What is the Main Function of Blood?

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iStock

What is the main function of blood?

Ray Schilling:

Blood has many functions.

1. Most of all, blood transports oxygen from the lungs to all the tissues by way of hemoglobin that is embedded in the red blood cells. On the way back to the heart and lungs it transports CO2, which is exhaled by the lungs.

2. Nutrients are taken up in the capillaries of the gut, transported via the portal vein into the liver. Here many metabolic pathways are followed and the nutrients are further transported through the blood to all of the body cells.

3. Clotting factors in the plasma of the blood together with platelets contained in the blood see to it that any tiny tears or holes are immediately plugged. Blood has a certain blood pressure, so any defect cannot be tolerated or this could lead to a major bleed. It is interesting that coagulation from clotting factors/platelets and fibrinolysis are constantly balancing each other automatically.

4. Infection is being contained by white blood cells (lymphocytes for viruses, neutrophils for bacteria) on the one hand and antibodies from plasma cells on the other hand. This is quite an effective system to fight infection. Occasionally antibiotics are needed when our immune system is overwhelmed.

5. Hormones and other signaling molecules (e.g. nitric oxide) integrate the function of various organs. As long as all hormones are present and balanced we have energy and all our organs function perfectly. But when hormones are missing, we feel miserable. As we age, some hormones are not produced sufficiently. Having reviewed the literature, bioidentical hormone replacement will allow our system to get rebalanced.

6. Heat distribution and blood redistribution are other aspect of perfusion of our limbs with blood, our abdominal organs, the head and skin. After a meal the blood is rushing to the gut and the liver as we start to digest our meal. We may get tired, because some of the blood from the brain gets pulled away to the stomach, small intestine and the liver. On a hot day our skin veins open up wide, we sweat and lose some of our body heat through our skin. It’s the body’s way to keep us cool inside.

7. There is one aspect that seems to be out of our control. When we get excited or a person is extremely shy, the head, neck, and the ears will turn red. This is out of our control. Some people have this more than others and some don't have it at all. It comes from dilated skin blood vessels. When they dilate, blood rushes into that region giving your skin a reddened appearance.

This post originally appeared on Quora. Click here to view.

What's the Difference Between Apple Juice and Apple Cider?

iStock/Alter_photo
iStock/Alter_photo

In a time before pumpkin spice went overboard with its marketing, people associated fall with fresh apples. Crisp and fresh, they practically beg to be crushed and pulped into liquid. But what’s the difference between apple juice and apple cider?

According to the state of Massachusetts, home to a variety of apple-picking destinations, both apple juice and apple cider are fruit beverages. But apple cider is raw, unfiltered juice—the pulp and sediment are intact. To make cider, the apples are ground into an applesauce-like consistency, then wrapped in cloth. A machine squeezes the layers and strains out the juice into cold tanks. That’s the cider that ends up on store shelves.

Apple juice, on the other hand, takes things a step further—removing solids and pasteurizing the liquid to lengthen its shelf life. It’s typically sweeter, possibly with added sugar, and may lack the stronger flavor of its relatively unprocessed counterpart. It’s also often lighter in color, since the remaining sediment of cider can give it a cloudy appearance.

But that’s just the Massachusetts standard. Each state allows for a slight variation in what companies are allowed to call apple cider versus apple juice. The cider may be pasteurized, or the cider and juice may actually be more or less identical. One company, Martinelli’s, states in its company FAQ that their two drinks are the same in every way except the label: "Both are 100 percent pure juice from U.S. grown fresh apples. We continue to offer the cider label since some consumers simply prefer the traditional name for apple juice."

The US Apple Association, a nonprofit trade organization that represents growers nationwide, indicates that apple juice can be made from concentrate, which is why you might see water as the first ingredient on the label. Generally, cider is the hard stuff: Crushed apples with minimal processing. Because it can ferment, it's usually found refrigerated. Apple juice can often be found elsewhere in stores, where it can remain stable.

Which you should buy comes down to personal preference. Typically, though, recipes calling for apple cider should use apple cider. Processed juice may be too sweet an ingredient. And you can always try making a pumpkin spice hot apple cider, although we may stop talking to you if you do.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

How Are Hurricane Categories Determined?

NOAA via Getty Images
NOAA via Getty Images

Residents of Panama City and other areas in the Florida Panhandle are in the midst of Hurricane Michael, a Category 4 storm that Governor Rick Scott warned is the "worst storm" to hit the area "in a century."

Given that North Carolina is still battling the effects of Hurricane Florence, which made landfall less than a month ago, we've become accustomed to hearing about hurricanes, and to predicting what sort of damage they might cause based on their category number. But how do meteorologists categorize these often-deadly storms, and how does that scale work?

