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).

• Oxygenated blood then travels through the aorta (the largest artery in the body), then smaller arteries to get to different parts of of the body:• Organs

• brain, heart, liver, kidney, muscles, skin, etc.

• Tissues (which make up organs)• Fat tissues, blood vessels,

epithelial tissues, etc.• Cells (which make up tissues)

LA

LV

Aorta

Left PVRight

PV

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 smallestblood 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 CO2concentration 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 bloodagain, and starts the cycle of the circulatory system again.

Circulatory System- Summary

Arteries carry oxygenated blood away from heart to tissues

Alveoli(Lungs)

Heart

CO2 O2

CO2 O2

AT TISSUESOxygen diffuses out of blood

into tissues

AT TISSUESCarbon dioxide diffuses out of

tissues into blood

Veins carry deoxygenated blood away from tissues to heart

Pulmonary arteries carry deoxygenatedblood away from heart to the lungs

Pulmonary veins carry oxygenatedblood away from lungs to heart

AT LUNGSCarbon dioxide diffuses out of

blood into alveoli

AT LUNGSOxygen diffuses out of alveoli

into blood

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.

Initial time of fart:Stink gases (red and blue) are concentrated near source

Over time:Stink gases (red and blue) diffuse to areas of low concentration in the room

area of high concentration

areas of low concentration