Understanding your digestive system

Image showing a womans hands on her abdomen, symbolising the theme of the article which is: "understanding your digestive system".

Welcome to your digestive system!

Another article today with the aim of improving your general understanding of your digestive system and its component parts and processes.

In this guide, I’m diving into the fascinating world of digestion, with the hopes of unravelling the complexities of the digestive system for you in simple terms, and exploring the crucial role it plays in our overall health and well-being.

Whether you’re new to the concept of gut health or looking to deepen your understanding, this article will serve as your roadmap to digestive wellness, and serves as a great starting point on my Gut Be Good website to learn more about your digestive system before making potential lifestyle changes to get on top of your gut health.

I’ve thoroughly enjoyed writing this one and feel that it’s really jammed full of helpful information for you.

If you have any further questions, please do get in contact with me here via email, or on Instagram @gemma.hartshorn.




You can also check out The Gut Be Good Podcast and YouTube episodes by clicking here.

Use the content list below for quick links to relevant sections within this article:

Introduction

Understanding the digestive system introduction

From beginning to end – the digestive pathway

Teeth

Saliva & Glands

Pharynx & Oesophagus

Stomach

Small Intestine:
overview, duodenum, jejunum, ileum

Large Intestine

Conclusion

Ready to embark on your gut health journey?

Final Message

Disclaimer/Disclosure

Sources

Introduction

Thank you for being here today!


By the end of this article your knowledge of the digestive system as a whole will be markedly improved upon, and should leave you feeling confident to take your next learning steps on my site and in your own life for a healthier gut.


Listen to the Spotify podcast or YouTube podcast too for more information about gut topics!


Click the links to head to those platforms directly or find them on this page of my site.

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    Understanding the Digestive System

    In this section, we’ll start by exploring the anatomy and physiology of the digestive system.

    We’ll break down each component, from the mouth to the rectum, highlighting its function and significance in the digestive process. By understanding how each part of the digestive system works, you’ll be able to understand the journey your food takes from ingestion to elimination.

    The digestive system is responsible for chemically and mechanically breaking down the food we eat from large components into smaller ones, with each section of the digestive system playing a different part in this process.

    Digestion such as this is essential for us to be able to access the nutrients contained within the food that we eat. As our digestive system breaks down food into smaller molecules, it can then be absorbed by the body through the lining of the intestinal wall and used by the body cells in a myriad of ways.

    From beginning to end – the digestive pathway

    Digestion begins in the mouth with the process of chewing your food and swallowing; but there’s so much more to it than just that!

    Teeth

    Our teeth’ shape and placement provide us with the opportunity to begin the digestive process through chewing, or mastication (the scientific name for chewing). Some teeth are pointed for piercing and tearing foods, while others have multiple sharp points to allow for grinding and crushing of foods.

    Saliva & Glands

    During this process of chewing (or mastication), saliva is produced and mixed with the food we’ve eaten until it forms a smaller, rounded mass called a bolus, which is swallowed easily because its well lubricated by our saliva.

    The salivary glands produce this saliva, and excrete it into the mouth from different points within the mouth. Because the glands lie external to the mouth they are actually considered accessory glands associated with the digestive system because they secrete saliva into part of the digestive system from the outside.

    Contained within our saliva are a variety of enzymes (most notable is likely the amylase enzyme which begins the break down of carbohydrates into smaller compounds) which initiate the breakdown of our food into smaller, more manageable bites; although the saliva also contains mineral salts, proteins, water and mucus as well as these digestive enzymes.

    Pharynx & Oesophagus

    Moving down the digestive tract, we find the pharynx, or throat, which is a tube-like structure that is involved in both digestive systems and respiratory, as it allows both air and food to pass through it.

    The pharynx transports the food in the form of a bolus from the mouth when we swallow, passing it into the oesophagus and then on into the stomach.

    Food is moved through the digestive system through a series of rhythmic contractions called peristalsis. This is the name for the wave-like contractions within the muscular walls of the intestine that cause the food contained within to be moved along.

    Stomach

    Upon reaching the stomach, our food encounters a highly acidic environment that further breaks down proteins and facilitates the release of enzymes and gastric juices necessary for digestion.

    These gastric juices are hydrochloric acid and an enzyme called pepsin. There’s also intrinsic factor present here, secreted by the stomachs cells to protect vitamin b12 so that it can be absorbed later on in the small intestine.

