The Essential Body Fluids

With a break down of approximately 45 percent cells and 55 percent plasma, blood is about 92 percent water. It's responsible for transporting nutrients and oxygen to, and taking waste from, cells. The most abundant protein in the blood is albumin, which pulls water into the circulatory system. Hemoglobin is another vital blood protein that contains iron, which delivers oxygen with the help of red blood cells. While iron levels vary, persistent low iron may be a sign of anemia.

There are three types of tears, each with a different composition. When eyes become irritated by substances such as dust or onions, reflex tears flush the eyes. Emotional tears could be the result of laughter or sorrow, and basal tears keep the cornea lubricated. All tears include water, salts, antibodies, and enzymes that protect the eyes from bacteria. Additional components include a protein-based hormone that's a natural painkiller in emotional tears. Inadequate tearing causes dry eyes and requires drops.

Cerumen or earwax has various functions. It protects ears from foreign substances such as insects and water, as well as fungi and bacteria. It also cleans and lubricates the skin of the ear canal. This bodily fluid is composed of skin, hair, and sweat gland secretions, and its waxy consistency is a combination of cholesterol, squalene, saturated and unsaturated fats, and alcohols. A person may have wet or dry earwax, depending on their genetics. Too much ear wax causes hearing loss and may require medical treatment.

Secreted by the salivary glands, human saliva is 99.5 percent water and acts as a lubricant. Electrolytes, mucus, epithelial and white blood cells, enzymes and antimicrobials comprise the other 0.5 percent. Ingested food is initially broken down by enzymes such as lipase and amylase, and fats and starches create a food bolus that facilitates swallowing. Xerostomia is a lack of adequate saliva that requires medical intervention.

Humans sweat due to increased heat or stress, which the hypothalamus controls. Sweat is odorless until metabolized with the skin's bacteria. The evaporation of sweat on the skin is a cooling mechanism. There are two types of sweat glands: eccrine and apocrine. Eccrine glands are found all over the skin, while apocrine glands exist only in certain parts of the body, such as the ear canal and armpits. Sweat is mostly water, with trace amounts of other substances such as sodium and potassium. Hyperhidrosis is excessive sweating all over the body and may indicate a more serious condition.

This clear, colorless body fluid is within the brain and spinal cord. Specialized cells produce approximately 500 milliliters daily, and small arachnoid protrusions, also in the brain, absorb it. Cerebrospinal fluid (CSF) is like blood plasma but without the proteins and with higher levels of chloride. It provides the brain with protection and buoyancy, preventing it from being impaired by its own weight. In addition to clearing waste, spinal fluid regulates the distribution of certain substances between cells and the brain. Those with low CSF, especially after surgery, need to be monitored.

Gastric acid is a combination of hydrochloric acid and potassium and sodium chlorides produced by the stomach lining. The substance helps the body digest proteins by breaking them down into long chains of amino acids, and depending on feedback, it ramps up the acids needed. The stomach also produces bicarbonate, which prevents the environment from getting too acidic. If this equalization fails, a doctor may prescribe antacids.

Bile is a dark green or yellow fluid the liver produces. It is stored in the gallbladder and helps the small intestines digest lipids or fats. The substance is about 97 percent water, with the other three percent composed of bile salts, bilirubin, fats, and other salts. Any blockage of the bile ducts leads to jaundice and requires hospitalization.

The sebaceous glands produce sebum, a natural lubricant secreted by the skin. Most of these glands are on the face and scalp, and there are none on the soles and palms of the feet and hands. Not all sebaceous glands are alike, specifically those around the inner cheeks, eyes, nipples, and lips. A certain type of sebum is secreted into tears. No matter the locations, sebum is mainly composed of triglycerides, wax esters, squalene, and fat metabolites. Excessive sebum promotes bacteria growth that can lead to acne.

While some may question whether feces is a fluid, fresh human feces is approximately 75 percent water. The substance is a form of solid or semisolid biological waste rotted down by bacteria. Odor depends on the person's health and what they are, but feces is mainly composed of methyl and hydrogen sulfides and benzopyrrole volatiles. The healthy brown color is bile and bilirubin, which comes from dead red blood cells. Any other fecal color, especially red or black, may be a sign of infection or sickness.