My Science School

Tympanic membrane, also called eardrum, thin layer of tissue in the human ear that receives sound vibrations from the outer air and transmits them to the auditory ossicles, which are tiny bones in the tympanic (middle-ear) cavity. 

The eardrum has three layers: the outer layer, inner layer, and middle layer. The middle layer is made of fibers that give the eardrum elasticity and stiffness. Cartilage holds the eardrum in place.

The eardrum covers the end of the external ear canal and looks like a flattened cone with its tip pointed inward toward the middle ear. It is transparent and is about the size of a dime.

The eardrum divides the outer ear from the middle ear. The eardrum sits between the end of the external ear canal and the auditory ossicles, which are three tiny bones in the middle ear, called the malleus, incus, and stapes.

Sometimes an infection may cause the eardrum to rupture. Symptoms of a ruptured eardrum include hearing loss, ear pain, itching, and fluid draining from the ear. Usually, eardrums that rupture heal on their own.

Picture Credit : Google

Our ear has three sections – outer, middle and inner ear. Stapes in the middle ear is the smallest bone in the human body. A stirrup-shaped bone, it transmits sound vibrations from the incus, another tiny bone in the middle ear, to the oval window, a membrane covering the entrance to the cochlea in the inner ear.

The two branches of the stapes, known as the inferior and superior crus, convey sound vibrations to the bone’s flat base.

From there, the vibrations enter the inner ear, where they are processed into neural data to be transmitted to the brain via the cochlear and the auditory nerve.

If the stapes becomes damaged, such as from severe head trauma, a person may lose some or all of their ability to hear. Because the ossicles are a chain of bones, this also holds true for the incus and malleus.

Picture Credit : Google

Do you know what's common among SARS-CoV-2, HIV AIDS, Ebola, SARS, MERS, Nipah, H1N1 flu (swine flu) and H5N1 flu (bird flu)? Yes, all of these are zoonoses, that is, they are animal-bome diseases.

A zoonosis is any disease or infection that is naturally transmissible from vertebrate animals to humans. Zoonoses have different modes of transmission. In direct zoonosis, the disease is transmitted from animals to humans through air, bites or saliva. In indirect zoonoses, the transmission occurs via an intermediate species (referred to as a vector), which carries the disease pathogen. These pathogens can be viruses, bacteria, fungi or parasites.

Though the world has seen the emergence of diseases throughout history, in the last 50 years, a host of new infectious diseases has spread rapidly after making the evolutionary jump from animals to humans. According to the World Health Organisation (WHO), 70% of emerging human pathogens come from animals. In the last century, at least 10 infectious diseases jumped from animals to humans, it says.

What has led to this?

Globalisation, deforestation, encroachment of wild environments, human-animal conflicts and wildlife trade have led to the spike in zoonosis outbreak, says a report by the WHO, released in September 2019. It has also warned that the risk of a global pandemic is growing and that zoonotic diseases will continue to emerge and re-emerge.

The deadly ones

As the world grapples with the new coronavirus, which is thought to have spread from bats, let's take a look at some of the major zoonotic diseases and their outbreaks...

Bubonic plague

Bubonic plague was the cause of the Black Death that swept through Asia, Europe and Africa in the 14th Century and killed an estimated 50 million people. It took centuries for some societies to recover. Plague is a bacterial disease caused by Yersinia pestis. It is carried by rodents and cats. The infection in humans is caused by the bite of an infected flea.

HIV-AIDS

HIV, the virus that causes AIDS, originated from chimps and other primates and is thought to have first infected humans at least a century ago. However, it was first recognised only in 1981. By the end of that year, there were 270 reported cases and 121 deaths. HIV destroys the immune system, opening the door to a host of deadly infections. The virus has now mutated to a separate human-only disease. Between 1981 and 2018, the disease caused an estimated 32 million deaths worldwide.

SARS An epidemic of SARS, caused by a strain of coronavirus SARSCOV, affected 26 countries and resulted in more than 8,000 cases in 2003.

SARS-CoV is thought to have spread from bats, which, in tumn, spread to other animals (civet cats) and perhaps first infected humans in southern China in 2002.

