Category Human Body

What does we are all stardust mean?

The human body is made up of four fundamental elements: carbon, hydrogen, oxygen and nitrogen (also called the CHON or HONC elements). So are rocks, plants, animals, water and air. Do you know where these elements came from? The STARS. Yes, even the calcium in your bone and iron in your blood came from the distant stars. In fact, every atom in your body was forged in the centre of stars years ago. Read on to know how…

When the universe began 13 or 14 billion years ago, with the Big Bang, the only elements that existed were hydrogen, helium and a small amount of lithium. Over time, gravity increasingly pulled gas molecules towards each other and eventually gave birth to the first generation of stars. These stars were much greater than our Sun in size and temperature. The nuclear fusion within those stars then produced heavier elements, including carbon, oxygen, and nitrogen. When the stars exploded in supernova at the end of their life-cycle, the elements were shot into the far-flung reaches of the universe. Those stellar explosions continued, making new stars and planets. As more, massive stars exploded heavier elements continued to be created. Stars and elements are still being born this way, even as you read this.

As far as our galaxy, Milky Way, is concerned, stars had generated most elements now present on Earth about 5 billion years ago. Within the next billion years, the first signs of life on Earth appeared. No one is exactly sure how life formed on the planet. But one thing is clear like Carl Sagan said. “The cosmos is also within us, we’re made of star stuff.

 

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Which is the gland that produces tears?

The tear glands (lacrimal glands), located above each eyeball, continuously supply tear fluid that’s wiped across the surface of your eye each time you blink your eyes. Excess fluid drains through the tear ducts into the nose.

The main function of the lacrimal gland is the production of lacrimal fluid, which is involved in the maintenance of a healthy ocular surface. Lacrimal fluid contains proteins, antimicrobial agents, water and electrolytes that ensure adequate lubrication, protection and nutrition of the ocular surface. 

Lacrimal fluid contains a significant amount of water that keeps the surface of the eye moist as well as dissolved elements that are necessary for normal cellular functioning. The fluid also contains antimicrobial agents including phospholipase, lysozyme, peroxidase, lactoferrin and immunoglobulins that provide defence against invading pathogens. In addition, the lacrimal gland produces numerous other substances and proteins including retinol (derived from Vitamin A) and growth factors such as epidermal, fibroblast and keratinocyte growth factors. These are involved in corneal regeneration and maintenance of corneal avascularity and transparency.

 

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What is pupil?

The pupil is the opening in the center of the iris (the structure that gives our eyes their color). The function of the pupil is to allow light to enter the eye so it can be focused on the retina to begin the process of sight.

Together, the iris and pupil control how much light enters the eye. Using the analogy of a camera, the pupil is the aperture of the eye and the iris is the diaphragm that controls the size of the aperture.

The size of the pupil is controlled by muscles within the iris — one muscle constricts the pupil opening (makes it smaller), and another iris muscle dilates the pupil (makes it larger). This dynamic process of muscle action within the iris controls how much light enters the eye through the pupil.

In low-light conditions, the pupil dilates so more light can reach the retina to improve night vision. In bright conditions, the pupil constricts to limit how much light enters the eye (too much light can cause glare and discomfort, and it may even damage the lens and retina).

 

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What is myopia?

Myopia, otherwise known as short-sightedness, is a common eye condition that causes objects in the distance to appear blurred while close objects are often seen clearly.

Myopia occurs when the eye has too much focusing power, either due to the eye being too long or the cornea being more curved than usual making the eye too strong. As a result, when someone with short-sightedness tries to look at distant objects, the rays of light are focused in front of the retina, rather than directly onto it, causing the appearance of those objects to become blurred.

Nearsightedness is the most common vision problem. Currently, about 1.5 billion people worldwide (nearly a quarter of the global population) are nearsighted. Myopia is especially prevalent in East Asia, where 70 to 80 percent of the residents of some countries are affected.

And the rate of myopia worldwide is increasing rapidly. It’s estimated that by the year 2050, roughly half of the world population will be nearsighted.

Researchers aren’t sure why myopia is becoming so common, but many eye doctors attribute it to eye fatigue from close-up work including reading, studying, using computers and portable electronic devices (including tablets and smartphones) and reduced time spent outdoors.

 

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Which are the special cells in the retina that help process light?

The retina is the back part of the eye that contains the cells that respond to light. These specialized cells are called photoreceptors. There are 2 types of photoreceptors in the retina: rods and cones.

The rods are most sensitive to light and dark changes, shape and movement and contain only one type of light-sensitive pigment. Rods are not good for color vision. In a dim room, however, we use mainly our rods, but we are “color blind.” Rods are more numerous than cones in the periphery of the retina. Next time you want to see a dim star at night, try to look at it with your peripheral vision and use your ROD VISION to see the dim star. There are about 120 million rods in the human retina.

The cones are not as sensitive to light as the rods. However, cones are most sensitive to one of three different colors (green, red or blue). Signals from the cones are sent to the brain which then translates these messages into the perception of color. Cones, however, work only in bright light. That’s why you cannot see color very well in dark places. So, the cones are used for color vision and are better suited for detecting fine details. There are about 6 million cones in the human retina. Some people cannot tell some colors from others – these people are “color blind.” Someone who is color blind does not have a particular type of cone in the retina or one type of cone may be weak. In the general population, about 8% of all males are color blind and about 0.5% of all females are color blind.

 

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What is the common cause of cataract, the clouding of the eye’s natural lens?

A cataract is a cloudy area in the lens of your eye. Cataracts are very common as you get older. In fact, more than half of all Americans age 80 or older either have cataracts or have had surgery to get rid of cataracts. 

Most cataracts are age-related — they happen because of normal changes in your eyes as you get older. But you can get cataracts for other reasons — for example, after an eye injury or after surgery for another eye problem (like glaucoma).

No matter what type of cataract you have, the treatment is always surgery.

Most cataracts are caused by normal changes in your eyes as you get older.

When you’re young, the lens in your eye is clear. Around age 40, the proteins in the lens of your eye start to break down and clump together. This clump makes a cloudy area on your lens — or a cataract. Over time, the cataract gets more severe and clouds more of the lens.

 

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