First, a quick primer: Hurricanes are tropical cyclones that occur in the Atlantic Ocean and have winds with a sustained speed of at least 74 mph. A tropical cyclone, in turn, is a storm system that develops in the tropics and is characterized by a low pressure center and thunderstorms that produce strong winds, rain, and storm surges. Tropical cyclone is a generic name that refers to the storms' geographic origin and cyclonic rotation around a central eye. Depending on their location and strength, the storms are called different things. What gets dubbed a hurricane in the Atlantic, for example, would be called a typhoon if it happened in the northwestern Pacific.

WHAT’S THE DIFFERENCE BETWEEN A HURRICANE AND A TROPICAL STORM?

Simply put: Wind speed. When tropical cyclones are just starting out as general areas of low pressure with the potential to strengthen, they’re called tropical depressions. They’re given sequential numbers as they form during a storm season so the National Hurricane Center (NHC) can keep tabs on them.

Once a cyclone’s winds kick up to 39 miles per hour and sustain that speed for 10 minutes, it becomes a tropical storm and the NHC gives it a name. If the cyclone keeps growing and sustains 74 mph winds, it graduates to hurricane.

ONCE WE CALL IT A HURRICANE, HOW DO WE CATEGORIZE IT?

In order to assign a numeric category value to a hurricane, meteorologists look to the Saffir-Simpson Hurricane Wind Scale, which was developed as a classification system for Western Hemisphere tropical cyclones in the late 1960s and early '70s by structural engineer Herbert Saffir and his friend, meteorologist Robert Simpson, who was the director of the NHC at the time.

When Saffir was working on a United Nations project to study low-cost housing in hurricane-prone areas, it struck him that there was no simple, standardized way of describing hurricanes and their damaging effects, like the way the Richter scale is used to describe earthquakes. He created a five-level scale based on wind speed and sent it off to Simpson, who expanded on it to include the effects on storm surge and flooding. Simpson began using it internally at the NHC, and then in reports shared with emergency agencies. It proved useful, so others began adopting it and it quickly spread.

HOW DOES THE SCALE WORK?

According to the NHC, the scale breaks down like this:

Category 1 storms have sustained winds of 74 to 95 mph. These “very dangerous winds will produce some damage: Well-constructed frame homes could have damage to roof, shingles, vinyl siding, and gutters. Large branches of trees will snap and shallowly rooted trees may be toppled. Extensive damage to power lines and poles likely will result in power outages that could last a few to several days."

Category 2 storms have sustained winds of 96 to 110 mph. These “extremely dangerous winds will cause extensive damage: Well-constructed frame homes could sustain major roof and siding damage. Many shallowly rooted trees will be snapped or uprooted and block numerous roads. Near-total power loss is expected with outages that could last from several days to weeks."

Category 3 storms have sustained winds of 111 to 129 mph. This is the first category that qualifies as a “major storm” and “devastating damage will occur: Well-built framed homes may incur major damage or removal of roof decking and gable ends. Many trees will be snapped or uprooted, blocking numerous roads. Electricity and water will be unavailable for several days to weeks after the storm passes."

Category 4 storms have sustained winds of 130 to 156 mph. These storms are “catastrophicand damage includes: “Well-built framed homes can sustain severe damage with loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or uprooted and power poles downed. Fallen trees and power poles will isolate residential areas. Power outages will last weeks to possibly months. Most of the area will be uninhabitable for weeks or months."

Category 5 storms have sustained winds of 157 mph or higher. The catastrophic damage entailed here includes: “A high percentage of framed homes will be destroyed, with total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas. Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for weeks or months."

While the Saffir-Simpson scale is useful, it isn’t the be-all and end-all for measuring storms, as the National Oceanic and Atmospheric Administration (NOAA) pointed out on Twitter in 2013:

IS THERE ANYTHING WORSE THAN A CATEGORY 5?

Not on paper, but there have been hurricanes that have gone beyond the upper bounds of the scale. Hypothetically, hurricanes could up the ante beyond Category 5 more regularly. The storms use warm water to fuel themselves and as ocean temperatures rise, climatologists predict that potential hurricane intensity will increase.

Both Saffir and Simpson have said that there’s no need to add more categories because once things go beyond 157 mph, the damage all looks the same: really, really bad. Still, that hasn't stopped several scientists from suggesting that maybe the time has come to consider a Category 6 addition.

Timothy Hall, a senior scientist at NASA's Goddard Institute for Space Studies, recently told the Los Angeles Times that if the current global warming trends continue, he can foresee a time—likely by the end of the century—where wind speeds could blow past 230 mph, which could create conditions similar to a F-4 tornado (which has the power to lift cars off the ground and send them hurtling through the air with relative ease).

“If we had twice as many Category 5s—at some point, several decades down the line—if that seems to be the new norm, then yes, we’d want to have more partitioning at the upper part of the scale,” Hall said. “At that point, a Category 6 would be a reasonable thing to do."

An earlier version of this article appeared in 2013.

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