Tag Archives: anatomy

Collateral circulation and the cat concerto

collateral-circulationLike the appendix , collateral circulation is another part of our anatomy that was more useful to our ancestors. Collateral circulation refers to systems of veins and arteries that allow blood to continue flowing when the main pathway is blocked or damaged.

These extra vessels sometimes develop in response to a circulation blockage. But certain parts of the body – the elbows, knees, shoulders – are equipped with these redundant vessels right from the start.

We’re not born with collateral circulation in those really important places like the brain and the heart. Why would we have these surplus vessels in the elbows, but not in the places that keep us alive?
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Still useful after all these years: The gall bladder

gallbaldderThe gall bladder is another useful but expendable organ (see recent posts on the appendix and the spleen). Unlike losing your spleen, living without a gall bladder is not detrimental to your health, though it may be inconvenient at times.

The gall bladder is located under the liver, on the right side of the body. It’s a small sac, about three inches long and 1 ½ inches wide when it’s full. It can hold a little under two ounces of bile (less than a quarter of a cup).

Bile is produced in the liver and stored in the gall bladder until it’s needed to digest fats. Fats need to be broken down (emulsified) before they can used by the body. When they’re not broken down, they pass right through the digestive track. That’s what can be inconvenient about not having a gall bladder. If you eat foods rich in fats, you may need to stay close to a restroom.
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Still useful after all these years: The spleen

The spleen

Source: danielle2

While some anatomical organs are dismissed as totally unnecessary (see Still useful after all these years: The appendix), others are considered useful but dispensable. Consider the spleen.

Located on the left side of the body, under the ribs and behind the stomach, the spleen is about five to six inches long and one and a half inches thick. It weighs about six ounces (the weight of a can of tuna).

Until recently, we thought the spleen was limited to filtering out red blood cells and supporting the immune system.

What we already knew the spleen did for us

Red blood cell gets old, tired and damaged after 120 days or so, at which point we make new replacement cells. The spleen filters out the old blood cells. Not only does the spleen remove the aging cells. It recycles them. It breaks down the hemoglobin so the liver can use it for bile, and it makes the iron in hemoglobin available for the manufacture of new red blood cells.
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Still useful after all these years: The appendix

You can live without an appendix, true, but you should no longer think of this “vestigial” organ as a useless part of your anatomy. The appendix is finally getting the respect it deserves.
We have ten times as many bacteria in the body as we have cells (and we have 10,000,000,000,000 cells). The human digestive system runs on bacteria, where they’re called gut flora. The appendix turns out to be a storage container for the beneficial bacteria that digest our food. When an illness such as cholera empties the contents of the digestive track too rapidly, we lose bacteria. The appendix reboots the digestive track by repopulating the intestines with the bacteria stored in its little pouch.

The downside of an overly hygienic society

Why did it take so long to appreciate the appendix? “It’s hard to figure out what the appendix does when you’re studying superclean animals and people,” according to Bill Parker, a Duke professor of surgery. The appendix evolved when lifestyles were much dirtier and were plagued with parasites. People got sick with diarrheal diseases much more often.

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How do you taste?

Got Taste?
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Beatles Russian nesting dolls from Russian Legacy

The reason animals, including humans, have a sense of taste is so we’ll know what’s good to eat and what’s not. But exactly how does taste happen? We experience taste as happening on the tongue, and advertisers often appeal to our “taste buds.” But is there really such a thing as a taste bud?

You can think of taste as a nested set of structures, a little like a collection of Russian nested dolls. In the Yellow Submarine dolls pictured here, John contains Paul contains George contains Ringo contains Yoko (Is that Yoko?). With taste, the tongue contains papillae, which contain taste buds, which contain taste cells, which contain taste receptors.
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A matter of taste

Got Taste?
Decorated Tongue

Tongue Tattoo from thescene

Try this simple test. Ideally you’ll need a fruit-flavored jelly bean, but you can also use hard candy, a cough drop, or a piece of Mentos “freshly picked” gum. It should be chewable and relatively odorless. You won’t need to swallow it, so you can do this even if you’re counting calories.

Hold your nose and put the jelly bean or equivalent in your mouth. Keep your nose closed and chew (with your mouth closed). Notice what you taste. If it’s fruit flavored, you probably notice a sweet and maybe a little sour taste. Now pay close attention as you let go of your nose. There’s a rush of flavor. If you were eating a strawberry jelly bean, you’d notice the complex fruit flavor that we identify as strawberry.

How we taste food: Flavor is more than taste

Technically, taste is what happens on your tongue. Flavor, on the other hand, is a combination of taste, smell, and touch. Our sense of smell allows us to distinguish thousands of different odors, whereas the tongue detects only five basic tastes: sweet, sour, salty, bitter, and savory (umami).

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Taste and Smell from AllPosters.com

When you eat a jelly bean, odors are released by chewing. These gaseous molecules get pumped up into your nasal cavity, where they interact with a postage-stamp sized area on the roof of the nasal cavity called the olfactory (smell) epithelium. There are millions of olfactory receptor cells here with microscopic hairs (cilia) waving in the passing air currents. Information from the receptor cells is sent to the olfactory bulb, which is part of the brain. From there, signals get relayed to other parts of the brain, including those involved in memory, speech, emotion, and decision making. There’s a very complex process going on whenever you identify a distinct odor or flavor.
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