Ebola

The 2014-2016 outbreak in West Africa was the largest Ebola outbreak since the virus was first discovered in 1976. The outbreak started in Guinea and then spread to other parts of the continent. The virus is transmitted to people from wild animals (such as chimpanzees, gorillas, monkeys, antelopes or porcupines). Human-to-human transmission happens through direct or indirect contact with the blood or bodily fluids of infected people. It is thought that fruit bats of the Pteropodidae family are natural Ebola virus hosts.

Nipah

Nipah virus (Niv) infection severely affects both animals and humans. The natural host of the virus are fruit bats. It can spread from bats to other animals to people or directly from bat to and between people. Even eating a fruit bitten by an infected bat can transfer Nipah to humans. The disease was first identified in 1998 during an outbreak in Malaysia, India has reported three NiV outbreaks in the past. The first two were in West Bengal: Siliguri in 2001 and Nadia in 2007. The third outbreak occurred in Kerala in May 2018.

Picture Credit : Google

Red moles are also known as cherry angiomas. You may have them on your skin and have never realized what they are. Most of the time they will appear on the chest, back, neck or face, but can pop up anywhere on the body. It’s understandable when you are concerned about the appearance of a red mole and want to undergo red mole removal immediately, but the truth is there’s usually nothing to worry about.

Cherry angiomas get their name from their appearance. Their bright red color occurs due to the dilated capillaries.

However, cherry angiomas can be a range of colors and may also appear blue or purple. If a person applies pressure to them, they do not usually turn white, or blanch.

These angiomas can also vary in size but commonly grow to be a few millimeters (mm) in diameter. As they get bigger, the angiomas usually form round, domed shapes with smooth, flat tops.

The growths can appear anywhere on the body but grow most often on the chest, stomach, and back. Multiple cherry angiomas often appear in groups.

The causes of cherry angiomas are largely unknown, though experts believe they tend to be genetic.

Age contributes heavily, and cherry angiomas increase in number and size after 40 years of age.

Picture Credit : Google

Warts are raised bumps on your skin caused by the human papillomavirus (HPV). Warts have plagued humans for thousands of years — they have been discovered on 3,000-year-old mummies and were mentioned by Shakespeare. Although warts generally aren’t dangerous, they are ugly, potentially embarrassing, and contagious. They can also be painful.

Most warts clear up without treatment. It can take from a few weeks to several years, depending on the location and number of warts. They usually disappear faster in children.

One third of children are estimated to have warts, but studies have found that 50 percent Trusted Sourceof these disappear within a year, and 70 percent are gone after 2 years.

However, if they do not disappear, or if a wart causes concern, medical help is available.

A doctor will examine the wart, they may ask about family history, and they may take some tissue for tests.

HPV viruses cause the excessive and rapid growth of keratin, which is a hard protein on the top layer of the skin.

Different HPV strains cause different warts. The wart-causing virus can be passed on by close skin-to-skin contact, and through contact with towels or shoes.

Picture Credit : Google

A skin tag is a small piece of soft, hanging skin that may have a peduncle, or stalk. They can appear anywhere on the body, but especially where skin rubs against other skin or clothing.

They often go unnoticed, unless they are in a prominent place or are repeatedly rubbed or scratched, for example, by clothing, jewelry, or when shaving.

Some people may have skin tags and never notice them. In some cases, they rub off or fall off painlessly. Very large skin tags may burst under pressure.

The surface of skin tags may be smooth or irregular in appearance. They are often raised from the surface of the skin on fleshy peduncles, or stalks. They are usually flesh-colored or slightly brownish.

Skin tags start small, flattened like a pinhead bump. Some stay small, and some grow bigger. They can range in diameter from 2 millimeters (mm) to 1 centimeter (cm), and some may reach 5cm.

Picture Credit : Google

Moles are very common, and most people have one or more. Moles are concentrations of pigment-producing cells (melanocytes) in your skin. People with light skin tend to have more moles.

Moles are caused when cells in the skin (melanocytes) grow in clusters or clumps. Melanocytes are distributed throughout your skin and produce melanin, the natural pigment that gives your skin its color.

Most moles are harmless. Rarely, they become cancerous. Monitoring moles and other pigmented patches is an important step in detecting skin cancer, especially malignant melanoma.

Moles can develop anywhere on your body, including your scalp, armpits, under your nails, and between your fingers and toes. Most people have 10 to 40 moles. Many of these develop by age 50. Moles may change in appearance or fade away over time. Hormonal changes of adolescence and pregnancy may cause moles to become darker and larger.

