Intestine, Large Health Article

Role in human health

The importance of the large intestine in human health is mostly derived from its role in removing water from food residues and transporting it into the bloodstream. Along with this water, dissolved minerals and ions, notably sodium, potassium, and chlorine, are also transported to the bloodstream. Without these chemicals, the blood is chemically unbalanced, a condition that can lead to serious illness and even death.

Common diseases and disorders

• Appendicitis. Appendicitis is an inflammation of the appendix. It occurs due to accumulated waste material that cannot move out of the appendix easily because it only has one opening. The symptoms of appendicitis are muscular rigidity, sharp pain in the right lower abdomen, and vomiting.
• Colitis. Colitis is commonly known as irritable bowel or spastic colon. It refers to the inflammation of the inner lining of the colon. Colitis is related to stress and can lead to ulcerative colitis, in which open sores appear in the mucous membrane of the colon.

KEY TERMS

Abdomen—A part of the body that lies between the thorax and the pelvis. It contains a cavity (abdominal cavity) that holds organs such as the pancreas, stomach, intestines, liver, and gallbladder. It is enclosed by the abdominal muscles and the vertebral column (spine).

Abdominal cavity—The hollow part of the body located between the diaphragm, which is the thin muscle below the lungs and heart, and the pelvis, the basin-shaped cavity that contains the reproductive organs, bladder, and rectum. The abdominal cavity contains the abdominal organs.

Anaerobes—Bacteria that live only in environments that are virtually oxygen-free.

Anal sphincter—The ring-like band of muscle that constricts or closes the anus.

Anus—The terminal opening of the digestive tract.

Appendix—A worm-shaped structure projecting from the cecum.

Bilirubin—A waste product from the breakdown of heme, the active group of hemoglobin, the molecule that carries oxygen in the blood. Bilirubin is produced in the liver and excreted in bile.

Cecum—The pouch-like start of the large intestine that links it to the small intestine.

Colon—Part of the large intestine, located in the abdominal cavity. It consists of the ascending colon, the transverse colon, the descending colon, and the sigmoid colon.

Digestion—The conversion of food in the stomach and in the intestines into substances capable of being absorbed by the blood.

Digestive system—Organs and paths responsible for processing food in the body. These are the mouth, the esophagus, the stomach, the liver, the gallbladder, the pancreas, the small intestine, the large intestine, and the rectum.

Feces—Waste product of digestion formed in the large intestine. About 75% of its mass is water, the remainder is protein, fat, undigested roughage, dried digestive juices, dead cells, and bacteria.

Fermentation—Enzymatic breakdown and utilization of foodstuffs by bacteria, as occurs in the large intestine.

Goblet cells—Mucus-secreting cells found scattered among other cells in the epithelium of many organs, especially in the intestinal and respiratory tracts. They are most abundant in the colon.

Hepatic flexure—Sharp right-angle bend of the ascending colon under the liver as it becomes the transverse colon.

Ion—Elements consist of positively charged nuclei surrounded by negatively charged electrons. These charges are balanced and the overall charge of an element is zero. An element becomes an ion, that is a charged species, if it gains or losses electrons. Many small ions are essential for the functioning of the body. The major ones include: the potassium ion (K⁺), the sodium ion (Na⁺), the chlorine ion (Cl), and the HCO₃^- ion.

Large intestinal motility—Muscle-assisted contractions occurring in the colon to facilitate movement of intestinal contents. There are four type of motility: segmentation contractions, peristaltic contractions, antiperistaltic contractions and giant migrating contractions.

Large intestine—The terminal part of the digestive system, site of water recycling, nutrient absorption, and waste processing located in the abdominal cavity. It consists of the caecum, the colon, and the rectum.

Mucous membrane—The lubricated lining of several body organs that contains mucus-secreting glands.

Mucus—The slimy secretion of glands found on mucous membranes composed of various proteins, salts, and white blood cells.

Pelvis—The basin-shaped cavity located below the abdomen that contains the reproductive organs, the bladder, and rectum.

Peristalsis—A pattern of wave-like muscle contractions that allows material to advance through the digestive tube.

Peritoneum—The thin membrane that lines the abdominal and pelvic cavities, and covers most abdominal organs.

Rectum—The rectum is a short, muscular tube that forms the lowest portion of the large intestine and connects it to the anus.

Small intestine—The part of the digestive tract located between the stomach and the large intestine. It consists of the duodenum, the jejunum, and the ileum.

Splenic flexure—Sharp right-angle bend of the transverse colon under the spleen as it becomes the descending colon.

• Colorectal cancers. Colorectal cancers start in the innermost layer of the tissues of the large intestine and can grow through some or all of the layers. They can develop in any of the four sections of the colon or in the rectum.
• Constipation. Constipation is caused primarily by insufficient fiber in the diet, lack of exercise, or not drinking enough fluids. As a result, fecal matter hard ens and large intestinal motility is impaired.
• Diarrhea. Diarrhea is a condition characterized by frequent, loose, watery stools that range from yellowish to light brown to green in color. If enough water is lost, dehydration occurs.
• Diverticulosis. Diverticulosis is characterized by out ward ballooning (diverticula) of the large intestine wall caused by chronic constipation.
• Dysentery. Dysentery is a general term for various dis orders characterized by severe diarrhea, inflamed intes tines, and intestinal bleeding. Some forms of dysentery may clear up by themselves, while other forms may continue for years without treatment.
• Hemorrhoids. Hemorrhoids are commonly known as piles. They are dilated veins in the anus and rectum.
• Peritonitis. Peritonitis refers to inflammation of the peritoneum, the membrane that lines the abdominal and pelvic cavities. It can occur as a result of a ruptured appendix, which empties its contents of fecal matter and waste into the abdominal cavity. This condition is extremely serious.
• Ptosis of the colon. Also known as prolapsed colon, this is a common condition that occurs when the colon falls from its normal position to a lower position.