A&P 2 Lab 4 – Circulatory System: Blood Flow Tracings | 2026 Verified Answers

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A&P2025/
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4 - Circulatory System- BloodExam
Flow Tracings
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A&P 2 Lab 4 - Circulatory System- Blood Flow Tracings

Arteries
 Defined as the EFFERENT blood vessels in the circulatory system
o Always carry blood away from the heart
o Typically carry oxygenated blood (with the exception of pulmonary arteries)
 Vessels start from large vessels and taper down into smaller vessels
 Conducting Arteries:
o Very large arteries that exit from the heart
 Aorta
 Pulmonary trunk
o Have and need ability to expand with every heart beat to withstand pressure from blood surge
 Must have layer of elastic tissue to recoil
o As arteries age, they lose their ability to stretch and recoil
o Atherosclerosis  when plaque builds up in arteries, so arteries stiffen
 Results in increase in pressure in blood vessels
 Increase in pressure can lead to development in an aneurysm
 A weak point in an artery  can eventually rupture with each beat of the heart
 Distributing Arteries (medium/muscular arteries)
o Direct branches from conducting arteries
 Aorta has direct branches that distribute blood to specific organs, muscles, etc.
o Very thick muscular wall, up to 40 layers of smooth layers
 Allows them to further withstand pressure
 Muscular wall makes up about 75% of arterial wall
 Also has layers of elastic tissue that allows it to stretch
o Brachial artery, femoral artery, etc. NAMED FOR WHERE THEY ARE DISTRUBTING THEIR BLOOD
 Resistance Arteries (small arteries)
o Very numerous
 Metarterioles
o Very short vessels that link the arterial system into the capillaries
o After blood flows into arterial system  capillary beds
o Capillaries = exchange vessels in circulatory system
 Very thin walls
 Where exchange of oxygen, glucose, nutrients in body occurs
 Connect smallest arteries to the smallest veins

Veins
 Defined as AFFERENT blood vessels in the circulatory system
o Because they are bringing blood BACK to the heart
o Typically carry deoxygenated blood (exception of pulmonary circuit)
 Called “capacitance vessels” because the typically hold a large amount of blood
 Can stretch more easily than arteries
 Have thin, flaccid walls
 Resting person – 11% of blood found in systemic arteries, 54% of systemic blood found in veins
 Subject to much lower blood pressure because they are further away from the heart
 Veins go from small veins into larger veins (opposite mapping circuit)
 Post-Capillary vein  post capillary venules  muscular venule
 Medium veins
o Drain blood from specific areas of the body, from specific organs, and muscles
o Radial vein, ulnar vein (drains blood out of forearm)
o Contain valves (flaps of tissue that extend into lumen of vein that point upward toward hard)
 Since veins have low BP, they don’t have the strength to pump blood back to heart against pull of gravity
o Skeletal muscles also help veins pump blood up toward the venous system
 Example: calf contraction  they squeeze around the vein and push blood up into the valve, and once the blood
moves up higher into the leg, valve below will shut to prevent backflow of blood
 “Skeletal muscle pump”
 Varicose veins: when valves weaken and cannot perform the job they were designed to do
 Veins visible through the skin due to blood pooling and backflowing
 Venous Sinuses
o Large vessels with very thin walls and very large lumens
o Coronary sinus of the heart



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o Dural sinuses in the brain
 Superior/Inferior Vena Cava
o Bring used blood back to the heart to start the system all over again
o Superior vena cave – drains from anything above the diaphragm
o Inferior vena cava – drains from anything below the diaphragm

Ascending Aorta
 After ascending aorta, left and right coronary arteries branch off to supply heart muscle with blood
 Once heart uses oxygen and blood is deoxygenated, it will flow into the venous system (coronary sinus)

Descending Aorta

Right/Left Coronary Arteries




Coronary Sinuses




Aortic Arch
 Contains 3 vessels that branch off:
Circulation to the head
o R. Brachiocephalic  further branches into Right Subclavian and a Right Vertebral




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 Right subclavian turns into Right Axillary to distribute blood to the Right Arm




o Left Subclavian  branches into Left Vertebral and a Left Axillary




 Left and right vertebral arteries travel upwards through the neck (cervical vertebrae) and merge into
Basilar Artery which leads to the Circle of Willis




 Circle of Willis is a circular arterial pathway in the brain that feeds the brain tissue with blood
 In human brain, provides collateral/alternative routes of circulation
 Any blockage, the brain can compensate and find alternative routes of circulation
 Once Circle of Willies provides the brain with its blood, it must be drained
 This is where we hit the venous pathway
 Venous Sinuses of the Dura Mater – Left (where majority of blood from brain will be drained)


 Will then flow into Internal Jugular vein




 From Internal jugular, it will drain into brachiocephalic VEINS, which will enter into superior vena cava, etc.


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