19 Effects of Diabetes on the Body Cataracts and Glaucoma The Effects of Diabetes on the Body After you eat or drink, your body breaks down the sugars in your blood and turns it into glucose. The glucose travels through your bloodstream and provides your body with energy. To accomplish this, your pancreas needs to produce a hormone called insulin. In a person with diabetes (diabetes mellitus), the pancreas either produces too little insulin or none at all, or the insulin can’t be used effectively. This allows blood glucose levels to rise while the rest of your cells are deprived of much needed energy. This can lead to a wide variety of problems affecting nearly every part of your body. There are two main types of diabetes. Type 1, also known as juvenile diabetes or insulin-dependent diabetes, is an immune system disorder. In Type 1 diabetes, the patient’s own immune system attacks the insulin-producing cells in the pancreas, destroying the ability to manufacture insulin. People with Type 1 diabetes must take insulin to live. Most people with Type 1 diabetes are diagnosed as children or young adults. The main problem in Type 2 diabetes is the presence of what is called insulin resistance.

In this sort of diabetes, the pancreas starts off robust in its production of insulin. However, cells that need energy don’t respond normally to the usual amounts of insulin. The pancreas has to produce much higher levels of the hormone in order to manage blood glucose levels. Over time, the insulin-producing cells in the pancreas can burn themselves out due to this overproduction. At this point a person with Type 2 diabetes begins to require insulin medication. However, in earlier phases of this more common type of diabetes, the illness can be effectively managed with diet, exercise, and careful monitoring of blood sugars. Some people with Type 2 diabetes may require a variety of oral medications and eventually, as described above, some will eventually need insulin. Gestational diabetes is high blood sugar that develops during pregnancy. Most of the time, gestational diabetes can be controlled through diet and exercise, and it typically resolves after the baby is delivered. Common symptoms of diabetes include excessive thirst, frequent urination, and sluggishness. Blood tests will reveal high sugar levels. Endocrine, Excretory, and Digestive Systems Your pancreas produces and releases insulin to help make energy out of sugars.

If your pancreas produces little or no insulin, or if your body can’t use it, alternate hormones are used to turn fat into energy. This can create high levels of toxic chemicals, including acids and ketone bodies, which may lead to a condition called diabetic ketoacidosis. This is a serious complication of the disease. Symptoms include extreme thirst, excessive urination, and fatigue. Your breath may have a sweet scent that is caused by the elevated levels of ketone bodies in the blood. High blood sugar levels and excess ketones in your urine can confirm diabetic ketoacidosis. Untreated, the condition can lead to loss of consciousness or even death. Diabetes can damage your kidneys, affecting their ability to filter waste products from your blood. Elevated amounts of protein in your urine (microalbuminuria) may be a sign that your kidneys aren’t functioning properly. Kidney disease related to diabetes is called diabetic nephropathy. This condition doesn’t show symptoms until it advances to later stages. People with diabetes should be evaluated for nephropathy in order to avoid irreversible kidney damage and kidney failure. Diabetic hyperglycemic hyperosmolar syndrome (HHS) occurs in Type 2 diabetes.

It involves very high blood glucose levels but without ketones. Symptoms also include dehydration and loss of consciousness. It usually happens to people whose diabetes is undiagnosed or who have not been able to control their diabetes. It can also be caused by heart attack, stroke, or infection. High blood glucose levels can make it hard for your stomach to completely empty (gastroparesis). In turn, the delay causes blood glucose levels to rise. Diabetes is the leading cause of gastroparesis. Symptoms include nausea, vomiting, bloating, and heartburn. Circulatory System High blood glucose levels can contribute to the formation of fatty deposits in blood vessel walls. Over time, that can restrict blood flow and increase the risk of hardening of the blood vessels (atherosclerosis). Lack of blood flow can affect your hands and feet. Poor circulation can cause pain in the calves while you’re walking (intermittent claudication). People with diabetes are particularly prone to foot problems due to narrowed blood vessels in the leg and foot. Your feet may feel cold, and you may be unable to feel heat due to lack of sensation.

