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Only one time in recorded history has the human population ever decreased. A teeny-tiny microscopic villain was the reason for all of the millions of deaths. During the 1300s, the bubonic plague, also known as the Black Plague, swept through Europe killing nearly 30 million people. The plague is caused by bacteria called Yersinia pestis, which is found mainly in rodents and fleas. Humans can catch the disease from rodent or fleabites. Yersinia pestis is a pathogenicorganism. Most pathogens are microorganisms, meaning they can only be seen with the help of a microscope. They include bacteria, viruses, fungi, protozoa, and parasites. In this lesson, you will learn about pathogens.
Right now, you are surrounded by bacteria. They are in the air, on your keyboard, and even inside your body. Bacteria are microscopic unicellular organisms. They are found all over the earth, from the deepest parts of the ocean to the highest mountain peaks. It is impossible to see bacteria with the naked eye. Bacteria cells are so small that hundreds of thousands would fit inside the period at the end of this sentence. This may seem troubling, but most bacteria are not harmful. Many kinds of bacteria living in our bodies actually help prevent disease.
Although bacteria can be helpful, some types are pathogenic. They produce poisons, or toxins, which can cause serious illness, such as pneumonia and tuberculosis. Most toxins are waste produces from growth and reproduction. Most bacteria reproduce by binary fission, in which one cell splits into two identical cells. Reproduction is very rapid. If a bacterium split every 30 minutes, 400 trillion (400,000,000,000,000) bacteria would result in only 24 hours. Click on the image below to see a slide show representing the speed of bacterial reproduction.Reproduction of BacteriaImages courtesy of CDC
In most cases, pathogenic bacteria exist outside the body. They are picked up through contact with infected organisms or contaminated objects. Cholera is a deadly disease caused by Vibrio cholerae. It is most commonly spread through contaminated food and water. These bacteria are called opportunistic because they only cause disease when they have the opportunity to enter the body. For example, bacteria on the skin usually do not cause illness. Cuts or scrapes provide bacteria a chance to enter the bloodstream. Once inside the body, the bacteria multiply and cause infection. Bacterial infections can be treated with antibiotics.
Have you ever had the flu? You probably felt miserable for about a week thanks to the influenza virus. Unlike bacteria, viruses are not true living organisms because they are not made of cells. Viruses are bundles of genetic material enclosed in a protein casing called a capsid. They are unable to reproduce themselves and must rely on a host cell for replication. Viruses are like cell hijackers. They inject their genes into the nucleus of a cell and make it create new viruses. Eventually the buildup of viruses causes the host cell to burst, releasing the new viruses.
Like bacteria, viruses are found just about everywhere on earth. They are able to infect every form of life on the planet, from blades of grass to human. Although viruses cannot survive very long without a host, they can remain inactive on nonliving surfaces such as countertops and doorknobs. Once picked up by a living host, the virus becomes active. Viruses can be contracted through air, water, bodily fluids, and direct contact. Unlike bacterial infections, many viral infections cause no symptoms. Often, people do not even know they are infected. Viral infections cannot be treated with antibiotics. Examples of viral infections include chickenpox, polio, and influenza.
Have you ever heard of malaria? It is a life-threatening disease spread by mosquitos in hot and tropical locations. Although mosquitos are responsible for spreading the disease, they do not cause it. Malaria is caused by tiny protozoa which live inside the mosquito. When a mosquito bites you, it transfers the organism into your blood stream. Protozoa are unicellular organisms belonging to the Protista kingdom. Protozoa are larger than viruses and bacteria, however, most are invisible to the naked eye. Pathogenic protozoa are usually parasites. They must be on or in a host in order to survive. Parasitic protozoa are mainly found in water or other fluids. Diseases are spread through unsanitary conditions, such as unsafe drinking water, contaminated bathing water, lack of sanitation facilities, and an abundance of insects.
Fungi can be multicellular or unicellular. Although they often look like plants, fungi do not have chlorophyll or true roots. They cannot perform photosynthesis and must rely on other organisms for food. Some fungi are parasites, while others aresaprophytes. Fungi include mushrooms, molds, and yeasts. Like bacteria, many fungi species are harmless. Some are even beneficial. The antibiotic penicillin is made from the penicillium mold.Pathogenic fungi are most commonly found in soil, unpasteurized milk, animal waste, and damp environments. Most fungal infections affect plants, however, many fungi can cause diseases in humans and other animals. In general, fungal infections develop more slowly, recur more frequently, and take longer to treat than bacterial infections. They are typically spread by spores that enter the body through inhalation or cuts in the skin. Fungal infections include athlete's foot and ringworm.
Bacterial infections are caused by _____.
Protozoan diseases are usually spread through _____.
Imagine you are the ruler of a kingdom. Your castle is being attacked by bandits in search of treasure. As the bandits advance on your castle, they meet by your first line of defense - the moat. The bandits are slowed by the moat, but not stopped. When they reach your castle wall, you give the order for your soldiers to attack. Some soldiers are lookouts who identify and point out the bandits. Other soldiers are sharpshooters who target and destroy the bandits. Eventually your soldiers win and the bandits retreat. You are safe from invasion.
