Human digestive system functions

Twelve key systems control the normal functioning of the human body. Examples include the cardiovascular, endocrine, muscular, and nervous systems. The digestive system of the human body plays an integral role in digestion. The human digestive system is divided into the gastrointestinal tract and accessory organs. The GIT is a continuous, winding canal formed by multiple hollow organs from the mouth to the anus. The organs that make up the GIT include the mouth, oesophagus, stomach, small intestine, large intestine, and anus. Furthermore, the accessory organs are the liver, gallbladder, and pancreas. The digestive system organs have different roles.

What is digestion?

Digestion refers to the mechanical and chemical breakdown of foods into substances absorbed in the blood. Food is digested as it moves through the human digestive system. The substances produced as a result of the degradation of foods are nutrients. Nutrients include carbohydrates, proteins, vitamins, fats, water, and minerals. These molecules play a role in energy production, tissue repair, and boosting the immune system.

What is the function of the human digestive system?

The organisation of the digestive system influences its functions. Its main functions include ingestion, digestion, secretion, absorption, and excretion. These functions occur at different organs of the digestive system. Nervous action and hormones regulate digestive functions.

Ingestion is the entry of food into the oral cavity. Digestion can be mechanical or chemical. Mechanical digestion involves the physical breakdown of food into smaller particles by muscular movement. Contrastingly, chemical digestion entails the disintegration of food particles into nutrients by the hydrolytic action of digestive enzymes. Secretion is the release of enzymes and fluids that promote chemical digestion. Additionally, absorption refers to the movement of nutrients from the alimentary canal into the blood. Moreover, excretion involves eliminating undigested material through the rectum and anus as faecal matter. 

How is food digested in the human digestive system?

The movement of food in the digestive tract occurs through peristalsis, mixing, and segmentation. Peristalsis is the wave-like motion occurring throughout the GIT from the pharynx to the anus to move food towards the anus after swallowing. These processes are controlled by the autonomic nervous system, hormones, and reflex action.

Mouth:

Food enters the mouth by ingestion. Here, the teeth grind the food in mechanical digestion or mastication. There are three pairs of salivary glands in the mouth that secrete saliva. Saliva comprises water, amylase enzyme, bicarbonate ion, and electrolytes. Saliva also moistens and dissolves the food. The chemical digestion of carbohydrates and lipids begins in the mouth with enzymes amylase and lipase.

Moreover, the tongue mixes food and saliva to form moist lumps called boluses. The tongue then propels these boluses into the pharynx during swallowing. There is a tissue called the epiglottis, which folds over the trachea to prevent choking. 

Pharynx and oesophagus:

Peristaltic activity propels food away from the oral cavity towards the oesophagus in the pharynx. The pharynx cells secrete a fluid to lubricate the food for easier movement. Peristaltic activity continues in the oesophagus until the food passes a sphincter to enter the stomach. Peristalsis is involuntary.

Stomach:

Before entering the stomach, the food bolus passes through the cardiac sphincter. Food stays in the stomach for two to four hours. The food and water particles interact with gastric juice to form chyme in the stomach. Gastric juice includes hydrochloric acid, pepsinogen, gastrin, and mucus. The nutrients digested in the stomach include carbohydrates, proteins, and lipids. Chyme is then expelled through the pyloric sphincter into the small intestine.

Pancreas:

The pancreas secretes pancreatic enzymes and sodium bicarbonate. Sodium bicarbonate neutralises the acidity of gastric contents. Furthermore, pancreatic enzymes are inactive when stored to prevent the disintegration of pancreatic cells. These pancreatic enzymes include amylase, lipase, nuclease, and proteinase. 

Liver and gallbladder:

Hepatic cells of the liver produce bile salts that emulsify fats. They also oxidise fatty acids and stimulate lipogenesis. Moreover, the gallbladder stores and concentrates bile after secretion from the liver.

Small intestine:

The small intestine is divided into the duodenum, the jejunum, and the ileum. The smooth muscles of the small intestine combine chyme and digestive fluids while propelling the mixture forward at a slow rate. The slow speed allows time for absorption and digestion. All nutrients are absorbed into the bloodstream. Ultimately, waste products move into the large intestine.

Large intestine:

The large intestine’s structure includes the appendix, cecum, colon, and rectum. Waste products include undigested food particles, liquids, and damaged cells from the GIT lining. The large intestine walls facilitate water absorption, convert liquid waste into stool, and peristalsis of waste products to the rectum. 

Rectum:

The rectum temporarily stores stool. Bowel movements drive the expulsion of stool through the anus. 

Human digestive system diagram.

Conclusion:

Digestion is crucial for obtaining nutrients from food. It is an involuntary process controlled by nervous stimulation and hormones. The components of the human digestive system each play a vital role in digestion. Their movements and enzymes assist in mechanical and chemical digestion. Furthermore, several disorders affect the human body’s digestive system, known as gastrointestinal diseases. These are temporary conditions such as constipation, diarrhoea, ulcers, and gallstones. Chronic GIT disorders include lactose intolerance, chronic acid reflux, Crohn’s disease, and Celiac disease. Understanding our digestive system is important. This knowledge enables us to comprehend the importance of various nutrients and prevent gastrointestinal disorders.