a bovine’s
head and horns. (Spacek 2012/p166/para2; p167/Figure2).
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SAY: The brachial artery is the major arterial supply of the upper arm. (Patton
2014/p395/Table 15-1) It is the continuation of the axillary artery. At the point of the
elbow joint, it divides into the ulnar and radial arteries. (Stedmans/brachial artery)
(Marieb 2016/p731/Figure 19.4)
The femoral artery is the major arterial supply of the thigh. (Patton 2014/p395/Table 15-
1)(Marieb 2016/p740/c2/para4) Near the knee, the femoral artery passes posteriorly
and through a gap in the muscle, where its name changes to the popliteal artery.
(Figure 2.1, Table 2.1). (Marieb 2016/p740/c2/para4)
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SAY: These are the major arteries that supply the upper and lower extremities.
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SAY: The brain receives its arterial blood supply from 2 sources:
• The internal carotid arteries, known as anterior circulation
• The vertebral arteries, known as posterior circulation (Brain in Morton 2011/p5/para3)
Anterior and posterior circulation will be covered in greater detail in Lesson 3 and
Lesson 4. Here, we will begin with an overview of the arteries that make up these
circuits.
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SAY: The left and right common carotid arteries branch to the internal and external
carotid arteries.
The internal carotid arteries enter the base of the skull, whereas the external carotid
arteries send branches to the neck and face. (Brain in Morton 2011/p5/para4)
The left subclavian artery arises from the aortic arch, and rises to the neck before
descending toward the ribs. (Osborn 1999/p15/c1/para1)
The vertebral artery arises from the brachiocephalic artery on the right and the
subclavian artery on the left.
It has 4 segments, and only the fourth, called V4, gives rise to branches that supply the
brainstem and cerebellum. (Smith in Harrison’s 2014/p46/para5) A branch of the
subclavian artery is the thyrocervical trunk. (Osborn 1999/p28/c2/para3)
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ASM 2011
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SAY: Recall that the vascular networks that supply blood to the brain can be divided
into 2 systems based on the anatomical regions of the brain that they supply: (Purves
2012/p736/c1/TableA4/para1-c2/para1)
• Anterior portions of the brain are supplied by the anterior circulation, formed from the
major branches that arise from the internal carotid arteries
• Posterior portions of the brain are supplied by the posterior circulation, formed from the
major branches of the vertebrobasilar system
The anterior and posterior circulation of the brain will be reviewed in the following 2
lessons. Let’s start by discussing the anterior circulation.
4x3_ASM_2011_Weldon_Close_04-28- 47
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• Name the artery that joins the anterior and posterior circulations
• Identify the segments and major branches of the anterior cerebral artery
• Name the artery the connects the 2 anterior cerebral arteries from each
hemisphere
• Identify the segments and major divisions of the middle cerebral artery
• Name the group of small arteries that arises from the middle cerebral artery
• Identify the brain regions that are supplied by the anterior and middle cerebral
arteries
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SAY: Please take a moment to review the learning objectives for this section.
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• 7 segments:
–Cervical
–Petrous
–Lacerum
–Cavernous
–Clinoid
–Ophthalmic
–Communicating
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SAY: The internal carotid arteries are 1 of the 2 pairs of arteries that supply blood to the
entire brain. The internal carotid arteries arise from the common carotid arteries to
supply about 80% of the brain, including the cerebral hemispheres and diencephalon.
(Vanderah 2016/p126/c2/para2) (Osborn 1999/p57/c1/para1; c2/para3)
The internal carotid artery can be divided into 7 anatomically distinct segments shown
here. (Osborn 1999/p57/c1/para2)
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Cervical Segment
• Only extracranial segment
• Common problems
– Coiling or complete looping
– Fibromuscular dysplasia
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SAY: The cervical segment of the internal carotid artery is the only extracranial
segment. It ends at the base of the skull and is prone to atherosclerotic disease.