The body's immune system is like a castle defending against invading pathogens. Your body has surface barriers that act as a first line of defense. It also has special cells that identify and flag pathogens, as well as cells that destroy them. In this lesson, you will learn how the immune system protects the body against disease.
The first line of defense against infection are surface barriers that keep pathogens from entering the body. In plants, the waxy cuticle is a surface barrier against pathogens. In humans and other animals, the main surface barrier is skin. Healthy, undamaged skin covers and protects the body. It secretes acidic chemicals that can destroy harmful microorganisms, keeping them out of the body. Hair and nails are special types of skin that help protect the body. Hair in your nose traps foreign material before it can enter the lungs. Similarly, eyelashes protect the eye from harmful airborne materials such as dust and mold. Together, skin, hair, and nails make up the intergumentary system.
Skin is an effective surface barrier, but it cannot cover the body entirely. If it did, you would not have a mouth, eyes, or any other body openings. Mucous membranes are another type of surface barrier that pick up where skin leaves off. Openings in the body are lined with special tissues that secrete mucus. The mucus helps trap foreign substances before they completely enter the body. The inside lining of your nose is an example of a mucous membrane.
When surface barriers fail and pathogens invade the body, the immune system kicks in. The immune system is a collection of proteins, cells, tissues, and organs that defend the body against pathogens. The cells of the immune system are calledleukocytes, or white blood cells. Leukocytes are produced and stored in many locations throughout the body, including the thymus, spleen, and bone marrow. Special clumps of tissue called lymph nodes also store white blood cells. When you are sick, your doctor may feel for swollen lymph nodes in your throat. Enlarged lymph nodes usually mean your body is creating many white blood cells to fight an infection.There are two types of white blood cells - macrophages and lymphocytes. Macrophages can pass through blood vessels and travel through tissues to the location of an infection. Once at the infection site, macrophages surround, ingest, and destroy the pathogens by phagocytosis. Macrophages die along with the pathogens they eat. Their death often causes the formation of a whitish-yellow substance called pus.
Lymphocytes identify foreign intruders and produce special proteins called antibodies. The surfaces of invading organisms have proteins called antigens. Antibodies lock onto antigens, neutralize their toxins, and flag them for destruction. Antibodies are highly specific. They fit into certain antigens like a key into a lock, but are harmless to other antigens. For example, the antibodies that fight chicken pox are useless against polio. Antibodies can take anywhere from a few days to many months to develop. Once produced, however, they continue to exist in the body. If the same antigen invades the body again, the antibodies are already there to destroy them. This is why certain diseases, like chicken pox, are only contracted once.
Protection against disease is called immunity. There are three types of immunity - innate, adaptive, and passive. Innate, or natural immunity, is a general type of protection our bodies are born with. Humans do not contract most animal or plant diseases because of natural immunity. The intergumentary system and the immune system are part of the body's innate immunity.
Adaptive, or active, immunity develops when antibodies are produced by lymphocytes. Antibodies can be produced from an actual infection or through immunization. Immunization involves exposing the body to an antigen in a weakened form. The exposure causes the immune system to manufacture specific antibodies. The end result is the same as if the body had contracted the disease naturally. When you get shots at the doctor's office, you are being immunized against certain diseases. Unfortunately, active immunity is not as powerful as natural immunity. Immunizations are not always 100 percent effective. Some people who are immunized against a disease will still contract it. Passive immunity is a temporary protection gained from another source. Breastfeeding, for example, transfers a passive immunity from mother to child. This immunity ends once breastfeeding stops.
Which of the following is a surface barrier to infection?
Have you ever caught a cold from a friend or family member? Maybe you have given a cold to someone else. The flu and common cold are communicable diseases, which means they can be spread from one individual to another. They are also called contagious, or infectious, diseases. Some communicable diseases, such as the flu, are not usually life threatening.Others, such as malaria, can cause serious illness and death. According to health officials, communicable disease is the leading cause of illness and death worldwide. In this lesson, you will learn about the transmission and prevention of communicable diseases.
Has anyone ever told you to cover your nose when you sneeze? It's good advice. Respiratory diseases, such as the flu, are usually transmitted by water droplets in the air. Sneezing, coughing, and talking release infected water droplets into the air. If these droplets are inhaled, they can cause infection. This type of spreading is called air-borne transmission. Gastrointestinal diseases, such as cholera, are usually transmitted through contaminated food and water. Sexually transmitted diseases, such as syphilis, are contracted through contact with bodily fluids including saliva, urine, and blood. Diseases spread through blood are sometimes called blood-borne diseases. Communicable disease can also be spread by nonliving objects, such as coins or doorknobs.
