The human digestive system is the process that transforms the food we eat into essential nutrients. When we consume food, digestive juices break it down into simple chemical compounds, which are then absorbed into the bloodstream and used to fuel our bodies. Without this efficient system, our bodies wouldn’t get the energy and nutrients needed to function properly.
The human digestive system, also known as the gastrointestinal tract (GI tract), is made up of two key types of organs –
- Primary organs of the digestive system
- Accessory organs of the digestive system
Primary organs of the digestive system
These are the main organs where the digestion and absorption of food particles take place.
The primary organs of the digestive system are
- Mouth
- Pharynx
- Esophagus
- Stomach
- Small intestine
- Large intestine
Mouth or Oral cavity or Buccal cavity
The oral cavity is equipped with the teeth, tongue, and salivary glands. The teeth chew and break down food, the tongue helps mix it, and the salivary glands release saliva to start the digestion process.
Pharynx
The pharynx is divided into three parts, namely
- Nasopharynx
- Oropharynx
- Laryngopharynx
only the oropharynx and laryngopharynx are part of the gastrointestinal tract. The nasopharynx is part of the respiratory system.
The pharynx divides into the larynx and esophagus. The larynx continues as the trachea, which is part of the respiratory system. When a bolus (food particles mixed with saliva) enters the lateral part of the pharynx, the epiglottis covers the glottis, causing a temporary arrest of breathing. This arrest of breathing during the pharyngeal stage of deglutition is called deglutition apnea. This process prevents the entry of the bolus into the respiratory tract and allows it to enter the esophagus.
Esophagus
The esophagus only secretes mucus. It allows the bolus from the pharynx to enter the stomach through peristaltic contractions.
Stomach
Stomach is a J-shaped muscular organ. Gastric glands present in the stomach secrete gastric juice; it is acidic in nature. Stomach is divided into four part-
- Cardiac part
- Fundus
- Body
- Pyloric part
The stomach stores food for 3 to 4 hours. It plays an important role in both mechanical and chemical digestion, mixing the acidic gastric juice with the bolus to produce chyme.
Small intestine
Small intestine divided into three part-
- Duodenum
- Jejunum
- Ileum
The small intestine is the major site of digestion and nutrient absorption due to the presence of villi and microvilli. Villi and microvilli are numerous hair-like projections extending from the wall of the small intestine into its lumen. They significantly increase the surface area of the small intestine, enhancing the absorption of nutrients from the lumen into the bloodstream.
Another crucial function of villi is the secretion of enzymes into succus entericus, which is the digestive fluid secreted by the small intestine.
Large intestine
Large intestine is formed by the following part
- Cecum and appendix
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
- Rectum
- Anal canal
The primary functions of the large intestine are to absorb water and electrolytes, form feces, and eliminate them from the body.
Accessory organs of the digestive system
These organs help the primary digestive organs.
The accessory organs of the digestive system are
- Teeth
- Tongue
- Salivary glands
- Liver
- Gallbladder
- Pancreas
Teeth
| Types of teeth | Function |
| Incisor | Cutting and biting food |
| Canine | Piercing and tearing food, especially meat |
| Premolar | Crushing and grinding food |
| Molar | Crushing and grinding food |
Tongue
The functions of the tongue are as follows
- Chewing and swallowing of the food
- Tongue contains taste buds for taste sensation
Salivary glands
The important salivary glands are
- Parotid gland
- Submaxillary gland or submandibular gland
- Sublingual gland
The secretion of the salivary glands contains important enzymes like
- Maltase
- Salivary amylase
- Lingual lipase
Salivary amylase and maltase are involved in carbohydrate digestion, whereas lingual lipase acts on lipid digestion, especially the triglycerides found in milk fat.
Liver
The liver is the largest gland in the human body and controls many metabolic activities. It is divided into several hepatic lobes, each of which is composed of numerous hepatic lobules. These hepatic lobules are made up of hepatocytes, which secrete bile. The liver also contains Kupffer cells, which are involved in phagocytosis.
Gallbladder
Bile is secreted by the hepatocytes of the liver and is stored in the gallbladder. Bile contains:
- Bile salts
- Bile pigments
- Fatty substances
- Water
The main functions of bile salts are the emulsification and absorption of fats.
Pancreas
The pancreas performs two important functions in the human body:
- Endocrine function
- Exocrine function
Endocrine Function of the Pancreas
The Islets of Langerhans are responsible for the endocrine function of the pancreas. They secrete the following hormones:
- Insulin
- Glucagon
- Somatostatin
Exocrine Function of the Pancreas
The exocrine function of the pancreas involves the secretion of digestive juices called pancreatic juice. Pancreatic juice primarily aids in the digestion of proteins and fats.
Conclusion
The process of digestion begins in the mouth and continues throughout the gastrointestinal tract (GI tract). Within the GI tract, food particles are broken down into simpler chemical compounds with the help of various digestive juices. These nutrients are then absorbed from the lumen of the GI tract into the bloodstream. The blood transports them to other organs for metabolic activities. These essential biomolecules support the body’s growth and help sustain life.
FAQs
Q. What are the folds found in the mucous lining of an empty stomach?
Ans- Rugae
Q. Which organ has finger-like outgrowths called villi?
Ans- Small intestine
Q. Which organ produces bile?
Ans- Liver
Q. Where does most digestion and absorption of food take place?
Ans- Small intestine
Q. Where does protein breakdown into free amino acids primarily occur in the GI tract?
Ans- Small intestine
Q. Where does maximum water absorption occur in the GI tract?
Ans- Large intestine
Kanka Adhikary is the creator behind Health Eulogy, blending a strong academic foundation with a passion for health education. With a B.Sc in Medical Physiology, where he earned a University Silver Medal from the University of North Bengal, and additional qualifications in education (D.Ed and B.Ed), Kanka brings over 7 years of teaching experience in Medical Physiology and Biology.
He also specializes in digital art and animation, using these skills to create engaging, interactive, and visually appealing educational content. His work reflects his dedication to making health education accessible and enjoyable for all.