Top 10 oddest birth...!!!

Whenever babies are born, people usually gush. They give compliments to the babies because of how cute they look. There are also times when some babies have unique features that set them apart from the rest. For instance, a baby may have the prettiest face in the nursery and it is obvious even when she is placed with other babies. However, there are times when people notice other babies because of different reasons. Some give attention to babies because of the defects that they have. It is a sad but true fact of life.

1- Siamese Twins

Top 1 in our list is Siamese Twins. Siamese twins have always been popular in different parts of the world. This is probably because so many Siamese twins have gained attention because of the fact that they are stuck together for good. Right now though, a lot of Siamese twins are separated when they are already strong enough to be separated. It is still sad though that sometimes, one twin has to die because of the lack of body parts available for one set of twins.

2- Ambras Syndrome

Coming in at number 2 in our list is the Ambras Syndrome. It is a very rare syndrome that affects only a few of the world’s population. To date, only 40 people in the world right now have this condition. It can be very sad for people with this disease because people reject them immediately because of their looks. People with this condition develop uncontrollable hair in their face and neck area. This is the reason why some people with this condition are taunted by their peers that they look like werewolves.

3- Fused Limbs

Number 3 in our list is Fused Limbs. Some people refer to this as mermaid syndrome but this is not actually true since some people born with this condition also have their arms fused together. There are times though when only the fingers or toes are joined together and not the whole limb.

4- Cyclopia

One of the most bizarre birth condition is the Cyclopia which is number 4 in our list of odd birth effects. The condition got its name from Cyclopes which is known to have only one eye. Babies born with this condition only have one eye in the middle of their forehead. Some believe that this happens because of the medications that women take during pregnancy.

5- Craniopagus Parasiticus

Another bizarre birth condition that is very rare is Craniopagus Parasiticus. This is the condition wherein an unborn twin is joined together with its living twin. Most of the time, the unborn twin is not living or does not show any signs of being alive. However, there is an instance wherein the unborn twin has shown some emotions as well. This odd birth condition has earned the number 5 spot on our list.

6- Foetus in Foetu

Another birth condition that is still related to twins is Foetus in Foetu which is the odd condition wherein the other twin is inside the stomach of the stronger twin. The twin is unborn and lives off from the born twin like a parasite. It is a good thing though that those with this condition can be operated on with no side effects that can affect the person. This condition is number 6 in our list.

7- Fibrodysplasia Ossificans Progressiva

Number 7 on our list is the condition called Fibrodysplasia Ossificans Progressiva. Those who are born with this condition usually get abnormal growth of bones in different parts of their body. Usually, the growth of bones happen when the child or the person hurts himself or herself. Instead of bleeding or scarring, new bones appear. This condition can be very uncomfortable especially because the bones cannot be removed. Surgically removing the bones will only cause more bones to grow from the surgical wounds.

8- Progeria

Getting the number 8 position on our list is Progeria. There have been movies that have been made based on this condition. This is the condition wherein children are aged well beyond their years. In a few months time, they will suddenly grow older. They will lose their teeth and hair and their skin condition will lose its luster. They will suddenly age. Arterial damage usually causes children to die when they reach puberty.

9- Vestigial Tail

Occupying the 9th spot in our list right now is Vestigial Tail. From the name itself, it is already obvious that children born with this condition have a tail that actually has a function. Some people believe that the reason why some babies are born with it is because of the fact that some genes have already been mutated.

10- Anencephaly

Read more: http://the10mostknown.com/top-10-oddest-birth-defects.html#ixzz2JYBSqFWK

Weird Diseases

Weird Diseases

Epidermodysplasia verruciformis
Epidermodysplasia is caused by a genetic skin defect, in which skin is filling up with various dirty looking warts.  Warts are found mainly in areas exposed to sunlight.

Calcinosis  
This is a rare disease in which calcium deposits in soft tissues. In practice the victim body is begins to flow thick white liquid like milk and various body joints leave their places.

Argyria 

This a weird disease in which skin turns blue. That disease is also called blue skin failure. This disease mostly effect on face and hands, but it can also affect the whole body.

