Module 1 : Arterial Circulatory System and Anatomy Flashcards
the three layers of the artery wall
- tunica intima
- tunica media
- tunica adventicia
tunica intima - characteristics
- inner most layer
- endothelial lining with connective tissue beneath its
- in contact with blood
tunica media - characteristics
- middle layer
- smooth muscle
- thickest component
tunica adventitia - characteristics
- outer layer
- connective tissue, nerve fibers, small vessel capillaries
(VASA VASORUM) - in contact with surrounding tissue
three classifications of arteries
- arterioles —- small and medium sized arteries — large elastic arteries
arteriole - characteristics
- “stopcocks”
- PRINCIPLE POINT OF RESISTANCE TO BLOOD FLOW
small and medium arteries - characteristics
- all arteries except aorta and its largest branches
large elastic arteries
- aorta and its largest branches
the brain is directly supplied by what four vessels
- two internal carotid arteries (ICA)
- two vertebral arteries
blood supply to the CNS come from what vessels
- the aortic arch
+ brachiocephalic, left common carotid, left subclavian - brachiocephalic divides into the RCCA and right subclavian at upper border of the right sternoclavicualr junction
left common carotid origin
- left CCA ascends from the arch and passes under the LEFT STERNOCLAVICULAR JOINT
Carotid characteristics
- no branches
- divide into ICA and ECA at the upper border of the thyroid cartilage
- at bifurcation the vessel enlarges and is referred to as carotid bulb
ICA - characteristics
- begin at carotid bif and travel as a single vessel then terminate where enter cranium
- supply most of the ANTERIOR CIRCULATION
- cervical (extracranial) has NO BRANCHES
- opthalmic artery if first branch of ICA and occurs at carotid siphon
- within cranium branches into MCA and ACA
carotid siphon (cavernous ICA) 3 parts
- parasellar portion (proximal)
- genu (bend)
- supraclinoid (distal segment)
ophthalmic artery
- occurs at carotid siphon (genu) and travels anterior through the optic canal to the orbit
- supplies blood to brain as collateral when ICA occluded
branches of the ophthalmic artery
- supraorbital artery
- frontal artery
- nasal artery
supraorbital artery
- lies over top of eyeball passing through supraorbital foramen
frontal artery
- lies along the top of the eye towards the inner aspect
nasal artery
- most medial branch terminating near the bridge of the nose
ECA role in collateralization
- normally do not supply blood to brain but their branches may anastomose with ICA or vertebrals to provide collateral flow in occlusion
- the branches that communicate with the ophthalmic artery are most important in collaterization
- branches that interconnect between the muscular branches of the occipital and vertebral arteries are also important
first branch off the ECA
- superior thyroid artery
ECA location
- found anterior and medial to ICA
vertebral artery
- supplies posterior circulation of the brain
- lies within transverse foramina of the upper cervical vertebrae
- travel cephalic and anteriorly until join basilar artery
- basilar artery has 4 branches that supply pons and cerebellum
circle of Willis
- formed by confluence of cerebral branches of the ICA and vertebral arteries
- most important aspect on inter cranial collateral circulation
- connects anterior and posterior circulation
- common site on aneurysm formation
- on ly 25% have normal circle
circle of willis structure
- hexagonal arrangement of anterior middle and posterior cerebral arteries found by anterior and posterior communicating arteries
- MCA supplies majority of blood to cerebral hemispheres
- many congenital variations with absence or hypoplasia of one or more communicating arteries
collateral flow in extremities
- in an extremity at rest total blood flow may be normal in presence of severe stenosis because of the work of collaterals
- locating collaterals helps identify level of obstruction
4 ways obstruction of an artery alters flow in collaterals
- increase volume
- reverse flow
- increasing velocity
- altering pulsatility
common anatomic variants of the upper extremity
- common origin of brachiocephalic and left common carotid (most common)
- high origin of radial artery
- duplicated brachial artery
collaterals in upper extremity
- stenosis is uncommon in arteries in upper body but smaller branches will act as collaterals when main vessels are occlude \+ subclavian \+ brachiocephalic \+ axillary \+ brachial artery
common anatomic variants of the lower extremity
- hypoplasia/aplasia of anterior tibial artery (most common)
- anomalous location of dorsals pedis
collateral route for distal aorta and bilateral common iliac obstruction
- thoracic and abdominal wall arteries
- mesenteric arteries
- lumbar arteries
collateral route for unilateral common iliac obstruction
- contralateral iliac or femoral artery via pelvic arteries
+ HYPOGASTRIC IS MOST COMMON
collateral route for external iliac and common femoral artery obstruction
- ipsilateral pelvis and femoral artery branches
collateral route for deep femoral artery obstruction
- proximal ipsilateral pelvic and femoral arteries
- distal superficial femoral artery
- popliteal artery
collateral route for superficial femoral and popliteal artery obstruction
- deep femoral branches
- popliteal to tibioperoneal trunk
collateral route for tibioperoneal trunk obstruction
- proximal calf branches
- distal peroneal branches to ATA and PTA
