Alimentary canal - Example, Defination, Diagram

The alimentary canal is a long, tubular structure of the digestive system in charge of intake and consumption followed by digestion, absorption, and elimination of food. It consists of several organs that include the mouth, oesophagus, stomach, intestines, and anus, which take up a very critical role in processing nutrients for survival. This topic in Biology is a part of the chapter on Digestion and Absorption in CBSE Class 11. Questions on the alimentary canal generally come up in exams like NEET, AIIMS, Nursing, and Paramedical, accounting for about 2-3% marks, and are essential to understanding the overall topic of human physiology and nutrition.

Segments of the Human Alimentary Canal

The alimentary canal, or digestive tract, is a long tube that forms a continuous pathway through which food passes as it undergoes digestion and nutrients are absorbed. The entire length of the canal measures approximately 9 meters in length, from the mouth to the anus. It begins in the mouth by mechanical and chemical breakdown, and ends with the absorption of nutrients in the small intestine, besides elimination from the anus.

The primary segments of the human alimentary canal are:

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Parts Of The Alimentary Canal

The three main parts of the human alimentary canal are

• Oral cavity

• Transport passage

• The digestive tract

Oral cavity

• The oral cavity is where food is swallowed. It is made up of tongue, teeth, and palate.
• Additionally, the teeth's movement breaks down the food into tiny pieces.
• Human saliva in the mouth cavity softens the food. Amylase and lysozyme found in saliva are released by the salivary gland.
• Food is moved more easily across the oral cavity thanks to the motion of the jaws and tongue.
• The foodstuff bolus is moistened and broken up after which it is delivered to the oesophagus via deglutition (swallowing).

Transport Cavity

• The transport channels do not cause any biochemical changes in the food bolus; they merely make it easier for it to move via peristalsis from one section of an alimentary canal to the next.
• These transport passageways are essentially muscular tubes with stratified squamous epithelium and a few mucous glands that produce lubricating mucus lining the inside.

Digestive Tract

The digestive system is further divided into many parts

• Stomach

• Small intestine

• Large intestine

Primary Function of the Alimentary Canal

Ingesting food material and separating it into smaller portions is the main purpose of the alimentary canal or digestive tract. The tiny fractions that are transformed into smaller molecules by a number of secretions, primarily digestive enzymes are taken up by the blood and lymphatic systems.

These small molecules, which serve as the building blocks for the creation of vital proteins, carbohydrates, and lipids, primarily consist of amino acids, short peptides, sugars, and fatty acids.

Supplementary Functions of the Alimentary Canal

The digestion of food and the absorption of nutrients from it are the main tasks of the alimentary canal. The alimentary canal also serves various secondary but crucial duties in addition to these basic ones. These are what they are:

• For a variety of dangerous bacteria, the alimentary canal serves as an immunological barrier. Gut-associated lymphoid tissue (GALT) and the various pH conditions that exist throughout the alimentary canal perform this role.

• Additionally, intestinal bacteria support immunological homeostasis.

• The colonic bacterial colony also hinders the development of dangerous germs in our gastrointestinal tract.

• Additionally, drug metabolism takes place in the alimentary canal, where the drug molecule is broken down into smaller pieces before being expelled from the body.

Common Disorders of the Alimentary Canal

Several disorders may remodel the functioning of the alimentary canal and lead to various symptoms and health issues.

Gastroesophageal Reflux Disease (GERD)

• Symptoms: Acid reflux, heartburn, regurgitation

• Cause: Malfunction of the lower oesophagal sphincter that normally prevents the backward flow of stomach acid from the stomach into the oesophagus.

Peptic Ulcers

• Symptoms: Abdominal pain, bloating, nausea.

• Cause: Chipped lining of stomach or duodenum usually after infection with H. pylori, or with prolonged NSAIDs.

Irritable Bowel Syndrome

• Symptoms: abdominal pain, cramping, bloating, changes in bowel habits.

• Cause: it includes altered gut-brain interaction, disorders of gut motility, and enhanced sensitivity.

Crohn's Disease

• Symptoms: Chronic inflammation, diarrhoea, abdominal pain, and weight loss

• Cause: This is an autoimmune disorder that makes the body attack any part of the gastrointestinal tract. Therefore, it causes chronic inflammation and damage.