Elephantiasis

This is the most bizarre Illness, in which lymph clogs the lymph vessels. This unusual blockage helps to increase the body part where the lymph vessel is blocked. A typical example is the elephant’s leg.

Werewolf Syndrome
It is a disease in which a victim grows at an abnormal amount of body hair in places where they usually not grow. Like on face and hands.

Pica Syndrome

It is a disease in which people tend to eat and taste things that are very bad in taste, like plastic, stones, paper, plaster, clay, rubber, soap, etc. Doctors believe that this disorder is developed in a person when the body has enough minerals, but do not know exactly how to start and or how to treat them.

Blaschko lines

This is a very strange and still unexplained syndrome, first described in 1901 by a German dermatologist Alfred Blaschko. Patients in this syndrome got visible stripes on the body in various shapes like V, and P. These lines have no connection with the nerve, muscle orlymphatic system.

Cutaneous horns

The reasons of this rare disease are unknown why some people develop these unusual horns, but the problem is linked to radiation exposure. This disease does occur in humans in areas where a lot of sunshine.

Necrotising fasciitis

This disease is also called meat eating bacteria disorder. It is caused by an infection of the lower layer of skin that usually gets there by various abrasions on the skin. This is a very dangerous disease, which leads to death.

Ehlers-Danlos Syndrome

This disease is also associated with the skin, in which the skin becomes thin and easily extensible.

hai...

Hari ni nak publish sikit je... hari ni Isnin minggu ketiga, semua pelajar dan guru diwajibkan memakai pakaian uniform... tahniah kepada yang berjaya memakai uniform lengkap...

Tips-tips menjawab Kertas 2 Sains SPM

 Terdapat 3 bahagian dalam kertas 2:

• Bahagian A (4 soalan struktur berorientasikan eksperimen)
• Bahagian B (5 soalan struktur berorientasikan teori)
• Bahagian C (3 soalan esei)

BAHAGIAN A:

• Obervation - jawapan boleh didapati terus daripada gambar rajah atau jadual yang disediakan.
• Manipulated Variables - lihat apakah yang berbeza pada gambar rajah yang disediakan atau jika pada jadual, kenalpasti ruang yang berada di sebelah kiri.
• Responding Variables - perhatikan apakah yang berubah atau hasil di akhir eksperimen. Jika terdapat jadual, ruang yang berada di sebelah kanan sekali itu adalah responding variables.
• Constant Variables - kenalpasti alat radas atau bahan-bahan yang sama sepanjang eksperimen dijalankan.
• Aim (objektif) - biasanya bermula dengan ayat 'To study.....' atau 'To investigate...'
• Graph - kalau dalam soalan tulis 'draw a graph...' maksudnya anda kena lukis graf yang biasa (sambungkan titik ke titik). Kalau 'draw a bar chart...' maksudnya anda kena lukis graf bar (kotak) yang berjauhan antara satu sama lain. Kalau 'draw a histogram...' maksudnya anda kena lukis graf bar (kotak) yang rapat antara satu sama lain.
• Relationship - Gunakan semula ayat daripada soalan. Contohnya, 'What is the relationship between the height of the seedling and time?' Jawapannya, 'When the time increases, the height of the seedling increases/decreases (bergantung kepada graf)'

BAHAGIAN B:

• Untuk bahagian ini, biasanya ditanya tentang Function, State, Method, Name, Effect.

BAHAGIAN C:

• Wajib jawab soalan 10 (merancang eksperimen) dan salah satu daripada soalan 11 atau 12.
• Soalan 10 biasanya diberi tentang satu pernyataan (statement) dan anda perlu menulis:
• (i) Hipotesis - Kaitkan antara manipulated variable dan responding variable.
• (ii) Aim - Mulakan dengan ayat 'To study...' dan salin daripada pernyataan yang diberikan.
• (iii) Variables - kena tulis ketiga-tiga variables.
• (iv) Apparatus and materials - kenalpasti semua alat radas dan bahan yang digunakan.
• (v) Procedure - Digalakkan melukis gambar rajah berlabel sebab ia boleh membantu mendapatkan markah.
• (vi) Data - Buat jadual yang mengandungi Manipulated variable (ruang sebelah kiri jadual) dan Responding variable (ruang sebelah kanan jadual). Ingat! Jangan isikan ruangan hasil eksperimen.

