As blood is changed from arterial to venuous, 25% is unloaded. What is the function of the remaining 75% O2?
411888
Only using 25% in normal circumstances allows increased uptake from the same blood flow if required.  This further removal from the haemoglobin being easily achieved with little drop in PO2 as it is on the steep  part of the dissociation curve.  "An exercising muscle can extract virtually all the oxygen from its blood supply."\nAlso agree with above answer that otherwise, if you missed a single breath, blood with no oxygen would enter the arteries.
829141
Higher partial pressure of O2 in atmosphere that that present in the blood.\n\nRemember, blood in the lungs will be DEOXYGENATED!
53262
O2 is an energy-rich oxidizing substance.  Sugar and fat are both energy-rich reducing substances.  When an oxidizer and a reducer react, electrons are exchanged, in what is called a redox reaction.  The redox reaction here creates CO2 and H2O, both of which are low-energy molecules.  The energy pulled out is used to make ATP (adenosine triphosphate), which fuels the body's activities.\n\nRespiration is where O2 is taken from the air and CO2 is released back in the air.  The epithelial tissue in the lungs is very, very thin, and there are many small blood vessels there which bring the blood close to the air.  O2 from the air is inhaled into the lungs, where it diffuses through the epithelium and into the bloodtream, and binds rather loosely to a substance called hemoglobin.  Likewise, the CO2 diffuses through the epitheluim and into your lungs, which you exhale. As the heart pumps, it pulls the oxygen-rich blood away from your lungs, toward the heart.  Then it is pumpmed out by the heart, going throughout the body to provide oxygen to the tissues.  As the hemoglobin goes to places deficient in oxygen, the oxygen will be released by the hemoglobin to supply the tissues.  Meanwhile, the CO2 byproduct in the tissues will bind to the hemoglobin (rather loosely) and be carried away.  After going past the tissues of the body, the blood, now oxygen poor, is returned to the heart, with a lot of CO2.  That blood is again pumped by the heart towards the lungs, and the exchange repeats all over again.
1130113
when you take a breath in the oxygen is taken into the blood and exchanged for carbon dioxide(which is the waste products of air), the same air is breathed out it takes a second to swap
130778
The respiratory system and the cardiovascular system\n\nto put oxygen in the blood and take C02 out, to pump the blood respectively
76097
blood, fluid pumped by the heart that circulates throughout the body via the arteries, veins, and capillaries (see circulatory system; heart). An adult male of average size normally has about 6 quarts (5.6 liters) of blood. The blood carries oxygen and nutrients to the body tissues and removes carbon dioxide and other wastes. The colorless fluid of the blood, or plasma, carries the red and white blood cells, platelets, waste products, and various other cells and substances
486604
The majority of CO2 in blood is converted to H + HCO3 by carbonic anhydrase to carry CO2 to the lungs. Carbonic anhydrase has higher activity in the RBCs, so CO2 diffuses in to be converted to H + HCO3. In order for HCO3 to leave the RBC, it goes through a chloride-bicarbonate exchanger -- Cl goes in, HCO3 out. The opposite then occurs when it gets to the alveoli.
946598
The blood woudn't be circulating in the body anymore. The cell wouldn't get their oxygen, and they would die.  So would you.
91981
Generally speaking a pulse oximeter measures the amount of oxygen that is being carried in the red blood cells. It is continuous all the time or it can be used for a short period to check the oxygen in the blood at that time. 100% is perfect. Anything less than 93-95% is bad.
