How Does a Babies Small Intestine Get Twisted

Anatomy of the Small Intestine

The small intestine is the part of the gastrointestinal tract where much of the digestion and absorption of food takes place.

Learning Objectives

Diagram the anatomy of the pocket-size intestine

Key Takeaways

Key Points

• The minor intestine is the part of the gastrointestinal tract that follows the stomach, which is in turn followed by the large intestine.
• The average length of the small intestine in an adult human male is 6.9 m (22 feet, 6 inches), and in the adult female 7.1 m (23 feet, 4 inches).
• The small intestine is divided into the duodenum, jejunum, and ileum.
• Much of the modest intestine is covered in projections chosen villi that increase the surface surface area of the tissue bachelor to absorb nutrients from the gut contents.

Key Terms

• duodenum: The showtime part of the pocket-sized intestine that starts at the lower end of the stomach and extending to the jejunum.
• ileum: The last, and usually the longest, sectionalization of the small intestine; the part between the jejunum and large intestine.
• small intestine: The upper part of the intestine, betwixt the tum and the large intestine, that is divided into the duodenum, the jejunum, and the ileum.
• jejunum: The central of the iii divisions of the small intestine that lies between the duodenum and the ileum.

The Small Intestine

The modest intestine is the part of the alimentary canal that follows the breadbasket, which is in turn followed past the large intestine. The small intestine is the site where most all of the digestion and absorption of nutrients and minerals from food takes place.

Small-scale intestine: An illustration of the small intestine with the duodenum, jejunum, and ileum labeled.

The average length of the small intestine in an adult human male is 6.9 m (22 feet, half-dozen inches), and in the adult female 7.1 m (23 feet, 4 inches). It tin can vary greatly, from equally brusque as iv.6 yard (xv feet) to equally long as 9.8 chiliad (32 feet). The small-scale intestine is approximately ii.5–3 cm in diameter, and is divided into three sections:

1. The duodenum is the first department of the small intestine and is the shortest function of the pocket-sized intestine. Information technology is where nigh chemic digestion using enzymes takes place.
2. The jejunum is the middle section of the small intestine. It has a lining which is designed to absorb carbohydrates and proteins. The inner surface of the jejunum, its mucous membrane, is covered in projections called villi, which increase the surface area of tissue bachelor to absorb nutrients from the gut contents. The epithelial cells which line these villi possess fifty-fifty larger numbers of microvilli. The ship of nutrients beyond epithelial cells through the jejunum includes the passive transport of some carbohydrates and the active send of amino acids, small peptides, vitamins, and most glucose. The villi in the jejunum are much longer than in the duodenum or ileum.
3. The ileum is the concluding section of the small intestine. The function of the ileum is mainly to blot vitamin B12, bile salts, and any products of digestion that were not absorbed past the jejunum. The wall itself is made up of folds, each of which has many tiny finger-like projections known as villi on its surface. The ileum has an extremely big surface area both for the adsorption of enzyme molecules and for the assimilation of products of digestion.

The Villi

The villi comprise large numbers of capillaries that take the amino acids and glucose produced by digestion to the hepatic portal vein and the liver. Lacteals are the pocket-sized lymph vessels that are present in villi. They absorb fat acids and glycerol, the products of fat digestion, into direct circulation.

Layers of circular and longitudinal shine muscle enable the digested food to be pushed along the ileum by waves of muscle contractions called peristalsis. The undigested food (waste and water) are sent to the colon.

Histology of the Small Intestine

The small intestine wall has four layers: the outermost serosa, muscularis, submucosa, and innermost mucosa.