Tips-tips menjawab Kertas 2 Sains SPM

 Terdapat 3 bahagian dalam kertas 2:

• Bahagian A (4 soalan struktur berorientasikan eksperimen)
• Bahagian B (5 soalan struktur berorientasikan teori)
• Bahagian C (3 soalan esei)

BAHAGIAN A:

• Obervation - jawapan boleh didapati terus daripada gambar rajah atau jadual yang disediakan.
• Manipulated Variables - lihat apakah yang berbeza pada gambar rajah yang disediakan atau jika pada jadual, kenalpasti ruang yang berada di sebelah kiri.
• Responding Variables - perhatikan apakah yang berubah atau hasil di akhir eksperimen. Jika terdapat jadual, ruang yang berada di sebelah kanan sekali itu adalah responding variables.
• Constant Variables - kenalpasti alat radas atau bahan-bahan yang sama sepanjang eksperimen dijalankan.
• Aim (objektif) - biasanya bermula dengan ayat 'To study.....' atau 'To investigate...'
• Graph - kalau dalam soalan tulis 'draw a graph...' maksudnya anda kena lukis graf yang biasa (sambungkan titik ke titik). Kalau 'draw a bar chart...' maksudnya anda kena lukis graf bar (kotak) yang berjauhan antara satu sama lain. Kalau 'draw a histogram...' maksudnya anda kena lukis graf bar (kotak) yang rapat antara satu sama lain.
• Relationship - Gunakan semula ayat daripada soalan. Contohnya, 'What is the relationship between the height of the seedling and time?' Jawapannya, 'When the time increases, the height of the seedling increases/decreases (bergantung kepada graf)'

BAHAGIAN B:

• Untuk bahagian ini, biasanya ditanya tentang Function, State, Method, Name, Effect.

BAHAGIAN C:

• Wajib jawab soalan 10 (merancang eksperimen) dan salah satu daripada soalan 11 atau 12.
• Soalan 10 biasanya diberi tentang satu pernyataan (statement) dan anda perlu menulis:
• (i) Hipotesis - Kaitkan antara manipulated variable dan responding variable.
• (ii) Aim - Mulakan dengan ayat 'To study...' dan salin daripada pernyataan yang diberikan.
• (iii) Variables - kena tulis ketiga-tiga variables.
• (iv) Apparatus and materials - kenalpasti semua alat radas dan bahan yang digunakan.
• (v) Procedure - Digalakkan melukis gambar rajah berlabel sebab ia boleh membantu mendapatkan markah.
• (vi) Data - Buat jadual yang mengandungi Manipulated variable (ruang sebelah kiri jadual) dan Responding variable (ruang sebelah kanan jadual). Ingat! Jangan isikan ruangan hasil eksperimen.

What is AIDS?

What does AIDS mean?

AIDS stands for Acquired Immune Deficiency Syndrome:

Acquired means you can get infected with it;

Immune Deficiency means a weakness in the body's system that fights diseases.

Syndrome means a group of health problems that make up a disease.

AIDS is caused by a virus called HIV, the Human Immunodeficiency Virus. If you get infected with HIV, your body will try to fight the infection. It will make "antibodies," special molecules to fight HIV.

A blood test for HIV looks for these antibodies. If you have them in your blood, it means that you have HIV infection. People who have the HIV antibodies are called "HIV-Positive.

Being HIV-positive, or having HIV disease, is not the same as having AIDS. Many people are HIV-positive but don't get sick for many years. As HIV disease continues, it slowly wears down the immune system. Viruses, parasites, fungi and bacteria that usually don't cause any problems can make you very sick if your immune system is damaged. These are called "opportunistic infections."

