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Blood Vessels: The Vascular
System• Taking blood to the tissues and back• Arteries
• Arterioles
• Capillaries
• Venules
• Veins
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The Vascular System
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Blood Vessels: Anatomy
• Three layers (tunics)
• Tunic intima
• Endothelium
• Tunic media
• Smooth muscle
• Controlled by sympathetic nerous system
• Tunic e!terna• "ostly #ibrous connectie tissue
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Arteries• Elastic
• "uscular
• Arterioles
Veins
• Venules• Veins
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$
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Capillaries
Structurally three types
%&Continuous
'&enestrated
&Sinusoids
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Capillary Beds• Capillary beds consist o#
t*o types o# essels• Vascular shunt + directly
connects an arteriole to a
enule
Figure 11.10
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"oement o# Blood Through
Vessels• "ost arterial blood ispumped by the heart• Veins use the milking
action o# muscles to help
moe blood
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"a,or Arteries o# Systemic
Circulation
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"a,or Veins o# Systemic Circulation
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Circulation o# the blood
o describe the circulation o# the blood through thelungs- naming the main essels inoled
o list the arteries supplying blood to all ma,or body
structureso describe the enous drainage inoled in
returning blood to the heart #rom the body
o
describe the arrangement o# blood esselsrelating to the portal circulation&
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Although circulation o# blood round the body
is continuous it is conenient to describe it in
t*o parts:
opulmonary circulation
o
systemic or general circulation
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.ulmonary Circulation
#rom the right entricle o# the heart to the lungs and back
to the le#t atrium
/n the lungs- carbon dio!ide is e!creted and o!ygen is
absorbed
The pulmonary artery or trunk- carrying deoxygenated
blood - leaes the upper part o# the right entricle o# the
heart
.asses up*ards and diides into le#t and right pulmonary
arteries at the leel o# the 0th thoracic ertebra&
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.ulmonary Arteries
o The left pulmonary artery runs to the root o# the
le#t lung *here it diides into t*o branches- one
passing into each lobe&
oThe right pulmonary artery passes to the root o#
the right lung and diides into t*o branches& The
larger branch carries blood to the middle and
lo*er lobes- and the smaller branch to the upper
lobe&
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o1ithin the lung these arteries diide and
subdiide into smaller arteries- arterioles and
capillaries&
oThe e!change o# gases takes place bet*eencapillary blood and air in the aleoli o# the lungs&
o/n each lung the capillaries containing
o!ygenated blood ,oin up and eentually #orm t*o
pulmonary eins&
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.ulmonary Veins
oTwo pulmonary veins leae each lung-
returning o!ygenated blood to the le#t
atrium o# the heart&
o2uring atrial systole this blood is pumped
into the le#t entricle- and during entricular
systole it is #orced into the aorta- the #irst
artery o# the general circulation&
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Systemic or general circulation
• The blood pumped out #rom the le#t
entricle carried by the branches o# the
aorta around the body superior and
inferior venae cavae right atrium o# theheart
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AortaoThe aorta begins at the upper part o# the le#t entricle
oa#ter passing up*ards #or a short *ay- it arches
back*ards and to the le#t
odescends behind the heart through the thoraciccaity a little to the le#t o# the thoracic ertebrae&
o At the leel o# the %'th thoracic ertebra it passes
behind the diaphragm then do*n*ards in the
abdominal caityo At the leel o# the 3th lumbar ertebra- it diides into
the right and left common iliac arteries&
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Branches o# Aorta
oThroughout its length the aorta gies o##
numerous branches&
oSome o# the branches are paired - i&e& there
is a right and le#t branch o# the same name-
#or instance- the right and le#t renal arteries
supplying the kidneys
osome are single or unpaired - e&g& the
coeliac artery&
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•The aorta *ill be described here
according to its location:
othoracic aorta
oabdominal aorta
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Thoracic aorta
• This part o# the aorta lies aboe the diaphragm and is
described in three parts:
%& ascending aorta'& arch o# the aorta
& descending aorta in the thora!