A condition called diabetic neuropathy causes decreased sensation in the extremities, which may prevent you from noticing an injury or infection. Diabetes increases your risk of developing infections or ulcers of the foot. Poor blood flow and nerve damage increase the likelihood of having a foot or leg amputated. If you have diabetes, it is critical that you take good care of your feet and inspect them often. Diabetes raises your risk of developing high blood pressure, putting strain on the heart. According to the National Diabetes Information Clearinghouse , people with diabetes have double the risk of heart disease or stroke than people without diabetes. Monitoring and controlling your blood glucose, blood pressure, and cholesterol can lower that risk. So can good eating habits and exercise. Diabetes and smoking are a very bad mix, increasing risk of cardiovascular problems and restricted blood flow. Integumentary System Diabetes can affect your skin. Lack of moisture can cause the skin on your feet to dry and crack. It is important to completely dry your feet after bathing or swimming. You can use petroleum jelly or gentle creams, but be careful: creams or oils left between your toes can become so moist that it can lead to infection. High-pressure spots under your foot can lead to calluses.

If you don’t take good care of them, they can become infected or develop ulcers. If you get an ulcer, see your doctor immediately to lower your risk of losing your foot. You may also be more prone to boils, infection of the hair follicles (folliculitis), sties, and infected nails. People with diabetes have a higher incidence of bacterial infections, including staph (Staphylococcus), than the general population. Moist, warm folds in the skin are susceptible to fungal or yeast infections. You’re most likely to develop this type of infection between fingers and toes, the groin, armpits, or in the corners of your mouth. Symptoms include redness, blistering, and itchiness. A condition called diabetic dermopathy can cause brown patches on the skin. There’s no cause for concern and no treatment is necessary. Eruptive xanthomatosis causes hard yellow bumps with a red ring. Digital sclerosis causes thick skin, most often on the hands or feet. Both of these skin conditions are signs of unmanaged diabetes. They usually clear up when you get your blood sugar under control.

Central Nervous System Diabetes causes damage to the nerves (peripheral neuropathy), which can affect your perception of heat, cold, and pain, making you more susceptible to injury. This also makes it more likely that you’ll ignore an injury, especially if it’s in a difficult place to see, such as between your toes, on your heels, or the bottoms of your feet. Swollen, leaky blood vessels in the eye (diabetic retinopathy) can damage your vision and even lead to blindness. Symptoms include floaters or spots in your field of vision. People with diabetes tend to develop cataracts at an earlier age than other people. They are also more likely to develop glaucoma. Symptoms of eye trouble can be mild at first, so it’s important to see your eye doctor regularly. Reproductive System The hormones of pregnancy can cause gestational diabetes. This also increases the risk of high blood pressure (preeclampsia or ecclampsia). In most cases, gestational diabetes is easily controlled, and glucose levels return to normal after the baby is born. Symptoms are the same as other types of diabetes, but may also include repeated infections affecting the vagina and bladder.

Women with gestational diabetes may have babies with higher birth weight, making delivery more complicated. Women who have had gestational diabetes should be monitored, as there’s an increased risk of developing diabetes within ten years. Recommended for You The Not-So-Sweet Facts of Diabetes Get an up-close look at the increasing impact type 2 diabetes has on everything from pregnancy to healthcare costs. Controllable risk factors – diabetes. (n.d.). Retrieved from Diabetes, heart disease, and stroke. (2014, February 19). Retrieved from Facts about diabetic retinopathy. (2012, June). Retrieved from Foot complications. (2014, May 22). Retrieved from Gastroparesis. (2012, June 15). Retrieved from High blood pressure. (2014, January 4). Retrieved from Kidney disease (Nephropathy). (2013, December 10). Retrieved from Mayo Clinic Staff. (2012, October 23). Diabetic ketoacidosis: Complications. Retrieved from Mayo Clinic Staff. (2012, October 23). Diabetic ketoacidosis: Definition.

Retrieved from Mayo Clinic Staff. (2012, October 23). Diabetic ketoacidosis: Symptoms. Retrieved from Skin complications. (2014, March 31). Retrieved from What is diabetes?. (n.d.). Retrieved from 24 Effects of HIV on the Body 24 Effects of HIV on the Body Written by Ann Pietrangelo Medically Reviewed by George Krucik, MD, MBA on EFFECTS OF HIV ON THE BODY EFFECTS OF HIV ON THE BODY The Effects of HIV on the Body Once the human immunodeficiency virus (HIV) enters your body, it launches a direct attack on your immune system. It gradually weakens your natural defenses against disease and infection and can affect every part of your body. Find out how. Immune System Under Attack Inflammation of the Brain and Spinal Cord Balance Issues A Strain on the Heart Diarrhea Itchiness Effects of HIV/AIDS on the Body The human immunodeficiency virus (HIV) seeks and destroys CD4+ cells, a type of T lymphocyte (T cell). T cells are critical to the immune system. They’re responsible for warding off diseases and most infections, including viral infections.

