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  • How our Digestive System Works?

  • Our digestive system is a combination of

  • mechanical and chemical actions.

  • Imagine, putting your food in a petri dish,

  • chopping it up, and exposing it

  • to a bunch of chemicals and microbes.

  • Can you imagine what it would look like in the end?

  • This is what the digestive system does.

  • MOUTH

  • The journey down the alimentary canal

  • begins in the mouth.

  • Here, the food is broken down

  • into smaller chewable pieces.

  • Chewing, breaks the food into pieces,

  • while the saliva mixes with food

  • to begin the process of breaking it down

  • into a form your body can absorb and use.

  • Rolling action of the tongue

  • and secretion of saliva

  • rolls food into a bolus.

  • The saliva contains water,

  • electrolytes,

  • antibacterial components,

  • and enzymes such as amylase.

  • Amylase converts carbohydrates into sugars.

  • THROAT

  • The throat is the region where the mouth cavity

  • and the nasal passages join.

  • Swallowing pushes the food

  • through the throat or pharynx

  • and into the esophagus.

  • An important function of the throat

  • is that it prevents the food

  • from entering into the trachea,

  • more commonly known as the windpipe.

  • When the food enters our throat,

  • the larynx or our voice box closes.

  • This results in epiglottis covering

  • the entrance of the trachea or windpipe.

  • The epiglottis is a flap of tissue.

  • ESOPHAGUS

  • Now that the food has reached the esophagus,

  • a wave of smooth muscle contractions occurs,

  • pushing the food into the stomach.

  • These smooth muscle movements

  • are called peristalsis.

  • The importance of sphincter muscles.

  • Three types of sphincter muscles

  • help in the digestive system.

  • Here, at the junction of the esophagus

  • and the stomach

  • is a thick ring of circular-smooth-muscle,

  • that prevents the movement of food

  • pass from esophagus into the stomach.

  • It is called the esophageal sphincter.

  • Another sphincter muscle, the pyloric sphincter,

  • directs the passage of food

  • from the stomach into the intestine.

  • The third sphincter muscle surrounds the anus.

  • STOMACH

  • Most of us eat our food in a matter of minutes,

  • but digesting it can take hours.

  • One of the important functions of our stomach

  • is to store food until it is digested.

  • Food can be stored here for 2-6 hours.

  • It also kills the microorganisms

  • we consume unconsciously along with our food,

  • and begins the digestion of the proteins

  • we took in our diet.

  • The stomach secretes gastric juice,

  • hydrochloric acid, water, mucus, pepsin, and renin,

  • that continue the process of breaking down the food.

  • Pepsin is secreted as pepsinogen

  • by cells in the gastric glands

  • that are present in the deep folds

  • of the stomach lining.

  • Other cells in the gastric glands

  • produce hydrochloric acid,

  • which has a pH balance between 1 and 3.

  • The low pH helps convert pepsinogen to pepsin

  • and is also the right pH

  • for pepsin enzymatic action.

  • Hydrochloric acid or HCl

  • also helps break the bonds

  • holding the ingested contents together.

  • The breakdown of these food contents

  • exposes more surface area

  • to the action of pepsin,

  • and later to the other digestive enzymes

  • in the small intestine.

  • Mucus secreted by the stomach

  • lines the walls of the stomach and protects them

  • from being digested by HCl and pepsin.

  • If this coating is eroded

  • at some place of the stomach,

  • for instance by the attack of

  • bacteria Helicobacter pylori,

  • it can cause an ulcer.

  • Contractions of the smooth muscles

  • in the walls of the stomach, roll around its contents,

  • mixing partly digested food with enzymes and acids.

  • This acidic fluid mixture of gastric juice

  • is called chyme.

  • Peristaltic movements of the stomach walls

  • push chyme towards the end of the stomach.

  • These waves of peristalsis

  • cause the pyloric sphincter

  • to relax briefly,

  • so that very little amount of chyme

  • can enter the small intestine.

  • In this way, our stomach empties itself gradually

  • over a period of almost four hours.

  • The small intestine works

  • on a small amount of food at a time.

  • We'll continue to explain the small intestine,

  • pancreas, liver, gall bladder,

  • down to colon and rectum in the next video.

  • Actually, we were told to make

  • this title into two parts,

  • so we can publish more.

  • It's a cheat, really.

  • But a new project is a kind of refreshing

  • to our animators and designers,

  • giving them some false sense of

  • novelty and freedom.

  • So, at least we've got that going for us,

  • which is nice.

How our Digestive System Works?

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B2 中高級 美國腔

我们的消化系统如何运作?(How our Digestive System Works?)

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    joey joey 發佈於 2021 年 04 月 24 日
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