Circulatory System
Matt Snyder, Tiger Mar, Will Votapka
Structure of the Circulatory System
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Consists blood vessels
o Transport blood, oxygen, and nutrients to
body’s cells, deliver deoxygenated blood
back to heart
o Blood vessels are the tubes in the body
carrying blood. Arteries, veins, capillaries,
and venules are all examples of blood
vessels
Arteries carry oxygenated blood throughout the
body from the heart
Veins carry deoxygenated blood back towards
the heart
Systemic Circuit
● Starts at left side of heart, blood pumped to
all metabolically active parts of body then
back to right side of heart (3)
https://www.youtube.com
/watch?v=PgI80Ue-AMo
Arteries
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Highest blood pressure of blood vessels
Many layers of smooth muscle cells
Strong and flexible
Elastic, which allows arteries to squeeze and release between
heart beats
● Muscular walls allow arteries to change blood flow rate
● Blood flows from large arteries into very small arterioles
● High blood pressure and less surface area than capillaries prevent
gas exchange from occurring in this area, blood is first pushed into
arterioles, then capillaries, where gas exchange will then take place
in capillary beds (3)
http://www.webmd.com/heart/picture-of-the-arteries
Veins
● Blood flows first into venules (very small
veins), then into veins leading to heart
● Much lower pressure than arteries (2)
● Some veins have valves to prevent blood
flow from reversing
Capillaries
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10-40 billion capillaries in a human body
Very close to every cell, meaning fast diffusion rates
Slows down blood flow from arterioles, allowing for capillary beds to exchange waste for
nutrients from the oxygenated blood
So narrow that red blood cells have to go through single file, allowing for lots of diffusion to take
place (red blood cells carry oxygen and hemoglobin, which is essential for gas exchange (2)
Oxygen, carbon dioxide, and other lipid soluble small substances can diffuse through endothelial
cell membrane and into its cytoplasm
Proteins move through endo- or exo- cytosis
Tiny blood vessels, between arteries and veins
Ideal environment for diffusion of diffusible substances, passing between blood and tissue
Tissues such as the heart that are very metabolically active have highest capillary density, very
energy intensive
Thin walls are essential part of structure: they allow for oxygen and nutrients to pass
across the membrane into tissues, and waste products then take their place in the blood
(1)
http://www.kidport.com/reflib/science/humanbody/cardiovascular/Capillaries.htm
Endothelial Cells
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Line all blood vessels
Can constantly remodel based on need
Allow for tissue growth and repair
Also work on fluid filtration
Works as semi-selective barrier of what enters/exits the bloodstream (3)
Essential for blood clotting
Just one single thin wall on inside of vessels (3)
Release nitric oxide (NO) to signal for smooth muscle to dilate
Endothelin release signals for smooth muscle to contract (3)
http://no-more-heart-disease.com/wp-content/uploads/2009/08/No-More-Heart-Disease-Video-Part3.bmp
Ultrafiltration and Reabsorption
● Concentration of water and solutes in blood and interstitial fluid are the
variables influencing the direction of blood flow
● At the beginning of capillary bed, inward osmotic force due to plasma
proteins is weaker than the outward-directed blood pressure force, then
protein-free plasma exits the cell through the capillary wall in a process
called ultrafiltration (3)
● The further into the bed, the more the balance changes
● Eventually, tissue flood is being drawn into the cell, in a process called
reabsorption (3)
● This process usually results in slight net movement of fluid leaving capillary
bed
Reabsorption diagram
http://www.austincc.edu/apreview/PhysText/Renal.html
The Heart
● The left side of the heart pumps oxygenated
blood out to the body
● Oxygen-poor blood flows back to heart’s
right half, which pumps it to the lungs, where
it becomes oxygenated and flows back to
the left half
● This cycle is called the pulmonary circuit
(3)
http://www.fetal.com/FetalEcho/02%20Anatomy.html
Works Cited
(1) "Blood Vessels." : Biology of the Heart and : Merck Manual Home Edition. Merck, n.d. Web. 17
Nov. 2014.
<http://www.merckmanuals.com/home/heart_and_blood_vessel_disorders/biology_of_the_heart
_and_blood_vessels/blood_vessels.html>.
(2) Kumar, Vinay, Ramzi S. Cotran, and Stanley L. Robbins. Robbins Basic Pathology. Vol. 9.
Philadelphia, PA: Saunders, 2003. Print.
(3) Starr, Cecie. Biology: The Unity and Diversity of Life. Pacific Grove Calif: Brooks/Cole, 2001.
Print.