How do you get AIDS?

You don't actually "get" AIDS. You might get infected with HIV, and later you might develop AIDS. You can get infected with HIV from anyone who's infected, even if they don't look sick and even if they haven't tested HIV-positive yet. The blood, vaginal fluid, semen, and breast milk of people infected with HIV has enough of the virus in it to infect other people. Most people get the HIV virus by:

* having sex with an infected person

* sharing a needle (shooting drugs) with someone who's infected

* being born when their mother is infected, or drinking the breast milk of an infected woman

Getting a transfusion of infected blood used to be a way people got AIDS, but now the blood supply is screened very carefully and the risk is extremely low.

There are no documented cases of HIV being transmitted by tears or saliva, but it is possible to be infected with HIV through oral sex or in rare cases through deep kissing, especially if you have open sores in your mouth or bleeding gums.

What happens if I'm HIV positive?

You might not know if you get infected by HIV. Some people get fever, headache, sore muscles and joints, stomach ache, swollen lymph glands, or a skin rash for one or two weeks. Most people think it's the flu. Some people have no symptoms.

The virus will multiply in your body for a few weeks or even months before your immune system responds. During this time, you won't test positive for HIV, but you can infect other people.

When your immune system responds, it starts to make antibodies. When this happens, you will test positive for HIV.

After the first flu-like symptoms, some people with HIV stay healthy for ten years or longer. But during this time, HIV is damaging your immune system.

One way to measure the damage to your immune system is to count your CD4 cells you have. These cells, also called "T-helper" cells, are an important part of the immune system. Healthy people have between 500 and 1,500 CD4 cells in a milliliter of blood.

Without treatment, your CD4 cell count will most likely go down. You might start having signs of HIV disease like fevers, night sweats, diarrhea, or swollen lymph nodes. If you have HIV disease, these problems will last more than a few days, and probably continue for several weeks.

How do I know if I have AIDS?

HIV disease becomes AIDS when your immune system is seriously damaged. If you have less than 200 CD4 cells or if your CD4 percentage is less than 14%, you have AIDS. See If you get an opportunistic infection, you have AIDS. There is an "official" list of these opportunistic infections put out by the Centers for Disease Control (CDC). The most common ones are:

* PCP (Pneumocystis pneumonia), a lung infection;

* KS (Karposi's sarcoma), a skin cancer;

* CMV (Cytomegalovirus), an infection that usually affects the eyes

* Candida, a fungal infection that can cause thrush (a white film in your mouth) or infections in your throat or vagina

AIDS-related diseases also includes serious weight loss, brain tumours, and other health problems. Without treatment, these opportunistic infections can kill you.

AIDS is different in every infected person. Some people die a few months after getting infected, while others live fairly normal lives for many years, even after they "officially" have AIDS. A few HIV-positive people stay healthy for many years even without taking antiretroviral medications (ARVs).

Is there a cure for AIDS?

There is no cure for AIDS. There are drugs that can slow down the HIV virus, and slow down the damage to your immune system. There is no way to "clear" the HIV out of your body.

Other drugs can prevent or treat opportunistic infections (OIs). In most cases, these drugs work very well. The newer, stronger ARVs have also helped reduce the rates of most OIs. A few OIs, however, are still very difficult to treat.

Digestive System

Each organ of the mammalian digestive system has specialised food–processing functions.

The general principles of food processing are similar for a diversity of animals, so we can use the digestive system of mammals as a representative example. The mammalian digestive system consists of the alimentary canal and various accessory glands that secrete digestive juices into the canal through ducts.

After food is chewed and swallowed, it takes only 5–10 seconds for it to pass down the oesophagus and into the stomach, where it spends 2–6 hours being partially digested. Final digestion and nutrient absorption occur in the small intestine over a period of 5–6 hours. In 12–24 hours, any undigested material passes through the large intestine, and faeces are expelled through the anus.

The general principles of food processing are similar for a diversity of animals, so we can use the digestive system of mammals as a representative example. The mammalian digestive system consists of the alimentary canal and various accessory glands that secrete digestive juices into the canal through ducts.

