Biology and IBD

 In order to understand Inflammatory Bowel Disease (IBD), you must understand the biology and some of the systems that make up our body and how they relate to the disease.


The First Word In IBD – Inflammatory

Inflammation is a defense mechanism in the body. The immune system recognizes damaged cells, irritants, and pathogens, and it begins the healing process.

The immune system works to keep germs out of the body and destroy any that get in. The immune system is made up of a complex network of cells and organs that protect the body from infection. Lymph nodes are part of the immune system. They release lymphocytes, a certain type of white blood cell that fights infection. The blood vessels and lymph vessels carry the lymphocytes to and from different areas in the body.

The Immune System

The Second Word in IBD – Bowel

Bowel refers to the digestive system, which is made up of the gastrointestinal tract—also called the GI tract or digestive tract—and the liver, pancreas, and gallbladder. The GI tract is a series of hollow organs joined in a long, twisting tube from the mouth to the anus. The hollow organs that make up the GI tract are the mouth, esophagus, stomach, small intestine, large intestine, and anus. The liver, pancreas, and gallbladder are the solid organs of the digestive system.

The small intestine has three parts. The first part is called the duodenum. The jejunum is in the middle and the ileum is at the end. The large intestine includes the appendix, cecum, colon, and rectum. The appendix is a finger-shaped pouch attached to the cecum. The cecum is the first part of the large intestine. The colon is next. The rectum is the end of the large intestine.

Bacteria in your GI tract, also called gut flora or microbiome, help with digestion. Parts of your nervous and circulatory systems also help. Working together, nerves, hormones, bacteria, blood, and the organs of your digestive system digest the foods and liquids you eat or drink each day.

Digestion is important because your body needs nutrients from food and drink to work properly and stay healthy. Proteins, fats, carbohydrates, vitamins, minerals, and water are nutrients. Your digestive system breaks nutrients into parts small enough for your body to absorb and use for energy, growth, and cell repair.

Proteins break into amino acids.
Fats break into fatty acids and glycerol.
Carbohydrates break into simple sugars.

The Digestive System

The Third Word in IBD – Disease

A disease is a particular abnormal condition that negatively affects the structure or function of part or all of an organism, and that is not due to any external injury. Diseases are often construed as medical conditions that are associated with specific symptoms and signs. A disease may be caused by external factors such as pathogens or by internal dysfunctions.

Inflammatory bowel disease (IBD) is a term for two conditions (Crohn’s disease and ulcerative colitis) that are characterized by chronic inflammation of the gastrointestinal (GI) tract. In IBD, the immune system responds incorrectly to environmental triggers, which causes inflammation of the gastrointestinal tract. There also appears to be a genetic component—someone with a family history of IBD is more likely to develop this inappropriate immune response.

Parts of Gastrointestinal Tract affected by Crohn’s Disease

Crohn’s Disease can affect any part of the GI tract (from the mouth to the anus)—Most often it affects the portion of the small intestine before the large intestine/colon. Damaged areas appear in patches that are next to areas of healthy tissue. Inflammation may reach through the multiple layers of the walls of the GI tract. Inflammation in the small intestine of a person with Crohn’s disease can interfere with the digestion and absorption of nutrients. Incompletely digested food that travels through the colon may cause diarrhea and abdominal pain.

Parts of Gastrointestinal Tract affected by Ulcerative Colitis

Ulcerative Colitis occurs in the large intestine (colon) and the rectum. Damaged areas are continuous (not patchy) – usually starting at the rectum and spreading further into the colon. Inflammation is present only in the innermost layer of the lining of the colon. In a person with ulcerative colitis, the small intestine works normally, but the inflamed colon does not absorb water properly, resulting in diarrhea, increased urgency to have a bowel movement and increased frequency of bowel movements.


The Immune System and IBD

Normally, the immune system defends the body from pathogens (organisms that cause diseases and infections). A bacterial or viral infection of the digestive tract can trigger an immune response.
As the body tries to fight off the invaders, the digestive tract becomes inflamed. When the infection is gone, the inflammation goes away. That’s a healthy response.
In people with IBD, however, digestive tract inflammation can happen even when there’s no infection. The immune system attacks the body’s own cells instead. This is known as an autoimmune response. In IBD the body is attacking parts of the digestive system at the cellular level.

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