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

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From Molecules to Organisms: Structures and Processes

9-12.HA.1.10

Anatomy of the Intestines

- L'intestin grêle et le gros intestinsont responsables de l'absorption des nutrimentset de l'eau. 
Bien que l'intestin grêle soit assez étroit,il mesure environ 7m de longet est compacté dans la cavité abdominale. 
Le chyme atteint d'abord le duodénum,puis arrive à la partie du milieu, la plus longue :le jéjunum. 
Là, la paroi interne contient des replis muqueux,couverts de villosités semblables à des doigts. 
La couche de cellules épithéliales qui les recouvrepossède des extensions cytoplasmiquesappelées microvillosités. 
Ces trois structuresaugmentent la surface de l'intestin grêlepour assurer une absorption optimale des nutriments. 
Au bout de l'intestin grêle se trouve l'iléon,qui s'attache au gros intestin par la valvule iléo-cæcale. 
Dans la première partie du gros intestin, le cæcum,il n'y a ni replis ni villosités. 
Elle héberge plutôt un grand écosystème bactérienqui réalise les dernières étapes de la digestion,en décomposant la cellulose. 
Suspendue au bout du cæcum se trouve l'appendice,une petite structure lymphatique. 
Au-dessus d'elle commence le côlon ascendant,suivi du côlon transverse,qui absorbe la plupart de l'eau restante et les électrolyteset transforme le chyme en fèces. 
Les dernières régions, côlons descendant et sigmoïdeet rectum, stockent les fècesjusqu'à leur élimination par l'anus.

Javitt, Norman B. « Histoire de la formation de la bile hépatique : vieux problèmes, nouvelles approches. » Avancées dans l’enseignement de la physiologie 38, n° 4 (1er décembre 2014) : 279-85. [<a href="https://doi.org/10.1152/advan.00076.2014">Source</a>]
Shetty, Sudarshan A., Floor Hugenholtz, Leo Lahti, Hauke Smidt et Willem M. de Vos. « Aménagement paysager du microbiome intestinal : aperçu de l’assemblage communautaire et implications pour les stratégies de modulation microbienne. » FEMS Microbiology Reviews 41, n° 2 (mars 2017) : 182-99. [<a href="https://doi.org/10.1093/femsre/fuw045 » target="__blank">Source</a>]
Wen, Li et Andrew Duffy. « Facteurs influençant le microbiote intestinal, l’inflammation et le diabète de type 2. » The Journal of Nutrition 147, n° 7 (juillet 2017) : 1468S-1475S. [<a href="https://doi.org/10.3945/jn.116.240754 » target="__blank">Source</a>]

anatomie des intestins

Bien que la digestion des protéines, des glucides et des lipides puisse commencer dans l’estomac, elle est terminée dans l’intestin. L’absorption des nutriments, de l’eau et des électrolytes à partir des aliments et des boissons se produit également dans l’intestin. Les intestins peuvent être divisés en deux organes structurellement distincts : l’intestin grêle et le gros intestin.
 
 <h4>L’intestin grêle</h4>
 
 L’intestin grêle est un tube d’environ 22 mètres de long avec un diamètre intérieur de seulement 2,5 cm. Puisque la plupart des nutriments sont absorbés ici, la paroi interne de l’intestin grêle est très contournée et recouverte d’extensions en forme de doigt appelées villosités, chacune contenant des centaines de microvillosités. Les plis, les villosités et les microvillosités de l’intestin grêle amplifient la surface de l’absorption de 60 à 120 fois. L’augmentation de la surface offre de nombreuses possibilités d’absorption des nutriments.
 
 L’intestin grêle se connecte à l’estomac par le sphincter pylorique, qui se ferme lorsque le chyme se déplace dans le duodénum, le début de l’intestin grêle. La partie moyenne et la plus grande de l’intestin grêle est le jéjunum. L’iléon termine l’intestin grêle, où il se fixe au gros intestin par la valve iléo-cæcale.
 
 <h4>Le gros intestin</h4>
 
 Le gros intestin commence au cæcum. L’appendice, une petite structure lymphatique, pendille du fond du cæcum. Au-dessus du cæcum, commence le côlon ascendant suivi par le côlon transversal. Ils absorbent la plupart de l’eau restante et les électrolytes du chyme, en le transformant en excréments. Le côlon descendant, le côlon sigmoïde et le rectum stockent les excréments jusqu’à l’élimination par l’anus.
 
 Dans l’ensemble, le gros intestin mesure environ 1,5 m de long avec un diamètre intérieur de 4,8 cm. Il ne contient pas de plis ni de villosités, mais les cellules épithéliales absorbantes ont des microvillosités. Le gros intestin abrite un écosystème bactérien qui effectue les dernières étapes de la digestion : décomposer la cellulose et les fibres, des composés que l’estomac et l’intestin grêle sont mal équipés pour traiter.
 
 <h4>La diversité bactérienne</h4>
 
 Le gros intestin contient plus de 700 espèces différentes de bactéries. On pense que la diversité bactérienne est liée à l’obésité et au développement du diabète de type 2. Les personnes obèses ont moins de souches bactériennes que leurs homologues non obèses. Une faible diversité bactérienne a également été associée à la résistance à l’insuline. L’écosystème bactérien intestinal — le biome intestinal — est établi peu de temps après la naissance, les bébés étant allaités développant leur biome intestinal à partir de bactéries présentes dans le lait maternel. Après la naissance, le biome est façonné par la génétique, l’alimentation, l’âge, le sexe et son système immunitaire. Des facteurs externes comme l’alimentation, l’état de santé, les médicaments et l’emplacement géographique influencent également de manière significative la complexité du biome intestinal.

Anatomie des intestins

Bien que la digestion des protéines, des glucides et des lipides puisse commencer dans l’estomac, elle se termine dans l’intestin. L’absorption des nutriments, de l’eau, ...

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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.

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2. Obtain, evaluate, and communicate information to describe how the structures of the integumentary system and its accessory organs contribute to its function. Examples: how the layers of the skin contribute to homeostasis, the role of glands in thermoregulation and in hydration of skin and mucous membranes, the protective functions of hair and nails

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a. Construct an explanation of the relationships between the integumentary system and other organ systems, including the body's mechanisms for maintaining homeostasis. Examples: Explain how changes in vessel diameter and evaporation of water over the skin contribute to thermoregulation (cardiovascular). Explain how sweat is used to excrete nitrogenous waste from the blood (cardiovascular). Explain how the skin and mucous membranes create a barrier against infection (immune system).

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5. Obtain, evaluate, and communicate information explaining the relationship between the structures and functions of the central nervous system and the peripheral nervous system.

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b. Construct an explanation of the role of reflex arcs, the central nervous system, and special senses in the response to stimuli to maintain homeostasis and guide behavior. Example: smelling a strong odor initiating a sneeze response using a reflex arc; pupil diameter changing in relation to the amount of light entering the eye Clarification: Discussion of the anatomy and physiology of the sensory organs is not required.

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c. Construct an explanation of the role of neurotransmitters in the functions and behavior of the nervous system. Clarification: Discussion of classes of neurotransmitters is not required.

9-12.HA.1.5.c

Small and Large Intestine Functions

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