(Osborn 1999/p58/c2/para2; p59/c1/para2; p361/c1/para5,6) (Cloud 2003/p27/c1/para1)
Some of the common problems that can occur in the cervical segment include:
• Coiling or complete looping of the cervical segment, and (Osborn 1999/p63/c1/para2)
• Fibromuscular dysplasia of the cervical segment (Bhuriya 2008/p41/c1/para1)
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Cavernous Segment
Three subsegments:
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Ophthalmic Segment
Two Branches:
1. Ophthalmic artery
– First major intracranial branch of the internal carotid artery
– Travels through the optic canal
– Supplies the retina, orbit, and part of the scalp
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SAY: The ophthalmic segment of the internal carotid artery has 2 branches. (Osborn
1999/p96/c2/para2) The first is the ophthalmic artery. It is the first major intracranial
branch of the internal carotid artery and travels through the optic canal to supply the
retina, orbit, and part of the scalp. (Osborn 1999/p96/c2/para3) (Brain in Morton
2011/p5/para5) The second branch is the superior hypophyseal artery. (Osborn
1999/p96/c2/para2)
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Communicating
2 Branches:
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SAY: The communicating segment of the internal carotid artery has 2 branches.
(Osborn 1999/p99/c2/para3) The first is the posterior communicating artery. By
connecting to the posterior cerebral artery, a branch of the vertebrobasilar system, the
posterior communicating artery connects the anterior and posterior circulations. (Osborn
1999/pp99/c2/para4) The second branch is the anterior choroidal artery. (Osborn
1999/p99/c2/para3)
This segment ends at the division of the internal carotid artery into its 2 terminal
branches, the anterior and middle cerebral arteries. (Osborn 1999/p99/c1/last para)
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SAY: The anterior cerebral artery is the smaller of the 2 terminal branches of the internal
carotid artery. (Osborn 1999/p117/c2/last para; p119/c1/para1) Each anterior cerebral
artery supplies the medial, also called the middle, surface of the anterior two thirds, or
the frontal and parietal lobes, of its cerebral hemisphere. (Marieb 2016/p732/c2/para4)
(Osborn 1999/p131/c1/para2) The anterior cerebral arteries from each hemisphere are
connected via the anterior communicating artery, a short artery at the base of the
cerebrum. (Osborn 1999/p119/c2/para1; Figure 6-2/legend)
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• A1
– Precommunicating segment
– Extends horizontally from the beginning of the
anterior cerebral artery to its junction with the
anterior communicating artery.
• A2
– Postcommunicating segment
– Extends vertical from the anterior communicating
artery
• A3
– Divides into 2 main arteries
– Pericallosal artery is the larger artery
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SAY: The anterior cerebral artery can be divided into 3 segments, A1-A3.
The A1 and A2 segments are also connected by the anterior communicating artery at
the base of the cerebrum. (Osborn 1999/p117/c1/para3; p119/c1/para2,3; Figure 6-
2/legend)
The A2 segment is called the postcommunicating segment and extends vertical from the
anterior communicating artery. (Osborn 1999/p119/c1/para3)
The A3 segment divides into 2 main arteries. The larger of the 2 is the pericallosal
artery, which represents the continuation of the main anterior cerebral artery trunk. It
travels posteriorly through the brain. (Osborn 1999/p130/c2/para5)
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• 4 segments:
– M1: Horizontal segment
– M2: Insular segment
– M3: Opercular segment
– M4: Cortical segment
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SAY: The middle cerebral artery is the larger of the 2 terminal branches of the internal
carotid artery. It is approximately twice the size of the anterior cerebral artery. The
middle cerebral arteries supply most of the lateral, or side, surface of the cerebral
hemispheres. (Osborn 1999/p135/c1/para1; p137/c2/para1)
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M1 Segment
Lenticulostriate Arteries
• Before the M1 segment of the middle cerebral
artery divides, a number of small arteries arise,
called the lenticulostriate arteries. These arteries
supply the deep lying structures of the brain
Superior Division
• The M1 segment of the middle cerebral artery
typically divides into a superior and inferior division.
The superior division supplies the frontal and
superior parietal lobes
Lenticulostriate Arteries
• The inferior division of the M1 segment supplies
the temporal and inferior parietal lobes
57
SAY: Before the M1 segment of the middle cerebral artery divides, a number of small
arteries arise, called the lenticulostriate arteries. These arteries supply the deep lying
structures of the brain
The M1 segment of the middle cerebral artery typically divides into a superior and
inferior division. (Osborn 1999/p 138/c1/para1) (Zivin 2008/p2703/c1/last para)
The superior division supplies the frontal and superior parietal lobes. The inferior
division of the M1 segment supplies the temporal and inferior parietal lobes. (Zevin
2008/p2703/c1/last para)
The inferior division supplies the temporal and inferior parietal lobes. (Zivin
2008/p2703/c1/last para)
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ASM 2011
58
SAY: As the occipital lobe and brainstem grow during embryonic development, the
formation of the posterior circulation is initiated. The basilar arteries are formed first
when the embryo is just 4 to 5 millimeters, followed by the vertebral arteries, when the
embryo is 7 to 12 millimeters. (Menshawi 2015/p145/c2/last para-p146/c1/para1)
The vertebrobasilar system primarily supplies blood to the posterior regions of the brain,
including the brainstem, cerebellum, as well as parts of the diencephalon, and the
occipital and temporal lobes. (Vanderah 2016/p126/c2/para2-p127/c1/para1)
4x3_ASM_2011_Weldon_Close_04-28- 58
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• Name the 2 main arteries that supply the posterior regions of the brain
59
SAY: Please take a moment to review the learning objectives for this lesson.