Learning Objectives

Describe the histology of the small intestine

Key Takeaways

Cardinal Points

• The outermost layer of the intestine, the serosa, is a smooth membrane consisting of a sparse layer of cells that secrete serous fluid, and a sparse layer of connective tissue.
• The muscularis is a region of musculus next to the submucosa membrane. It is responsible for gut movement (as well called peristalsis ). It normally has two distinct layers of smoothen muscle: circular and longitudinal.
• The submucosa is the layer of dense irregular connective tissue or loose connective tissue that supports the mucosa; it too joins the mucosa to the bulk of underlying polish musculus.
• 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. The jejunum and ileum do not have Brunner's glands in the submucosa, while the ileum has Peyer'due south patches in the mucosa, but the duodenum and jejunum do non.

Key Terms

• Brunner's glands: Compound, tubular, submucosal glands found in that portion of the duodenum that is above the hepatopancreatic sphincter (sphincter of Oddi).
• Peyer's patches: Patches of lymphoid tissue or lymphoid nodules on the walls of the ileum in the minor intestine.
• intestinal wall: The wall of the small intestine is composed of four layers, from the outside to the inside: serosa, muscularis, submucosa, and mucosa.

The Small Intestine'southward Layers

Department of duodenum: This prototype shows the layers of the duodenum: the serosa, muscularis, submucosa, and mucosa.

The small intestine has 4 tissue layers:

1. The serosa is the outermost layer of the intestine. The serosa is a smooth membrane consisting of a thin layer of cells that secrete serous fluid, and a thin layer of connective tissue. Serous fluid is a lubricating fluid that reduces friction from the motility of the muscularis.
2. The muscularis is a region of muscle adjacent to the submucosa membrane. It is responsible for gut movement, or peristalsis. It usually has 2 singled-out layers of smooth muscle: round and longitudinal.
3. The submucosa is the layer of dense, irregular connective tissue or loose connective tissue that supports the mucosa, as well as joins the mucosa to the bulk of underlying smooth muscle.
4. The mucosa is the innermost tissue layer of the modest intestines, and is a mucous membrane that secretes digestive enzymes and hormones. The abdominal villi are part of the mucosa.

The three sections of the pocket-sized intestine look like to each other at a microscopic level, but there are some important differences. The jejunum and ileum practice not accept Brunner's glands in the submucosa, while the ileum has Peyer'south patches in the mucosa, but the duodenum and jejunum do not.

Brunner's Glands

Brunner'due south glands (or duodenal glands) are compound tubular submucosal glands found in the duodenum. 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.

Peyer's Patches

Peyer'south patches are organized lymph nodules. They are aggregations of lymphoid tissue that are institute in the everyman portion of the small intestine, which differentiate the ileum from the duodenum and jejunum.

Because the lumen of the gastrointestinal tract is exposed to the external surroundings, much of information technology is populated with potentially pathogenic microorganisms. Peyer'due south patches function as the immune surveillance system of the intestinal lumen and facilitate the generation of the immune response inside the mucosa.

Intestinal Villi

Micrograph of the small intestine: A depression-magnification micrograph of small intestinal mucosa that shows villi.

Intestinal villi (singular: villus) are tiny, finger-similar projections that protrude from the epithelial lining of the mucosa. Each villus is approximately 0.v–ane.vi mm in length and has many microvilli (atypical: microvillus), each of which are much smaller than a single villus.

Villi increase the internal surface area of the abdominal walls. This increased surface expanse allows for more abdominal wall area to be available for absorption. An increased absorbent expanse is useful because digested nutrients (including sugars and amino acids) pass into the villi, which is semi-permeable, through diffusion, which is effective only at brusk distances.

In other words, the increased surface area (in contact with the fluid in the lumen) decreases the average distance traveled by the nutrient molecules, so the effectiveness of improvidence increases.

The villi are connected to claret vessels that acquit the nutrients away in the circulating blood.

Digestive Processes of the Modest Intestine

The small intestine uses different enzymes and processes to digest proteins, lipids, and carbohydrates.