    The stomach also has a muscular wall which contracts and mixes the food thoroughly with the gastric juices until a semi solid mixture is formed called chyme. It’s thought that the muscular contractions in the stomach are what results in peristalsis (the wave like motion within the intestinal walls which moves food along the digestive tract) through out the rest of the digestive system.

    Use the content list below for quick links to relevant sections within this article:

    Introduction
    Understanding the digestive system introduction
    From beginning to end – the digestive pathway
    Teeth
    Saliva & Glands
    Pharynx & Oesophagus
    Stomach
    Small Intestine:
    overview, duodenum, jejunum, ileum
    Large Intestine
    Conclusion
    Ready to embark on your gut health journey?
    Final Message
    Disclaimer/Disclosure
    Sources

    Small Intestine

    Overview

    When our food has been thoroughly mixed into chyme within the stomach, it then starts to leave and passes into the beginning of the small intestine which is made up of three distinct sections: the duodenum, the jejunum, and the ileum. The whole small intestine is about 7 metres long and takes its name, “the small intestine” from the fact that it is narrow in diameter when compared to the large intestine.

    Within the small intestine are thousands of microscopic intestinal glands which secrete intestinal digestive juice containing large amounts of enzymes to digest fats, proteins and carbohydrates that are then absorbed in the intestine.

    In order to increase the small intestine’s absorption capabilities, the small intestinal lining has multiple circular folds called plicae. These folds are also covered in thousands of finger-like projections, collectively called villi, which are present to increase the surface area of the small intestine and allow for maximum nutrient absorption capability by the small intestine.

    Digestive system simple diagram with labels showing names of organs of the digestive system
    Digestive system diagram

    Fig 1: Lamb, P. (2019). As published in Nigam Y et al (2019) Gastrointestinal tract 4: anatomy and role of the jejunum and ileum. Nursing Times [online]; 115: 9, 43-46.

    On each individual villi, called a villus, you’ll find epithelial cells which have a brush-like border on them composed of microvilli. Their purpose is to further increase the surface area for nutrient absorption in the small intestine.

    Inside an individual villus you’ll find a rich blood supply through a large network of blood capillaries. It is here that nutrient absorption takes place, as smaller products from the digestion of carbohydrates and proteins are absorbed into the bloodstream in the form of sugars and amino acids. You’ll also find fats being absorbed here by the lymph capillaries.

    The Duodenum

    The duodenum forms the first section of the small intestine which is connected to the stomach. Most of the chemical digestive processes of the small intestine take place here, as acidic chyme from the stomach enters the small intestine.

    Within the middle of the duodenum you’ll also find two ducts which allow pancreatic digestive juices and bile from the liver and gallbladder (the storage place for bile created by the liver) to flow into the small intestine. The function of bile here is to help break down and emulsify fats into their smaller components for digestion.

    When chyme containing lipids (fats) enters the duodenum, the body initiates a mechanism which contracts the gallbladder and forces the bile into the small intestine.

    Fats in chyme also trigger the secretion of a hormone called cholecystokinin or CCK from the intestinal mucosa within the duodenum. The role of CCK is to stimulate the contraction of the gallbladder to release bile as well as controlling the opening of the ducts that allow the bile to flow into the small intestine.

    The Jejunum & Ileum

    These next two sections of the small intestine mostly take on the role of absorption of the smaller components that were chemically broken down in the first section of the small intestine, the duodenum.

    You’ll find most of the smaller components of broken down foods being absorbed here in the jejunum and ileum such as lipids, monosaccharides and amino acids, among others. Some absorption does also take place in the duodenum, but not as much.

    As I also mentioned earlier, the small intestine is covered in folds and finger-like projections called villi to increase the surface area of the small intestine for maximum nutrient absorption; it’s at the site of each individual villus that this absorption is taking place within the jejunum and the ileum, as shown below in the diagrams.

    Villi diagram of the small intestinal lining where nutrient absorption takes places
    Villi diagram

    Fig 2: Lamb, P. (2019). As published in Nigam Y et al (2019) Gastrointestinal tract 4: anatomy and role of the jejunum and ileum. Nursing Times [online]; 115: 9, 43-46.

