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Parts-per-million cube of relative abundance by mass of elements in an average adult human body down to 1 ppm. About 99% of the mass of the human body is made up of six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus. Only about 0.85% is composed of another five elements: potassium, sulfur, sodium, chlorine, and magnesium ...
Arterial blood carries oxygen from inhaled air to all of the cells of the body, and venous blood carries carbon dioxide, a waste product of metabolism by cells, to the lungs to be exhaled. However, one exception includes pulmonary arteries, which contain the most deoxygenated blood in the body, while the pulmonary veins contain oxygenated blood.
Respiration is one of the key ways a cell releases chemical energy to fuel cellular activity. The overall reaction occurs in a series of biochemical steps, some of which are redox reactions. Although cellular respiration is technically a combustion reaction , it is an unusual one because of the slow, controlled release of energy from the series ...
Lactic acid fermentation is relatively inefficient. The waste products lactic acid and ethanol have not been fully oxidized and still contain energy, but it requires the addition of oxygen to extract this energy. [8] Generally, lactic acid fermentation occurs only when aerobic cells are lacking oxygen.
One of the main roles of extracellular fluid is to facilitate the exchange of molecular oxygen from blood to tissue cells and for carbon dioxide, CO 2, produced in cell mitochondria, back to the blood. Since carbon dioxide is about 20 times more soluble in water than oxygen, it can relatively easily diffuse in the aqueous fluid between cells ...
Barotrauma is physical damage to body tissues caused by a difference in pressure between a gas space inside, or in contact with, the body and the surrounding gas or liquid. [ 76 ] [ 33 ] The initial damage is usually due to over-stretching the tissues in tension or shear , either directly by an expansion of the gas in the closed space or by ...
Liquid hydrogen also has a much higher specific energy than gasoline, natural gas, or diesel. [12] The density of liquid hydrogen is only 70.85 kg/m 3 (at 20 K), a relative density of just 0.07. Although the specific energy is more than twice that of other fuels, this gives it a remarkably low volumetric energy density, many fold lower.
The tears are unique among body fluids in that they are exposed to the environment. Much like other body fluids, tear fluid is kept in a tight pH range using the bicarbonate buffer system. [15] The pH of tears shift throughout a waking day, rising "about 0.013 pH units/hour" until a prolonged closed-eye period causes the pH to fall again. [15]