HIV targets the type of cells that would normally fight off an invader like HIV. As the virus replicates, it damages or destroys the infected CD4+ cell and produces more virus to infect more CD4+ cells. Without treatment, this cycle continues in most infected people until the immune system is badly compromised, leaving them open to many serious infections and illnesses. Many of the illnesses that people compromised immune systems get are rare in people with functioning immune systems. How quickly the virus progresses varies from person to person. Factors like your age, overall health, and how quickly you’re diagnosed and treated can make a difference. Acquired immunodeficiency syndrome (AIDS) is the final stage of HIV. At this stage, the immune system is severely weakened, and the risk of contracting opportunistic infections is much greater. Not everyone with HIV will go on to develop AIDS. Importantly, many of the effects described here are related to the failure of the immune system in progressing HIV and AIDS. Many of these effects are preventable with early antiretroviral treatment, which can preserve the immune system. However, for anyone without access to effective antiretroviral treatment, these effects remain possible.

Immune System Your immune system prevents your body from acquiring the diseases and infections that come your way. White blood cells defend you against viruses, bacteria, and other organisms that can make you sick. When HIV enters the body, it goes straight for the CD4+ T cells that are a lynchpin for the operation of the entire immune system. As the virus infects and kills more of these T cells, your immune system grows weaker, and you become more susceptible to illness. Early on, symptoms may be mild enough to be dismissed. Within a few months of becoming infected, most people experience a flu-like sickness that lasts a few weeks. Symptoms may include: fever swollen lymph glands mouth or genital ulcers The first stage of HIV is called the acute infection stage. The virus reproduces rapidly at this stage. You may not have much in the way of serious symptoms, but there are usually large quantities of virus in your blood. Many people are unaware of their HIV status at this point, but the risk of transmission during the acute infection stage is very high. Acute infection may cause flu-like symptoms, including decreased appetite, headache, night sweats, and others. The next stage is called the clinical latent infection state.

On average, it lasts 8 to 10 years. In some cases, it lasts much longer than that. You may or may not have symptoms during this stage. As the virus advances, CD4 count decreases more drastically. This can lead to symptoms like: fatigue weight loss diarrhea If HIV infection advances to AIDS, the body becomes prone to opportunistic infections. People with advanced HIV/AIDS are at increased risk of a number of infections, including a herpes virus called cytomegalovirus. It can cause problems with your eyes, lungs, and digestive tract. Kaposi’s sarcoma, another possible infection, is a cancer of the blood vessel walls. It’s rare among the general population, but common in people who are HIV-positive. Symptoms include red or dark purple lesions on the mouth and skin. It can also cause problems in the lungs, digestive tract, and other internal organs. HIV/AIDS also puts you at higher risk of developing lymphomas. An early sign of lymphoma is swollen lymph nodes. Respiratory and Cardiovascular Systems HIV increases the risk of colds, influenza, and pneumonias. According to the American Lung Association , HIV/AIDS can lead to opportunistic lung diseases.

Without preventive treatment, people with advanced HIV are susceptible to tuberculosis, pneumonia, and a disease called pneumocystis carinii pneumonia (PCP). PCP causes trouble breathing, cough, and fever. HIV raises the risk of pulmonary arterial hypertension (PAH). PAH s a type of high blood pressure in the arteries that supply the lungs. It puts added strain on the heart. If you have HIV and have become immunocompromised (have a low T cell count), you’re susceptible to tuberculosis (TB), a leading cause of death in people who have AIDS. TB is an airborne bacterium that affects the lungs. Symptoms include chest pain and a bad cough that may contain blood or phlegm. Symptoms can linger for months. Digestive System A common HIV-related infection is called candidiasis. Symptoms include inflammation of and a white film on the tongue. It can also cause inflammation of the esophagus, which can make it difficult to eat. Another viral infection that affects the mouth is oral hairy leukoplakia, which causes white lesions on the tongue. Salmonella infection is spread through contaminated food or water and causes diarrhea, abdominal pain, and vomiting.

