The human body contains coordinated, complex components that work
together to efficiently extract oxygen from the air and deliver it to the intracellular sites
where it is essential for life. Oxygen’s journey for life begins in the lung where it is
transported by a system of branching tubes of decreasing size, the bronchus,
bronchioles and bronchi. The lungs are made of a wonderful collection of cells that are
organized into a unique, spongy tissue that contains the bronchial tubes with air sacs,
the alveoli, at their termini. The interior surface area of the alveoli, collectively, is
equal to the area of a tennis court. An intricate system of blood capillaries, arteries, and
veins envelops each alveolus and circulates a large supply of blood that arrives
deoxygenated and leaves oxygenated. The lung works efficiently by using air pressure
and diaphragm muscles to expand and decrease lung volume during breathing. Oxygen
is not sufficiently soluble in blood to supply the body’s needs. However, a complex
oxygen-carrying molecule, hemoglobin, is packaged into special cells, the red
corpuscles where truly magnificent biochemistry reigns. The process works, by
analogy, like a subway system to load and unload oxygen and carbon dioxide from
alveoli to cells throughout the body. Hemoglobin does double duty and reverses the
sequence by loading carbon dioxide from tissues and unloading it in alveoli. The heart
supplies the pumping force that moves the red cells which arrive at ever smaller arteries
and then to capillaries which intercalate with tissues that must have a continuous
supply of oxygen to function. All cells require oxygen to supply the bulk of their
energy needs, and some for other purposes, but the brain is especially oxygen hungry
and uses approximately 25% of the total resting needs by the body for oxygen.
Working muscle is provided with hemoglobin’s cousin, myoglobin, which can store
oxygen and release it to contracting muscle cells. Oxygen is nearly perfect for
bioenergetics and it also has the right stuff to be efficiently transported.
Keywords: Alveolus, Anoxia, Aorta, Asthma, Atelectasis, Bronchial tubes,
Glyceraldehyde phosphate, Hemoglobin, Hypoxic, Myoglobin, Oxygen, Oxygen
radicals, Plasma oxygen concentration, Red corpuscles, Regulation, Respiration,
Surfactant, Vena cava.
