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Alimentary Canal

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  • Last Updated : 17 Nov, 2022
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In order to absorb nutrients, complex food particles must be broken down into simpler forms during digestion. The alimentary canal is a part of the human digestive system. There are several glands connected to it.

  • Hydrolysis: Water is added to a substance to cause it to break apart. 
  • Extracellular/Intercellular Digestion: Digestion occurs external to the cell. For instance, human digestion. Inside-the-cell digestion is referred to as intracellular digestion. like an amoeba
  • Mechanical Digestion: The breaking down of a larger food item into a smaller one. In mechanical digestion, our teeth are helpful. Chemicals like enzymes are used in the digestion of food.

Human Alimentary Canal Histology

Alimentary Canal


The wall of the alimentary canal has four layers that extend from the esophagus to the rectum:

  • The top layer, known as the serosa, is composed of connective tissues and mesothelium.
  • Inner circular and outer longitudinal smooth muscles make up the muscularis.
  • Lymph, blood, and nerves are located within the submucosa, which is composed of loose connective tissues. The portion of the duodenum has glands.
  • The uppermost layer, known as the mucosa, is where the stomach’s gastric glands and irregular folds are located. The small intestine contains villi, microvilli, and Lieberkuhn crypts, which significantly increase the surface area of absorption. The goblets cells of the mucosal epithelium secrete mucus, which aids in lubrication.

Alimentary Canal

Human digestion occurs within the alimentary canal, a long, tubular structure. From the mouth to the anus is the alimentary canal. The following sections comprise the alimentary canal:


  • The upper gastrointestinal system starts with the mouth, which has various structures that start the earliest stages of digestion.   These include the tongue, teeth, and salivary glands. There are two parts to the mouth: the vestibule and the actual oral cavity. 
  • The vestibule is the space in front of the teeth, between the lips and cheeks, and the remainder is the actual oral cavity. The oral mucosa, a mucous membrane that produces a lubricating mucus that is very little needed, lines the majority of the mouth cavity. 
  • Varied parts of the body have different mucous membrane structures, but they all produce lubricating mucus that is either secreted by surface cells or, more frequently, by underlying glands. 
  • The thin mucosa that lines the tooth bases is a continuation of the mucous membrane in the mouth. A glycoprotein by the name of mucin serves as the primary constituent of mucus, and the kind released changes depending on the place in question. 
  • Mucin is sticky, transparent, and viscous. A tiny layer of smooth muscle tissue lies beneath the mucous membrane in the mouth, and the membrane’s slack attachment to the muscle gives it its remarkable elasticity.
  • The mucin that is generated coats the cheeks, inner surfaces of the lips, and the floor of the mouth, and it is quite effective at preventing tooth decay. 
  • The palate is the structure that covers the roof of the mouth and divides the nasal cavity from the oral cavity. Being formed of muscle and connective tissue, the palate is softer and more malleable at the back of the mouth where it may move to help a person swallow food and liquids. The palate is firm at the front of the mouth where the overlying mucosa is covering a plate of bone. 
  • The uvula is where the soft palate ends. The hard palate surface enables the pressure required for eating while maintaining a clear nasal route. 
  • The fauces are the openings into the throat, while the oral fissure is the entrance between the lips. 
  • The palatoglossus muscles, which also extend into parts of the tongue, are located on either side of the soft palate. To make it possible to swallow food, these muscles lift the back of the tongue and also seal both sides of the fauces.  In its capacity to soften and gather food in the development of the bolus, mucus aids in the mastication of food.

Buccopharyngeal Cavity

There are two sections of the buccopharyngeal cavity:

  1. The buccopharyngeal cavity’s inner and center region is known as the oral, buccal, and mouth cavity. The palate is the roof of the mouth cavity.
  2. Buccal Vestibule: The buccal vesicle is a small portion of the buccopharyngeal cavity. Food is temporarily kept in the buccal vestibule, which is the area between the cheeks and the gums.

Oral Cavity

  • The mouth and all of its components, including the lips, tongue, teeth, roof, and floor, are together referred to as the human oral cavity. 
  • The oral cavity, which mostly belongs to the digestive system, is crucial to breathing.

The Oral Cavity has two Components. The hollow is separated into two sections by its oval form.

  1. Oral Vestibule: The teeth, gums, and alveolar processes (the strong bony ridge housing the tooth sockets), which are located at the back, enclose the vestibule, the first portion of the oral cavity, which opens with the oral fissure. The fleshy, moveable portion of the tongue is also a component of it. The labial commissures (lip corners), which are made up of muscle and flesh, join the muscular and fleshy upper and lower lips together. The superior and inferior labial frenulum, which are made up of muscle and flesh, join the upper and lower lips with the gums, the reddish or pinkish connective tissues that surround and support the teeth. The toughest structure in the human body is the enamel layer on teeth.
  2. Oral Cavity Proper: The mouth proper is the term used to describe the back of the oral cavity. The upper front boundary is formed by the hard palate, while the upper rear barrier is formed by the soft palate. It connects the tongue to the oral cavity floor inferiorly through the flexible band of tissues known as the lingual frenulum and has a variety of oral muscles, glands, and attachments. Additionally, a mucous membrane that originates from the vestibular walls surrounds the mouth cavity properly. To prevent food from entering the nasal passage, the uvula, a fleshy projection at the back of the soft palate, moves with it. 