Picture Credit : Google

Fleas are tiny bugs. They don’t grow much larger than the tip of a pen, and they range from light brown to almost black in color. They don’t have wings, so they get around by jumping from place to place. Their thin, flat bodies and hard shells mean you often need to squeeze them between fingernails or two hard surfaces to kill them. Even then, where there is one, many often follow. Fleas reproduce quickly, especially if you have pets in the house. But even if you don’t have pets, your yard can potentially play host to fleas, and you may end up with a bunch of mysterious bites. They’re almost impossible to get rid of without a pesticide treatment.

Fleabites are pretty distinctive. They look like small, red bumps in clusters of three or four or a straight line. The bumps remain small, unlike mosquito bites. You might notice a red “halo” around the bite center. The most common places to find these bites are around the legs or ankles. Fleabites are also common around the waist, armpits, breasts, groin, or in the folds of the elbows and knees.

For humans, the risk of contracting another disease from the flea is very small. Yet bacteria can get into your body through the bite and cause an infection, especially if you scratch it. An infected bite will turn red, warm, and it may release pus. Fleabites can also cause an allergic reaction in people who are sensitive to them. Symptoms can range from raised welts on the skin to difficulty breathing. Fleabites can also cause complications in pets, such as allergic reactions and even anemia from blood loss. That’s why it’s important to take animals to a vet if they have fleas.

Picture Credit : Google

A person can get it by eating food or drink contaminated with human or animal feces where the parasite is present.

Many parasitic worms enter their hosts by active invasion. Their transmission success is often based on a mass production of invasive stages. However, most stages show a highly specific host-finding behaviour. Information on host-finding mechanisms is available mainly for trematode miracidia and cercariae and for nematode hookworms. The larvae find and recognise their hosts, in some cases even with species specificity, via complex sequences of behavioural patterns with which they successively respond to various environmental and host cues. There is often a surprisingly high diversity of host-recognition strategies. Each parasite species finds and enters its host using a different series of cues. For example, different species of schistosomes enter the human skin using different recognition sequences. The various recognition strategies may reflect adaptations to distinct ecological conditions of transmission. Another question is how, after invasion, parasitic worms find their complex paths through their host's tissues to their often very specific microhabitats. Recent data show that the migrating parasite stages can follow local chemical gradients of skin and blood compounds, but their long-distance navigation within the host body still remains puzzling. The high complexity, specificity and diversity of host-recognition strategies suggest that host finding and host recognition are important determinants in the evolution of parasite life cycles.

Picture Credit : Google

Amebiasis is a parasitic infection of the intestines caused by the protozoan Entamoeba histolytica, or E. histolytica. The symptoms of amebiasis include loose stool, abdominal cramping, and stomach pain. However, most people with amebiasis won’t experience significant symptoms.

The cause of amebiasis is infection by the protozoan parasite Entamoeba histolytica. It begins when a person drinks contaminated water or eats foods contaminated with the cystic form (infective stage), comes in contact with contaminated colonic irrigation devices or the fecally contaminated hands of food handlers, or by oral-anal sexual practices.

The cystic form changes into trophozoites (invasive form) in the ilium or colon and invade the mucosal barrier, leading to tissue destruction and diarrhea. These trophozoites can reach the portal blood circulation to the liver and eventually go to other organs. It only infects humans, and the CDC does not classify it as a free-living organism.

Picture Credit : Google

A parasite is an organism that lives in another organism, called the host, and often harms it. It depends on its host for survival.

The parasite uses the host’s resources to fuel its life cycle. It uses the host’s resources to maintain itself.

Parasites vary widely. Around 70 percentTrusted Source are not visible to the human eye, such as the malarial parasite, but some worm parasites can reach over 30 meters in length.

Parasites are not a disease, but they can spread diseases. Different parasites have different effects.

There are many types of parasite, and symptoms can vary widely. Sometimes these may resemble the symptoms of other conditions, such as a hormone deficiency, pneumonia, or food poisoning.

Parasitic infections cause a tremendous burden of disease in both the tropics and subtropics as well as in more temperate climates. Of all parasitic diseases, malaria causes the most deaths globally. Malaria kills more than 400,000 people each year, most of them young children in sub-Saharan Africa.

Picture Credit : Google