Peristalsis, rhythmic waves of contraction by smooth muscles in the wall of the canal, pushes the food along the tract. At some of the junctions between specialised segments of the digestive tube, the muscular layer is modified into ringlike valves called sphincters, which close off the tube like drawstrings, regulating the passage of material between chambers of the canal. The accessory glands of the mammalian digestive system are three pairs of salivary glands, the pancreas, the liver and the gallbladder, which stores a digestive juice.

Using the human digestive system as a model, let′s now follow a meal through the alimentary canal, examining in more detail what happens to the food in each of the processing stations along the way.

The Oral Cavity, Pharynx, and Oesophagus
Both physical and chemical digestion of food begin in the mouth. During chewing, teeth of various shapes cut, smash, and grind food, making it easier to swallow and increasing its surface area. The presence of food in the oral cavity triggers a nervous reflex that causes the salivary glands to deliver saliva through ducts to the oral cavity. Even before food is actually in the mouth, salivation may occur in anticipation because of learned associations between eating and the time of day, cooking odours, or other stimuli. Humans secrete more than a liter of saliva each day.

Saliva contains a slippery glycoprotein (carbohydrate–protein complex) called mucin, which protects the lining of the mouth from abrasion and lubricates food for easier swallowing. Saliva also contains buffers that help prevent tooth decay by neutralising acid in the mouth. Antibacterial agents in saliva kill many of the bacteria that enter the mouth with food.

Chemical digestion of carbohydrates, a main source of chemical energy, begins in the oral cavity. Saliva contains salivary amylase, an enzyme that hydrolyses starch (a glucose polymer from plants) and glycogen (a glucose polymer from animals). The main products of this enzyme′s action are smaller polysaccharides and the disaccharide maltose.

The tongue tastes food, manipulates it during chewing, and helps shape the food into a ball called a bolus. During swallowing, the tongue pushes a bolus to the back of the oral cavity and into the pharynx.

The region we call our throat is the pharynx, a junction that opens to both the oesophagus and the windpipe (trachea). When we swallow, the top of the windpipe moves up so that its opening, the glottis, is blocked by a cartilaginous flap, the epiglottis. You can see this motion in the bobbing of the “Adam′s apple” during swallowing. This tightly controlled mechanism normally ensures that a bolus is guided into the entrance of the oesophagus.

Food or liquids may go “down the wrong pipe” because the swallowing reflex didn′t close the opening of the windpipe in time. The resulting blockage of airflow (choking) stimulates vigorous coughing, which usually expels the material. If it is not expelled quickly, the lack of airflow to the lungs can be fatal.

The oesophagus conducts food from the pharynx down to the stomach by peristalsis. The muscles at the very top of the oesophagus are striated (voluntary). Thus, the act of swallowing begins voluntarily, but then the involuntary waves of contraction by smooth muscles in the rest of the esophagus take over.

The Stomach
The stomach stores food and performs preliminary steps of digestion. This large organ is located in the upper abdominal cavity, just below the diaphragm. With accordionlike folds and a very elastic wall, the stomach can stretch to accommodate about 2 L of food and fluid. It is because the stomach can store an entire meal that we do not need to eat constantly. Besides storing food, the stomach performs important digestive functions: It secretes a digestive fluid called gastric juice and mixes this secretion with the food by the churning action of the smooth muscles in the stomach wall.

Gastric juice is secreted by the epithelium lining numerous deep pits in the stomach wall. With a high concentration of hydrochloric acid, gastric juice has a pH of about 2—acidic enough to dissolve iron nails. One function of the acid is to disrupt the extracellular matrix that binds cells together in meat and plant material. The acid also kills most bacteria that are swallowed with food. Also present in gastric juice is pepsin, an enzyme that begins the hydrolysis of proteins. Pepsin breaks peptide bonds adjacent to specific amino acids, cleaving proteins into smaller polypeptides, which are later digested completely to amino acids in the small intestine. Pepsin is one of the few enzymes that works best in a strongly acidic environment. The low pH of gastric juice denatures (unfolds) the proteins in food, increasing exposure of their peptide bonds to pepsin.