Anyone can get it, but if you have HIV, you’re at higher risk of serious complications from this infection. Consuming contaminated food or water can also result in a parasitic intestinal infection called cryptosporidiosis. It affects the bile ducts and intestines. It can be particularly severe and cause chronic diarrhea in people who have AIDS. Cryptosporidiosis infection can occur in people with effective immune systems, but it can become a chronic problem in people with CD4 levels under 200. HIV-associated nephropathy (HIVAN) is when the filters in your kidneys become inflamed, making it harder to remove waste products from your bloodstream. Problems with your digestive tract can decrease your appetite and make it difficult to eat properly. Weight loss is a common side effect of HIV. Central Nervous System There are significant neurological complications of AIDS. Even though HIV doesn’t generally directly infect nerve cells, it does infect the cells that support and surround nerves in the brain and throughout the body. All of the mechanisms of HIV-associated neurologic damage aren’t completely understood, but it’s likely that infection of these support cells contribute to nerve injury. Advanced HIV infection can damage nerves (neuropathy).

Small holes in the conducting sheaths of peripheral nerve fibers (vacuolar myelopathy) can cause pain, weakness, and difficulty walking. HIV/AIDS can cause HIV-associated dementia or AIDS dementia complex, two conditions that seriously affect cognitive function. Toxoplasma encephalitis is another possible complication of advanced HIV. People with AIDS are at increased risk of inflammation of the brain and spinal cord due to this parasite found commonly in cat feces. Symptoms include confusion, headaches, and seizures. Some common complications of AIDS include memory impairment, anxiety, and depression. In very advanced cases, hallucinations and frank psychosis can occur. Some people experience headaches, balance issues, and vision problems. Skin One of the more obvious signs of HIV/AIDS can be seen on the skin. A weakened immune response leaves you more vulnerable to viruses like herpes. Herpes can cause you to develop sores around your mouth or genitals. People with HIV are at increased risk of shingles, which is caused by herpes zoster, the virus that gives you chickenpox. Symptoms of shingles include a painful rash, often with blisters. A viral skin infection called molluscum contagiosum involves an outbreak of bumps on the skin.

Another condition is called prurigo nodularis. It causes crusted lumps on the skin, as well as severe itching. HIV directly attacks your immune system. As the virus reproduces and replaces healthy cells, you become more vulnerable to disease and infection. Read more. Fever, chills, night sweats, and other flu-like symptoms are often early signs of HIV. Read more. Common symptoms of HIV include headache, muscle aches, joint pain, and sore throat. Read more. Swollen glands (lymph nodes) could mean that your body is trying to fight off an infection. Read more. Ulcers around the mouth could be the result of an infection such as herpes. Read more. Fatigue is a very common symptom of an immune system under attack. Read more. HIV makes it hard to fight off respiratory problems like the common cold, the flu, and pneumonia. Read more. A chronic cough — especially if it contains blood or phlegm and is accompanied by chest pain — may be a sign of TB or other serious pulmonary infections. Read more. Pulmonary arterial hypertension is a type of high blood pressure affecting the arteries that supply your lungs. Read more.

High blood pressure from PAH can lead to congestive heart failure. Read more. If you’re HIV-positive, you might experience inflammation of the tongue. You may also develop lesions or a white film on your tongue. Read more. A number of infectious agents can lead to diarrhea. If you have HIV, diarrhea may be more severe or become chronic. Read more. A condition called HIV-associated nephropathy can cause inflammation in the kidneys. Read more. Problems affecting the mouth, tongue, and esophagus can make it difficult to eat, which can result in weight loss. Read more. Pain and weakness may be due to nerve damage. Read more. Cognitive function may be impaired, and as HIV advances, there’s a greater risk of dementia. Read more. HIV increases the risk of inflammation of the brain and spinal cord, including toxoplasma encephalitis. Read more. Complications of HIV/AIDS include feelings of anxiety and depression. Read more. Balance and coordination problems are among the neurological symptoms of HIV/AIDS. Read more. Inflammation in the brain can cause seizures. Read more. Infections like herpes are harder to fight off when your immune system is weak.