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Posterior Circulation
Which of the following primarily supplies the posterior regions of the brain?
d) Vertebral artery
60
SAY: Which artery primarily supplies the posterior regions of the brain?
60
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Posterior Circulation
Which of the following primarily supplies the posterior regions of the brain? 1
d) Vertebral artery
61
SAY: That’s correct. The vertbral artery primarily supplies the posterior regions of the
brain
OR
That’s incorrect. The vertbral artery primarily supplies the posterior regions of the brain
61
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Vertebral Arteries
62
SAY: The Vertebral arteries are 1 of 2 pairs of arteries that supply blood to the entire
brain (the other is the internal carotid arteries). (Vanderah 2016/p126/c2/para2)
The Vertebral arteries arise from the subclavian arteries and run along the anterior
surface of the brainstem. (Marieb 2016/p732/c2/last para) (Vanderah 2016/p130/c1/last
para)
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Vertebral Arteries
Divided into 4 Segments:
63
SAY: Each vertebral artery is divided into 4 segments known as V1 through V4.
V1 through V3 are extracranial segments, while V4 is an intracranial segment. (Exaire
2004/p1/para5)
The V4 segment of the vertebral artery enters the cranium by piercing the dura and
arachnoid mater at the base of the skull. (Exaire 2004/p1/para5)
63
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Vertebral Arteries
Branches of the Vertebral
Arteries:
– Posterior Inferior Cerebellar Arteries
• Supply much of the inferior surface
of the cerebellum
64
SAY: Once inside the cranium, each vertebral artery branches to give rise to the
posterior inferior cerebellar artery.
The posterior inferior cerebellar artery, as it’s name implies, supplies much of the inferior
surface of the cerebellum. (Vanderah 2016/p130/c2/last para; p132/c2/para1)
64
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Basilar Artery
The right and left vertebral arteries fuse to form the midline basilar artery
65
SAY: The right and left vertebral arteries fuse to form the midline basilar artery. (Marieb
2016/p733/c1/para1) The basilar artery continues to ascend along the surface of the
brainstem. (Vanderah 2016/p130/c1/last para-c2/para1)
The anterior inferior cerebellar arteries travel along the inferior surface of the
cerebellum. (Brain in Morton 2011/p6/last para) They supply the cerebellum, parts of
the brainstem, and the inner ear. (Marieb 2016/p733/c1/para1-c2) (Vanderah
2016/p132/c2/para1)
The superior cerebellar arteries travel along the superior surface of the cerebellum.
(Brain in Morton 2011/p7/para1) They supply the cerebellum, parts of the brainstem,
and the inner ear. (Marieb 2016/p733/c1/para1-c2/para2) (Vanderah
2016/p132/c2/para1)
Near the top of the brainstem, the basilar artery divides into a pair of posterior cerebral
arteries that supply the medial and inferior surfaces of the occipital and temporal lobes.
(Vanderah 2016/p132/c2/para1; p133//c2/para1)
65
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Circle of Willis
• Arterial polygon at the base of the
brain that consists of parts of:
– Internal carotid artery
– Anterior cerebral artery
– Posterior cerebral artery
66
SAY: The Circle of Willis, or cerebral arterial circle, is the arterial polygon at the base of
the brain that consists of parts of the internal carotid, anterior cerebral, and the posterior
cerebral arteries, interconnected by the anterior and posterior communicating arteries.