Salivary Gland

Salivary Gland


The parotid, submandibular (submaxillary), and sublingual glands are the three principal pairs of salivary glands. The parotid glands’ secretions are collected in the vestibule area while the submandibular and sublingual glands open into the actual mouth cavity.


  • With the help of the tongue’s activity and saliva secretion, food enters the mouth, where the initial stage of the digestive process takes place. 
  • The taste buds on the papillae on the surface of the tongue, a fleshy and muscular sensory organ, are where the first sensory information is obtained. If the flavor appeals to the palate, the tongue will work to manipulate the food in the mouth, stimulating the salivary glands to secrete saliva.
  •  Saliva’s liquid consistency aids in the food’s softening, and its enzyme content begins to break down the food while it is still in the mouth.
  • The starch of carbohydrates is the first component of the meal to be broken down (by the enzyme amylase in the saliva).
  • The tongue has a broad range of motion for manipulating food (and speech), which is best regulated by the action of many muscles and constrained in its external range by the stretch of the frenum. The tongue is joined to the floor of the mouth by a ligamentous band called the frenum. 
  • Four intrinsic muscles that originate in the tongue and are involved in its shaping and four extrinsic muscles that originate in the bone that is involved in its movement make up the tongue’s two sets of muscles.


Teeth are intricate structures made of substances that are unique to them. They are composed of dentin, a substance similar to bone, which is covered with enamel, the body’s toughest tissue. To accommodate the various mastication techniques used to shred and chew food into ever-tinier pieces, teeth come in a variety of forms. As a result, the surface area on which digestive enzymes can function is greatly increased. Indicators are used for cutting or biting off bits of food, canines are used for ripping, premolars and molars are used for chewing and grinding, and the names of the teeth are based on their specific functions in the process of mastication.

A soft bolus is created when the meal is masticated with the aid of saliva and mucus, which can then be swallowed to allow it to pass through the upper gastrointestinal tract and into the stomach. Saliva’s digestive enzymes assist in keeping teeth clean by dissolving any food particles that may have become lodged in the teeth. 


The Esophagus is a long, straight, tubular tube that originates in the pharynx and opens into the stomach near the heart. The esophagus is also known as Food Pipe.

  • Length: 25 cm 
  • Position: Behind the trachea
  • Esophageal length is influenced by neck length.
  • The voluntary muscles make up the upper third of the esophagus, the voluntary + involuntary muscles make up the middle third of the esophagus, and the involuntary muscles make up the lower third of the esophagus.
  • The esophagus experiences peristaltic action, which aids in the downward/stomach ward flow of bolus (food and saliva).
  • Inside the esophagus, there is no digesting gland.
  • The gullet is the name for the esophageal opening.
  • The glottis is the opening of the trachea.


  • The longest segment of the alimentary canal.
  • Positioned on the abdominal cavity’s left side.
  • An empty stomach resembles a J-shaped bag.
  • The peritoneal membrane covering.
  • Gastric glands are found in the stomach and aid in the secretion of gastric juice, which aids in digesting and killing microorganisms.
  • Oblique Muscles are additional muscles that are solely present in the stomach.

FAQs on Alimentary Canal

Question 1: What are the 4 different types of teeth and what functions do they do?


The jaw muscles propel the teeth, and saliva, which is produced in the salivary glands, is used to lubricate them. Vertebrates have a variety of tooth types and numbers. There are four types of teeth: Incisors, Premolars, Canines, and Molars

  • Utilizing incisors for cutting
  • Premolars are used for chopping
  • Canines are used for tearing
  • Molars for Chewing and Grinding

Question 2: Explain Food Digestive System


Food digestion begins in the mouth itself. A tiny food mass known as a bolus is created when saliva and masticated food are combined. Through the process of deglutition, the bolus travels to the pharynx and esophagus (swallowing). At various points in the alimentary canal, different enzymes mix with the food to aid in digestion.

Question 3: What do Vills do? Where are they located, and what do they do?


They are tiny folds in the small intestine that resemble fingers. The villi are supplied by a capillary network and a large lymphatic artery known as the lacteal. These are located in the inner walls of the small intestine. The absorbing surface area is increased by villi. Every cell in the body receives ingested food through the blood arteries of the villi, where it is used to produce energy, create new tissues, and restore damaged ones.

Question 4: What are parietal cells used for?


Parietal cells sometimes referred to as oxyntic cells, are stomach epithelial cells that release intrinsic factors and hydrochloric acid (HCl). These cells are present in the stomach’s gastric glands, which are situated in the fundus and body regions.

Question 5: What Is Oral Cavity?


The teeth, gums, soft and hard palates, tonsils, salivary glands, and tongue are all parts of the oral cavity, sometimes known as the mouth. These structures enable the creation of voice sounds and food ingestion. Additionally, the oral cavity acts as a supplementary airway for the respiratory system. This channel, however, does not warm and moisten the air, as well as the nasal cavity, does since it is shorter and free of hair and mucus. The mouth cavity can, however, carry more air into the lungs more quickly due to its bigger width.

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