Library · Physiology
From the lungs to the tissues: oxygen transport
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Breathing brings oxygen into the body, and in the blood it travels attached mostly to a single carrier. On its way from the lungs into the blood, it latches onto hemoglobin, the protein in red blood cells whose job is to carry it. The heart pumps that loaded blood throughout the body, and when it reaches the tissues, hemoglobin releases the oxygen there. It is a delivery service: units that load up at one point and unload at the destination.
So how much oxygen a tissue actually receives depends on two things at once, not one: how much blood the heart pumps, and how much oxygen that blood is carrying. And that second part depends mostly on hemoglobin and on its saturation, which is the share of it that is occupied by oxygen, that is, how full the delivery units are.
In brief
Oxygen passes from the lungs into the blood, where it binds mainly to hemoglobin, the oxygen-carrying protein in red blood cells.
The heart pumps that blood, and hemoglobin releases oxygen in the tissues.
Delivery depends on how much blood the heart pumps each minute and on how much oxygen that blood carries. The latter depends mainly on the amount of hemoglobin and on its saturation, the proportion carrying oxygen.
The route is continuous: lung, blood, heart, tissue. A problem at any step can reduce oxygen delivery to the cells.
Sources (2)
- National Library of MedicinePhysiology, Oxygen TransportPublished
- National Library of MedicineOxygen Transport
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