GRADE 6 2020-2021 - Digestion

Digestion

The digestive system is a group of organs working together to convert (change) food into energy and basic nutrients to feed the entire body. Food passes through a long tube inside the body known as the alimentary canal. The alimentary canal is made up of the oral cavity (mouth), pharynx (throat), esophagus (food pipe or gullet), stomach, small intestines, and large intestines. There are other organs of the digestive system. They aren’t a part of the alimentary canal because food doesn’t pass through them but still perform a function during digestion. These organs include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

The whole process starts in the oral cavity, where saliva from the salivary glands mixes with the food and starts to begin the breakdown of food. From the mouth, the food passes to the hollow tube-like organ the esophagus. From the esophagus, food then travels to the stomach, where it breaks down further with the help of the acids and powerful enzymes secreted by the stomach. This semi-digested food then travels down to the small intestine, where secretions from the liver, gallbladder, and pancreas further act on the food particles. The small intestine is divided into three parts called the duodenum, jejunum, and ileum. Most of the digestion takes place here in the small intestine, where absorption also occurs. Once most of the absorption of water and digested nutrients is completed in the small intestine, the remaining waste products move to the large intestine. The large intestine divides into the appendix, caecum, colon, and rectum. The faecal matter from the large intestine comes out through the anus.

Functions of Digestive Organs

The teeth are used for cutting and grinding food into smaller pieces.

The tongue grips food as it is moved around in the mouth. The taste buds on the surface of the tongue detect taste molecules in food and connect to nerves in the tongue to send taste information to the brain. The tongue also helps to push food toward the back part of the mouth for swallowing.

The salivary glands are organs that produce a watery substance known as saliva. Saliva helps to moisten food and begins the digestion of carbohydrates. The body also uses saliva to lubricate food as it passes through the mouth, pharynx, and esophagus.

The pharynx, or throat, is a funnel-shaped tube connecting the mouth to the esophagus. The pharynx is responsible for the passing of chewed food from the mouth to the esophagus. Another role of the pharynx is to transport air on its way to the lungs. Because the pharynx serves two different functions, it contains a flap of tissue known as the epiglottis that acts as a switch to send food to the esophagus and air to the larynx (trachea or windpipe).

The esophagus is a muscular tube connecting the pharynx to the stomach. It transport food to the stomach.

The stomach is a muscular sac located more to the left side of the abdominal cavity (belly). In an average person, the stomach is about the size of their two fists placed next to each other. This major organ acts as a storage tank for food so that the body has time to digest large meals properly. The stomach also contains hydrochloric acid and digestive enzymes that continue the digestion of food that began in the mouth.

The small intestine is a long tube, which loosely coils in the abdomen area. Here, enzymes from the pancreas and liver further break down the food. Three segments make up the small intestines, which are the duodenum, jejunum, and ileum. The contractions of the small intestine help in the movement of food, along with its breakdown, after mixing with the digestive secretions. The jejunum and ileum areas of the small intestine are responsible for the absorption of food into the blood, through their villi.

Pancreas, Liver and Gall Bladder

These organs also play a significant role in the human digestive system. The pancreas secretes enzymes which help in the breakdown protein, fat, and carbohydrate. The liver secretes bile and cleanses and purifies the blood coming from the small intestine. The gallbladder stores the bile that the liver produces. It releases bile into the small intestine to aid in the digestion process.

The large intestine is a long muscular tube that has different parts, which are caecum, colon, and rectum. The waste that is left over after digestion of food, reaches the rectum through the peristaltic movements of the colon.