Sometimes, communicable diseases are spread by vectors. A vector is an organism that carries a disease, but is not harmed by it. For example, a fly landing on animal feces contaminates its legs with bacteria. If the fly then lands on food, it will transfer the bacteria from its legs to the food. The infectious agents do not harm the fly, but can cause the person who eats the food to become sick. Some vectors carry diseases inside their bodies and spread it through bites. Malaria is a serious disease spread by mosquito bites.
Good hygiene, safe behaviors, and immunization are the best ways to prevent communicable diseases. Hands should be washed after using the bathroom, sneezing, coughing, and caring for a sick person. It is also important to also wash hands before preparing or eating food. Blood-borne and sexually transmitted diseases are best prevented by practicing safe behaviors. Other illnesses, such as the flu and chicken pox, can be avoided through immunization and vaccination.
Did you catch a cold or the flu this year? Each year, approximately 20 percent of the United States population catches influenza. Influenza, commonly called the flu, is a contagious respiratory illness caused by influenza viruses. In most cases, symptoms are mild, but many people are hospitalized each year from flu complications. Children, the elderly, and individuals with other health conditions are at the highest risk for developing flu complications.
Fever, headache, fatigue, cough, congestion, and sore throat are the most common symptoms of the flu. Nausea, vomiting, and diarrhea can also occur. Pneumonia, ear infections, sinus infections, and dehydration are the most common complications. Since it is a respiratory illness, the flu is spread mainly through coughing, sneezing, and direct contact with other sick people. Antiviral medication can be prescribed, but the best treatment for the flu is getting plenty of rest and drinking fluids. Over-the-counter medications for headache and congestion can also be taken.
The common cold and the flu are often confused. Although both are respiratory illnesses, they are caused by different viruses. There are over 200 different viruses that can cause colds, which means there are no effective vaccinations against the illness. The most common pathogen is the rhinovirus. Symptoms of a cold are very similar to those if the flu. In general, colds are milder than the flu and do not cause serious complications. Like the flu, colds are spread through physical contact, coughing, and sneezing. Prevention and treatment for the cold are the same as for the flu.
Have you ever had chickenpox? This communicable disease is caused by the varicella-zoster virus (VZV). Chickenpox is spread by direct contact or through the air from an infected person's coughing or sneezing. The most characteristic symptom is a blister-like rash, which begins on the trunk and face, then spreads to the rest of the body. Fever and fatigue are also common symptoms. Most cases of chickenpox occur in children, but adults can contract the disease, too. Before the introduction of the chickenpox vaccine, almost four million people in the United States contracted the disease each year. Today, children are routinely immunized for chickenpox during their first year of life. The vaccine is about 80% effective in preventing mild infection, and over 95% effective in preventing severe infection.
Taylor forgets cover her nose when she sneezes. Which of the following diseases could she spread to others?
Which of the following statements is true?
Marina was immunized against chicken pox when she was young. Which of the following statements is true?
Do you know anyone who has diabetes? How about someone with cancer? Perhaps you have an elderly relative with arthritis. Cancer, diabetes and arthritis are chronic diseases. More than 90 million Americans live with a chronic disease.Each year, over 1.4 trillion dollars is spent caring for people with chronic diseases. This represents more than 75 percent of total medical care costs in the United States. In this lesson, you will learn about the causes and prevention of chronic diseases.
Chronic diseases are the leading causes of death and disability worldwide. They cause almost 60 percent of deaths each year. A chronic disease is an illness that lasts three or more months. Most cannot be prevented by vaccination or cured by medication. Unlike some communicable diseases like the common cold, chronic diseases do not go away with time. Sick individuals must live with the illness for life.
Generally, chronic diseases are noncommunicable, which means they cannot be spread from one person to another. The leading chronic diseases are cardiovascular disease, diabetes, and cancer. The three primary risk factors for developing a chronic disease are an unhealthy diet, physical inactivity, and use of tobacco. Adopting a healthy lifestyle is the best way to avoid developing most chronic diseases.
Coronary heart disease is caused by reduced blood flow to the heart. Overtime, fatty deposits build up in the arteries of the heart. The arteries become narrower and blood flow is reduced. Eventually, the arteries become completely blocked, and blood cannot reach the heart. Imagine arteries as a busy highway. Fatty deposits are like construction zones on the highway. They force traffic to merge into fewer lanes, causing a general slow-down. Eventually, traffic stops and a heart attack occurs. Most people do not know they have coronary heart disease until they experience chest pain or have a heart attack. The symptoms of a heart attack are chest pain, weakness, sweating, and nausea.
Coronary heart disease can be treated with medication or surgery. Chest pain caused by a narrowing of the arteries can be relieved by taking special medication that widen blood vessels, allowing blood to flow more efficiently. Surgical procedures, such as bypass surgery and angioplasty, can also improve blood flow. The best way to prevent coronary heart disease is to eat healthy foods, exercise regularly, and avoid smoking. Eating foods that are high in vitamins and minerals will help prevent the unhealthy build up of fat in the walls of main arteries. Avoidance of tobacco and regular exercises also keeps the heart strong.
