Digestive System, Enzymes, Absorption in the Small Intestine

7 Parts:

Digestive System

Enzymes

Human Gut Wall

The Villi

Questions and Answers

Referencing this Article

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The digestive system is a reasonably complex set of organs that work collectively to break down ingested food and convert it to energy, vitamins, and nutrients needed to fuel and feed the body. It could be stated that the entire anatomical structure is assembled around the digestive system and for good reason. The human body is constructed to ingest food, transform it into energy and transport the energy throughout the body efficiently and effectively.

Alimentary Canal Parts

Once you've stuffed your face with that steak hoagie, it takes quite a trip through your body, making stops throughout the digestive system in order to break down ingested food into nutrients. The first stop is at the Alimentary Canal or GI tract. The Alimentary Canal consists of:

• Oral Cavity.
• Pharynx.
• Esophagus.
• Stomach.
• Small Intestine.
• Large Intestine.

Digestion Accessory Organs

All of the components of the Alimentary Canal have food pass through them and deal directly with the food ingested. There are also accessory organs that aid in digestion but do not have food pass through them directly. Organs that act as accessories to digestion include:

• Salivary Glands.
• Liver.
• Gallbladder.
• Pancreas.

The digestive system has six major stages in the conversion of food to energy:

1. 1
   Ingestion

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   Intake of food or fluids.

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2. 2
   Secretion

   .

   The body secretes fluids and digestive enzymes.

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3. 3
   Mixing and movement of food and waste throughout the body.

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4. 4
   Digestion

   .

   Breaking down of food.

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5. 5
   Absorption of nutrients into the body

   .

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6. 6
   Excretion of waste out of the body

   .

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Types of Digestion:

1. 1
   Mechanical Digestion

   :

   is a process that uses force to break down food into smaller elements. Such as, grinding and churning of food.

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2. 2
   Chemical Digestion

   :

   is described as the use of chemicals, like enzymes (saliva, pepsin, renin, amylase, protease, lipase,..) in the digestion process.

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Process of Digestion

1. 1
   Once the food enters the mouth, it undergoes mechanical digestion to break the larger particles of food into smaller ones, then these small particles are mixed with saliva (digestive juice of the mouth) to form a bolus

   .

   At this level, starch (complex sugar also called polysaccharide) is broken down with the help of amylase enzyme into maltose (di-saccharide).

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2. 2
   After being swallowed, the bolus travels down the oesophagus by a process called the peristaltic movement to reach the stomach

   .

   Involuntary muscle contractions push the food down the esophagus and through the intestines. The diagram below outlines the peristaltic movement of the esophagus. The food is propelled similarly through the intestines. Please note that "Esophagus" is the American spelling, while "Oesophagus" is the British spelling.

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3. 3
   When food particles enter the stomach, they are mixed with the gastric juice (containing the enzymes of the stomach), and also churned to be digested properly

   .

   At this level, the proteins are broken down to peptides by the help of the proteases and then transported to the small intestine.

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4. 4
   In the small intestine, the food particles are digested to their smallest elements called "nutrients"

   .

   At this level, the peptides are broken down into amino acids, whereas the di-saccharides are broken down into simple sugars (mono-saccharides), and the fats are broken down to fatty acids and glycerol. All these processes happen with the help of the bile (a greenish liquid secreted by the liver that emulsifies the fats), the pancreatic juices (that secrete enzymes directly into the small intestine), and the intestinal juices.

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5. 5
   Once the food is completely digested, the nutrients are absorbed by the blood through the intestinal villi (brush-like elements found on the walls of the small intestine)

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6. 6
   The remaining food, that is deprived of nutrients, passes from the small intestine to the large intestine where water is retained, and then the rest of the molecules are exported out of the body as waste "feces" through the anus.

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For more information about enzymes see Enzymes. Enzymes, also known as "biological catalysts", are chemical elements that catalyze, and speed up the breakdown of complex food into simple nutrients. Here are a few and what they do:

Enzymes are sensitive. Each enzyme acts at a specific temperature, specific pH, and on a specific substrate (food upon which the enzymes act). For example, salivary amylase (found in the saliva of the mouth) works best at neutral pH, whereas gastric enzymes work best in acidic medium, and the intestinal or pancreatic enzymes work best in basic medium. The Optimum Temperature of enzymes is 37 &degrees;C, which is the normal human body temperature. The enzymes become inactive at 0 &degrees;C and are destroyed at 60 &degrees;C.

The diagram below illustrates the of the human gut wall including the differing layers. The lumen is an empty space in the gut where nutrients are accumulated. The first actual layer is the mucosa. It has a layer of epithelium, made of epithelial cells, which have projections called villi.

In the diagram, you should also notice the capillaries, part of the blood network which absorbs the nutrients. And also, the lacteal ducts which are special tubes that carry fat molecules to the lymph. lymphatic system.

By the time food reaches to the villi, it is already digested to small nutrients. These small nutrients can pass through the alimentary tract lining and can readily be absorbed by the blood. The food products pass into the blood stream through villi, which are small folded structures that cover the internal surface of the small intestine.

It is important to know that there are a number of factors that improve the efficiency of absorption. The villi on their own increase the surface area. However, the microvilli which are smaller projections (see diagram) further increase the surface area and speed up the absorption process.

