Alimentary Canal Anatomy

Alimentary canal, also known as the digestive tract or gastrointestinal tract, is a long muscular tube that extends from the mouth to the anus. Alimentary Canal is responsible for the digestion and absorption of food, which provides the body with the necessary nutrients for growth and energy. The alimentary canal plays a vital role in the digestive process and is essential for maintaining proper nutrition and overall health.

What is the Alimentary Canal?

Human digestion occurs within the alimentary canal, which is a long, tubular structure. From the mouth to the anus is the alimentary canal. Human Digestive System consists of the alimentary canal and other digestive organs. The Alimentary canal starts with the mouth which intakes the food and ends at the anus from which waste material is excreted from the body.

The process of digestion starts in the mouth, where food is mechanically broken down by the teeth and mixed with saliva, which contains enzymes that start the breakdown of carbohydrates. The food then travels through the esophagus to the stomach, where it is further broken down by stomach acid and enzymes.

From the stomach, the partially digested food enters the small intestine, where it is further broken down by enzymes coming from the pancreas and bile from the liver. Nutrients are then absorbed through the walls of the small intestine via diffusion, Facilitated diffusion, and also via carrier protein depending on the size, and then into the bloodstream.

The remaining waste products then pass into the large intestine, where water is absorbed and the waste products are formed into feces. The feces are stored in the rectum until they are eliminated through the anus during a bowel movement.

Organs of the Alimentary Canal

The alimentary canal is composed of different organs, including the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus. All these organs work together to break down food into smaller particles and molecules that can be absorbed into the bloodstream.

Mouth 

The upper alimentary canal 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. 

Buccopharyngeal Cavity

There are two sections of the buccopharyngeal cavity:

1. The buccopharyngeal cavity’s inner and central 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 for 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

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.

Tongue

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. It is attached to the base of the oral cavity. The lingual papillae are present o the surface of the tongue. The taste buds on the papillae are fleshy and muscular sensory organs are where the first sensory information is obtained. Three types of lingual papillae are present those are: Circumvallate, filiform, and fungiform.

Teeth

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.

Type	Function
Incisor	Used for biting
Canines	Used for tearing
Premolars	Tearing and grinding food
Molars	Chewing and grinding food

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. 

Esophagus

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.

Stomach

The stomach is the longest segment of the alimentary canal. Positioned on the abdominal cavity’s left side. An empty stomach resembles a J-shaped bag. The stomach has a 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. The stomach is differentiated into four parts:

• Cardiac: Cardiac is the first part from where the stomach starts. Esophagus opens into this part of the stomach. It is present near the heart.
• Fundus: Fundus is a dome-shaped structure normally it is filled with air.
• Body: It is the main part of the stomach.
• Pyloric: Pyloric is the lowest part of the stomach, pyloric open to the small intestine, and this is regulated by the pyloric sphincter.

Small Intestine

The stomach’s lowest part pyloric opens into the duodenum. The small intestine is the longest part of the alimentary canal. Innerly it is covered with villi which increases the surface area of the intestine. The small intestine is further divided into three parts those are:

• Duodenum: It is the connection between the stomach and the intestine, it is S-shaped. In the duodenum, all the pancreatic, bile juice, and hepatic secretions mix with the food via the hepatopancreatic duct.
• Jejnum: It is the middle part of the small intestine.
• Ileum: The ileum connects the small intestine with the large intestine and it is highly coiled.

Large Intestine

It is the last part of the alimentary canal. The large intestine is further divided into 3 parts those are:

• Caecum: Caceum is a small sac-like structure that contains microorganism which shows a symbiotic relationship. Caecum is the part from which the vestigial organ is attached i.e., the vermiform appendix.
• Colon: It is the mid part of the large intestine. It is further divided into:
  • Ascending Colon
  • Transverse Colon
  • Descending Colon
  • Sigmoid Colon
• Rectum: Rectum opens into the anus, the form where the waste material is excreted.

FAQs on Alimentary Canal

Q1: What is the second name of the alimentary Canal?

Answer:

The Alimentary canal is also known as the Digestive tract or gastrointestinal tract.

Q2: How long is the alimentary canal?

Answer:

It is a 6-9 (30 feet) meter-long canal from the esophagus to the anus.

Q3: Which is the shortest part of the alimentary canal?

Answer:

Caecum is the shortest part of the alimentary canal. 

Q4: How long is the small intestine?

Answer:

The small intestine is the longest part of the alimentary canal. It is around 22 feet long.