Imagine a car with a faulty engine which cannot effectively change the gas into energy. Over time, gas builds up in the engine and causes a variety of mechanical problems. A person with diabetes is similar to a car with an ineffective engine. When your body eats food, a special hormone called insulin helps change glucose (sugar) into energy. Diabetics have a shortage of insulin or a decreased ability to use it. When diabetes is uncontrolled, glucose builds up in the blood. High glucose levels can cause heart disease, stroke, blindness, kidney failure, and death.
Diabetes is the third most common chronic disease among American adults. One in five adults over the age of 65 has the disease. There are two main types of diabetes. Type 1 is most common in children and is thought to be hereditary, meaning it is inherited from parents. Type 2, also called adult-onset diabetes, is caused by obesity and lack of physical activity. This type of diabetes is not hereditary. Over 90 percent of diabetes cases are Type 2.
Symptoms of diabetes include excessive thirst and urination. The disease is diagnosed through blood tests. Type 1 diabetes is mainly treated with regular insulin injections. Type 2 diabetes is treated with a strict diet and exercise routine. Like cardiovascular disease, Type 2 diabetes can be prevented by maintaining a healthy lifestyle. Inactivity combined with a high fat, high sugar diet is a leading cause of Type 2 diabetes. Eating nutritious food and exercising regularly helps keep glucose levels in check.
Have you ever been in line at an amusement park or movie theater? When people behave and follow the rules, the line moves in an orderly fashion. But when someone in the back starts pushing, the line breaks down and becomes chaotic. Under normal circumstances, cells in the body divide and grow in an orderly manner. Sometimes, this process is disrupted and cell division becomes harmful. Cancer is characterized by the rapid, unrestrained growth of abnormal cells in the body. Over time, the abnormal cells grow beyond their normal boundaries and invade body organs.
Nearly 13 percent of all deaths worldwide are caused by cancer. Since it affects cell growth and division, cancer can attack any part of the body. There are many different types of cancer, from skin cancer to stomach cancer. Sometimes, cancer cells enter the blood stream or lymphatic vessles inside body tissue. The harmful cells use the blood and lymph to spread to other areas of the body. The spread of cancer is called metastasis. Cancer symptoms usually depend on the type of cancer and the organs involved. The most common warning signs are unexplained weight loss, frequent headaches, and the presence of lumps in body.
Cancer develops when changes happen to the genes responsible for cell growth and repair. These changes can be caused by genes or external agents called carcinogens. Carcinogens can be physical, chemical, or biological. Ultraviolet (UV) radiation from sunlight is an example of a physical carcinogen. Tobacco is an example of a chemical carcinogen. Biological carcinogens include viruses, such as human papiloma virus (HPV), and bacteria. Cancers caused by genes are inherited from parents and are not preventable. Those caused by carcinogens may be prevented by living a healthy lifestyle. Health officials estimate that almost 40 percent of cancers can be prevented by a healthy diet, physical activity, and avoidance of tobacco. In fact, tobacco use is the single most preventable cause of cancer in the world.
Treatment for cancer usually involves surgery and some form of radiation therapy or chemotherapy. Radiation therapy tries to destroy abnormal cells by directing radioactive rays through the patient's skin to the diseased tissue. Chemotherapy seeks to destroy abnormal cells by injecting anticancer drugs directly into the affected tissue. However, since chemotherapy also destroys normal cells, it can cause painful side effects.
Coronary heart disease is caused by:
Cardiovascular disease _____.
The leading preventable cause of cancer is _____.
Have you ever gotten into an argument with a friend? It probably started out as a disagreement, but then grew more and more heated. Before you knew it, you and your friend were both yelling. The disagreement had degenerated into a fight. When something degenerates, it gets worse over time. A light summer shower can degenerate into a howling thunderstorm. An orderly line can degenerate into a chaotic crowd. Many diseases can cause the body to degenerate. As the disease progresses, symptoms become worse. In this lesson, you will learn about degenerative diseases.
A degenerative disease is an illness that causes a progressive decline in health. In other words, the disease get worse over time. Degenerative diseases are usually noncommunicable, which means they cannot be spread from one person to another. Many degenerative diseases destroy motor neurons. The motor neurons control important muscle activity such as speaking, walking, breathing, and swallowing. Over time, the ability to control voluntary muscles can be completely lost. Other degenerative diseases attack joints, bones, brain neurons, and body organs. Most degenerative diseases have no cures, limited treatments, and little preventions.
Sometimes, the line between chronic and degenerative diseases is blurred. Cancer, for example, is considered a chronic condition because it lasts for longer than three months. There are preventative measures to avoid the disease and several treatments. Often the disease goes into remission and the patient is healthy again. However, when treatments fail, and the patient continues to worsen, cancer is considered degenerative.
