Unit 1 human nutrition(1)
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The human digestive tract begins with the mouth and ends with the anus. It contains the mouth, esophagus, stomach, and small and large intestines. Accessory organs include the liver, gallbladder and pancreas. Digestion involves ingestion, mechanical and chemical breakdown of food, absorption of nutrients, and excretion of waste. Enzymes and acids in saliva, stomach, pancreas and intestines break down food into smaller molecules for absorption. Nutrients then enter the bloodstream and cells while waste is excreted.
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Unit 1 human nutrition(1)
- 2. STRUCTURE OF HUMAN DIGESTIVE TRACT Humans have a a complete digestive tract, which begins with the mouth and ends with the anus. The major structures of the human digestive tract are the : mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum and anus.
- 3. The accessory organs of digestion are the Liver Salivary glands gall bladder pancreas
- 5. HUMAN DIGESTIVE PROCESS Why is digestion important? To convert large, often insoluble molecules of food into smaller soluble molecules capable of being absorbed into the blood or lymph capillaries associated with the digestive tract and used for various metabolic processes.
- 6. DIGESTIVE PROCESS INGESTION DIGESTION MECHANICAL AND CHEMICAL ABSORPTION ASSIMILATION EXCRETION
- 7. PATHWAY OF FOOD AND RELATED PROCESSES IN THE BODY
- 8. MOUTHIngestion: Food is placed into mouth. Teeth: - Incisors cut or bite the food. - Canines used to tear meat. - Molars and pre-molars grind the food fine. Mechanical digestion
- 9. STRUCTURE OF A MOLAR
- 10. SALIVA Secreted by the salivary glands (parotid gland, sublingual gland and sub- maxillary gland) Mix with the food to form a bolus. Saliva contains the enzyme amylase, that breaks down cooked starch into maltose. Chemical digestion.
- 11. TONGUE Mixes food with saliva and pushes food between teeth. Makes swallowing easier.
- 12. ESOPHAGUS The bolus is forced down the esophagus when the muscular pharynx contract swallow process. Peristalsis (contraction and relaxation of antagonistic circular and longitudinal muscle) of the esophagus pushes the food downwards into the stomach, through the cardiac valve. No absorption takes place The epiglottis that covers the trachea prevents food from going into the trachea when you swallow.
- 13. EPIGLOTTIS
- 15. PERISTALSIS
- 16. STOMACH Food enters the stomach (fundus region) through the cardiac valve. Remains a half an hour still before the stomach muscles (circular-, longitudinal- and oblique muscles) starts contracting and relaxing (peristalsis). The food move with circular movements through the stomach (corpus and pyloric regions) and mixes with all the gastric juices. Mechanical digestion
- 17. Gastric juices are secreted after the hormone, gastrin stimulates the parietal cells in the fundus region of the stomach. Gastric juices consist of HCl (Acidify stomach and neutralizes the bolus, antiseptic solution, emulsifies fats), digestive enzymes (pepsin, rennin and lipase), mucus (help protect the inner lining of the stomach against enzyme activity) and water.
- 18. These gastric juices help with chemical digestion of food and the bolus is now called a chym. Some absorption occurs in the stomach. Some water, glucose, salt and certain drugs and alcohol pass into the blood capillaries of the stomach wall.
- 20. SMALL INTESTINE As the chym enters the duodenum (first part of the small intestine) through the pyloric valve it mixes with bile (secreted from the liver or gall bladder) and pancreatic juices.
- 21. CHEMICAL DIGESTION Secretin is the hormone that stimulates the pancreas to secrete pancreatic juice into the duodenum. The pancreatic juice contain sodium bicarbonate (neutralizes the chym, antiseptic) and digestive enzymes (Trypsin, amylase and lipase) Bile is produced in the liver and stored by the gall bladder. When fatty rich food enters the small intestines, bile is secreted by the gall bladder and transported to the duodenum.
- 23. FUNCTIONS OF BILE Neutralizes acid from stomach Emulsifies fats (increase surface area of fats for better digestion) Aid in the absorption of fats. Reduce the fluidity of the chym Antiseptic prevent decomposition Assist in the absorption of the fat- soluble vitamins.
- 24. The chym then moves through the jejenum (second part of small intestines) It mixes with intestinal juice (succus entericus) that contains the digestive enzymes for the final digestion of food Peptidase, lipase, lactase, maltase, sucrase Succus entericus is secreted by 2 glands: Crypt of Lieberkuhn and the glands of Brunner (both situated in the lining of the small intestine).
- 25. MECHANICAL DIGESTION The 2 muscle layer of the small intestine helps with the process of peristalsis. Cross section through the small intestine
- 26. FUNCTIONS OF THE LIVER The liver produces and secretes bile. It stores glucose in the form of glycogen and is controlled by the hormone insulin. When the body requires glucose, glycogen is changed back into glucose. The liver also converts glycerol, into glucose. It can convert excess carbohydrates into fatty acids which combine with glycerol to form fats. The liver stores blood temporarily, blood is also formed in the liver of embryos. The liver manufactures plasma proteins e.g. albumen and fibrinogen. The liver forms heparin which prevents the clotting of blood inside the blood vessels. The liver detoxifies the body.
- 27. The liver breaks down surplus amino acids through the process of deamination Change amino acid into ammonia. Two ammonia molecules combine with one molecule of carbon dioxide to form urea and water. Deaminated amino acids are converted into glucose (glucose is converted to glycogen and stored in the liver) Urea is conveyed to the kidneys for
- 28. References Cinli3753, published Sep 3, 2018 Advanced nutrition and human metabolism. Published in: Lifestyle, license: CC Atribution-noncommercial license. Sfwgevhqe, published Aug 29, 2018 Advanced nutrition and human metabolism. Published in: Lifestyle Pooja Singh, published Sep 3, 2018 Human digestive system, digestive glands and the disorders images source. Published in: Science Simren Cena, published Aug 14, 2009. published in: Education. Westje, published Jun 8, 2009. AN interactive educational powerpoint on the human. Published in: Health & Medicine, Education