There are several structures and appendages that are present in the human body. Some of which have very specific functions and other a bit undefined, and its use is more or less residual.
The human appendix is one of such structures in the human body, whose use is not really defined, but they are useful, and when things go wrong with them, they could be fatal to humans.
The appendix is a worm-shaped tube attached to the large intestine in the human body. It is an organ that is credited with very little significance and often removed indiscriminately to avoid complications due to infection.
The function of the appendix is unknown. One theory is that the appendix acts as a storehouse for good bacteria, “rebooting” the digestive system after diarrheal illnesses. Other experts believe the appendix is just a useless remnant from our evolutionary past. Your appendix is a thin tube in your lower right abdomen. It sits where your small intestine meets your large intestine. Historically, many people have believed the appendix serves little purpose.  Researchers are learning that your appendix may play a role in good health.
The appendix is a small, tube-like structure once believed to be a useless vestigial organ. More recently, the idea  never entirely abandoned that it is important for immune function has been gaining ground.
Although some scientists believe that the human appendix has useful functions in the body, they still recommend the removal of the diseased appendix, as appendicitis or appendix cancer when left untreated, can be fatal and also because the removal of the appendix is not seen to cause any ill effects in the human body. A delay can result in a burst appendix, which can be life-threatening.

• Role in the immune system:
Research in recent years has shown that the human appendix has lymphoid cells, which help the body fight infections. This strongly suggests that the appendix plays a role in the immune system.
The appendix has been found to play a role in mammalian mucosal immune function. It is believed to be involved in extrathymically derived T-lymphocytes and B-lymphocyte-mediated immune responses. It is also said to produce early defences that help prevent serious infections in humans.

• Role in the digestive system:
There is a  higher Purpose for the Appendix. Researchers deduce that the appendix is designed to protect good bacteria in the gut. That way, when the gut is affected by a bout of diarrhea or other illness that cleans out the intestines, the good bacteria in the appendix can repopulate the digestive system and keep you healthy.
The  appendix does have a key function – it produces and stores good microbes for the human gut.
The research team, comprising immunologists,  say that our digestive system is rich in bacteria that are not only harmless but also helpful to us in the digestion of food that we eat.
These good microbes are often flushed out from the body when we suffer from diseases such as dysentery or cholera, thus upsetting the digestive system. This is when our appendix releases its stock of good bacteria and “reboots” our digestive system, according to the researchers.
There are certain things that can go wrong with the appendix:

Conditions affecting the appendix:
In humans, common diseases affecting the appendix are appendicitis and carcinoid tumors. Although scientists believe that the appendix has useful functions in the body, they recommend the removal of the diseased appendix, as untreated appendicitis or appendix cancer can be fatal and also because its removal is not seen to cause any ill effects.
• Appendicitis
The inflammation of the appendix is called appendicitis. It is caused by the blockage of the appendix and is very painful and potentially fatal. Appendicitis is the top most cause of acute abdominal pain necessitating surgery , affecting more than 5% of the population at some point of time.
Indigestible food passes from the small intestine to the large intestine and into the appendix. The muscular walls of the appendix contract and expel this food. When there is a blockage at the point where the appendix and large intestine meet, it can cause the inflammation of the appendix. This can lead to severe abdominal pain, nausea, fever and vomiting. Symptoms of appendicitis can vary in different people. If left untreated, a clogged appendix can rupture and release harmful bacteria into the abdomen eventually causing peritonitis.
Appendicitis is an inflammation of the appendix, a 3 1/2-inch-long tube of tissue that extends from the large intestine. One study suggests that the appendix may have some role in gut immunity, but nothing is definite. One thing we do know: We can live without it, without apparent consequences.
Appendicitis is a medical emergency that almost always requires prompt surgery to remove the appendix. Left untreated, an inflamed appendix will eventually burst, or perforate, spilling infectious materials into the abdominal cavity. This can lead to peritonitis, a serious inflammation of the abdominal cavity’s lining (the peritoneum) that can be fatal unless it is treated quickly with strong antibiotics.
•    Sometimes a pus-filled abscess (infection that is walled off from the rest of the body) forms outside the inflamed appendix. Scar tissue then “walls off” the appendix from the rest of the abdomen, preventing infection from spreading. An abscessed appendix can perforate or explode and cause peritonitis. For this reason, almost all cases of appendicitis are treated as emergencies, requiring surgery.
Mild appendicitis can be treated using antibiotics. Severe cases are usually treated by surgically removing the appendix. This procedure is called appendectomy and can be performed either by laparotomy in which a single incision is made in the right lower portion of the abdomen to remove the appendix or laparoscopic surgery which is carried out by making many small incisions through which special tools are inserted to remove the appendix.
Doctors often remove a healthy appendix while performing other abdominal surgeries like a hysterectomy. This is to avoid appendicitis in the future, as the appendix is prone to bacterial infections.