Imagine misplacing your homework, forgetting how to tie your shoes, and getting lost on your way to school. Now imagine it happening every day for the rest of your life. Alzheimer's disease is a degenerative illness in which nerve cells in the brain die. Over time, the loss of nerve cells causes dementia, a brain disorder that affects memory, thought, and language. At first, symptoms of Alzheimer's disease are mild and easy to overlook, such as forgetfulness. As the disease progresses, symptoms worsen. People with Alzheimer's disease may have difficulty remembering recent events, the names of familiar people, or how to perform simple tasks like brushing teeth. They often have trouble speaking, reading, or writing. They may become aggressive, confused, or anxious. Eventually, the patient requires complete care.
About four million Americans suffer from Alzheimer's disease. It is most common in people over 65. The causes are not completely understood, but scientists believe genetics may play a role. Age is the most important risk factor. The number of people with the disease doubles every 5 years beyond age 65. High blood pressure, high cholesterol, and head injuries may also be factors. Currently, there is no cure for Alzheimer's disease. Certain medications may lessen or slow symptoms, but they cannot stop the progression of the disease. Recent research indicates that exercise, a healthy diet, and brain activity, such as crossword puzzles, may help delay development of Alzheimer's disease.
Like Alzheimer's disease, Amyotrophic lateral sclerosis (ALS) is a degenerative nerve disease. Instead of attacking brain neurons, ALS affects motor neurons that run from the brain to the spinal cord and from the spinal cord to muscles. ALS causes motor neurons to shrivel, which makes muscles atrophy. As the disease progresses, the brain loses control of muscle movement. Early symptoms of ALS usually include muscle weakness, clumsiness, slurred speech, and difficulty swallowing or breathing. Over time, symptoms worsen and total paralysis occurs.
Scientists are still uncertain about the cause of ALS. Research suggests that about 10 percent of cases are inherited. The remaining 90 percent of ALS cases have no clear causes or risk factors. Currently, there is no cure for ALS. Medication may slow the progression of the disease, but most treatments simply lessen symptoms. Health officials estimate that as many as 30,000 Americans are living with ALS. In the United States, ALS is often called Lou Gehrig's disease, after Hall of Fame baseball player Lou Gehrig, who died of the disease in 1941.
You may already know a little about Parkinson's disease thanks to the education efforts of celebrities such as Muhammad Ali and Michael J. Fox. Today, the general public is more informed about this degenerative condition which attacks the neurons in the part of the brain controlling muscle movement. The disease usually develops in people over 60, but it can strike at much younger ages. Like Alzheimer's, early symptoms are generally mild and may go unnoticed. Lack of energy, depression, and slight muscle tremors are common in the early stages of the disease. Later symptoms include muscle stiffness, poor balance, difficulty speaking, increased muscle tremors, and dementia.
Parkinson's disease can affect both young and older people. Age is the main risk factor, but scientists believe that genetics and environmental factors also play a role. Exposure to toxins, such as pesticides, can increase the chance of developing the disease. Having one or more close relatives with Parkinson's disease also increases the odds. Although no cures exist, certain medications can manage muscle tremors and improve motion. Physical therapy, a healthy diet, and exercise can also help lessen symptoms. In some instances, surgical brain implants are used to stimulate neuron activity in the brain. Surgery is not as common as in the past, however, it is still used when medication fails.
Genetics may play a role in the development of _____.
What do you know about the person whose face is honored on the dime? Franklin D. Roosevelt was an important American president. In 1921, before his presidency, Roosevelt contracted polio. Roosevelt was eventually paralyzed by polio, and spent the remainder of his life in a wheelchair. Polio is a communicable disease that can cause paralysis and death. After Roosevelt became president, a close friend of his began coordinating annual fundraising birthday parties. The money raised was used to fund programs for polio prevention and treatment. Today, children receive vaccinations against polio. As a result, the number of cases worldwide has dropped to only a few hundred each year. In this lesson, you will learn about the importance of vaccination.
Most people have probably heard of smallpox, a highly contagious, and sometimes fatal, disease. Smallpox is caused by the variola virus. Symptoms include high fever, painful sores, and fatigue. Recently, smallpox has received a lot of attention because of the threat of biological warfare, but the disease has been around for over three thousand years. During the1700s, a technique called variolation was used to protect people from smallpox infection. Dried smallpox scabs were blown into the nose of a patient who would then contract a mild case of the disease. Once recovered, the individual was immune to smallpox. The technique was effective, but risky. Many patients died from the procedure.
The next time you have a shot at the doctor's office, you can thank Edward Jenner. The safety of Jenner's method resulted in the end of variolation. His technique became known as vaccination. The term comes from the Latin word vacca, meaning cow. Today, vaccination is the most successful protection against diseases caused by viruses. According to health officials, vaccination prevents over two million deaths worldwide each year.
