The Circulatory System Circulatory System- overview

• The circulatory system is made up of blood vessels (arteries and veins) that carry blood towards the heart and away from the heart • Arteries- carry blood away from the heart to tissues • Veins- carry blood away from tissues towards the heart

• The circulatory system carries oxygen, nutrients, and hormones to tissues of the body and removes waste product (like carbon dioxide) away from tissues of the body. Blood Flow (Heart to tissues)

• Oxygenated blood gets pumped out of the heart by the left ventricle (LV). Aorta

• Oxygenated blood then travels Left through the aorta (the largest Right LA PV artery in the body), then PV smaller arteries to get to different parts of of the body: • Organs • brain, heart, liver, kidney, muscles, skin, etc. LV • Tissues (which make up organs) • Fat tissues, blood vessels, epithelial tissues, etc.

• Cells (which make up tissues) Note: Dotted lines show path of aorta posterior to pulmonary trunk. Arrow indicates path of blood from LV to aorta. Blood Flow (Heart to Tissues)

• Once at the tissues/cells oxygenated blood passes through capillaries.

• Capillaries are the smallest blood vessels in the body.

• Capillaries are small enough to allow gases and nutrients to exchange between cells and the blood. Blood Flow (At Tissues)

• Tissue cells of the body use up oxygen (O2) to make energy (ATP), decreasing oxygen concentrations in cells.

• Carbon dioxide (CO2) is a toxic byproduct of making ATP, so CO2 concentration increases in tissue cells.

• Since cells need to use oxygen to make energy to perform their functions, cells have a • low O2 concentration, and a • high CO2 concentration Blood Flow (At Tissues)

• Oxygenated blood arriving from arteries at tissue cells has a

• high O2 concentration, and a • low CO2 concentration • (opposite of cells)

• Gases naturally diffuse (travel) from an area where they are in high concentration to an area of low concentration

• Because of the difference in O2 and CO2 concentrations between oxygenated blood and body cells:

• O2 will diffuse from blood INTO cells • CO2 will diffuse from cells INTO blood Blood Flow (Tissues to Heart)

• The diffusion of O2 out of the blood and into tissue cells and of CO2 out of the tissue cells and into the blood results in oxygenated blood becoming deoxygenated blood at the capillaries.

• Deoxygenated blood moves from the capillaries, into veins, and back to the right atria of heart.

• Once back at the heart, deoxygenated blood moves into lungs, becomes oxygenated blood again, and starts the cycle of the circulatory system again. Circulatory System- Summary

AT LUNGS AT LUNGS CO O2 Carbon dioxide diffuses out of 2 Oxygen diffuses out of alveoli blood into alveoli into blood

Alveoli (Lungs) Pulmonary arteries carry deoxygenated Pulmonary veins carry oxygenated blood away from heart to the lungs blood away from lungs to heart

Veins carry deoxygenated blood away Heart Arteries carry oxygenated blood away from tissues to heart from heart to tissues

CO2 O2 AT TISSUES AT TISSUES Carbon dioxide diffuses out of Oxygen diffuses out of blood tissues into blood into tissues Diffusion Review (in case you need it) • Diffusion is the act of spreading something more widely. • Gasses naturally diffuse from areas of high concentration to areas • Example: someone farting in a room • Initially, the stinky smell (hydrogen sulfide and mercaptan gas) is located where the person that farted is located. • Over time, the stinky gas spreads to the entire room. • The spread of stinky gas is because of diffusion. area of high areas of low concentration concentration

Initial time of fart: Over time: Stink gases (red and blue) are Stink gases (red and blue) diffuse to concentrated near source areas of low concentration in the room