Sores on the skin, mouth, and genitals may occur. Read more. People with HIV are more susceptible to shingles, which is caused by the same virus responsible for chicken pox. Read more. A variety of viral skin infections can cause lumps, bumps, and irritated skin. Read more. Itchiness is a common symptom of some of the skin-related disorders associated with HIV. Read more. 1 How the Ebola Virus Affects the Human Body: Learn the Symptoms of Ebola How the Ebola Virus Affects the Human Body written by: Rafael•edited by: Paul Arnold •updated: 10/8/2014 The Ebola virus is a member of the Filoviridae family of RNA viruses. It causes an often fatal disease in humans called Ebola hemorrhagic fever. slide 1 of 6 Ebola Virus The recent outbreak of the ebola virus has turned national attention on this deadly disease. Named after the Ebola River in Africa, Ebola hemorrhagic fever (Ebola HF) affects humans and primates and has emerged sporadically since its first appearance in 1976.

The virus appears to be native to the African continent (it has appeared in the Democratic Republic of Congo, Gabon, Sudan, the Ivory Coast, and Uganda). Its natural host is not known nor is its mechanism for survival in nature. slide 2 of 6 How Is the Ebola Virus Transmitted? Since the natural reservoir of the virus is not known, the way the virus is transmitted to the first patient is not known. However, once one person is infected, the virus can be transmitted in several ways. One way is through direct contact with the blood and/or secretions of an infected person. Thus, family members and friends are prone to get infected. Another route for the virus transmission is within the healthcare facility. Healthcare workers (doctors, nurses) can become infected when they are in contact with needles used on patients. If appropriate protective measures are not taken (use of mask, gowns, etc.), healthcare personnel can be easily infected. The disease can also be passed from primates to humans. slide 3 of 6 How the Ebola Virus Affects the Human Body The Ebola virus infection is systemic, meaning that it attacks every organ and tissue of the human body except the bones and skeletal muscles.

Ebola HF is marked by blood clotting and hemorrhaging. Although it is not known exactly how the virus particles attack cells, it is postulated that one factor that allows them to do so is that they release proteins that dampen down the immune system response. The Ebola virus attacks connective tissue multiplying rapidly in collagen. Collagen is the tissue that helps to keep the organs in place. The tissue is basically digested by this virus. The virus causes small blood clots to form in the bloodstream of the patient; the blood thickens and the blood flow slows down. Blood clots get stuck into blood vessels forming red spots on the patient skin. These grow in size as the disease progress. Also, blood clots does not allow a proper blood supply to many organs such as the liver, brain, lungs, kidneys, intestines, breast tissue, testicles, etc. Spontaneous bleeding then occurs from body orifices and gaps in the skin, such as needle puncture marks and rips that can suddenly appear. Death is caused by huge loss of blood, renal failure, or shock. slide 4 of 6 What Are the Symptoms of Virus Ebola?

The first symptoms of Ebola virus infection are a sudden increase in body temperature, strong headaches, and joint and muscle pain. Diarrhea, vomiting, and stomach pain usually follow with internal and external bleeding in many cases. Bleeding can occur from the eyes, nose, and tongue. slide 5 of 6 Is There a Cure for the Ebola Virus? Unfortunately there is no cure for this disease. Survival is very low. Research is geared towards creating a vaccine. However, at present time there is no available vaccine for this virus. The American citizens most recently affected have been treated with an experimental new drug, and have been shown to be recovering. This gives us hope for a definitive cure in the future. slide 6 of 6 Sources: Gear H S. 1989. Clinical aspects of African viral hemorrhagic fevers. Reviews of Infectious Diseases. 11(suppl 4): 5777-5782 Peters, C J and LeDuc, JW , eds. 1999. Ebola: the virus and the disease. J infect Dis . 179(suppl 1): ix-xvi.

20 amazing facts about the human body | Science | The Guardian The Observer 20 amazing facts about the human body Many of the most exciting discoveries in all fields of science are being played out in the human body From DNA to the atoms inside us, the human body is a scientific marvel. Photograph: David Smith/Alamy Brian Clegg Saturday 26 January 2013 19.04 EST First published on Saturday 26 January 2013 19.04 EST 1 APPENDIX TO LIFE body appendix Photograph: Corbis The appendix gets a bad press. It is usually treated as a body part that lost its function millions of years ago. All it seems to do is occasionally get infected and cause appendicitis. Yet recently it has been discovered that the appendix is very useful to the bacteria that help your digestive system function. They use it to get respite from the strain of the frenzied activity of the gut, somewhere to breed and help keep the gut's bacterial inhabitants topped up. So treat your appendix with respect. 2 SUPERSIZED MOLECULES Practically everything we experience is made up of molecules.