1068530
Wow, I don't know if they'd let me type 1000 pages on the subject to cover your question even close to adequately, but I'll give the Reader's Digest version a go...\n\nThe circulatory system is a liquid highway your body uses to transport oxygen and nutrients everywhere they need to go and waste products away from those tissues to be disposed.  The heart is a just a positive displacement pump that keeps your blood flowing through the arteries and veins.  Lungs serve as an interface between the circulatory system and the outside world, a place where oxygen can be drawn into the body through the thin membranes of the alveoli to be absorbed by red blood cells and bound by the hemoglobin molecules within, to be carried to every point in the body.  The lungs are also the place where carbon dioxide, also bound by hemoglobin and brought to lungs for disposal, can pass back out and be exhaled.  Much of this system is automatic and completely involuntary, and some of it isn't even controlled by the brain, at least not directly -- you can hold your breath, for instance, but you do have to consciously think about not breathing.  Your brain does have some say in how fast everything works, sending a message to your heart and lungs during times of stress or exertion to say, "Hey!  We're working kind of hard here; maybe we need more oxygen to the muscles!  Work a little faster, please!" and you start to breathe hard and your heart starts to beat faster.
546613
The heart is what pumps blood and is the centerpiece of the circulatory system. Without it the blood could not carry the nutrients the body needs. The lungs take in oxygen to help feed the bloodstream. Basically both organs do the same job, just in different ways and for the same end. Keeping YOUR blood infused with the nutrients the body requires to sustain itself. Hope this helps.
1031103
Your heart is a pump that circulates blood through the many veins and arteries in your body...oxygenated blood leaves your heart ,in your arteries, flows to your tissues, organs and cells depositing oxygen then returns through your veins back through your lungs to heart to re oxygenate the the cycle starts over.
303652
All right, I'm first going to explain, briefly, the structure of the cardiovascular system, and then I'll move on to how the blood transports oxygen specifically.\n\nYour heart pumps blood from the right ventricle to your lungs, where it exchanges carbon dioxide for oxygen, and then continues to your left atria. The left atria pumps the blood to the left ventricle, which pumps blood through your arteries  to your capillaries, where the oxygen is released so that cells can use it. Carbon dioxide is picked up, and the blood continues to the veins, and back to the right atria.\n\nNow, your blood contains red blood cells, which contain two important molecules, hemoglobin and myoglobin. Both have a high affinity for oxygen, so, in your lungs, where there is a high oxygen concentration, oxygen binds to each of these two molecules (until the equilibrium point is reached). The red blood cells are pumped throughout the body. \n\nIn the body, the concentration of oxygen is lower than in the surrounding atmosphere, so the amount of hemoglobin (and myoglobin) which is binding oxygen decreases until it reaches the new equilibrium point. Active tissues use oxygen quickly, forming lots of CO2, which enters the blood, and is converted to carbonic acid by red blood cells, using the enzyme carbonic anhydrase. The change in pH lowers the affinity of hemoglobin for oxygen, so more oxygen is released from other red blood cells near working tissues. The carbonic acid is released back into the blood from red blood cells, where it dissociates into a proton (H+) and a bicarbonate ion. It travels through the blood back to the lungs, where it is converted back into CO2, and diffuses across the transport surfaces of the lungs due to the concentration gradient. Then the cycle starts over.
634757
Oxygen Transport\nIn the lungs, oxygen diffuses from alveolar air into the blood because the venous blood has a lower partial pressure. The oxygen dissolves in the blood. Only a small amount is carried as a physical solution (0.31 ml per 100 ml). The remainder of the oxygen is carried in chemical combination with the hemoglobin in red blood cells (erthrocytes).\n\nfrom http://www.elmhurst.edu/~chm/vchembook/260acidbasebal.html\n\n\nNormal analysis results\nNormal blood gas values are as follows:\n partial pressure of oxygen (PaO2): 75-100 mm Hg \n\n\nfrom http://www.healthatoz.com/healthatoz/Atoz/ency/blood_gas_analysis.jsp
131253
Cause cells need oxygen.
894662
Well break the words down. Capillaries are closer to the surface of the skin, that is where gases exchange and where waste is disposed of. Veins are a little deeper and have more pressure on them, they are returning blood back to the heart.\nSee you have arteries, veins, and capillaries.\nThe arteries are the pipes going out of the heart, they have the most pressure on them. Because they have to deliver all the blood with the o2 in it to the capillaries all over your body. After the gas exchange at the capillary level, it then turns in to your veins, that return to the heart.
118751
its where the blood picks up the oxygen.