Therefore, through the Circle of Willis, the arteries that deliver blood to the entire brain
are joined to create a single vascular network. (Vanderah 2016/p134/c1/para1)
The Circle of Willis also functions as a safety valve by providing a mechanism for blood
to be rerouted in the event that one of the major arteries is blocked. In addition, these
connections ensure that blood pressure will be similar throughout the brain. (Marieb
2016/p733/c2/para2) (Vanderah 2016/p134/c1/para1)
66
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ASM 2011
67
SAY: The external carotid artery is the smaller of the 2 terminal branches of the
common carotid artery; the other is the internal carotid artery. The external carotid artery
delivers blood to most of the tissues in the head and neck, except for the brain and eye.
It also has many important connections with the internal carotid arteries and the
vertebrobasilar system. (Osborn 1999/p31/c1/para1,2)
4x3_ASM_2011_Weldon_Close_04-28- 67
12/19/2018 11:00 AM
• Identify the regions of the head and neck that are supplied by the branches
of the external carotid artery
68
SAY: Please take a moment to review the learning objectives for this lesson.
68
12/19/2018 11:00 AM
• Mnemonic:
– Some Anatomists Like Freaking Out
Poor Medical Students
69
SAY: As shown here, the external carotid artery runs toward to the top of the skull. The
main trunk rapidly decreases in size as it gives off branches to the tongue, face, and
neck. It ends by dividing into 2 main branches. (Osborn 1999/p37/c1/last para-c2/para1)
There are 8 major branches of the external carotid artery. (Osborn 1999/p37/c1/last
para;c2/Box/branches) There is a mnemonic phrase that exists to help you remember
these branches. The first letter of each word in the phrase corresponds to 1 of the 8
branches of the external carotid artery. The mnemonic is: Some Anatomists Like
Freaking Out Poor Medical Students.
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a) Basilar artery
b) Facial artery
e) Vertebral artery
70
SAY: Let’s try it out. Based only on the mnemonic, can you tell which of the following are
branches of the external carotid artery?
70
12/19/2018 11:00 AM
a) Basilar artery
b) Facial artery
e) Vertebral artery
71
SAY: That’s correct. The Facial, Posterior auricular, and Superior thyroid arteries are
branches of the external carotid artery.
OR
SAY: That’s incorrect. The Facial, Posterior auricular, and Superior thyroid arteries are
branches of the external carotid artery.
71
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72
SAY: The superior thyroid artery is the first branch to arise from the anterior wall of the
external carotid artery. It travels down toward the thyroid gland and supplies the larynx
and the upper portion of the thyroid gland. (Osborn 1999/p37/c1/para2;p38/c1/para2)
72
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73
SAY: The ascending pharyngeal artery is the smallest branch of the external carotid
artery. It is the first to arise from its posterior wall of the external carotid artery and
ascends to supply the pharynx, middle ear, and the dura. (Osborn 1999/p38/c1/last
para-c2/para1)
73
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Lingual Artery
Some Anatomists Like Freaking Out Poor Medical Students
74
SAY: The lingual artery is the second anterior branch of the external carotid artery. It
supplies the tongue and mouth. (Osborn 1999/p39/c1/para2)
74
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Facial Artery
Some Anatomists Like Freaking Out Poor Medical Students
75
SAY: The facial artery is the third anterior branch of the external carotid artery. It travels
toward the lower jaw and also across the cheek to terminate near the eye. It supplies
most of the face, palate, lips, and cheeks. (Osborn 1999/p39/c1/para3-6)
75
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Occipital Artery
Some Anatomists Like Freaking Out Poor Medical Students
76
SAY: The occipital artery is the second and largest posterior branch of the external
carotid artery. It travels toward the back of the head to supply the posterior neck and
scalp as well as some of the dura. (Osborn 1999/p39/c1/para7,8; p45/c2/para2)
76
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77
SAY: The posterior auricular artery is the third small posterior branch of the external
carotid artery. It also travels toward the back of the head to supply the scalp and
external parts of the ear. (Osborn 1999/p39/c2/para2)
77
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Maxillary Artery
Some Anatomists Like Freaking Out Poor Medical Students
78
SAY: The maxillary artery (sometimes called the internal maxillary artery) is the larger
terminal branch of the external carotid artery. It arises behind the lower jaw and travels
forward toward the middle of the head to supply the upper and lower jaw, deep facial
areas, and the nasal cavity. (Osborn 1999/p39/c2/para5) (Marieb 2016/p732/c2/para3)
78
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79
SAY: The superior temporal artery is the other, smaller terminal branch of the external
carotid artery. As the superior temporal artery ascends it becomes more superficial to
supply the anterior two thirds of the scalp, parts of the ear, and the parotid salivary
gland.
