What is the digestive system? How does this work and its pictorial description.
definition of human digestive system :
The human digestive system consists of an alimentary canal and accessory glands. The alimentary canal is made up of mouth, oral cavity, pharynx, esophagus, stomach, small intestine, colon, rectum and anus. The accessory digestive glands are the salivary glands, liver (including gall bladder), and pancreas.
The digestive system of humans consists of a variety of organs and sub-processes that together make it possible to digest food. Forms the alimentary canal and associated glands for the digestive system. The alimentary canal (digestive tract) consists of tube-like structures that form a passage from the mouth to the anus.
Major organs of the digestive system :
The list of major organs of the digestive system is given below:
- Small intestine
- Large intestine
What does the digestive system do?
The main job of your digestive system is to convert your food into the nutrients and energy you need to survive.
1. Mouth :
It consists of palate, tongue and teeth. The palate forms the roof of the mouth and separates the mouth from the nasal chamber. The tongue is muscular, on which taste buds are found to absorb taste. Teeth are placed in tooth sockets on the jaw. An adult human has 16 teeth in each jaw. The oral cavity contains many teeth and a muscular tongue. Each tooth is located in a mold made in the jaw. This kind of arrangement is called thecodont.
2. Pharynx :
It is a small sized (12-14 cm) conical part, where the food and airways intersect each other. It is divided into three parts, nasopharynx behind the nasal cavity, oropharynx behind the oral cavity, pharynx the lower part of the pharynx.
3. Esophagus :
It is long (22-25 cm), narrow, muscular and has a tubular structure. Esophagus is a thin long tube, which passes through the neck, thorax and diaphragm and opens into the J-shaped sac-like stomach in the posterior part. The opening of the esophagus into the stomach is controlled by a muscular (gastro-esophageal) sphincter.
4. Pancreatic :
The stomach (located in the upper left part of the cavity), can be divided mainly into three parts, cardiac stomach, pyloric stomach and fundic stomach. The internal mucosa of the stomach also produces a large number of longitudinal valves, which are called gastric vesicles. Excess accumulation of HCL in the stomach causes peptic ulcer. The pyloric portion, which opens into the esophagus, the phthisis region, and the pyloric portion, which drains into the small intestine.
5. Liver :
It is the largest gland found in humans. Bile fluid is discharged from the liver which takes place in the gall bladder. It is helpful in digestion. The main function of bile fluid is to break the fat into smaller parts and make it digestible, so that it can be easily digested. In Manav Pachan Tantra the acidic food of the stomach now becomes alkaline.
6. Stomach :
After food enters your stomach, the stomach muscles mix the food and liquid with digestive juices. The stomach slowly empties its contents into your small intestine, called chyme.
7. small intestine :
The muscles of the small intestine mix food with digestive juices from the pancreas, liver, and intestine and push the mixture forward for further digestion. The small intestine produces digestive juices, which combine with bile and pancreatic juice to complete the breakdown of proteins, carbohydrates and fats. Bacteria in the small intestine make certain enzymes needed to digest carbohydrates. The small intestine moves water from the bloodstream into your GI tract to help break down food. The small intestine also absorbs water along with other nutrients. The waste products of the digestive process then move into the large intestine through peristalsis.
8. large intestine :
The undigested portions of food, fluids, and old cells lining the GI tract are called waste from the digestive process. In the large intestine, more water passes from the GI tract into the bloodstream. The large intestine absorbs water. Bacteria in your large intestine help break down remaining nutrients and create vitamin K. The waste products of digestion, including parts of food that are still too large, become stool. Peristalsis helps move stool into your rectum
9. Rectum :
The lower end of the large intestine, the rectum, stores stool until it pushes the stool out through your anus during a bowel movement.
digestion of food :
The process of digestion is accomplished through mechanical and chemical methods. The oral cavity has two main functions, chewing of food and swallowing. With the help of saliva, teeth and tongue work to chew and mix food properly. Salivary mucus helps in sticking of food particles and converting them into bolus. After this, the bolus passes from the pharynx to the esophagus through the act of swallowing. The bolus moves into the esophagus by peristalsis of muscular contractions.
The gastroesophageal sphincter controls the entry of food into the stomach. Saliva (oral cavity) contains electrolytes (Na+, K+, Cl-, HCO3) and enzymes (salivary amylase or tylin and lysozyme). The chemical process of digestion begins in the oral cavity with the activation of the carbohydrate hydrolyzing enzyme tylin or salivary amylase. About 30 percent of the starch is decomposed into dicotyledonous maltose by the activity of this enzyme (PH 6.8). Lysozyme present in saliva prevents bacterial infection.
digestive glands :
Digestive glands secrete digestive juice for digestion of food. These are of four types.
salivary glands :
It produces saliva. There are three pairs. Parotid glands, Submaxillary glands, Sublingual glands.
gastric glands :
It is present in the stomach. These are of three types. Cardiac glands secrete alkaline mucus. Gastric glands secrete alkaline mucus. Fundic glands contain four types of cells.
This is the largest gland. Towards its right lobe is the gall bladder, which stores the bile juice secreted by the liver. Bile juice does not contain any enzymes, but it contains bile salts and bile pigments bilirubin-yellow and biliverdin-green, which help in the digestion of fats.
This mixed gland secretes enzymes that digest fats, proteins and carbohydrates in pancreatic juice.