How to remember the enzymes in the digestive system?

I am doing access course in biology about the digestive system. I have an exam on the digestive system and enzyme

ScienceAid QnA. There are several ways you can remember the names of enzymes.

1) Sometimes, the name of the enzyme shows what substrate it acts on. For example, protease and peptidase digest proteins and peptides respectively. Whereas lipase digests lipids, and amylase acts on sugars.

2) In the digestive system, each enzyme is secreted and acts in a different medium. For example, pepsin (for proteins) is an enzyme that acts in acidic medium (therefore it should act in the stomach). Trypsin is an enzyme that acts in basic medium, therefore, it should act in the small intestine.

3) Third, by using logic. Remember, the sugar digestion starts in the mouth and continues in the small intestine, so the enzymes of the sugar molecules should be found in the mouth and the small intestine. The protein digestion starts in the stomach and continues to the small intestine, therefore, the proteases and the peptidases should be in the stomach and the small intestine. The lipid digestion starts in the small intestine, therefore lipases will be in the small intestine.

I don't know how detailed your course is, If you have further questions do not hesitate to contact us.

Thank you

How can I write an essay question on enzymes in digestion?

I have to write an essay for my college course on the digestive system can you help me?

ScienceAid QnA. We can give you hints and help you find the source. However, you have to read and write on your own.

For example, you can first define digestion, then in the body paragraphs, you can talk about the 2 types of digestion, and in each part mention where each type of digestion takes place and what are the enzymes involved. As a conclusion, you can talk about the different enzymes and how specific they are.

Do you have any names or dates I can use to reference this article?

Hi Jamie,... I am referencing your article and not sure who to put as the author or the publication date, as this information I cannot find on the page. Thought I should contact you, any details would be greatly appreciated. Regards. (I'm not entirely certain what to put here, I haven't seen anybody ask this question already)

ScienceAid QnA. To reference an article from the website please check the part: "Referencing this article" If you need further assistance please do not hesitate to contact us

I am just reviewing the digestive system. Looking for information to help clarify peristaltic movement through longitudinal and circular muscles?

I really appreciate this website. I am enjoying reviewing the process of the digestive system. And I look forward sharing the site with my Biology students to also review over. I have not finished the article, I am looking for a website to help my students review information on the digestive system. I am trying to find two items in specific, list of enzymes that note where reactions occur and information on longitudinal/circular muscles.

I'm happy to hear that you are enjoying the site! Without know the age or level of your students, I'm not sure how accurate the information I've compiled for you is, BUT I was able to find some resources for you that I hope will help.

Enzymes

1. 1
   CliffNotes

   .

   You gotta love CliffNotes! I've used these when teaching for students who struggled with more complex concepts. CliffNotes has a wonderful way of really explaining concepts without "dumbing" them down. Check out online CliffNotes exploring 6 enzymes here.

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2. 2
   Worthington

   .

   The biochemical company has a really great site that explores enzymes. Access it here: [Access it here http://www.worthington-biochem.com/introbiochem/naming.html Access it Here]

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3. 3
   Science Learning Hub

   .

   Excellent resource with TONS of information. Find it Here

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Circular Muscles

1. 1
   Science Learning Hub

   .

   They've done it again! I'm not sure on the level of your students but there's a lot of information on circular muscles with really excellent videos, images and explanations.

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2. 2
   Study.com

   .

   They also have some great resources and similar to CliffNotes in explanation. Find it here.

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3. 3
   Pathology Education Instructional Centre

   .

   This is a much higher presentation of histologic but incredibly useful for teachers. Access it here.

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I hope these resources help!

Name the enzymes that are found in the mouth: duodenum, and ileum?

I was given an assignment which is due tomorrow. I was asked to name the enzymes that are found in the digestive system. The answers that I want are not given.I really need these answers as it can broaden up my mind and help me to gain better understanding

The enzymes found in the mouth are:

• Salivary Amylase.
• Lysozyme.
• Lingual Lipase.
• Salivary Kallikrein.

How to address inability to absorb FATS as documented CDS(stool) analysis?

What are probable causes for lipase deficiency /malabsorption (requiring 40,000 units lipase per meal); suspect either "gut" issue, bile acids, small intestine issue). or ?????? . Noted is a healthy, adult with a Mediterranean diet and supplements of epa/dha;. no health issues except treated hypothyroid ; additionally, very low neurotransmitters (possibly related to fats deficiency) and adrenal dysfunction (low cortisol).. Possible correlation of all the above ? . Family issues of pancreatic problems.. Thinking about above as possibly an absorption issue..... or a genetic issue.. Also raises question of hydrochloric /hcl acid insufficiency?. Because FATS are FUEL, could this impact energy level?. If FATS absorption is a problem , would increasing carbs for energy be something to consider? . What life style and/or diet changes would help.. What tests can shed light on the above problem of fats malabsorption?. How to proceed in terms of energy improvement, neurotransmitter raising and adrenal improvement. . Villi strengthening is of interest along with perhaps removing toxic metals.....and perhaps ?stress?..... for better absorption and digestion..... Of note is a small hiatal hernia and some reflux along with a documented gluten. and lactose allergy (both precautions observed).... appreciate input. Making correlations to brain, adrenals might enlarge the scope of the information presented, along with thoughts on malabsorption causes

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