These vary in size from simple pairs of atoms, like an oxygen molecule, to complex organic structures. But the biggest molecule in nature resides in your body. It is chromosome 1. A normal human cell has 23 pairs of chromosomes in its nucleus, each a single, very long, molecule of DNA. Chromosome 1 is the biggest, containing around 10bn atoms, to pack in the amount of information that is encoded in the molecule. 3 ATOM COUNT It is hard to grasp just how small the atoms that make up your body are until you take a look at the sheer number of them. An adult is made up of around 7,000,000,000,000,000,000,000,000,000 (7 octillion) atoms. 4 FUR LOSS body chimp Photograph: Alamy It might seem hard to believe, but we have about the same number of hairs on our bodies as a chimpanzee, it's just that our hairs are useless, so fine they are almost invisible. We aren't sure quite why we lost our protective fur.

It has been suggested that it may have been to help early humans sweat more easily, or to make life harder for parasites such as lice and ticks, or even because our ancestors were partly aquatic. But perhaps the most attractive idea is that early humans needed to co-operate more when they moved out of the trees into the savanna. When animals are bred for co-operation, as we once did with wolves to produce dogs, they become more like their infants. In a fascinating 40-year experiment starting in the 1950s, Russian foxes were bred for docility. Over the period, adult foxes become more and more like large cubs, spending more time playing, and developing drooping ears, floppy tails and patterned coats. Humans similarly have some characteristics of infantile apes – large heads, small mouths and, significantly here, finer body hair. 5 GOOSEBUMP EVOLUTION body goosebumps Photograph: Alamy Goosepimples are a remnant of our evolutionary predecessors. They occur when tiny muscles around the base of each hair tense, pulling the hair more erect. With a decent covering of fur, this would fluff up the coat, getting more air into it, making it a better insulator.

But with a human's thin body hair, it just makes our skin look strange. Similarly we get the bristling feeling of our hair standing on end when we are scared or experience an emotive memory. Many mammals fluff up their fur when threatened, to look bigger and so more dangerous. Humans used to have a similar defensive fluffing up of their body hairs, but once again, the effect is now ruined. We still feel the sensation of hairs standing on end, but gain no visual bulk. 6 SPACE TRAUMA body astronaut Photograph: Alamy If sci-fi movies were to be believed, terrible things would happen if your body were pushed from a spaceship without a suit. But it's mostly fiction. There would be some discomfort as the air inside the body expanded, but nothing like the exploding body parts Hollywood loves. Although liquids do boil in a vacuum, your blood is kept under pressure by your circulatory system and would be just fine. And although space is very cold, you would not lose heat particularly quickly. As Thermos flasks demonstrate, a vacuum is a great insulator. In practice, the thing that will kill you in space is simply the lack of air.

In 1965 a test subject's suit sprang a leak in a Nasa vacuum chamber. The victim, who survived, remained conscious for around 14 seconds. The exact survival limit isn't known, but would probably be one to two minutes. 7 ATOMIC COLLAPSE The atoms that make up your body are mostly empty space, so despite there being so many of them, without that space you would compress into a tiny volume. The nucleus that makes up the vast bulk of the matter in an atom is so much smaller than the whole structure that it is comparable to the size of a fly in a cathedral. If you lost all your empty atomic space, your body would fit into a cube less than 1/500th of a centimetre on each side. Neutron stars are made up of matter that has undergone exactly this kind of compression. In a single cubic centimetre of neutron star material there are around 100m tons of matter. An entire neutron star, heavier than our sun, occupies a sphere that is roughly the size across of the Isle of Wight. 8 ELECTROMAGNETIC REPULSION The atoms that make up matter never touch each other.

