Circulatory System Matt Snyder, Tiger Mar, Will Votapka

Structure of the Circulatory System ●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)

/watch?v=PgI80Ue-AMo

Arteries ●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)

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 ●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)

Endothelial Cells ●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)

3.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

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)

Works Cited (1)"Blood Vessels." : Biology of the Heart and : Merck Manual Home Edition. Merck, n.d. Web. 17 Nov _and_blood_vessels/blood_vessels.html (2)Kumar, Vinay, Ramzi S. Cotran, and Stanley L. Robbins. Robbins Basic Pathology. Vol. 9. Philadelphia, PA: Saunders, Print. (3)Starr, Cecie. Biology: The Unity and Diversity of Life. Pacific Grove Calif: Brooks/Cole, Print.