Name: small and large intestine functions
Uploaded: 2019-03-11T09:21:25.000Z
Duration: 1 min 23 s
Channel: JoVE

K12 Standards

Alabama Course of Study Science

9-12

Human Anatomy and Physiology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms: Structures and Processes

9-12.HA.1.10

Anatomy of the Intestines

- [Verteller] De dunne en dikke darm zijn verantwoordelijk voor de opname van voedingsstoffen en water. Terwijl de dunne darm vrij smal is, is het orgaan ongeveer 22 voet lang en samengeperst in de buikholte. Chyme bereikt eerst de twaalfvingerige darm en gaat dan naar het middelste en langste deel, de jejunum.

Hier bevat de tussenvoering slijmvliesplooien die bedekt zijn met vingerachtige villi. De bovenliggende laag epitheelcellen hebben cytoplasmatische extensies die microvilli worden genoemd. Deze drie structuren vergroten het oppervlak van de dunne darm om ervoor te zorgen dat de voedingsstoffen optimaal worden opgenomen.

Aan het eind van de dunne darm is de ileum die zich aan de dikke darm hecht door de ileocaecale klep. In het eerste deel van de dikke darm, de cecum, zijn er geen plooien of villi. In plaats daarvan is het de thuisbasis van een groot bacterieel ecosysteem dat de laatste stadia van de spijsvertering uitvoert, het afbreken van cellulose.

Aan de onderkant van de cecum bungelt de appendix, een kleine lymfatische structuur. Daarboven begint de verticale karteldarm, gevolgd door de horizontale karteldarm, die het grootste deel van het resterende water en elektrolyten absorbeert, waardoor chyme omgevormd wordt tot feces. De laatste regio's, de colon descendens, de sikkelvormige karteldarm, en het rectum, slaan de uitwerpselen op tot de uitscheiding via de anus.

anatomie van de darmen

Hoewel de vertering van eiwitten, koolhydraten en lipiden in de maag kan beginnen, wordt deze in de darm voltooid. De opname van voedingsstoffen, water en elektrolyten uit voedsel en drank vindt ook plaats in de darm. De darmen kunnen worden verdeeld in twee structureel verschillende organen—de dunne en dikke darm.

<h4>TDunne darm</h4>

De dunne darm is een ongeveer 7 meter lange buis met een binnendiameter van slechts 2,5 cm. Omdat de meeste voedingsstoffen hier worden opgenomen, is de binnenwand van de dunne darm zeer ingewikkeld en bedekt met vingerachtige uitsteeksels, villi genaamd, die elk honderden microvilli bevatten. De plooien, villi en microvilli van de dunne darm vergroten het absorptieoppervlak 60 tot 120 keer. Het grotere oppervlak biedt voldoende mogelijkheden voor opname van voedingsstoffen.

De dunne darm is verbonden met de maag door de pylorussfincter, die afsluit wanneer de chymus de twaalfvingerige darm binnengaat—het begin van de dunne darm. Het middelste deel van de dunne darm is het jejunum. Het ileum eindigt de dunne darm, waar het zich via de ileocecale klep aan de dikke darm hecht.

<h4>TDe dikke darmen</h4>

De dikke darm begint bij de blindedarm. De appendix, een kleine lymfatische structuur, bungelt aan de onderkant van de blindedarm. Boven de blindedarm begint het stijgende colon, gevolgd door het transversale colon. Ze absorberen het grootste deel van het resterende water en elektrolyten uit de chymus, waardoor het in ontlasting verandert. De dalende dikke darm, de sigmoïde dikke darm en het rectum slaan de ontlasting op totdat deze via de anus wordt geëlimineerd.

In totaal is de dikke darm ongeveer 1,5 m lang met een binnendiameter van 4,8 cm. Het bevat geen plooien en villi, maar de absorberende epitheelcellen hebben microvilli. De dikke darm herbergt een bacterieel ecosysteem, dat de laatste stadia van de spijsvertering uitvoert—het afbreken van cellulose en vezels, stoffen die de maag en de dunne darm slecht kunnen verwerken.

<h4>TBacteriële diversiteit</h4>

De dikke darm bevat ruim 700 verschillende soorten bacteriën. Er wordt aangenomen dat bacteriële diversiteit relatie houdt met obesitas en de ontwikkeling van type 2-diabetes. Zwaarlijvige mensen hebben minder bacteriestammen dan hun niet-zwaarlijvige tegenhangers. Een lage bacteriële diversiteit is ook in relatie gebracht met insulineresistentie. Het darmbacteriële ecosysteem – het darmbioom – ontstaat kort na de geboorte, waarbij de baby’s die borstvoeding krijgen hun darmbioom ontwikkelen door bacteriën die aanwezig zijn in de moedermelk. Na de geboorte wordt het bioom gevormd door de genetica, het dieet, de leeftijd, het geslacht en het immuunsysteem van een individu. Externe factoren zoals voeding, gezondheidstoestand, medicijnen en geografische locatie hebben ook een aanzienlijke invloed op de complexiteit van het darmbioom.

Anatomie van de darmen

Although digestion of proteins, carbohydrates, and lipids may begin in the stomach, it is completed in the intestine. The absorption of nutrients, water, ...

Education

JoVE Core

Biology

Biologie

Human Biology

Menselijke biologie

Nutrition and Digestion

Voeding en Spijsvertering

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

small and large intestine functions

The small and large intestines complete digestion and absorb nutrients, water, and electrolytes. They are two structurally distinct organs with different shapes and jobs. Together, they move food material from the stomach toward elimination.

