Human Digestive System – Diagram, Parts, Functions

The human alimentary canal is one of the most clearly defined systems in the body. It consists of a long passageway called the digestive tract and other associated glands. This digestive tract is also called the gastrointestinal (GI) tract.  The organs of the digestive system contain the pharynx, esophagus, stomach, and small and large intestines. The mouth is also an essential aspect of the digestive system and is the first of the human digestive system parts. The liver, pancreas, and gallbladder are a part of the gastrointestinal tract as well.

Food enters through the mouth and passes through the anus through the various organs of the digestive system. It is important to understand the digestive system’s function as it breaks down the consumed food into various nutrients that are required by the body for energy, growth, and cell repair. Food eventually gets converted into carbohydrates, proteins, fats, and vitamins which in turn aids the body to function at its optimal best.

The Structure of the human digestive system

The human digestive system is an intricate network of organs and glands working together in a harmonious tandem to facilitate the journey of food and drink through the body. Understanding the human digestive system’s function and structure is important to appreciate the beauty of this biological marvel.

Human Digestive System Diagram

The schematic human digestive system diagram is given below,

Human Digestive System

Human Digestive System Parts

As the above human digestive system diagram shows, the various parts of the digestive system are :  


The journey of the human digestive system begins in the oral cavity, where mechanical breakdown commences through chewing, and enzymatic action is initiated by saliva. 


The food, now partially broken down, travels through the esophagus via peristalsis, a series of rhythmic muscle contractions. 


Upon reaching the stomach, gastric juices and enzymes further break down the food into a semi-liquid substance known as chyme. 

Small Intestine: 

The small intestine, the longest part of the human digestive system structure, is where the majority of nutrient absorption occurs. Its inner surface is lined with tiny finger-like projections called villi, maximizing the absorption surface area. 

Large Intestine: 

The remaining indigestible material passes into the large intestine, where water is absorbed, and the formation of faeces takes place. 

Rectum and Anus: 

The final stage involves the rectum storing faeces until elimination through the anus.

The Process of the human digestive system

The functioning of the human digestive system involves the propulsion of food along the gastrointestinal (GI) tract. The process of digestion initiates in the mouth through the act of chewing and culminates in the small intestine. Throughout the journey along the GI tract, food undergoes mixing with digestive juices, leading to the breakdown of large food molecules into smaller ones. Subsequently, the body absorbs these diminished molecules through the walls of the small intestine, facilitating their entry into the bloodstream. The bloodstream then transports these nutrients to various parts of the body. Waste materials resulting from the digestion process travel through the large intestine and are expelled from the body in the form of solid waste known as stool.

The Human Digestive Process in Simple Terms

Organ  Movement   Digestive juices used   Food particles bread down 
Mouth   Chewing   Saliva  Starches 
Oesophagus   Swallowing  None  None 
Stomach  Upper muscles in the stomach relax to let food enter and lower muscles mix food with digestive juices  Stomach acid  Protein 
Small intestine   Peristalsis  Small intestine digestive juice  Starches, proteins, and carbohydrates 
Pancreas   None  Pancreatic juice  Starches, fats and proteins 
Liver  None  Bile acids  Fats 

Functions of the human digestive system

Understanding the multifaceted functions of the digestive system is crucial for appreciating its role in maintaining overall health and well-being. 

Understanding each stage of digestion – from ingestion to elimination – is crucial for comprehending the intricate processes that sustain human life and well-being. These processes work in tandem to ensure the body receives essential nutrients while efficiently eliminating waste. 


The process of taking in food into the body initiates the digestive cascade.
Mechanical Breakdown: Ingestion involves the mechanical breakdown of food by chewing, facilitated by the teeth. This initial step increases the surface area of the food particles, making it easier for enzymes to act on them during later stages of digestion.
Saliva, produced by salivary glands, contains enzymes like amylase that initiate the chemical breakdown of carbohydrates in the mouth. This process transforms complex carbohydrates into simpler sugars. After a mechanical and chemical breakdown in the mouth, the partially digested food is formed into a bolus and swallowed. The swallowing reflex is a coordinated muscular action that propels the bolus down the esophagus. 


Mechanical and chemical breakdown of food into smaller, absorbable components. Digestion is the process of breaking down ingested food into simpler, absorbable substances.
In the stomach, gastric juices containing hydrochloric acid and pepsin help break down proteins into smaller peptides. The stomach also mechanically churns the food, creating a semi-liquid mixture known as chyme. The small intestine is the primary site of digestion. Pancreatic enzymes (lipase, protease, and amylase) and bile from the liver further break down fats, proteins, and carbohydrates, respectively. Digestion results in the breakdown of complex molecules into simpler forms. Proteins are broken into amino acids, fats into fatty acids and glycerol, and carbohydrates into simple sugars. 


The absorption of nutrients, such as carbohydrates, proteins, fats, vitamins, and minerals, into the bloodstream for distribution to cells.The majority of nutrient absorption occurs in the small intestine. The inner surface of the small intestine is lined with villi, tiny finger-like projections that increase the surface area for absorption. Nutrients, including amino acids, fatty acids, glucose, vitamins, and minerals, are transported across the intestinal wall into the bloodstream. Some fats and fat-soluble vitamins are absorbed into the lymphatic system before entering the bloodstream. 


The utilization of absorbed nutrients by cells for various physiological functions, including energy production and cellular maintenance.
After absorption, nutrients are transported to cells throughout the body. Amino acids are used for protein synthesis, glucose for energy production, and fats for various cellular functions. Different nutrients play specific roles in various tissues and organs. For example, calcium is crucial for bone health, iron for oxygen transport in blood, and vitamins for various biochemical processes. 


The removal of indigestible waste material as feces, ensures the body’s efficient waste management.
In the large intestine, water is absorbed from the remaining chyme, forming solid feces. Feces are stored in the rectum until they reach a sufficient volume, triggering the urge to defecate. The expulsion of feces through the anus completes the process of elimination, ensuring the removal of indigestible waste from the body.


Safeguarding a robust and well-functioning digestive system is of utmost significance for one’s comprehensive state of well-being. The achievement of optimal digestive health involves a combination of various factors, including adequate hydration, a judiciously balanced diet with a focus on fiber-rich foods, and the incorporation of regular physical activity into one’s lifestyle. These elements collectively contribute to the seamless operation of the digestive processes, promoting not only the efficient breakdown and absorption of nutrients but also fostering overall bodily health.

Knowledge of the functions of each component within the digestive system empowers individuals to make informed choices regarding their dietary and lifestyle habits. Awareness of how the mouth, stomach, small intestine, and large intestine work in harmony allows individuals to appreciate the importance of nutrient breakdown, absorption, and waste elimination. This understanding fosters a mindful approach to eating and lifestyle choices that positively impact digestive health. 

By intertwining these elements – hydration, a fiber-rich diet, regular physical activity, and a comprehensive understanding of digestive functions – individuals can proactively contribute to the maintenance of a healthy digestive system. This, in turn, not only ensures the efficient processing of nutrients for bodily functions but also plays a pivotal role in supporting overall vitality and wellness. 

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