Vaccination works in one of two ways. In most cases, a weakened or inactive form of a virus is injected under the skin. Since the virus is in a weakened form, few to no symptoms occur. The immune system responds by producing specific antibodies for the virus. These antibodies remain in the body, providing immunity to future exposures to the virus. The flu shot is an example of this type of vaccination. In some instances, antibodies from donated blood are injected under the skin. These antibodies provide protection for many diseases, such as German measles, mumps, and hepatitis.
The immunity provided by vaccination is artificial. It is not as effective as natural immunity. Most artificial immunizations must be re-administered on a regular basis. Some vaccinations last for years, while other must be given much more frequently. Immunization is performed in one of two ways. Usually, immunization follows a "herd" strategy, in that a large majority of a population is vaccinated. This strategy assumes that even if some individuals become sick, the probability of transmission to other unprotected individuals is low. In some instances, only individuals most likely to contract the disease are vaccinated. This method is used for certain diseases that have been eliminated in the United States, but still exist in other countries. Currently, yellow fever vaccinations are required for United States citizens traveling to Africa.
Have you ever had mumps? What about measles or whooping cough? Most children in the United States do not contract these illnesses because of routine vaccinations. In this country, children are vaccinated on a regular schedule for thirteen diseases, including measles, mumps, polio, and chickenpox. At one time, these diseases were a serious threat to the health of children. Successful immunization programs have reduced the threat of these diseases to their lowest levels in history. Currently, there are nine routinely administered vaccinations. The vaccines for diphtheria, tetanus and pertussis (whooping cough) are given all at once in a DTaP shot. Sometimes, vaccination can cause mild reaction, such as soreness or fever. Serious allergies are rare.
Health officials recommend following an immunization schedule for children from birth until 18 years of age. Vaccines are listed under the recommended age(s) for immunization. Any dose not given at the recommended age should be given as a "catch-up" immunization. Most vaccines are 90 to 100 percent effective at preventing disease. Medical research continues to improve the safety and effectiveness of current vaccines. Advances are also being made in other areas, such as the development of needle-free vaccinations.
Vaccination works by _____.
At which age do health officials recommend vaccinations begin?
Which of the following statements is true?
Do you or someone you know wear glasses? Before the invention of contact lenses, glasses were the only choice you would have to correct poor vision. Today, people with poor vision can choose between glasses, contact lenses, and laser vision correction. Medical advances have been made throughout history. In recent years, these advances have been closely tied with technology. Computers, cameras, and robots are the wave of the future in medicine. In this lesson, you will learn about current medical technology and cutting edge medical advances.
Imagine digging a hole in your backyard to plant a tree and discovering an ancient dinosaur fossil. Often in science, discoveries are made by accident. In 1895, a German scientist named Wilhelm Conrad Röentgen accidentally discovered X-rays during an experiment with electrons.Today, X-rays are invaluable medical procedures. They are used to view bones and teeth, locate foreign objects in the body, and even see internal body damage. Bones and teeth are more dense than skin. They absorb more X-rays and show up more clearly on X-ray film. Metal is even more dense than bone or teeth. Foreign metal objects inside the body will show up even more clearly than bones on an X-ray. Differences in tissue density also makes some organs appear darker than others on X-ray film. In a chest X-ray, for example, the lungs, heart, aorta, and bones are clearly visible. Specially trained doctors can use chest X-rays to diagnose pneumonia, asthma, heart problems, and cancer.
Sometimes, several X-rays are combined using a computer to create a detailed image. This type of procedure is called a CAT or CT scan. During a CAT scan, the patient lies inside a large X-ray machine. The machine takes several X-ray images and sends them to a computer. The computer processes the images and creates an image of the body. The computer can even combine images to create a three-dimensional picture. CAT scans are most often used to view internal damage caused by serious injury. They are also used to diagnose brain injury, tumors, and infections.
Have you ever used a scanner to make a digital copy of a photograph? Magnetic resonance imaging (MRI) is similar to a giant scanner. It uses radio waves and magnetic fields to create a picture of internal organs and tissues. During an MRI, the patient lies on a movable bed inserted into a tube-like scanner. The tube is surrounded by a large magnet. The powerful magnetism causes protons in the body to send out radio signals, which are picked up by the MRI scanner. The information is sent to a computer that makes a detailed picture of organs and tissue in the body. Unlike CAT scans, MRIs do not use X-rays. The clarity of MRI images allows doctors to see bleeding or swelling in the brain, blockages in the heart, and tears in tissue. MRIs are also used to diagnose sports-related injuries, joint problems, and spinal cord damage.
For years, doctors have used special cameras called endoscopes to view internal body structures. An endoscope is a small camera attached to a long, thin, flexible tube. The tube can be inserted into various places in the body, such as the mouth or anus. Tiny cuts can also be made to create openings into joints and other organs. Recent advances in technology have created cameras small enough to be easily swallowed. The "camera pills" can take over 50,000 images of a patient's digestive tract. Images are sent by radio signal to a recording device worn by the patient. After eight to ten hours, the recording device is returned to the doctor, who transfers the images to a computer. The pill itself is painlessly passed out of the body as waste. Images can be used to diagnose a variety of health issues, from Celiac's disease to tumors.
