What is Human Digestive System?
o The food provides us with the nutrients that we need for the functioning of the body.
o Human digestive system helps in breaking down the food for energy and other nourishment.
o The conversion of complex food to absorbable form is Digestion.
o Digestive system is used for the physical chemical digestion of food, absorption of the food and to collect and remove the unusable components from the body.
• Ingestion: Consumption of food is the first step for the digestion. Entry of food into the mouth is the process of ingestion.
• Mechanical digestion: Food that has entered needs to be broken down into smaller pieces and then various enzymes act upon it. Mechanical digestion is done by the chewing of food, then mastication and churning up of the food in the stomach.
• Chemical digestion: In this process the complex components of food (carbohydrate, protein and fats) are converted into smaller molecules so it is easy for absorption by the cells. This is function of the different enzymes and water by the process of hydrolysis.
• Absorption: The simpler molecules pass through the small intestine lining. Here, the process of absorption takes place.
• Elimination: Food molecules that are not absorbed by the intestine or not digested are removed from the body as wastes.
Structure and Function Human Digestive System
o The digestive system consists of alimentary canal that starts with the mouth and ends in the anus.
o Below the structure of digestive system has been discussed briefly:
1. Mouth: Digestion process begins as soon as the food enters the mouth.
o The process chewing helps in the breakdown of food and mixes with the saliva (digestive enzyme) and further breaks down the complexity of the food particle.
Human Digestive System Diagram
2. Pharynx: Food that has been chewed is swallowed and moves to the pharynx region to the esophagus.
3. Esophagus: It is the long muscular tube from the pharynx to the stomach responsible of various contraction (peristalsis) resulting into movement of food from pharynx to the stomach.
4. Stomach: Sac like structure responsible for the holding of the food. Stomach is responsible for the secretion of acid and other enzymes that mixes with food and churns it more.
o Stomach makes the food more like a paste so that the absorption becomes easy for the intestines.
5. Small intestine: Small intestine has three parts namely duodenum, jejunum and ileum. Its further breakdown the food with the help of secretion from pancreas and liver.
o The peristalsis action is also observed here for the movement of the food and mixing it with the digestive secretions.
o Duodenum has major role in the breakdown of food, whereas jejunum and ileum are responsible for the absorption of food in the small intestine lining.
6. Pancreas: Major function is to secrete pancreatic enzymes into the small intestine that’s helps in the breakdown of protein, fat and carbohydrate.
7. Liver and gallbladder: function of liver is to secrete bile into small intestine and purify blood from small intestine.
o Gall bladder stores the bile that is secreted from liver. After the food is completely absorbed the leftover liquid and unabsorbed food in passed into large intestine.
8. Large intestine: long muscular tube having different parts called cecum, ascending colon, transverse colon, descending colon, sigmoid colon connecting to the rectum.
o Waste product is passed into the large intestine through peristalsis movement.
o Water is completely absorbed and the waste product is moved towards the rectum for the removal of feces.
9. Rectum: It is a chamber which receives stool from the large intestine, sends signal to brain when it needs to be evacuated.
10. Anus: The last part of the digestive tract consisting two anal sphincter and pelvic muscle.
o These parts are responsible for the removal of the stool or not.
o Internal sphincter is helps in preventing the removal of stool when are asleep or unaware of the presence of stool in the rectum.
Human Digestive System Disorder
It is a major process to digest the food completely and without any error. But there some factors that can lead to digestive system problems and associate with disorder.
1. Choking: When food is passed on from mouth to the pharynx there can be a possibility of food getting into the air passage and choking the person.
o This happens when the food is not chewed properly or the contraction of the muscles has been disturbed.
2. Vomiting: The ejection of contents back to the mouth from the stomach. This is controlled by the medulla.
3. Infections and inflammation: The intestinal tracts inflammation can be caused due to the bacterial or viral infections or also due to presence of parasites like tapeworm, roundworm etc.
4. Jaundice: In this disorder the liver is affected and due to the deposition of the bile pigments the skin appears yellow in color.
5. Diarrhea: This occurs when there is issue with the absorption of food and the bowel movement is irregular and there is increase in the liquidity in the feces.
6. Constipation: This is also an irregular bowel movement but here the feces is retained in the rectum and does not pass easily.
7. Indigestion: In this the food is not digested properly because the enzyme secretions is not enough or any other underlying problem like food poisoning, over eating or consumption of spicy food or even anxiety can be the reason.
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Human Digestive System Citations
- The timing and sequence of events in the development of the human digestive system and associated structures during the embryonic period proper. Anat Embryol (Berl) . 1978 Jun 2;153(2):123-36.
- Nitric oxide producing neurons in the monkey and human digestive system. J Comp Neurol . 1994 Apr 22;342(4):619-27.