A Walking, Talking Water Balloon
Under PressureREAD MORE
As in an actual water balloon, a closed system saturated with liquid will be under pressure. All of the organs and systems in our body rely either directly or indirectly on water-based pressure for their form and function. In fact, the four primary vital signs — the indications that we are indeed alive — are all pressure readings:
- Blood pressure: Is there enough pressure within vessels to send blood and oxygen to the body’s organs? Is there too much pressure on arteries when the heart contracts or rests?
- Pulse: Is the heart beating fast enough to maintain pressure? Is it racing to recover pressure?
- Respiratory rate: Is enough pressure being exerted on the thoracic cavity to draw and exhale air?
- Temperature: Is blood and oxygen being circulated to warm the body adequately?
Pressure: The Smaller Picture
At the molecular level, pressure is partly responsible for exchanging water between blood and tissue. Though water molecules don’t exit large blood vessels, higher blood pressure in the narrow passageways of capillaries expels the molecules into neighboring tissues. Capillaries are the smallest blood vessels; and you may remember that water pressure increases when a constant volume is passed through a narrower channel, like water flowing from a drainpipe versus spraying from a hose. That’s the pressure that strains water from the capillaries.
The exchange of water between blood and tissue is crucial to life, because (a) cells need the oxygen and solutes carried by water; and (b) if water couldn’t get into cells they would dehydrate, resulting in cell death. LESS
It’s not simple, but the concept is a bit like water seeking its own level in a pot; it will travel from higher to lower until it’s level. Similarly, water will travel in and out of cells until solute concentrations are even. When concentration is higher inside a cell, water moves into the cell via osmosis to make things level. The reverse is true as well: if the environment outside a cell has a higher concentration, water will move via osmosis into the extracellular environment. LESS
Water BabiesREAD MORE
The baby not only floats in the sphere of protective fluid, but “breathes” it; every three hours, amniotic fluid is circulated as the baby swallows the fluid and releases it through urine. Until a child is born, all the oxygen and nutrients she needs come through the umbilical cord and placenta.
Photo courtesy of Verena Vonasek