Alimentary Canals in Different Animals

The alimentary canal of different animals has a wide range of anatomical differences. While some animals only have a single chamber in their stomach, others have many chambers (multiple-chamber stomachs).

Alimentary Canal of Rabbits

Rabbits have larger caecum and small intestines to provide a broad surface area again for nutrient absorption from plant matter.

Alimentary Canal of Birds

Birds have a gizzard, a proventriculus, and a two-chambered stomach. The proventriculus employs stomach fluids to aid in digestion, as opposed to the gizzard where food is mechanically broken down, stored, and then later digested again. Furthermore, birds vomit up uneaten food.

Due to the absence of fangs in their mouth cavity, birds do not masticate their food. Given that their beaks are made to be used for chewing food, several bird species have unique beak shapes. While waste is ejected through the cloaca or entrance, nutrients are absorbed in the small intestine.

Alimentary Canal of Ruminants

Ruminants with several stomachs include sheep, cattle, goats, and others. The primary goal of this adaptation is to help ruminants digest dietary cellulose, which makes up the majority of their diet of plants. There are four compartments that make up the stomach which are as follows :

• Rumen

• Reticulum

• Omasum

• Abomasum

The abomasum is viewed as being equivalent to a mono-gastric stomach or entire stomach because it secretes gastric juices.

Similar to how ruminants and reticulum break down cellulose in food, the stomach is filled with microbial flora that aids in digestion. Additionally, the food that is consumed undergoes fermentation in these chambers, creating a substantial amount of fumes.

These glasses are occasionally released by the animal. Ruminants rechew and regurgitate the food substance in the reticulum chamber before moving it to the omasum, the fourth chamber.

The omasum expels water. After that, the food is sent from the omasum to the abomasum for enzyme and gastric secretion digestion before being eventually transferred to the small bowel. Nutrients are taken up in the small intestine, and waste is removed from the body through the large intestine.

Alimentary Canal of Pseudo-Ruminants

Pseudo-ruminants, like camels, have multiple stomachs in contrast to ruminants. Camels don't have a rumen. The camel's stomach has three compartments: the omasum, abomasum, and reticulum. It's interesting to note that camels have larger Caecum. Camels have a Caecum which is rich with microbial flora and is in charge of breaking down the plant-based roughage that makes up the majority of their diet.

Alimentary Canal of Cockroach

In insects like cockroaches, the alimentary canal divides into three sections and extends from the mouth to the anus.

The pharynx, oesophagus, crop, and gizzard make up the anterior stomodaeum (foregut).

Middle stomach Proctodaeum in the posterior hindgut The intestine (or small bowel), stomach (or intestine), and rectum make up this.

Alimentary Canal of the Earthworm

The alimentary canal of an earthworm is a straight tube with specialized regions:

• Pharynx: For swallowing.
• Esophagus: For transport.
• Crop: For storage.
• Gizzard: For grinding food.
• Intestine: For absorption.

Tips, Tricks, and Strategies to Prepare for Alimentary Canal

• Study aids: Use diagrams or flowcharts to visualize each part's structure and functions.
• Use Mnemonics. You may find it easier to remember the structures if you recall: M.E.S.S.I.L.R.A, Mouth, Esophagus, Stomach, Small Intestine, Large Intestine, Rectum, Anus.
• Multimedia Learning: Watch videos or animations showing the process of digestion to get a better grasp.
• Analogies Using: An example to remember is the alimentary canal compared to a food processing factory.
• Flashcards: These are a great way to make flashcards for keywords like peristalsis, bile, or absorption and quickly revise them.
• Link to Real Life: Relate the alimentary canal to common health conditions, such as indigestion or acid reflux, to be able to understand it better in real-life applications.

Weightage of Questions from Alimentary Canal in Different Exams

Here's a summary of the weightage of questions related to the alimentary canal in various exams:

Types of Questions Asked on Alimentary Canal in Different Exams

Conclusion

The alimentary canal is involved in digestion and nutrient absorption in humans and other organisms. The knowledge of the structure and function of the alimentary canal will throw light on how different species may modify their digestive systems as per the requirements of the diets. Knowing about the alimentary canal is one of the important requirements for students from Class 9 to NEET levels.

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