The closer they get, the more repulsion there is between the electrical charges on their component parts. It's like trying to bring two intensely powerful magnets together, north pole to north pole. This even applies when objects appear to be in contact. When you sit on a chair, you don't touch it. You float a tiny distance above, suspended by the repulsion between atoms. This electromagnetic force is vastly stronger than the force of gravity – around a billion billion billion billion times stronger. You can demonstrate the relative strength by holding a fridge magnet near a fridge and letting go. The electromagnetic force from the tiny magnet overwhelms the gravitational attraction of the whole Earth. 9 STARDUST TO STARDUST body atoms Photograph: Alamy Every atom in your body is billions of years old. Hydrogen, the most common element in the universe and a major feature of your body, was produced in the big bang 13.7bn years ago. Heavier atoms such as carbon and oxygen were forged in stars between 7bn and 12bn years ago, and blasted across space when the stars exploded. Some of these explosions were so powerful that they also produced the elements heavier than iron, which stars can't construct.

This means that the components of your body are truly ancient: you are stardust. 10 THE QUANTUM BODY One of the mysteries of science is how something as apparently solid and straightforward as your body can be made of strangely behaving quantum particles such as atoms and their constituents. If you ask most people to draw a picture of one of the atoms in their bodies, they will produce something like a miniature solar system, with a nucleus as the sun and electrons whizzing round like planets. This was, indeed, an early model of the atom, but it was realised that such atoms would collapse in an instant. This is because electrons have an electrical charge and accelerating a charged particle, which is necessary to keep it in orbit, would make it give off energy in the form of light, leaving the electron spiralling into the nucleus. In reality, electrons are confined to specific orbits, as if they ran on rails. They can't exist anywhere between these orbits but have to make a "quantum leap" from one to another. What's more, as quantum particles, electrons exist as a collection of probabilities rather than at specific locations, so a better picture is to show the electrons as a set of fuzzy shells around the nucleus.

11 RED BLOODED body blood cells Photograph: Alamy When you see blood oozing from a cut in your finger, you might assume that it is red because of the iron in it, rather as rust has a reddish hue. But the presence of the iron is a coincidence. The red colour arises because the iron is bound in a ring of atoms in haemoglobin called porphyrin and it's the shape of this structure that produces the colour. Just how red your haemoglobin is depends on whether there is oxygen bound to it. When there is oxygen present, it changes the shape of the porphyrin, giving the red blood cells a more vivid shade. 12 GOING VIRAL body dna Photograph: Getty Surprisingly, not all the useful DNA in your chromosomes comes from your evolutionary ancestors – some of it was borrowed from elsewhere. Your DNA includes the genes from at least eight retroviruses. These are a kind of virus that makes use of the cell's mechanisms for coding DNA to take over a cell. At some point in human history, these genes became incorporated into human DNA. These viral genes in DNA now perform important functions in human reproduction, yet they are entirely alien to our genetic ancestry.

13 OTHER LIFE On sheer count of cells, there is more bacterial life inside you than human. There are around 10tn of your own cells, but 10 times more bacteria. Many of the bacteria that call you home are friendly in the sense that they don't do any harm. Some are beneficial. In the 1920s, an American engineer investigated whether animals could live without bacteria, hoping that a bacteria-free world would be a healthier one. James "Art" Reyniers made it his life's work to produce environments where animals could be raised bacteria-free. The result was clear. It was possible. But many of Reyniers's animals died and those that survived had to be fed on special food. This is because bacteria in the gut help with digestion. You could exist with no bacteria, but without the help of the enzymes in your gut that bacteria produce, you would need to eat food that is more loaded with nutrients than a typical diet. 14 EYELASH INVADERS body mite Depending on how old you are, it's pretty likely that you have eyelash mites. These tiny creatures live on old skin cells and the natural oil (sebum) produced by human hair follicles.

They are usually harmless, though they can cause an allergic reaction in a minority of people. Eyelash mites typically grow to a third of a millimetre and are near-transparent, so you are unlikely to see them with the naked eye. Put an eyelash hair or eyebrow hair under the microscope, though, and you may find them, as they spend most of their time right at the base of the hair where it meets the skin. Around half the population have them, a proportion that rises as we get older. 15 PHOTON DETECTORS body eye Photograph: Getty Your eyes are very sensitive, able to detect just a few photons of light. If you take a look on a very clear night at the constellation of Andromeda, a little fuzzy patch of light is just visible with the naked eye. If you can make out that tiny blob, you are seeing as far as is humanly possible without technology. Andromeda is the nearest large galaxy to our own Milky Way. But "near" is a relative term in intergalactic space – the Andromeda galaxy is 2.5m light years away. When the photons of light that hit your eye began their journey, there were no human beings.