The classic symptoms of appendicitis include:
1. Dull pain near the navel or the upper abdomen that becomes sharp as it moves to the lower right abdomen. …
2. Loss of appetite.
3. Nausea and/or vomiting soon after abdominal pain begins.
4. Abdominal swelling.
5. Fever of 99-102 degrees Fahrenheit.
6. Inability to pass gas.

Appendicitis occurs when the appendix becomes blocked, often by stool, a foreign body, or cancer. Blockage may also occur from infection, since the appendix can swell in response to any infection in the body.
Almost half the time,

Other symptoms of appendicitis appear, including:
•    Dull or sharp pain anywhere in the upper or lower abdomen, back, or rectum
•    Painful urination and difficulty passing urine
•    Severe cramps
•    Constipation or diarrhea with gas
If you have any of the mentioned symptoms, seek medical attention immediately, because timely diagnosis and treatment is very important. Do not eat, drink, or use any pain remedies, antacids, laxatives, or heating pads, which can cause an inflamed appendix to rupture.

Ruptured appendix
If the appendix ruptures, the bacteria and fecal particles within the organ can spread into your abdomen. This may lead to a serious infection called peritonitis. You can also develop an abscess if your appendix ruptures. Both are life-threatening situations that require immediate surgery.

The removal – appendectomy
An appendectomy is the surgical removal of the appendix. It’s a common emergency surgery that’s performed to treat appendicitis, an inflammatory condition of the appendix.
The appendix is a small, tube-shaped pouch attached to your large intestine. It’s located in the lower right side of your abdomen. The exact purpose of the appendix isn’t known. However, it’s believed that it may help us recover from diarrhea, inflammation, and infections of the small and large intestines. These may sound like important functions, but the body can still function properly without an appendix.
When the appendix becomes inflamed and swollen, bacteria can quickly multiply inside the organ and lead to the formation of pus. This buildup of bacteria and pus can cause pain around the belly button that spreads to the lower right section of the abdomen. Walking or coughing can make the pain worse. You may also experience nausea, vomiting, and diarrhea.
• It’s important to seek treatment right away if you’re having symptoms of appendicitis. When the condition goes untreated,  the appendix can burst (perforated appendix) and release bacteria and other harmful substances into the abdominal cavity. This can be life-threatening, and will lead to a longer hospital stay.
• An appendectomy is often done to remove the appendix when an infection has made it inflamed and swollen. This condition is known as appendicitis. The infection may occur when the opening of the appendix becomes clogged with bacteria and stool. This causes your appendix to become swollen and inflamed.
The easiest and quickest way to treat appendicitis is to remove the appendix. Your appendix could burst if appendicitis isn’t treated immediately and effectively. If the appendix ruptures, the bacteria and fecal particles within the organ can spread into your abdomen. This may lead to a serious infection called peritonitis. You can also develop an abscess if your appendix ruptures. Both are life-threatening situations that require immediate surgery.
Although pain from appendicitis typically occurs in the lower right side of the abdomen, pregnant women may have pain in the upper right side of the abdomen. This is because the appendix is higher during pregnancy.
• Go to the emergency room immediately if you believe you have appendicitis. An appendectomy needs to be performed right away to prevent complications.
Appendectomy is the standard treatment for appendicitis. It’s crucial to remove the appendix right away, before the appendix can rupture. Once an appendectomy is performed, most people recover quickly and without complications.