    Villus diagram showing labelled parts and how transport of nutrients takes place at an individual villus within the small intestine
    Villus Diagram

    Fig 3: Lamb, P. (2019). As published in Nigam Y et al (2019) Gastrointestinal tract 4: anatomy and role of the jejunum and ileum. Nursing Times [online]; 115: 9, 43-46.

    The main functions of the jejunum and ileum are to finish nutrient absorption; to do this, the small intestinal walls have smooth muscle within them which contract and relax repeatedly in a process called segmentation, which moves the chyme backwards and forwards to mix it with digestive juices; as it does so, it pushes the chyme against the walls of the intestine for nutrients to be absorbed.

    The rough, folded interior of the small intestine is an ideal surface for also slowing down the forward movement of food through the body; after all, you want this process to be fairly slow to allow the body enough time to absorb as many nutrients as possible from the foods.

    Once the small intestine has absorbed as many nutrients as it can from the food, the contraction and relaxing of the smooth muscle stops and is replaced by the peristalsis movement instead. As I mentioned earlier, peristalsis is the wave-like motion which pushes food forward along the digestive tract and on to its next step in the digestive process: in this case, the large intestine.

    Use the content list below for quick links to relevant sections within this article:

    Introduction
    Understanding the digestive system introduction
    From beginning to end – the digestive pathway
    Teeth
    Saliva & Glands
    Pharynx & Oesophagus
    Stomach
    Small Intestine:
    overview, duodenum, jejunum, ileum
    Large Intestine
    Conclusion
    Ready to embark on your gut health journey?
    Final Message
    Disclaimer/Disclosure
    Sources

    Large Intestine

    The large intestine is so named for it’s diameter; although it is shorter than the small intestine at only 1.5 metres, the diameter is much larger. Within the large intestine, undigested and unabsorbed food is passed from the small intestine through the ileocecal valve.

    By the time food gets to the large intestine though, it can no longer be called chyme and begins to look more like faecal matter. Here, the consistency changes as water and salts are reabsorbed from the food during its passage through.

    The most significant part of the large intestine though is perhaps not human at all, but made up of bacteria as our large intestine plays host to what some call, our “second brain”, the microbiome.

    This incredible and uncountable amount of working bacteria act upon any undigested and unabsorbed food which not only serves them as a food source, but also serves us, as by-products of their action releases further nutrients from food which we may not have had access to otherwise.

    Bacteria here can break down cellulose and release nutrients from fibrous material in our foods and from this, we are able to absorb nutrients and vitamins that allow us to thrive. We co-exist with our microbiome, offering these tens of millions of bacteria a home whilst they in turn offer us access to nutrients that our bodies need for survival.

    Most notably perhaps are vitamin K and some of the B vitamins, which are released from this food matter in the large intestine by bacteria and then absorbed by the body for important functions such as normal blood clotting.

    One big difference between the small and large intestine’ is the fact that the large intestine is not so well designed for nutrient absorption. Where the small intestine is capable of both passive and active transport of nutrients via the villi, the large intestine has no villi and mostly uses active transport to absorb nutrients, which requires energy to achieve.

    Because of the lack of villa and surface area in the large intestine, food matter also passes through this area of the body much slower than in the small intestine, with foods taking as long as 3-5 days to fully pass through.

    It is also from the large intestine that food eventually makes its departure journey out of our bodies, via the last segment of the large intestine, the anus. On its journey to get here, the food matter passes from the ileum of the small intestine into the first section of the large intestine called the cecum.

    From the cecum, food matter travels upwards through the ascending colon, through the traverse colon, down the descending colon, into the sigmoid colon and on to the terminal portion of the rectum called the anal canal, which finally ends with the external opening called the anus.

    There are two sphincter muscles that control the opening and closing of the anus, one which is involuntary and an outer one which is voluntary. These are the inner and outer sphincters. It’s thought that we have two so that as faecal matter reaches the inner sphincter and our body makes us aware of our need to defecate (to poo, that is!), we then are capable of holding this in until a time we’re able to go to the toilet.

    Think about it this way, have you ever had the sensation come on that you needed to poo, but through conscious thought about being in the wrong place or not near a toilet, this immediate need temporarily passed and you were able to wait minutes, maybe even hours before actually going?

