intestinal wall

Examples of intestinal wall in the following topics:

• Histology of the Small Intestine

  • The small intestine wall has four layers: the outermost serosa, muscularis, submucosa, and innermost mucosa.
  • The intestinal villi are part of the mucosa.
  • The main function of these glands is to produce a mucus-rich, alkaline secretion (containing bicarbonate) in order to neutralize the acidic content of chyme that is introduced into the duodenum from the stomach, and to provide an alkaline condition for optimal intestinal enzyme activity, thus enabling absorption to take place and lubricate the intestinal walls.
  • Villi increase the internal surface area of the intestinal walls.
  • This increased surface area allows for more intestinal wall area to be available for absorption.

• Absorption in the Small Intestine

  • Absorption of nutrients occurs partially by diffusion through the wall of the small intestine.
  • The small intestine is the part of the gastrointestinal tract between the stomach and the large intestine, and is where much of the digestion of food takes place.
  • Digested nutrients pass into the blood vessels in the wall of the intestine through a process of diffusion.
  • The inner wall, or mucosa, of the small intestine is lined with simple columnar epithelial tissue.
  • Structurally, the mucosa is covered in wrinkles or folds called plicae circulares, considered permanent features in the wall of the organ.

• Histology of the Large Intestine

  • The large intestine has taeniae coli and invaginations (the intestinal glands), unlike the small intestines.
  • The large intestine differs in physical form from the small intestine in being much wider.
  • The wall of the large intestine is lined with simple columnar epithelium.
  • Instead of having the evaginations of the small intestine (villi), the large intestine has invaginations (the intestinal glands) .
  • In the intestine, the digestive enzymes are not secreted by the cells of the intestine.

• Anatomy of the Large Intestine

  • The large intestine is about 4.9 feet (1.5 m) long—about one-fifth of the whole length of the intestinal canal.
  • The large intestine differs in physical form from the small intestine in several ways.
  • The wall of the large intestine is lined with simple columnar epithelium.
  • Instead of having the evaginations of the small intestine (villi), the large intestine has invaginations (the intestinal glands).
  • While both the small intestine and the large intestine have goblet cells, they are more abundant in the large intestine.

• The Gallbladder

  • The gallbladder has a muscular wall that contracts in response to cholecystokinin, a peptide hormone that is synthesized by the small intestine.
  • When food containing fat enters the digestive tract, the secretion of cholecystokinin (CCK) is stimulated, and the gallbladder releases the bile into the small intestine.

• Processes and Functions of the Digestive System

  • Absorption occurs in the small intestines, where nutrients directly enter the bloodstream.
  • The process starts in the mouth and continues into the intestines.
  • During absorption, the nutrients that come from food (such as proteins, fats, carbohydrates, vitamins, and minerals) pass through the wall of the small intestine and into the bloodstream.
  • The small intestine increases surface area for absorption through tiny interior projections, like small fingers, called villi.
  • In the large intestine there is resorption of water and absorption of certain minerals as feces are formed.

• Lactose Intolerance

  • Secondary, acquired, or transient lactase deficiency is caused by an injury to the small intestine, usually during infancy, from acute gastroenteritis, diarrhea, chemotherapy, intestinal parasites, or other environmental causes.
  • Lactose cannot be directly absorbed through the wall of the small intestine into the bloodstream so, in the absence of lactase, it passes intact into the colon.
  • To assess lactose intolerance, intestinal function is challenged by ingesting more dairy products than can be readily digested.
  • This might be caused by slow intestinal transit and intestinal flora changes during pregnancy.

• Gross Anatomy of the Stomach

  • The stomach is a thick, walled organ that lies between the esophagus and the first part of the small intestine (the duodenum).
  • The pylorus or atrium, the lower section of the organ that facilitates the emptying of the contents into the small intestine.
  • Pyloric sphincter or pyloric orifice that divides the stomach from the small intestine.
  • Nerve plexuses are found in the submucous coat and between the layers of the muscular coat as in the intestine.

• Anatomy of the Small Intestine

  • The small intestine is the part of the gastrointestinal tract that follows the stomach, which is in turn followed by the large intestine.
  • The duodenum is the first section of the small intestine and is the shortest part of the small intestine.
  • The jejunum is the middle section of the small intestine.
  • The ileum is the final section of the small intestine.
  • The wall itself is made up of folds, each of which has many tiny finger-like projections known as villi on its surface.

• Associated Organs

  • The enzymes and bile travel through special channels called ducts and into the small intestine where they help break down the food.
  • The enzymes are activated once they reach the small intestine.
  • Once released in the intestine, the enzyme enterokinase, which is produced by the intestinal mucosa, activates trypsinogen by cleaving it to form trypsin.
  • It also produces bile, which is important in digestion, and receives and processes the products of digestion from the small intestine.
  • The muscular wall of the gallbladder contracts, releasing the bile in response to the release of cholecystokinin, a digestive hormone produced by the small intestine.