79
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b) Lingual artery
c) Occipital artery
d) Maxillary artery
80
SAY: Which branch supplies the upper and lower jaw, deep facial areas, and the nasal
cavity?
80
12/19/2018 11:00 AM
b) Lingual artery
c) Occipital artery
d) Maxillary artery
81
SAY: That’s correct. The Maxillary artery supplies the upper and lower jaw, deep facial
areas, and the nasal cavity
OR
SAY: That’s incorrect. The Maxillary artery supplies the upper and lower jaw, deep facial
areas, and the nasal cavity
81
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Collateral Circulation
82
SAY: Collateral circulation refers to the network of vascular connections that stabilize
cerebral blood flow by providing secondary channels through which blood can flow to
and from a tissue if the principal artery becomes obstructed. This type of compensatory
circulation is established through connections between arteries that supply adjacent
vascular territories. (Taber’s 2017/p1/collateral circulation) (Liebeskind
2003/p2279/c1/para1)
Recall from earlier, that the circle of Willis provides a collateral circulation pathway for
cerebral blood flow between major arteries of the brain.
There are many connections between the branches of the external carotid artery and
the internal carotid system that may serve as an important supply of collateral blood
flow. (Brain in Morton 2011/p7/para2)
82
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Collateral Circulation
83
SAY: As shown here, there are many connections between the branches of the external
carotid artery and the internal carotid system that may serve as an important supply of
collateral blood flow. (Osborn/p31/c1/para2; p38/c2/para3/Table 2-1)
83
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84
SAY: Neurons in the brain require a constant supply of nutrients to remain viable. As a
result, any interruption in blood flow to the brain that lasts more than a few minutes can
cause irreversible damage. (Zivin 2008/p2705/c2/para1) The amount of brain damage
and the types of symptoms experienced by the patient depend on the area of the
vascular tree that is affected. (Vanderah 2016/p141/c2/para2)
84
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85
85
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Glossary
• artery: A vessel through which the blood passes away from the heart to the various parts of the body. 1
• atherosclerotic: A condition during which the arteries become narrowed or hardened due to a buildup of fats, cholesterol
and other substances (plaques) along the artery walls, which can restrict blood flow. 2
• autonomic nervous system: The parts of the nervous system that control unconscious, involuntary, and visceral body
functions (e.g., smooth muscle tone, blood pressure, temperature, fluid composition, state of digestion, metabolic activity,
and sexual activation). 3
• brachiocephalic trunk: The first branch of the aortic arch, which divides into the right common carotid and right subclavian
arteries, with distribution to the right side of the head and neck and to the right upper limb; also called brachiocephalic
artery, and innominate artery.1
• cerebral hemisphere: Either of the 2 hollow convoluted lateral halves of the cerebrum. 1
• cerebrospinal fluid: A clear, colorless liquid that continuously circulates through cavities in and around the brain, and
protects the brain from chemical and physical injuries. It also carries oxygen, glucose, and other chemicals needed from
the blood. 4
• cranium: The large round superior part of the skull, enclosing the brain; made up of the cranial bones. 1
• extracranial: Located or occurring outside of the portion of the skull that surrounds and protects the brain (cranium). 3
1. [Dorland’s]. 2. NIH MedlinePlus 2018/p1/para1, 3. [Taber’s], 4. Tortora 2009 Ch14, p499, c2, para3
86
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12/19/2018 11:14 AM
Glossary
• fibromuscular dysplasia: The abnormal growth of cells in the walls of arteries causing the vessels to narrow or bulge. The
carotid arteries in the neck are commonly affected, which can lead to reduced blow flow to the brain. 1
• grey matter: Neural tissue composed mostly of nerve cell bodies, unmyelinated nerve fibers, and supportive tissue. 2
• intracranial: Located or occurring within the portion of the skull that protects the brain (cranium). 3
• larynx: A tube composed of cartilage that forms the initial segment of the respiratory tree. It houses the vocal chords and