What prevents pepsin from destroying the cells of the stomach wall? First, pepsin is secreted in an inactive form called pepsinogen by specialised cells called chief cells located in gastric pits.

Other cells, called parietal cells, also in the pits, secrete hydrochloric acid. The acid converts pepsinogen to active pepsin by removing a small portion of the molecule and exposing its active site. Because different cells secrete the acid and pepsinogen, the two ingredients do not mix—and pepsinogen is not activated—until they enter the lumen (cavity) of the stomach. Activation of pepsinogen is an example of positive feedback: Once some pepsinogen is activated by acid, activation occurs at an increasingly rapid rate because pepsin itself can activate additional molecules of pepsinogen. Many other digestive enzymes are also secreted in inactive forms that become active within the lumen of the digestive tract.

The stomach′s second defense against self–digestion is a coating of mucus, secreted by the epithelial cells of the stomach lining. Still, the epithelium is constantly eroded, and mitosis generates enough cells to completely replace the stomach lining every three days. Gastric ulcers, lesions in this lining, are caused mainly by the acid–tolerant bacterium Helicobacter pylori
Though treatable with antibiotics, gastric ulcers may worsen if pepsin and acid destroy the lining faster than it can regenerate.

About every 20 seconds, the stomach contents are mixed by the churning action of smooth muscles. You may feel hunger pangs when your empty stomach churns. (Sensations of hunger are also associated with brain centres that monitor the blood′s nutritional status and levels of the appetite–controlling hormones discussed earlier in this chapter.) As a result of mixing and enzyme action, what begins in the stomach as a recently swallowed meal becomes a nutrient–rich broth known as acid chyme.

Most of the time, the stomach is closed off at both ends. The opening from the oesophagus to the stomach, the cardiac orifice, normally dilates only when a bolus arrives. The occasional backflow of acid chyme from the stomach into the lower end of the oesophagus causes heartburn. (If backflow is a persistent problem, an ulcer may develop in the oesophagus.) At the opening from the stomach to the small intestine is the pyloric sphincter, which helps regulate the passage of chyme into the intestine, one squirt at a time. It takes about 2 to 6 hours after a meal for the stomach to empty in this way.

The Small Intestine 
With a length of more than 6 m in humans, the small intestine is the longest section of the alimentary canal (its name refers to its small diameter, compared with that of the large intestine). Most of the enzymatic hydrolysis of food macromolecules and most of the absorption of nutrients into the blood occur in the small intestine.

Most digestion is completed early in this journey, while the chyme is still in the duodenum. The remaining regions of the small intestine, called the jejunum and ileum, function mainly in the absorption of nutrients and water

Absorption of Nutrients
To enter the body, nutrients in the lumen must cross the lining of the digestive tract. A few nutrients are absorbed in the stomach and large intestine, but most absorption occurs in the small intestine. This organ has a huge surface area—300 m2, roughly the size of a tennis court. Large circular folds in the lining bear fingerlike projections called villi, and each epithelial cell of a villus has many microscopic appendages called microvilli that are exposed to the intestinal lumen

(The microvilli′s shape is the basis of the term brush border for the intestinal epithelium.) This enormous microvillar surface is an adaptation that greatly increases the rate of nutrient absorption.

Penetrating the core of each villus is a net of microscopic blood vessels (capillaries) and a small vessel of the lymphatic system called a lacteal. (In addition to their circulatory system, vertebrates have an associated network of vessels—the lymphatic system—that carries a clear fluid called lymph. Nutrients are absorbed across the intestinal epithelium and then across the unicellular epithelium of the capillaries or lacteals. Only these two single layers of epithelial cells separate nutrients in the lumen of the intestine from the bloodstream.