The small intestine is about 7 meters long and has an inner diameter of only 2.5 cm. Most nutrient absorption happens here, so its inner lining is highly folded and covered with villi, which are finger-like projections. Each villus contains hundreds of microvilli, and the folds, villi, and microvilli increase the surface area for absorption by 60 to 120 times.

The small intestine connects to the stomach through the pyloric sphincter. When chyme moves into the duodenum, which is the start of the small intestine, this sphincter closes off. The middle section is the jejunum, and the ileum is the final part. The ileum joins the large intestine at the ileocecal valve.

The large intestine begins at the cecum. The appendix, a small lymphatic structure, hangs from the bottom of the cecum. Above it are the ascending colon and then the transverse colon. These sections absorb most of the remaining water and electrolytes from chyme and help turn it into feces.

The descending colon, sigmoid colon, and rectum store feces until they leave the body through the anus. The large intestine is about 1.5 m long and has an inner diameter of 4.8 cm. Unlike the small intestine, it does not have folds or villi, although its absorptive epithelial cells do have microvilli.

The large intestine also supports a bacterial ecosystem that carries out the final stages of digestion. These bacteria can break down cellulose and fiber, which the stomach and small intestine are not well equipped to process. The large intestine contains over 700 different species of bacteria, and this diversity may be linked to obesity and Type 2 diabetes. People with obesity tend to have fewer bacterial strains than people who are not obese, and low diversity has also been associated with insulin resistance.

The gut biome is established shortly after birth. Babies who are breastfed develop it from bacteria present in breast milk. After birth, genetics, diet, age, sex, and the immune system help shape the biome. External factors such as diet, health status, medications, and geographical location also affect how complex the gut biome becomes.

Small and Large Intestine Functions

overview of human digestion

Saliva, Stomach Acid, and Gut Health

The human digestive system is monogastric, which means the stomach has one chamber for digestion. Several other animals also have monogastric digestive systems, including pigs, horses, dogs, and birds. This chapter focuses on the human digestive system. Saliva is a watery fluid released by the salivary glands into the mouth. It is about 99.5% water and also contains electrolytes, mucus, white blood cells, epithelial cells, enzymes, and antimicrobial agents. The enzymes in saliva begin...

anatomy of the intestines

The small and large intestines complete digestion and absorb nutrients, water, and electrolytes. They are two structurally distinct organs with different shapes and jobs. Together, they move food material from the stomach toward elimination. The small intestine is about 7 meters long and has an inner diameter of only 2.5 cm. Most nutrient absorption happens here, so its inner lining is highly folded and covered with villi, which are finger-like projections. Each villus contains hundreds of...

accessory organs

Digestive Glands and Enzymes

Digestive glands and accessory organs help break down food even though food does not pass through them. They add enzymes and other fluids to the digestive tract to support digestion. The salivary glands release saliva, a fluid that contains water, mucus, and amylase. Amylase is a digestive enzyme that starts breaking down starches and other carbohydrates before food reaches the stomach. The liver, gallbladder, and pancreas also support digestion. They send their secretions into the duodenum,...

lipid digestion

Lipases and Bile in Fat Breakdown

Lipases and bile help the body break down lipids, which are large molecules that do not mix well with water. Because most digestive enzymes are water-based, lipids need special steps before the body can use them. Lingual lipase is an enzyme made by acinar cells in the sublingual gland. It is found in saliva, but it has only a small role in the mouth. Its best pH, or acidity level, is 3.5-6.0, so it becomes active after chewed food reaches the acidic stomach. Gastric lipase is another acidic...

protein digestion

Protein Breakdown and Amino Acid Use

Protein digestion starts in the stomach, where strong acid helps unfold protein structure and expose peptide bonds in polypeptide chains. Digestive enzymes then begin breaking those chains into smaller pieces that can be processed by the body. Pepsin is a protease, which means it is a protein-digesting enzyme. It is made in the stomach and works with chymotrypsin and trypsin, enzymes released in the small intestine. These enzymes cut specific links between amino acids and form shorter...

carbohydrate digestion

Carbohydrate Breakdown in the Digestive Tract

Carbohydrate digestion breaks food carbohydrates into saccharides, or sugars, that the body can use for energy. It begins in the mouth during mastication, which means chewing. The masticated carbohydrates then pass through the stomach without being broken down further. Digestion starts again in the duodenum, the first part of the small intestine. There, pancreatic alpha-amylase and brush border enzymes on the microvilli help convert complex carbohydrates into monosaccharides. These simple...

neural regulation

Brain and Gut Control of Digestion

Brain and gut control digestion through a cephalic phase and the enteric nervous system. The cephalic phase begins when the brain sees or smells food. It sends impulses through cranial nerves to the salivary glands and stomach so the body is ready to eat. This first response is a conditioned, or learned, reaction to familiar foods. Appetite also changes the response. People may make more saliva and hear more stomach rumbling when they think about apple pie than broccoli. The hypothalamus and...

hormonal regulation

Digestive Hormones and Stomach Control

Digestive hormones control when the stomach makes acid and when food moves into the small intestine. They work with the neuroendocrine system, which links nerve signals and hormone release during digestion. In the stomach, proteins are detected by sensory neurons in the enteric nervous system. This stimulates the pyloric gland to release gastrin. Gastrin then helps trigger histamine release, and together they start hydrochloric acid production. The acid helps break food down into chyme. As the...

key terms and concepts

Explore how the small and large intestines absorb nutrients, water, and electrolytes, and learn how gut bacteria help finish digestion in high school biology.

Small and Large Intestine Functions | JoVE K12

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Next Generation Science Standards

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HS-LS1-2

Florida Department of Education

SC.912.L.14

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Small and Large Intestine Functions

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