is involved in producing sounds. It also protects the trachea from aspirated foods and liquids. 3
• left ventricle: The lower chamber of the left side of the heart, which pumps oxygenated blood out through the aorta into the
systemic arteries. 2
• medial: Pertaining to the middle; closer to the median plane, middle layers, or the midline of a structure. 2
• meninges: The 3 membranes that envelop the brain and spinal cord: the dura mater, the arachnoid mater, and the pia
mater.2
• pharynx: A passageway for air from the nasal cavity to the larynx (voice box) and for food from the mouth to the
esophagus. 3
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Glossary
• proprioception: The awareness of posture, movement, and changes in equilibrium and the knowledge of position, weight,
and resistance of objects in relation to the body.1
• right ventricle: The lower chamber of the right side of the heart, which pumps venous blood through the pulmonary trunk
and arteries to the capillaries of the lungs. 2
• skull: The skeleton of the head, including the cranium and the mandible. 2
• startle reflex: Sudden movements of the head, eyes, and trunk that occur when you are surprised by a loud noise (e.g., a
gunshot). 3
• subarachnoid space: The space between the arachnoid mater and the pia mater, containing cerebrospinal fluid. 2
• thyroid gland: A large gland at the base of the neck from which thyroid hormones are produced. These hormones regulate
a person’s metabolic rate throughout the body. 1
• trachea: The tube by which air passes to and from the lungs.4
• white matter: Neural tissue composed mostly of myelinated nerve fibers that conduct information. 2
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References
• Bhuriya R, Arora R, Khosla S. Fibromuscular dysplasia of the internal carotid circulation: an unusual presentation. Vasc
Med. 2008;13(1):41-43. [Bhuriya 2008]
• Cloud GC, Markus HS. Diagnosis and management of vertebral artery stenosis. QJM. 2003;96(1):27-34. [Cloud 2003]
• Demertzis S, Hurni S, Stalder M, Gahl B, Herrmann G, Van den Berg J. Aortic arch morphometry in living humans. J Anat.
2010;217(5):588-596. [Demertzis 2010]
• Dorland’s Online Medical Dictionary. https://www.dorlands.com. Accessed February 19, 2018. [Dorland’s]
• Exaire JE, Yadav JS. Basic Anatomy. In: Bhatt DL, ed. Guide to Peripheral and Cerebrovascular Intervention. London,
England: Remedica; 2004. https://www.ncbi.nlm.nih.gov/books/NBK27421/. Accessed February 15, 2018. [Exaire 2004]
• Layton KF, Kallmes DF, Cloft HJ, Lindell EP, Cox VS. Bovine aortic arch variant in humans: clarification of a common
misnomer. AJNR Am J Neuroradiol. 2006;27(7):1541-1542. [Layton 2006]
• Liebeskind DS. Collateral circulation. Stroke. 2003;34(9):2279-2284. [Liebeskind 2003]
• Marieb EN, Hoehn K. Human Anatomy & Physiology. 10th ed. Boston, MA: Pearson Education, Inc; 2016. [Marieb 2016]
• Menshawi K, Mohr JP, Gutierrez J. A functional perspective on the embryology and anatomy of the cerebral blood supply.
J Stroke. 2015;17(2):144-158. [Menshawi 2015]
• Morton DA, Foreman K, Albertine KH, eds. The Big Picture: Gross Anatomy. New York, NY: McGraw-Hill; 2011.
http://accessmedicine.mhmedical.com/content.aspx?bookid=381§ionid=40140024. Accessed January 29, 2018.
[Brain in Morton 2011]
• National Institute of Neurological Disorders and Stroke. Fibromuscular dysplasia information page.
https://www.ninds.nih.gov/Disorders/All-Disorders/Fibromuscular-Dysplasia-Information-Page. Accessed February 22,
2018. [NINDS 2018]
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References
• National Institutes of Health. MedlinePlus. Atherosclerosis. https://medlineplus.gov/atherosclerosis.html. Accessed
February 22, 2018. [NIH MedlinePlus 2018]
• Osborn AG. Diagnostic Cerebral Angiography. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 1999. [Osborn
1999]
• Patton KT, Thibodeau GA. The Human Body In Health & Disease. 6th ed. Maryland Heights, MO: Mosby, an imprint of
Elsevier Inc; 2014. [Patton 2014]
• Purves D, Augustine GJ, Fitzpatrick D, Hall WC, LaMantia AS, White LE, eds. Neuroscience. 5th ed. Sunderland, MA:
Sinauer Associates, Inc; 2012. [Purves 2012]
• Smith WS, Johnson SC, Hemphill JC III. Cerebrovascular diseases. In: Longo DL, Fauci AS, Kasper DL, Hauser SL,
Jameson J, Loscalzo J, eds. Harrison's Principles of Internal Medicine. 19th ed. New York, NY: McGraw-Hill; 2015.
http://accessmedicine.mhmedical.com/content.aspx?bookid=1130§ionid=79755261. Accessed February 25, 2018.
