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Category Human Body

Where are T-cells made?

T cells originate from haematopoietic stem cells which are produced in the bone marrow. Some of these multipotent cells will become progenitor cells that leave the bone marrow and travel to the thymus via the blood. In the thymus these cells mature: T cells are named after their thymus-dependent development.

T cells undergo a selection process in the thymus, which the majority of developing T cells (called thymocytes) will not survive. Thymocytes that interact with self-MHC molecules receive positive signals for survival, and thymocytes that have receptors to self-antigen molecules receive negative signals and are removed from the repertoire.

Each T cell will develop its own T cell receptor (TCR) that is specific for a particular antigen. T cells that survive thymic selection will mature and leave the thymus. They will circulate through the peripheral lymphoid organs, each ready to encounter a specific antigen and become activated. Once activated, the T cell will proliferate and differentiate into an effector T cell.

The thymus involutes as we age and so produces fewer naïve T cells over time. This means that older people have reduced T cell diversity, which contributes to the increased susceptibility to infections seen with age.

 

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How white blood cells help to fight infection?

Germs look for ways to get under your skin — literally. They could get in through a cut, ride in on something you ate, filter through the air, or wait on a coin for you to touch it and then rub your eyes.

Once inside, they start to breed. You’re infected, and it can make you feel sick.

Your immune system should know that there’s a problem. It reads a tell-tale “fingerprint” of proteins on the surface of cells, so it can tell the difference between your own cells and what shouldn’t be there. 

Your white blood cells aim to destroy the unwelcome guests.

They get their start in your bone marrow. They have a short life — ranging from a few days to a few weeks — so your body constantly makes more. There are different types, and they all have the same goal: to fight infection.

 

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Where do newborns get their immune cells from?

Antibodies are passed from mother to baby through the placenta during the third trimester (last 3 months of pregnancy). This gives the baby some protection when they are born. The type and amount of antibodies passed to the baby depends on the mother’s own level of immunity.

During birth, bacteria from the mother’s vagina is passed on to the baby. This helps to build the colony of bacteria in the gut that contributes to their immunity.

After birth, more antibodies are passed on to the baby in colostrum and in breast milk. But babies’ immune systems are still not as strong as adults’. Premature babies are at greater risk of infection because their immune systems are even more immature and they haven’t had as many antibodies passed to them from their mothers.

Babies produce their own antibodies every time they are exposed to a virus or germ, but it takes time for this immunity to fully develop.

The passive immunity passed on from the mother at birth also doesn’t last long and will start to decrease in the first few weeks and months after birth.

 

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Which element helps in heart beat regulation?

Potassium plays a role in every heartbeat. A hundred thousand times a day, it helps trigger your heart to squeeze blood through your body.

It also helps your muscles to move, your nerves to work, and your kidneys to filter blood

The U.S. Department of Agriculture recommends 4,700 milligrams per day for healthy people. The easiest way to get this amount is by adding high-potassium fruits and vegetables to your diet.

It’s possible to get too much of a good thing, though. Ask your doctor before starting a potassium supplement.

If you have kidney failure or other kidney problems, talk with your doctor about how much potassium you should get.

 

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Which element is found in your bones and teeth?

Mineralized tissues, such as bone, teeth, antler and horn, are important elemental storage sites in animals. These tissues contain necessary elements, both major, such as calcium (Ca), phosphorus (P), magnesium (Mg) and sulphur (S), and trace elements, such as iron (Fe), zinc (Zn), manganese (Mn) and cadmium (Cd).

Bones are living tissue. They’re made up of the protein collagen and the mineral calcium phosphate. This enables bones to be strong but flexible.

Collagen is like scaffolding that provides the bone’s framework. The calcium fills in the rest. The inside of the bone has a honeycomb-like structure. It’s called trabecular bone. Trabecular bone is covered by cortical bone.

Teeth are not living tissue. They’re comprised of four different types of tissue: dentin, enamel, cementum, pulp

While teeth and bones might appear to be the same material at first glance, they’re actually quite different. Bones can repair and heal themselves, while teeth cannot. Teeth are more fragile in that respect, which is why it’s so important to practice good dental hygiene and see a dentist regularly.

 

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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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