Diagram of Digestive System

Digestive system consists of the alimentary canal and the associated glands. The alimentary canal consists of the mouth, buccal cavity, esophagus, pharynx, stomach, small intestine, large intestine, rectum, and anus and the accessory digestive glands are the salivary glands, the pancreas, liver, and gall bladder. The function of the digestive system is to convert complex food to simple, easily digestible, and absorbable forms by using both mechanical and biochemical methods. In this article, we will study the diagram of the digestive system and briefly about its various parts.

What is Digestive System?

The digestive system or gastrointestinal tract, is approximately 5 to 7 meters (16 to 23 feet) long, from the mouth to the anus. It is mainly responsible for digestion and absorption of nutrients. The process begins with mastication in the mouth, where saliva, initiates the breakdown of carbohydrates. The food then moves through the esophagus and reaches the stomach where protein digestion takes place. In the small intestine, the most of digestion and nutrient absorption occurs. The primary role of the large intestine is water absorption and the formation of feces. The rectum stores feces until they eliminated through the anus. This process is essential for breaking down food into its basic components, which enables nutrient uptake for energy and body function.

Diagram of Digestive System

A well labelled diagram of the Digestive System showing its different parts is shown below:

Mouth

The mouth is present in the anterior part, which opens into the oral cavity. The mouth consists of lips, cheeks, palate (roof of the mouth), tongue, and teeth. The lips and cheeks help contain food in the mouth, while the mouth is separated from the nasal cavity through palate. The tongue is a muscular organ that help in food mixes with saliva and speech, and teeth are responsible for grinding and chewing of food.

Teeth

Teeth consists enamel that forms the outer layer of the tooth followed by dentin and pulp.There are 32 permanent teeth are divided into four types depending on its functions (Heterodont dentition), namely, incisors (I), canine (C), premolars (PM) and molars (M). The upper and lower jaw each contain a set of teeth arranged in the order I, C, PM, M. The dental formula in the human is 2123/2123 .

Salivary Gland

Salivary glands are present in the oral cavity and it produces saliva. Saliva contains enzymes like amylase that starts the process of digestion of carbohydrates. Saliva also lubricates food, making it easier to swallow. There are three types of salivary gland submandibular, sublingual and the parotid gland.

Pharynx

The pharynx is a thin muscular tube measuring 5 inches (12.7 centimeters) in length in the throat. The esophagus and larynx is connected to the oral and nasal cavity through pharynx. Pharynx is divided into three parts: the nasopharynx, oropharynx, and laryngopharynx. The wind pipe or trachea and oesophagus open into the pharynx. It act as a common passageway for both air and food.

Esophagus 

The esophagus is a thin muscular tube that measures approximately 10 to 13 inches in length. It starts in the posterior part and pass through the neck, thorax and diaphragm. It opens into a ‘J’ shaped bag like structure known as stomach. Its primary function is to allow the movement of liquid and food to the stomach from the mouth for digestion. During swallowing, a thin flap-like structure known as the epiglottis in the throat, ensures that liquid and food enter the esophagus and not the windpipe.

Stomach

The stomach is present in the upper left part of the abdominal cavity between the esophagus and the small intestine. It consists of three main parts, that are, a cardiac portion where the oesophagus opens, a fundic portion and a pyloric part both of which leads to the first part of small intestine. Gastric glands found in the stomach secretes gastric juice, along with hydrochloric acid and digestive enzymes aids in digestion of protein and killing microorganisms.

Small Intestine

Small intestine measures about 20 feet in length and is a slender tube-like structure. It is divided into three parts, a ‘C’ shaped duodenum, in the middle part jejunum which is coiled in shape and ileum that is highly coiled. Its primary functions include nutrient absorption, particularly of carbohydrates, proteins, and fats, facilitated by the extensive surface area provided by villi and microvilli.

Large Intestine

The large intestine, is approximately 5 to 6 feet in length and is also known as the colon. In the large intestine the final stages of digestion, water absorption, and the elimination of waste products takes place. It follows the small intestine in the digestive tract and is formed of various parts including the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum.

Liver

The liver is the largest reddish-brown, and triangular-shaped organ in the human body. It is present in the upper right part of the abdomen. It takes part in digestion, metabolism, and detoxification. Functions of the liver include producing bile to aid in fat digestion, processing nutrients, storing glycogen and filtering toxins from the blood.

Functions of Digestive System

The digestive system or gastrointestinal tract, carries out various essential functions in the human body. These functions include:

1. Ingestion: It involves taking in liquid and food through the mouth for digestion and absorption.
2. Mechanical and chemical Digestion: Physical and enzymatic breakdown of food, that is macronutrients like carbohydrates, protein and fats are broken down into smaller, and absorbable molecules.
3. Absorption: Absorption involves uptake of nutrients, including glucose, amino acids, and fatty acids, into the bloodstream for distribution to the body’s cells.
4. Transport: Through the peristaltic contractions the movement of food and digestive contents take place in the digestive tract.
5. Storage: In the stomach temporary storage of food takes place and undigested waste is stored in the colon.
6. Excretion: The indigestible food material and waste products is eliminated from the body.
7. Immune Defense: Protection against pathogens and antigens in ingested food through the gut-associated lymphoid tissue (GALT).
8. Hormonal Regulation: Release of digestive hormones (e.g., gastrin, secretin, CCK) that control various aspects of digestion and appetite.

FAQ’s – Digestive System

1. What are Major Steps of Digestion?

The major steps of digestion include mechanical and chemical breakdown of food in the mouth, stomach, and small intestine, followed by nutrient absorption in the small intestine, and finally, the elimination of waste from the large intestine.

2. What are the Main Organs of the Digestive System?

The primary organs include the mouth, esophagus, stomach, small intestine, and large intestine (colon). Accessory organs like the liver, gallbladder, and pancreas also play important roles.

3. How does Digestion Begin in the Mouth?

Digestion starts with mastication (chewing) in the mouth, where enzymes in saliva begin breaking down carbohydrates.

4. What is the Role of the Stomach in Digestion?

The stomach performs mechanical mixing and chemical digestion with gastric juices, breaking down proteins and preparing food for further digestion in the small intestine.

5. Where Does the Majority of Nutrient Absorption Occur?

Nutrient absorption primarily happens in the small intestine, specifically in the jejunum and ileum, facilitated by villi and microvilli.