    Well, this is the work of the outer and voluntary sphincter – we’re able to control (in most cases that is) when we actually poo! A handy ability if in the wrong place at the wrong time when the need comes on to “go”, wouldn’t you agree?

    Conclusion

    By understanding the function and significance of each component of the digestive system and how they work together in harmony, I hope you’ll now have a deeper appreciation for the complexity and efficiency of the body’s digestive processes.

    Hopefully now you’ll feel more equipped to read other material on my site and to discover other aspects of gut health and gluten free living.

    I hope you feel empowered with knowledge and can go ahead and make more informed choices to support optimal digestive health and overall well-being for yourself going forward.

    Ready to embark on your gut health journey?

    Join my email list for exclusive insights, subscribe to the Gut Be Good Podcast, and follow The Gut Be Good YouTube channel for more in-depth discussions and helpful (but also, fun) videos!

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      Keywords: Digestive system, Gut health, Anatomy, Physiology, Saliva, Stomach, Small intestine, Large intestine, Nutrient absorption, Microbiome

      Final message:

      Remember, empowering yourself with knowledge and seeking professional guidance are paramount in navigating the complexities of diagnosis and ensuring the appropriate steps toward better health.


      Remember, I’m always here to help!

      Get in contact here if you need me.

      Gemma x

      DISCLAIMERS & DISCLOSURES

      This post may contain affiliate links, which means I may receive a commission, at no extra cost to you, if you make a purchase through a link.
      Please see my full disclosure for further information
      DISCLOSURE
      & my full Disclaimer for further information – DISCLAIMER

      Any advice offered within this article is meant for educational purposes only and should not be used as a sole resource for understanding the medical conditions discussed within. Any changes made to your diet, lifestyle and general well-being should be discussed with your GP or similar healthcare professional who is aware of your unique medical history and not made according to advice provided within this article or anywhere else on this website.


      While the utmost care has been taken in devising the information residing on this website, it is your sole responsibility as the reader to utilise the information as you see fit and by reading the information present on this website you accept personal responsibility over any health outcomes related to you and your condition which occur as a direct or indirect result of using the information on this website in any way.

      Always Check Ingredients Labels for Allergen Information
      before consuming a product.

      This is important in case there are changes in
      manufacturing since the date of publication of this article.

      It’s also a good idea in general, especially if you have allergies rather than intolerances/sensitivities to certain ingredients to check ingredients labels before consuming a product.

      Use the content list below for quick links to relevant sections within this article:

      Introduction
      Understanding the digestive system introduction
      From beginning to end – the digestive pathway
      Teeth
      Saliva & Glands
      Pharynx & Oesophagus
      Stomach
      Small Intestine:
      overview, duodenum, jejunum, ileum
      Large Intestine
      Conclusion
      Ready to embark on your gut health journey?
      Final Message
      Disclaimer/Disclosure
      Sources

      Sources

      Encyclopaedia Britannica. (n.d.). Saliva. In Encyclopaedia Britannica. Retrieved from https://www.britannica.com/science/saliva

      National Institute of Diabetes and Digestive and Kidney Diseases. (n.d.). Digestive System: How It Works. Retrieved from https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works

      Nigam Y et al (2019) Gastrointestinal tract 4: anatomy and role of the jejunum and ileum. Nursing Times [online]; 115: 9, 43-46.

      Nigam Y et al (2019) Gastrointestinal tract 5: the anatomy and functions of the large intestine. Nursing Times [online]; 115: 10, 50-53.

      Patton, K. T., & Thibodeau, G. A. (2018). The human body in health & disease. 7th edition. St. Louis, Missouri, Elsevier.

      WebMD. (n.d.). Your Digestive System. Retrieved from https://www.webmd.com/digestive-disorders/your-digestive-system

      Gemma Hartshorn

      Gemma is a mum to twins with non-coeliac gluten sensitivity and has been living a gut-health focused life for many years herself. She has 5 years adult nursing experience in the UK and achieved a distinction in her Diploma of Higher Education in Healthcare from Oxford Brookes University. She is currently completing a BSc in Health Science and has a keen interest and knowledge of all things gut health. Listen to her Gut Be Good podcast or join her on the Gut Be Good youtube channel for more insights, sharing and helpful information on all things gut health related alongside her website here. Contact Details: glutenfreeshopeasy@gmail.com Unit 80366, PO Box 6945, London, W1A 6US

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