Learning Objectives

Describe the small intestine'southward role in the digestive process

Key Takeaways

Key Points

• The small intestine is where most chemical digestion in the human body takes place.
• Most of the digestive enzymes in the pocket-size intestine are secreted by the pancreas and enter the modest intestine via the pancreatic duct.
• The three major classes of nutrients that undergo digestion are proteins, lipids (fats), and carbohydrates.

Key Terms

• digestive enzymes: Enzymes that break downwardly polymeric macromolecules into their smaller building blocks to facilitate their absorption by the trunk.

Chemic Digestion in the Minor Intestine

The modest intestine is where most chemical digestion takes place. Most of the digestive enzymes in the small intestine are secreted past the pancreas and enter the pocket-size intestine via the pancreatic duct.

These enzymes enter the modest intestine in response to the hormone cholecystokinin, which is produced in response to the presence of nutrients. The hormone secretin likewise causes bicarbonate to be released into the small intestine from the pancreas to neutralize the potentially harmful acrid coming from the tum.

The three major classes of nutrients that undergo digestion are proteins, lipids (fats), and carbohydrates.

Proteins

Proteins are degraded into pocket-size peptides and amino acids earlier absorption. Their chemic breakdown begins in the stomach and continues through the large intestine.

Proteolytic enzymes, including trypsin and chymotrypsin, are secreted by the pancreas and cleave proteins into smaller peptides. Carboxypeptidase, a pancreatic brush border enzyme, splits one amino acid at a time. Aminopeptidase and dipeptidase free the end amino acid products.

Lipids

Lipids (fats) are degraded into fatty acids and glycerol. Pancreatic lipase breaks down triglycerides into free fat acids and monoglycerides. Pancreatic lipase works with the help of the salts from bile secreted by the liver and the gallbladder.

Bile salts attach to triglycerides and help to emulsify them; this aids access by pancreatic lipase because the lipase is water-soluble, simply the fatty triglycerides are hydrophobic and tend to orient toward each other and abroad from the watery intestinal environment.

The bile salts human action to hold the triglycerides in their watery surroundings until the lipase can intermission them into the smaller components that are able to enter the villi for absorption.

Carbohydrates

Some carbohydrates are degraded into simple sugars, or monosaccharides (due east.grand., glucose, galactose) and are absorbed by the small intestine. Pancreatic amylase breaks down some carbohydrates (notably starch) into oligosaccharides. Other carbohydrates laissez passer undigested into the big intestine, where they are digested by intestinal bacteria.

Brush border enzymes take over from in that location. The almost important brush edge enzymes are dextrinase and glucoamylase, which further break downwardly oligosaccharides. Other castor edge enzymes are maltase, sucrase, and lactase.

Lactase is absent in almost adult humans and for them lactose, like most poly-saccharides, is not digested in the pocket-size intestine. Some carbohydrates, such every bit cellulose, are not digested at all, despite being fabricated of multiple glucose units. This is because the cellulose is made out of beta-glucose that makes the inter-monosaccharidal bindings different from the ones nowadays in starch, which consists of alpha-glucose. Humans lack the enzyme for splitting the beta-glucose-bonds—that is reserved for herbivores and bacteria in the big intestine.

Major Digestive Enzymes
Enzyme	Produced In	Site of Release	pH Level
Saccharide Digestion
Salivary amylase	Salivary glands	Mountain	Neutral
Pancreatic amylase	Pancreas	Small intestine	Basic
Maltase	Small intestine	Small intestine	Basic
Protein Digestion
Pepsin	Gastric glands	Stomach	Acidic
Trypsin	Pancreas	Small intestine	Basic
Peptidases	Small-scale intestine	Small intestine	Bones
Nucleic Acrid Digestion
Nuclease	Pancreas	Small-scale intestine	Basic
Nucleosidases	Pancreas	Pocket-size intestine	Basic
Fat Digestion
Lipase	Pancreas	Small intestine	Bones

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Source: https://courses.lumenlearning.com/boundless-ap/chapter/the-small-intestine/

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