In some cases, transport of nutrients across the epithelial cells is passive. The simple sugar fructose, for example, apparently moves by diffusion down its concentration gradient from the lumen of the intestine into the epithelial cells and then into capillaries. Other nutrients, including amino acids, small peptides, vitamins, and glucose and several other simple sugars, are pumped against concentration gradients by the epithelial membranes. This active transport allows the intestine to absorb a much higher proportion of the nutrients in the intestine than would be possible with passive diffusion.

Amino acids and sugars pass through the epithelium, enter capillaries, and are carried away from the intestine by the bloodstream. After glycerol and fatty acids are absorbed by epithelial cells, they are recombined into fats within those cells. The fats are then mixed with cholesterol and coated with proteins, forming small globules called chylomicrons, most of which are transported by exocytosis out of the epithelial cells and into lacteals

The lacteals converge into the larger vessels of the lymphatic system. Lymph, containing chylomicrons, eventually drains from the lymphatic system into large veins that return blood to the heart.

In contrast to the lacteals, the capillaries and veins that drain nutrients away from the villi all converge into the hepatic portal vein, a blood vessel that leads directly to the liver. This ensures that the liver—which has the metabolic versatility to interconvert various organic molecules—has first access to amino acids and sugars absorbed after a meal is digested. Therefore, blood that leaves the liver may have a very different balance of these nutrients than the blood that entered via the hepatic portal vein. For example, the liver helps regulate the level of glucose molecules in the blood, and blood exiting the liver usually has a glucose concentration very close to 0.1%, regardless of the carbohydrate content of a meal (see Figure 41.3). From the liver, blood travels to the heart, which pumps the blood and the nutrients it contains to all parts of the body.

The large intestine or colon, is connected to the small intestine at a T–shaped junction, where a sphincter (a muscular valve) controls the movement of material. One arm of the T is a pouch called the caecum. Compared to many other mammals, humans have a relatively small caecum. The human cecum has a fingerlike extension, the appendix, which is dispensable. (Lymphoid tissue in the appendix makes a minor contribution to body defense.) The main branch of the human colon is about 1.5 m long.

A major function of the colon is to recover water that has entered the alimentary canal as the solvent of the various digestive juices. About 7 L of fluid are secreted into the lumen of the digestive tract each day, which is much more liquid than most people drink. Most of this water is reabsorbed when nutrients are absorbed in the small intestine. The colon reclaims much of the remaining water that was not absorbed in the small intestine. Together, the small intestine and colon reabsorb about 90% of the water that enters the alimentary canal.

The wastes of the digestive tract, the faeces, become more solid as they are moved along the colon by peristalsis. The movement is sluggish, and it generally takes about 12 to 24 hours for material to travel the length of the organ. If the lining of the colon is irritated—by a viral or bacterial infection, for instance—less water than normal may be reabsorbed, resulting in diarrhea. The opposite problem, constipation, occurs when peristalsis moves the feces along the colon too slowly. An excess of water is reabsorbed, and the faeces become compacted.

Living in the large intestine is a rich flora of mostly harmless bacteria. One of the common inhabitants of the human colon is Escherichia coli, a favourite research organism of molecular biologists. The presence of Escherica coli in lakes and streams is an indication of contamination by untreated sewage. Intestinal bacteria live on unabsorbed organic material. As by–products of their metabolism, many colon bacteria generate gases, including methane and hydrogen sulfide. Some of the bacteria produce vitamins, including biotin, folic acid, vitamin K, and several B vitamins. These vitamins, absorbed into the blood, supplement our dietary intake of vitamins.

Faeces contain masses of bacteria, as well as cellulose and other undigested materials. Although cellulose fibers have no caloric value to humans, their presence in the diet helps move food along the digestive tract.

The terminal portion of the colon is called the rectum, where faeces are stored until they can be eliminated. Between the rectum and the anus are two sphincters, one involuntary and the other voluntary. One or more times each day, strong contractions of the colon create an urge to defecate.

Some Misconception...

Human body and health

Different tastes actually can be detected on all parts of the tongue by taste buds, with slightly increased sensitivities in different locations depending on the person, contrary to the popular belief that specific tastes only correspond to specific mapped sites on the tongue. The original tongue map was based on a mistranslation by a Harvard psychologist of a discredited German paper that was written in 1901. 

