small intestine

Examples of small intestine in the following topics:

• 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.
  • An illustration of the small intestine with the duodenum, jejunum, and ileum labeled.

• 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.
  • The primary function of the small intestine is the absorption of nutrients and minerals found in food.
  • The inner wall, or mucosa, of the small intestine is lined with simple columnar epithelial tissue.
  • Describe the role played by the small intestine in absorption of nutrients

• Digestive Processes of the Small Intestine

  • The small intestine uses different enzymes and processes to digest proteins, lipids, and carbohydrates.
  • The small intestine is where most chemical digestion takes place.
  • Most of the digestive enzymes in the small intestine are secreted by the pancreas and enter the small intestine via the pancreatic duct.
  • These enzymes enter the small intestine in response to the hormone cholecystokinin, which is produced in response to the presence of nutrients.
  • Lactase is absent in most adult humans and for them lactose, like most poly-saccharides, is not digested in the small intestine.

• Histology of the Small Intestine

  • The small intestine wall has four layers: the outermost serosa, muscularis, submucosa, and innermost mucosa.
  • The mucosa is the innermost tissue layer of the small intestines, and is a mucous membrane that secretes digestive enzymes and hormones.
  • The intestinal villi are part of the mucosa.
  • The three sections of the small intestine look similar to each other at a microscopic level, but there are some important differences.
  • They are aggregations of lymphoid tissue that are found in the lowest portion of the small intestine, which differentiate the ileum from the duodenum and jejunum.

• Digestive System: Small and Large Intestines

  • Nutrients are absorbed in the small intestine and waste is prepared for elimination in the large intestine.
  • The second part of the small intestine is called the jejunum.
  • The ileum is the last part of the small intestine.
  • The human large intestine is much smaller in length than the small intestine, but larger in diameter.
  • Describe the parts of the digestive system from the small intestine through the accessory organs

• 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.
  • 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 that secrete mucin to form mucus in water, they are abundant in the large intestine.
  • In histology, an intestinal crypt—called the crypt of Lieberkühn—is a gland found in the epithelial lining of the small intestine and colon.

• Absorption of Monosaccharides, Amino Acids, Dipeptides, Tripeptides, Lipids, Electrolytes, Vitamins, and Water

  • The small intestine is where most chemical digestion occurs.
  • Most of the digestive enzymes that act in the small intestine are secreted by the pancreas and enter the small intestine via the pancreatic duct.
  • The enzymes enter the small intestine in response to the hormone cholecystokinin, which is produced in the small intestine in response to the presence of nutrients.
  • The fat soluble vitamins A, D, and E are absorbed in the upper small intestine.
  • Describe the process of absorption of nutrients in the small intestine

• Anatomy of the Large Intestine

  • It starts in the right iliac region of the pelvis, just at or below the right waist, where it is joined to the bottom end of the small intestine (cecum).
  • The large intestine differs in physical form from the small intestine in several ways.
  • 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 sacculations, called haustra, are characteristic features of the large intestine, and distinguish it from the small intestine.

• Organs of the Digestive System

  • The upper digestive tract consists of the esophagus, stomach, and the small intestine; the lower tract includes all of the large intestine, the rectum, and anus.
  • The chyme moves on into the small intestine, where nutrients are absorbed.
  • The small intestine is an impressive digestive tube, spanning an average of 20 feet in length.
  • Soapy bile from the liver, stored in the gallbladder, gets squirted into the small intestine to help emulsify—or break apart—fats.
  • It shows how the oral cavity connects to the esophagus and descends into the stomach and then the small intestine.

• Absorption and Feces Formation in the Large Intestine

  • After the food has been passed through the small intestine, it enters the large intestine.
  • Within the large intestine, digestion is retained long enough to allow fermentation via gut bacteria, which break down some of the substances that remain after processing in the small intestine.
  • Although this source of vitamins provides only a small part of the daily requirement, it makes a significant contribution when dietary vitamin intake is low.
  • Other bacterial products include gas (flatus), which is a mixture of nitrogen and carbon dioxide, with small amounts of the gases hydrogen, methane, and hydrogen sulphide.
  • Describe the process of absorption and feces formation in the large intestine