[Smith in Harrison’s 2014]
• Spacek M, Veselka J. Bovine arch. Arch Med Sci. 2012;8(1):166-167. [Spacek 2012]
• Stedman’s Online Medical Dictionary. http://stedmansonline.com/index. Accessed February 24, 2018. [Stedman’s]
• Taber’s Online Medical Dictionary. https://www.tabers.com/tabersonline/ub. Accessed February 19, 2018. [Taber’s]
• Tortora GJ, Derrickson B. Principles of Anatomy and Physiology. 12th ed. Hoboken, NJ: John Wiley & Sons, Inc; 2009.
[Tortora 2009]
• US National Institutes of Health, National Cancer Institute. SEER Training Modules, Cancer Registration & Surveillance
Modules: Circulatory Pathways. Accessed February 24, 2018.
https://training.seer.cancer.gov/anatomy/cardiovascular/blood/pathways.html. [SEER 2018]
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References
• Vanderah TW, Gould DJ. Nolte’s the Human Brain: An Introduction to its Functional Anatomy. 7th ed. Philadelphia, PA:
Elsevier; 2016. [Vanderah 2016]
• Zivin JA. Approach to cerebrovascular disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, PA:
Saunders Elsevier; 2008: 2701-2707. [Zivin 2008]
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Complete the final assessment at https://courses.jnjinstitute.com
to receive CE credits applicable to your learning.
92
92
Knowledge Check
Let’s see what you just learned. Answer the question below.
1. Which of the following terms can be used to describe structures in front of or behind,
respectively?
93
Knowledge Check
Let’s see what you just learned. Answer the question below.
2. Which of the following are the 4 principle regions of the brain? Select all that apply.
✓ Brainstem
✓ Cerebellum
✓ Cerebrum
Cortex
✓ Diencephalon
Pons
Thalamus
94
Knowledge Check
Let’s see what you just learned. Answer the question below.
3. Which of the following list the layers of the brain from external to internal?
95
Knowledge Check
Let’s see what you just learned. Answer the question below.
4. Which of the following lobes of the brain is associated with executive functions, motor
performance, and production of language?
✓ Frontal lobe
Occipital lobe
Parietal lobe
Temporal lobe
96
Knowledge Check
Let’s see what you just learned. Answer the question below.
5. Which of the following lobes of the brain contains the auditory cortex as well as areas of the
brain involved in aspects of memory and learning?
Frontal lobe
Occipital lobe
Parietal lobe
✓ Temporal lobe
97
Knowledge Check
Let’s see what you just learned. Answer the question below.
6. Which of the following describe common bovine arch variations?
✓ The left common carotid artery and the brachiocephalic artery share a common origin
The left subclavian artery and the brachiocephalic artery share a common origin
98
Knowledge Check
Let’s see what you just learned. Answer the question below.
7. The brain receives its arterial blood supply from which of the following arteries?
99
Knowledge Check
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8. The internal carotid artery divides into which of the 2 terminal branches? Select all that apply
Basilar artery
100
Knowledge Check
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9. Which of the following branches of the internal carotid artery connects the anterior and
posterior circulations?
Ophthalmic artery
101
Knowledge Check
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10. Which of the following arteries connects the 2 anterior cerebral arteries from each
hemisphere?
Pericallosal artery
Lenticulostriate artery
102
Knowledge Check
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11. The anterior cerebral artery supplies the medial surface of which of the following lobes of the
brain? Select all that apply.
✓ Frontal
✓ Parietal
Temporal
Occipital
103
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12. Which of the following arteries arises from the subclavian arteries and run along the anterior
surface of the brainstem?
Basilar artery
✓ Vertebral artery
104
Knowledge Check
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13. Which of the following arteries is a branch of the vertebral artery?
105
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14. Which of the following arteries make up the circle of Willis? Select all that apply.
106
Knowledge Check
Let’s see what you just learned. Answer the question below.
14. What is the name of the network of vascular connections that allows blood to continue to flow
from one tissue to another if the principal artery becomes obstructed?
✓ Collateral circulation
Compensatory circulation
Secondary circulation
Systemic circulation
107