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

- [Istruttore] L'intestino
tenue e crasso sono responsabili

dell'assorbimento di
sostanze nutritive e acqua.

Mentre l'intestino tenue
è piuttosto stretto,

l'organo è lungo circa 0,67 metri

e compattato nella cavità addominale.

Il chimo raggiunge prima il duodeno

e poi viaggia in mezzo,
e la parte più lunga,

il digiuno.

Il rivestimento interno
contiene le pieghe della mucosa,

dove sono ricoperti di
villi simili a dita.

Lo strato sovrastante
delle cellule epiteliali

ha estensioni citoplasmatiche
chiamate microvilli.

Queste tre strutture
aumentano la superficie

dell'intestino tenue per garantire che i

principi nutritivi siano
assorbiti in modo ottimale.

Alla fine dell'intestino tenue c'è l'ileo,

che si attacca all'intestino crasso

dalla valvola ileocecale.

Nella prima parte
dell'intestino crasso, il cieco,

non ci sono pieghe o villi.

Piuttosto, è sede di un
grande ecosistema batterico

che esegue le fasi
finali della digestione,

abbattere la cellulosa.

Ciondolante sul fondo
del cieco è l'appendice,

una piccola struttura linfatica.

Sopra inizia il colon ascendente,

seguito dal colon trasverso,

che assorbe la maggior parte
dell'acqua e degli elettroliti

rimanenti trasformando il chimo in feci.

Le ultime regioni, il colon
discendente, il colon sigmoide,

e retto, conservano le
feci fino all'eliminazione

attraverso l'ano.

Javitt, Norman B. "Storia della formazione della bile epatica: vecchi problemi, nuovi approcci". Advances in Physiology Education 38, n. 4 (1 dicembre 2014): 279–85. [<a href="https://doi.org/10.1152/advan.00076.2014">Sorgente</a>]
Shetty, Sudarshan A., Floor Hugenholtz, Leo Lahti, Hauke Smidt e Willem M. de Vos. "Paesaggio del microbioma intestinale: approfondimenti sull'assemblaggio della comunità e implicazioni per le strategie di modulazione microbica". Recensioni di microbiologia FEMS 41, n. 2 (marzo 2017): 182–99. [<a href="https://doi.org/10.1093/femsre/fuw045" target="__blank">Sorgente</a>]
Wen, Li e Andrew Duffy. "Fattori che influenzano il microbiota intestinale, l'infiammazione e il diabete di tipo 2". The Journal of Nutrition 147, n. 7 (luglio 2017): 1468S-1475S. [<a href="https://doi.org/10.3945/jn.116.240754" target="__blank">Sorgente</a>]

anatomia degli intestini

Anche se la digestione di proteine, carboidrati e lipidi può iniziare nello stomaco, è completata nell'intestino. L'assorbimento di sostanze nutritive, acqua ed elettroliti da cibo e bevande si verificano anche nell'intestino. L'intestino può essere diviso in due organi strutturalmente distinti: l'intestino piccolo e grande.

<h4>Il Piccolo Intestino</h4>

L'intestino tenue è un tubo lungo 22 metri con un diametro interno di soli 2,5 cm. Poiché la maggior parte dei nutrienti sono assorbiti qui, il rivestimento interno dell'intestino tenue è altamente contorto e coperto di estensioni simili a dita chiamate villi, ognuna contenente centinaia di microvilli. Le pieghe, villi, e microvilli dell'intestino tenue amplificano la superficie di assorbimento 60 a 120 volte. L'aumento della superficie offre ampie opportunità di assorbimento dei nutrienti.

L'intestino tenue si collega allo stomaco dallo sfintere pilorico, che si chiude quando il chime si muove nel duodeno, l'inizio dell'intestino tenue. La parte centrale e più grande dell'intestino tenue è il jejunum. L'ileo termina l'intestino tenue, dove si attacca all'intestino crasso dalla valvola ileocecale.

<h4>Il grande intestino</h4>

L'intestino crasso inizia dal cecum. L'appendice, una piccola struttura linfatica, penzola dal fondo del cecum. Sopra il cecum, inizia il colon ascendente seguito dal colon trasversale. Assorbono la maggior parte dell'acqua e degli elettroliti rimanenti dal chimo, trasformandolo in feci. Il colon discendente, il colon sigmoide e il retto conservano le feci fino all'eliminazione attraverso l'ano.

Complessivamente l'intestino crasso è lungo circa 1,5 m con un diametro interno di 4,8 cm. Non contiene pieghe e villi, ma le cellule epiteliali addominali hanno microvilli. L'intestino crasso ospita un ecosistema batterico, che esegue le fasi finali della digestione, abbattendo cellulosa e fibra, composti che lo stomaco e l'intestino tenue sono mal equipaggiati per elaborare.

<h4>Diversità batterica</h4>

L'intestino crasso contiene oltre 700 specie diverse di batteri. Si ritiene che la diversità batterica sia correlata all'obesità e allo sviluppo del diabete di tipo 2. Gli individui obesi hanno meno ceppi batterici rispetto ai loro omologhi non obesi. Bassa diversità batterica è stata anche associata con l'insulino-resistenza. L'ecosistema batterico intestinale, il bioma intestinale, è stabilito poco dopo la nascita, con i bambini allattati al seno che sviluppano il loro bioma intestinale da batteri presenti nel latte materno. Dopo la nascita, il bioma è modellato dalla genetica, dalla dieta, dall'età, dal sesso e dal suo sistema immunitario di un individuo. Fattori esterni come la dieta, stato di salute, farmaci, e la posizione geografica influenzano anche in modo significativo la complessità del bioma intestinale.

Anatomia degli intestini

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

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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.

Small and Large Intestine Functions | JoVE K12

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Small and Large Intestine Functions

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