11 Body Fluids We Couldn’t Live Without

5. Pus

Pus sounds even more disagreeable but serves as a sign that the immune system is working. A white, yellow or brown viscous fluid that accumulates at sites of infection, pus usually consists of bacteria, white blood cells, and other proteins and cell debris. Pus under the skin is often found in a pimple, but deeper in the body a larger collection is known as an abscess. Pimples and abscesses represent the body’s attempt to contain the spread of an infection.

For many centuries, one of the dictums of the barber-surgeon was, “Where there is pus, evacuate it,” thereby purging the infection from the body. Until several decades ago, drainage required a surgical procedure. Today, however, many abscesses are drained using just a needle and catheter, with ultrasound or CT imaging for guidance. This less invasive approach reduces the need for anesthesia, recovery time and cost.

6. Semen

Semen, the fluid released by males at ejaculation, generally contains spermatozoa, the gametes that fertilize the female egg, though this is not the case for males who have undergone the most common sterilization procedure, vasectomy.

In addition to providing a medium through which sperm can “swim,” semen also contains fructose, a sugar that nourishes the sperm, as well as alkaline secretions that help to neutralize the normally acidic environment of the vagina.

Females are born with all the eggs they will ever have, but males continuously produce gametes from puberty onward, and the average healthy male’s ejaculate of about five milliliters contains approximately 300 million spermatozoa.

Why such large quantities are produced when only one sperm can fertilize an egg is a bit of a puzzle, but one explanation may be that the competition between sperm helps to select for the fittest.

7. Saliva

Saliva is secreted by salivary glands in and around the mouth. The average adult produces about a liter of saliva per day, with peak secretion at meals. Like mucus, saliva contains antibacterial enzymes and antibodies, as well as mucus itself. Saliva helps to moisten food, which is important to lubricate chewing and swallowing. It also enhances taste, because if the chemicals in food were not in a liquid medium, they could not be detected by taste receptors.

Some of the enzymes in saliva also begin to break down substances in food, such as starches, which are broken down by amylase. Because such enzymes are generally neutralized within seconds after reaching the highly acidic secretions in the stomach, they probably function mainly to break down food particles trapped between teeth, helping to prevent cavities.

Patients who lack sufficient saliva have much higher rates of tooth decay and gum disease.