What's the smallest unit of measurement you can think of? A millimeter? Think even smaller. How about a micrometer? At one millionth a meter, a micrometer (µm), also called a micron, is extremely small. One micron is roughly one-tenth the diameter of a drop of mist! Nanotechnology combines science and technology in the control and creation of matter smaller than one micrometer. In medicine, nanotechnology is opening new doors in the treatment of cancer and other diseases. Scientists have developed nanoparticles that are able to slip through blood vessels and latch directly onto cancer cells. The cancer cells are tricked into eating the nanoparticles, which destroy the cells with a specially designed drug. Once this technology is tested and approved, it will revolutionize the treatment of many diseases.
In 1991, doctors in New York used computers and robots to perform surgery on a woman in Strasbourg, France. Using a three-armed robot and a high-speed computer connection, doctors removed the woman's gallbladder from over 3,800 miles away. Although "distance surgery" is not yet widely available, other types of robotic surgery are currently being used in hospitals around the country. Many robots are able to make smaller and more precise movements than humans. Robotic surgery can reduce the pain, bleeding, scarring, and recovery time for some open-heart surgeries. The robots can also be used for lung and esophagus surgeries. As this technology develops, it will make dramatic impacts on patient health.
Which of the following is not the wave of the future in the medical field?
What does an MRI do?
Some medical cameras are small enough to be swallowed and enter the digestive tract.
Nanotechnology may soon improve the way medical professionals treat cancer by causing cancer cells to replicate.
During World War II, German troops used a deadly chemical called hydrogen cyanide to kill enemy fighters. Ammonia is used to fertilize crops and kill harmful bacteria. Benzene is used to make rubbers, plastics, explosives, and pesticides. What do these three chemicals have in common? They are all ingredients in cigarettes. Clearly, smoking introduces dangerous chemicals into the body. In this lesson, you will learn about smoking and other unhealthy behaviors.
Almost everyone knows how important it is to maintain a healthy weight. Over 32 percent of adults and 18 percent of children in the United States are overweight. Being overweight can increase the risk of many health issues, including high blood pressure, diabetes, and heart disease. Unfortunately, some people are so afraid of becoming overweight that they eat very little or vomit immediately after eating. Both of these behaviors are unhealthy. Over time, they can develop into serious eating disorders called anorexia and bulimia. Although eating disorders mostly affect girls, boys are at a risk as well – particularly boys in wrestling and other weight-oriented sports.
People with anorexia nervosa are severely obsession with weight. They eat very small amounts of food and often exercise for hours to burn calories. Although most anorexics are severely underweight, people with anorexia believe they are fat. No matter how much weight they lose, they still think they need to lose more. The body needs a certain amount of fat to stay healthy. Anorexia can cause heart, liver, kidney, and brain damage, as well as dizziness, headaches, and depression. Other health issues include brittle hair and nails, dry, yellowish skin, and weak bones.
Tobacco is another name for the plant Nicotiana tabacum. The plant is grown for its leaves, which are dried and smoked as cigarettes, in pipes, and in cigars. Tobacco can also be chewed. There are serious health dangers associated with tobacco. Scientists have found more than 4,000 different chemicals in tobacco smoke. More than fifty are known to cause cancer. Smoking also increases the chances of developing chronic bronchitis and emphysema. Bronchitis and emphysema are characterized by increased shortness of breath and coughing. A person who dies from emphysema basically suffocates.
X-ray showing lung cancer
Image courtesy of National Cancer Institute
Lung cancer is the cause of 28 percent of all cancer deaths in the United States. Less than 15 percent of patients survive lung cancer. Most people know that smoking is the number one cause of lung cancer. What they don't know is that smoking is a leading cause of many other types of cancer, including mouth, esophagus, pancreas, uterus, and bladder. Smoking can damage almost every organ in the entire body. It is a dangerous habit that can ultimately lead to death.
Although it may not seem like it, alcohol is a drug. In fact, alcohol is the most widely abused drug by both adults and teens. It has dangerous short and long-term effects on health. Alcohol is a depressant that causes changes in mood and behavior. The effects of alcohol on the body and mind are determined by the amount that is consumed. Drinking small amounts can reduce anxiety, relieve tension, and create a false sense of confidence. This can make the drinker more willing to do things he or she normally would not do, such as get into fights. In larger amounts, alcohol can cause loss of balance, poor coordination, slurred speech, slowed reflexes, and mood swings. Nausea and headache are also common symptoms ofintoxication.
