Bob Doyle, Columnist
Last week’s column dealt with organs you can do without, our DNA (molecular blueprint for our bodies) and hair. My reference is “Body: Discover What’s Beneath Your Skin,” a Miles Kelly Book, written by John Farndon and Nicki Lampon and published in 2010. This column will consider finger and toe nails, breathing and coughing, saliva, mucus and your food’s long and torturous journey. Most cities and mid sized towns have nail shops where you can have your finger nails and toe nails adorned. Nail painting can be traced back 5,000 years.
Both finger and toe nails are formed from dead cells mixed with keratin, a protein. This is the same substance that antlers are made of. Nails grow from a nail root, hidden by a flap of skin called a cuticle. The lighter part of the nail is called the lunula, resembling the moon’s shape.
Finger nails grow 0.5 millimeters or 0.02 inches each month. Nails grow faster in the summer and more slowly in the winter. If you are right handed, the finger nails on that hand will grow faster than the fingers on your left hand. A similar statement applies to left handed people.
Breathing is automatic with an average breath taking in 0.4 liters or nearly one pint of air every four seconds. Your diaphragm arches upward against your lungs as you exhale and downward as you inhale.
We breathe to get oxygen, which makes up 21 percent of the air. The airways are coated with mucus to trap dust and other small particles so they don’t go into your lungs. Your lungs have about 300 million alveoli (air sacs) where the oxygen can pass into capillaries and bind with a red blood cell.
The carbon dioxide (our waste gas) is dissolved in the blood plasma. Then the blood carries its load of carbon dioxide into the alveoli where it is released to the air there and discharged upon exhaling.
Coughing is the body’s way of removing dust or irritants in the airways and lungs. When you cough, you are expelling 2.5 liters of air out of your lungs. Coughing is usually a reflex action, although you can cough voluntarily.
Saliva is fluid that is mixed with your food as you chew it in your mouth. It is made by salivary glands in the mouth. Saliva contains enzymes that start the digestion process. Your mouth makes up to 1.5 liters of saliva a day.
Mucus is valuable in trapping small particles in the air that we breathe. Your stomach has a protective layer of mucus on its interior lining to prevent the strong gastric acids from digesting the stomach itself. Your small intestine is also lined with a protective layer of mucus to keep the small intestines from dissolving itself.
Your digestive tract is nearly six times as long as you are tall. It needs to be that long so you can properly extract nourishment from your food. After being chewed, the food passes down the esophagus into your stomach.
An empty stomach is only 0.5 liters in volume (about a pint) but after a big meal can stretch to four liters in volume. The stomach churns the food into a gooey substance called chyme, taking up to five hours to process the food before it is released. Next is the small intestine, about six meters or nearly 20 feet long. In the first part of the small intestine, the chyme is infused with enzymes and bile to break it down into molecules. In the second part of the small intestine, the food is absorbed.
All through the digestive tract the food is pushed along by waves of contraction called peristalsis. This action is involuntary; your innards know what to do with food.
The main part of your large intestine is the colon, almost as long as your height. Here is where liquids are converted into solid waste. Your colon soaks up to three quarts of water every day.
There is a vast multitude of bacteria living in the colon (dozens of trillions). The bacterial residents there make vitamins K and B. Then the feces collect at the end of the colon and await a time when they can be excreted.
SKY SIGHTS AHEAD: The evening moon passed by Mars yesterday; tomorrow, the moon will be below the planet Saturn. The moon is full on July 12 at daybreak (6:26 a.m.) so the moon will appear nearly full on both Friday and Saturday evenings.
There are two predawn planets – brilliant Venus and dimmer Mercury. Find a site with a flat eastern horizon and look about 5 a.m. Mercury will be below and to the left of Venus.
Bob Doyle invites any readers comments and questions. E-mail him at firstname.lastname@example.org . He is available as a speaker on his column topics.