What is this and why’s it here?

It’s common knowledge that one cannot live without a heart or brain. Both the liver and pancreas ar

It’s common knowledge that one cannot live without a heart or brain.

Both the liver and pancreas are also vital.

Given the complexity of the human body, it is hard to fathom that each of us is actually full of bits and pieces that serve little or no apparent function.

Some of those parts are likely remnants from ancient ancestors while others appear to be left over from prenatal development, said Steven Stain, chairman of the department of surgery at Albany Medical Center.

Below, Stain and Scott Gallagher, assistant professor of surgery at the University of Southern Florida in Tampa, shed some light on the body’s most intriguing “spare parts.”

Appendix

About the size of a pinky finger, the appendix dangles from the lower right side of the large intestine. For reasons that aren’t clear, this part of the intestinal tract sometimes becomes blocked, infected or inflamed. That’s when it changes from a body part that isn’t serving any prominent purpose to one that is a major health risk.

That’s also when it must be removed right away; otherwise, it may rupture, causing a life-threatening infection.

Researchers say the appendix houses some of the body’s good bacteria and once fought off bacterial outbreaks such as dysentery. But as those types of pandemics became less prominent, so did the role of the appendix.

Tonsils

Tonsils act like specialized lymph nodes and are filters for bacteria and viruses in the back of the throat. Removal is recommended for people with repeated bouts of bacterial throat infections such as strep, a condition most common in children.

The tonsils tend to shrink with age, which is one reason that infections, swelling and inflammation are less common and problematic in adults. Once removed, other lymphoid tissues, including the lymph nodes, take over.

Adenoids

The ade noids are similar to the tonsils, but they sit in the back of the nose where the nasal passages meet the mouth and throat. These can also become inflamed, infected and swollen. So when the tonsils are removed, these are generally removed simultaneously. As with the tonsils, other lymphoid tissue takes over in their absence.

Gallbladder

The gallbladder rests just under the liver and looks like a small bag. It stores digestive juices that are made by the liver. Sometimes, these juices, known as bile, become solid and form gallstones.

Cholecystectomy, or removal of the gallbladder, may be necessary if it becomes inflamed. Infection may require emergency surgery. The most common cause of gallbladder trouble, however, is gallstones that block the tube through which bile is secreted into the intestinal tract.

In the gallbladder’s absence, it would seem there is no place for bile to be stored, but it turns out the body can store it within the liver.

Spleen

This largely misunderstood organ, which is made up of lymphoid tissue, filters the blood, removing infectious organisms, aging blood cells and anything else traveling through the blood that doesn’t belong there.

Sometimes, it can become overly active and remove needed cells. For example, idiopathic thrombocytopenic purpura may develop when platelets, the blood cells responsible for clotting and the prevention of excessive bleeding, are removed from circulation. With few platelets left in the bloodstream, bruising and bleeding may be life-threatening. Although medications can help, removal of the spleen usually cures the condition. In addition to ITP, trauma, including sports injuries and car accidents, is a common reason for removing the spleen.

When the spleen is removed, the body is equipped to take over its functions with the liver and lymphatic system.

Cranial cavities

Consider the paranasal sinuses. No one knows for certain why these air pockets in the skull exist.

They do make our heads lighter and help warm and moisten the air we breathe, but that’s about it.

In animals with an acute sense of smell, however, the sinuses are lined with olfactory tissues. Experts suspect our ancestors probably had a far more keen sense of smell (our DNA contains broken genes for additional odor receptors) but we lost that ability. All we’re left with are sometimes troublesome holes in our heads.

Wisdom teeth

Speaking of troublesome, wisdom teeth are also on the list of useless body parts. Sprouting in late adolescence, these molars seldom develop normally. Only 5 percent of the human population has a healthy set.

Why, then, do we have them?

The wisdom teeth, said Gallagher, are interesting because they represent a freeze-frame of human evolution. The “third molars,” as they are more precisely known, are remnants from a day when humans didn’t know how to cook their food. Once cooking was discovered, foods became immensely softer and chewing, therefore, required less effort.

Additionally, the human jaw has been steadily decreasing in size for millenniums, and few people now have a jaw large enough to accommodate four more teeth in the back of the mouth.

As a result, many wisdom teeth grow in sideways, emerge only partway from the gum or remain impacted, forever trapped beneath it. According to recent estimates, 80 percent to 90 percent of Americans experience at least one impacted wisdom tooth at some point.

Tailbone

Also known as the coccyx, the tailbone is a set of fused vertebrae at the base of the spinal column and is another useless vestige of our ancestral past. Gallagher said it is all that is left of our tails, which disappeared from primate species before they began walking upright.

Many muscles

Humans possess various other useless parts, some of which are muscles.

The extrinsic ear muscles, for example, allow many animals to move their ears independently of their heads, while all we can manage is a slight wiggle.

And the subclavius muscle, stretching beneath the shoulder from the first rib to the collarbone, would be useful if we still walked on all fours. But it has become so useless now that some people don’t even have it, Gallagher said.

Eleven percent of the population lacks the palmaris muscle, a long, narrow muscle that runs from the elbow to the wrist and may have been important when we were tree climbers, and 9 percent of individuals have lost the plantaris muscle, useful for gripping things with one’s feet.

More than 20 percent of people don’t have their pyramidalis muscle, a tiny, triangular pouch-like muscle attached to the pubic bone that may be a relic from the days of our marsupial ancestors.

Gallagher said he can only imagine what will become of even our most vital organs over the course of the next few million years because evolution is “always happening.”

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