There is no single theory that satisfactorily explains myopia—in particular, studies show that so-called eyestrain from close reading and computer games does not explain myopia. There is also no evidence that reading in dim light or sitting close to a television causes vision to deteriorate.

Shaving does not cause hair to grow back thicker or coarser or darker. This belief is due to the fact that hair that has never been cut has a tapered end, whereas, after cutting, there is no taper. Thus, it appears thicker, and feels coarser due to the sharper, unworn edges. Hair can also appear darker after it grows back because hair that has never been cut is often lighter due to sun exposure. 

Hair and fingernails do not continue to grow after a person dies. Rather, the skin dries and shrinks away from the bases of hairs and nails, giving the appearance of growth.

Although there are hair care products which are marketed as being able to repair split ends and damaged hair, there is no such cure. A good conditioner might prevent damage from occurring in the first place, but the only way to get rid of split ends after they appear is by a hair cut.

Snapping or cracking one's knuckles does not cause arthritis.

Sugar does not cause hyperactivity in children. Double blind trials have shown no difference in behaviour between children given sugar full or sugar-free diets, even in studies specifically looking at children with attention-deficit/hyperactivity disorder or those considered "sensitive" to sugar. In fact, it was found that the difference in the children's behaviour was all in the parents' minds.

It is a common misconception that sleepwalkers should not be awakened. While it is true that a person may be confused or disoriented for a short time after awakening, it is actually quite dangerous not to wake a sleepwalker as they may injure themselves if they trip over objects or lose their balance while sleepwalking. Such injuries are common among sleepwalkers. 

While the vitamin A in carrots does help to build healthy vision (among other things), it does not improve the eyesight of a person already in possession of healthy vision nor does it improve night vision. In fact, an excess of carrots can cause vitamin A toxicity and carotenemia in rare cases. This misconception arose from an RAF attempt to hide the discovery of radar from the Axis forces by claiming that their pilots had gained vastly improved night vision from being fed carrots, rather than from any technological advancement.

In Korea, it is commonly believed that sleeping in a closed room with an electric fan running can be fatal in the summer. According to the Korean government, "In some cases, a fan turned on too long can cause death from suffocation, hypothermia, or fire from overheating." The Korea Consumer Protection Board issued a consumer safety alert recommending that electric fans be set on timers, direction changed and doors left open. Belief in fan death is common even among knowledgeable medical professionals in Korea. According to Dr. Yeon Dong-su, dean of Kwandong University's medical school, "If it is completely sealed, then in the current of an electric fan, the temperature can drop low enough to cause a person to die of hypothermia."

High levels of testosterone do not necessarily make humans more aggressive and less cooperative, even though this is observed in other animals. Human behaviour is very complicated and heavily affected by social condition and beliefs.

Biology

Warts on human skin are caused by viruses that are unique to humans (Human papillomavirus). Humans cannot catch warts from toads or other animals; the bumps on a toad are not warts.

The claim that a duck's quack does not echo is false, although the echo may be difficult to hear for humans under some circumstances.

The notion that goldfish have a memory of only three seconds is false. They have been trained to navigate mazes and can recognize their owners after an exposure of a few months.

Lemmings do not engage in mass suicidal dives off cliffs when migrating. They will, however, occasionally, and unintentionally fall off cliffs when venturing into unknown territory, with no knowledge of the boundaries of the environment. The misconception is due largely to the Disney film White Wilderness, which shot many of the migration scenes (also staged by using multiple shots of different groups of lemmings) on a large, snow-covered turntable in a studio. Photographers later pushed the lemmings off a cliff.

Bats are not blind. While most bat species do use echolocation to augment their vision, all bats have eyes and are capable of sight.

It's a common myth that an earthworm becomes two worms when cut in half. This is not correct. An earthworm can survive being bisected, but only the front half of the worm (where the mouth is located) can survive, while the other half dies. On the other hand, species of the planaria family of flatworms actually do become two new planaria when bisected or split down the middle.