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Ascending aorta
• This is the short section o# the aorta that
rises #rom the heart& /t is about 0 cm long
and lies behind the sternum
• The right and left coronary arteries are its
only branches and they arise #rom the aorta
,ust aboe the leel o# the aortic ale&
These important arteries supply the
myocardium&
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Arch o# the aorta
oContinuation o# the ascending aorta
obegins behind the manubrium o# the
sternum and runs up*ards- back*ards and
to the le#t in #ront o# the trachea&
opasses do*n*ards to the le#t o# the
trachea and is continuous *ith the
descending aorta&
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Branches #rom arch or aorta
• Three branches are gien o## #rom its upper aspect:
obrachiocephalic artery or trunk
o le#t common carotid artery
o
le#t subclaian artery&
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Brachiocephalic artery
• The brachiocephalic artery is about 3 to 0
cm long and passes obli4uely up*ards-
back*ards and to the right&
• At the leel o# the sternoclaicular ,oint it
diides into the right common carotid artery
and the right subclavian artery &
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Circulation o# blood to the head and
neck• The paired arteries supplying the head and neck are the
ocommon carotid arteries
o
the ertebral arteries
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Carotid arteries
• The right common carotid artery is a
branch o# the brachiocephalic artery&
• The left common carotid artery arises
directly #rom the arch o# the aorta&
• They pass up*ards on either side o# the
neck and hae the same distribution on
each side
• each diides into an internal carotid artery
and an external carotid artery &
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Carotid sinuses
•slight dilations at the point o# diision
(bi#urcation) o# the common carotid
arteries into their internal and e!ternalbranches&
•contain numerous nere endings o#
the glossopharyngeal neres& Thesenere endings are baroreceptors
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Carotid bodies
• t*o small groups o# specialised cells- called
chemoreceptors- one lying in close
association *ith each common carotid
artery at its bi#urcation&
• They are supplied by the glossopharyngeal
neres and their cells are stimulated by
changes in the carbon dio!ide and o!ygencontent o# blood&
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E!ternal carotid artery
• This artery supplies the super#icial tissues o# the head and
neck- ia a number o# branches:
• The superior thyroid artery supplies the
thyroid gland and ad,acent muscles&• The lingual artery supplies the tongue- the
lining membrane o# the mouth- the
structures in the #loor o# the mouth- thetonsil and the epiglottis&
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• The #acial artery supplies the muscles o#
#acial e!pression and structures in the
mouth&
• The occipital artery supplies the posterior
part o# the scalp&
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• The temporal artery supplies the #rontal-
temporal and parietal parts o# the scalp&
The pulse can be #elt in #ront o# the upper
part o# the ear&
• The ma!illary artery supplies the muscles
o# mastication and a branch o# this artery-
the middle meningeal artery- runs deeply tosupply structures in the interior o# the skull&
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/nternal carotid artery
• This is a ma,or contributor to the circulus
arteriosus (circle o# 1illis)- *hich supplies
the greater part o# the brain&
• /t also has branches that supply the eyes-
#orehead and nose&
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Circulus arteriosus (circle o# 1illis)
• The greater part o# the brain is supplied *ith
arterial blood by an arrangement o# arteries
called the circulus arteriosus or the circle of Willis
• our large arteries contribute to its #ormation:%& the t*o internal carotid arteries
'&t*o vertebral arteries
• The ertebral arteries arise #rom the subclaian
arteries-
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Basilar Artery
• Vertebral arteries enter the skull through
the #oramen magnum- then ,oin to #orm the
basilar artery &
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• Anteriorly- the t*o anterior cerebral arteries arise #rom the
internal carotid arteries and are ,oined by the anterior
communicating artery &
• .osteriorly- the t*o vertebral arteries ,oin to #orm the
basilar artery& A#ter traelling #or a short distance thebasilar artery diides to #orm t*o posterior cerebral
arteries- each o# *hich is ,oined to the corresponding
internal carotid artery by a posterior communicating
artery - completing the circle&
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• The circulus arteriosus is there#ore #ormed by:
• • ' anterior cerebral arteries
• • ' internal carotid arteries
• • % anterior communicating artery• • ' posterior communicating arteries
• • ' posterior cerebral arteries
• • % basilar artery&
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• rom this circle- the anterior cerebral arteries pass
#or*ard to supply the anterior part o# the brain- the middle
cerebral arteries pass laterally to supply the sides o# the
brain- and the posterior cerebral arteries supply the
posterior part o# the brain&• Branches o# the basilar artery supply parts o# the brain
stem&
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