Functioning mechanism of the alimentary canal in humans
The human digestive system, a longitudinal muscular tube accompanied by various accessory organs such as the salivary glands, pancreas, and gall bladder, is responsible for the processes of food ingestion, digestion, absorption, and elimination.
The Role of the Large Intestine
The large intestine, consisting of the caecum, colon, rectum, and anal canal, plays a significant part in the digestive system. Measuring approximately 1.5 meters and having an average diameter of about 6 centimeters, its main functions include water and electrolyte recovery, faeces formation and storage, as well as the fermentation of certain indigestible food matter by bacteria.
Ingestion: The Introduction of Food
Upon food ingestion, it initially enters the mouth and is mechanically broken down by the teeth into smaller pieces. This physical breakdown triggers a nervous reflex that encourages the salivary glands to secrete a watery fluid called saliva. This fluid moistens and lubricates the food, making it easier to swallow, and aids in the dissolution of some of the food components, thereby allowing for taste.
Present within saliva is the digestive enzyme amylase, which initiates the chemical breakdown of starch.
The Role of the Small Intestine
The small intestine, approximately 5-6 meters in length, is the primary location for both mechanical and chemical digestion, as well as nutrient absorption. Initially, the food is broken down further into smaller components through these processes, enabling nutrient absorption.
Millions of tiny finger-like structures called villi project inwards from the lining of the small intestine, significantly increasing the surface area for absorption. Once digested into smaller molecules, these products are absorbed rapidly into the bloodstream for transportation to the liver by means of the hepatic portal vein.
Absorption: The Uptake of Soluble Digestion Products
The process of absorption happens after most of the chemical digestion occurs within the first meter of the small intestine. The majority of the nutrients, including carbohydrates, fats, minerals, proteins, and vitamins, are absorbed in this section.
The small intestine's surface area is designed to maximize absorption efficiency, with millions of tiny villi projecting inwards from its lining.
Egestion: The Elimination of Undigested Materials
Upon reaching the end of the small intestine, all digested food products along with useful minerals and vitamins should have been removed from the watery contents. Any remaining indigestible components, such as cellulose from plant-based food, are then passed on to the large intestine for water absorption and eventual waste elimination.
The Bacterial Population in the Large Intestine
The large intestine houses a diverse bacterial population, estimated to number over 500 species. These friendly bacteria perform various functions, such as breaking down undigested carbohydrates (fiber) into short-chain fatty acids and producing small quantities of vitamins like vitamin K and the vitamin B group for absorption into the bloodstream.
The Small Intestine: A Critical Component
The small intestine plays a crucial role in the human digestive system, primarily responsible for the breakdown and absorption of nutrients. It is divided into three main segments: the duodenum, jejunum, and ileum, each performing specific functions.
- The duodenum receives chyme from the stomach and digestive juices from the pancreas and gallbladder.
- The jejunum primarily absorbs most of the nutrients.
- The ileum specifically absorbs vitamin B12 and reabsorbs conjugated bile salts.
The small intestine utilizes enzymes from the pancreas and bile from the liver to facilitate digestion, with bile aiding in the emulsification of fats. Upon the completion of its function, undigested materials move into the large intestine for water absorption and waste elimination.
The role of science in understanding health-and-wellness is critical, as it helps in investigating medical-conditions related to the human digestive system, such as the functioning of the large intestine and small intestine. The large intestine, a part of the digestive system, not only aids in the water and electrolyte recovery, faeces formation, and storage, but also participates in the fermentation of certain indigestible food matter by bacteria, making it essential for our overall health.