We were yet to evolve. You are seeing an almost inconceivable distance and looking back in time through 2.5m years. 16 SENSORY TALLY Despite what you've probably been told, you have more than five senses. Here's a simple example. Put your hand a few centimetres away from a hot iron. None of your five senses can tell you the iron will burn you. Yet you can feel that the iron is hot from a distance and won't touch it. This is thanks to an extra sense – the heat sensors in your skin. Similarly we can detect pain or tell if we are upside down. Another quick test. Close your eyes and touch your nose. You aren't using the big five to find it, but instead proprioception. This is the sense that detects where the parts of your body are with respect to each other. It's a meta-sense, combining your brain's knowledge of what your muscles are doing with a feel for the size and shape of your body. Without using your basic five senses, you can still guide a hand unerringly to touch your nose. 17 REAL AGE body ovum Photograph: Getty Just like a chicken, your life started off with an egg.

Not a chunky thing in a shell, but an egg nonetheless. However, there is a significant difference between a human egg and a chicken egg that has a surprising effect on your age. Human eggs are tiny. They are, after all, just a single cell and are typically around 0.2mm across – about the size of a printed full stop. Your egg was formed in your mother – but the surprising thing is that it was formed when she was an embryo. The formation of your egg, and the half of your DNA that came from your mother, could be considered as the very first moment of your existence. And it happened before your mother was born. Say your mother was 30 when she had you, then on your 18th birthday you were arguably over 48 years old. 18 EPIGENETIC INFLUENCE We are used to thinking of genes as being the controlling factor that determines what each of us is like physically, but genes are only a tiny part of our DNA. The other 97% was thought to be junk until recently, but we now realise that epigenetics – the processes that go on outside the genes – also have a major influence on our development.

Some parts act to control "switches" that turn genes on and off, or program the production of other key compounds. For a long time it was a puzzle how around 20,000 genes (far fewer than some breeds of rice) were enough to specify exactly what we were like. The realisation now is that the other 97% of our DNA is equally important. 19 CONSCIOUS ACTION body mri Photograph: Alamy If you are like most people, you will locate your conscious mind roughly behind your eyes, as if there were a little person sitting there, steering the much larger automaton that is your body. You know there isn't really a tiny figure in there, pulling the levers, but your consciousness seems to have an independent existence, telling the rest of your body what to do. In reality, much of the control comes from your unconscious. Some tasks become automatic with practice, so that we no longer need to think about the basic actions. When this happens the process is handled by one of the most primitive parts of the brain, close to the brain stem.

However even a clearly conscious action such as picking up an object seems to have some unconscious precursors, with the brain firing up before you make the decision to act. There is considerable argument over when the conscious mind plays its part, but there is no doubt that we owe a lot more to our unconscious than we often allow. 20 OPTICAL DELUSION The picture of the world we "see" is artificial. Our brains don't produce an image the way a video camera works. Instead, the brain constructs a model of the world from the information provided by modules that measure light and shade, edges, curvature and so on. This makes it simple for the brain to paint out the blind spot, the area of your retina where the optic nerve joins, which has no sensors. It also compensates for the rapid jerky movements of our eyes called saccades, giving a false picture of steady vision. But the downside of this process is that it makes our eyes easy to fool. TV, films and optical illusions work by misleading the brain about what the eye is seeing.

This is also why the moon appears much larger than it is and seems to vary in size: the true optical size of the moon is similar to a hole created by a hole punch held at arm's length. Puckered skin may have helped our ancestors grasp slippery food and keep their footing on treacherous ground Published: 10 Jan 2013 Trip to Mars in pretend spaceship on Moscow industrial estate affects sleep, activity levels and motivation of six-man crew Published: 7 Jan 2013 A stroke left Alan Burgess with hemispatial neglect – an inability to pay attention to sensory stimuli on his left side Published: 23 Nov 2012 Humans reached a peak of intelligence more than 2,000 years ago and it's been downhill ever since, a scientist speculates Published: 12 Nov 2012

Question: Myosis affects which part of the human body?
Answer: Eye