Dependence on alcohol is called alcoholism. It is characterized by an addiction to alcohol and an inability to stop drinking. Many health and mental disorders are related to alcoholism. Liver scarring (cirrhosis), nervous system disorders, heart and circulatory problems, and stomach ulcers are health problems resulting from alcohol abuse. In addition to health issues, many accidents are caused by alcohol. Each year, there are tens of thousands of alcohol related automobile accidents. In2005, nearly 40 percent of all fatal automobile accidents were alcohol related. Many of these accidents occur during the holiday party months of November and December. Often, these crashes kill innocent people who were not drinking. Health officials estimate that excessive alcohol use is the third leading lifestyle related cause of death in the United States.
Anorexia can cause _____.
What is the number one cause of lung cancer?
Which of the following statements is true?
Have you ever missed breakfast or skipped a meal? Have you ever gone to bed too late and missed out on needed sleep?Maybe you have spent too many afternoons watching television or playing video games. All of these behaviors are unhealthy. It is important to eat healthy meals, get enough sleep, and exercise. A healthy body is stronger, more productive, and less likely to get sick than an unhealthy body. In this lesson, you will learn about healthy living.
Good nutritionis important for a healthy body. Nutrients in food give the body energy, allow it to function, and provide the necessary ingredients to repair or replace old and damaged parts. Dozens of nutrients are needed for the body to survive and function properly. Some nutrients are made by the body, but others must be eaten as part of a healthy diet. These nutrients are called "essential" nutrients. Iron, vitamin A, and calcium are examples of essential nutrients.
Imagine the body as a high-performance car. To perform its daily functions, the body needs fuel in the form of food. Junk foods like potato chips, cookies, and ice cream are not healthy fuels. They are high in fast, sugars, and calories, but very low in nutrients. Over time, these foods can lead to weight gain, heart disease, diabetes, and other health issues. In order to stay healthy, the body needs a balance of fats, carbohydrates, and proteins. Fats should be limited to small amounts. Carbohydrates should come from whole grains, fruits, and vegetables. Proteins can be found in lean meats, such as fish and skinless chicken. The body also needs fiber, which is found in plant foods, such as vegetables and fruits.
Unhealthy eating habits can lead to weight gain as well as poor nutrition. One of the illnesses associated with poor nutrition is anemia. A person with anemia does not have a normal amount of red blood cells. They usually feel weak or tired. Anemia is usually caused by a lack of iron. Iron is found in meat, beans, and green leafy vegetables. Osteoporosis is another disease caused by poor nutrition. It is caused by a lack of calcium. When the body does not get enough calcium, bones become weak and brittle. Weak bones can break very easily. Kids usually do not get osteoporosis until they are adults. However, eating a calcium-rich diet today can help prevent the disease later in life. Calcium can be found in dairy products, such as milk and yogurt.
In addition to fuel, the body needs exercise to stay healthy. Long periods of inactivity cause muscles to weaken and work less efficiently. Inactivity affects both the skeletal muscles that move the body and cardiac muscles found in the heart. Over time, inactivity can lead to high blood pressure, high cholesterol, and diabetes. It can also increase stress, anxiety, fatigue, and depression.
There are many mental and physical benefits to regular exercise. Often, the most noticeable effect of exercise is a boost in mood. Exercise causes the brain to release special chemicals called endorphins. Endorphins block pain signals from reaching the brain. They naturally decrease pain, stress, anxiety, and depression. Other benefits of exercise are increased strength, flexibility, and energy. Exercise can also improve the quality of sleep and help manage weight. Finally, regular exercise reduces the risk of heart disease, high blood pressure, diabetes, and stroke.
Health officials recommend at least 30 minutes of exercise three to four times a week. Almost anything that moves the body can be considered exercise. Running, walking, hiking, swimming, and jumping rope are only a few examples. Light weight lifting or calisthenics can be used to improve muscle strength. Calisthenics is a special type of exercise that uses the body as a weight. Push-ups, pull-ups, and leg lunges are examples of calisthenics. Flexibility can be improved by stretching after exercising.
Eating a nutritious diet and exercising are not the only ways to keep the body healthy. Making smart decisions is an important part of living a healthy life. Good personal hygiene is another way to maintain body health. Keeping teeth, skin, hair, and nails clean decreases the risk of infection and illness. For example, cavities form when bacteria stays on the surface of a tooth. The bacteria forms a sticky, film-like substance called plaque. Over time, plaque turns into an acid and destroys the tooth. Gums can also become diseased as a result of poor hygiene. The early stage of gum disease is called gingivitis. More severe disease is known as periodontitis.
"Just say no" may seem like an overused phrase, but it is the best advice when it comes to making smart decisions about smoking, alcohol, and other drugs. Use of tobacco, alcohol, and other drugs can cause a wide variety of health issues from yellow teeth to cancer to death. Many drugs, including tobacco and alcohol, are addictive. This means that it can be extremely difficult to stop using them. Most people need the help of counselors, doctors, and therapists to stop abusing drugs. The best way to stay healthy is to avoid drugs altogether.
Amelia does not eat enough meat or beans. What is she at risk for developing?
Brie needs to add fiber to her diet. Which of the following foods should she eat?broccoi
What can exercise do?
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