Digestive system.pptx//////////////////////////////////////////////////////////////
- 2. Oral cavity
- 3. Oral cavity • It is the first part of the digestive system • Structures in the mouth that aids in digestion are: - Teeth : cut and grind food . - Salivary gland : secrete saliva into the oral cavity . - Saliva : moistens the food and contains enzymes that help in the digestion of food .
- 4. Oesophagus • Tube connecting mouth to stomach . • It goes behind trachea :The wind pipe • It has epiglottis which prevents food from entering trachea. • Food passes through trachea through Peristalsis.
- 5. • Oesophageal sphincter: Food has to pass through a valve at the lower end of oesophagus to reach stomach. • It prevents stomach acids from flowing back into the oesophagus.
- 6. Stomach • J shaped muscular sac. Function: performs mechanical digestion by mixing it with gastric juices secreted from the stomach lining. Gastric juices: HCL,Enzymes,water and mucus HCL: Hydrochloric acid: 1.Antiseptic and antibacterial action 2.stimutales secretion of pancreatic juice and bile 3.helps in absorption of Iron and Ca. 4.provides medium necessary for the action of pepsin on proteins.
- 8. • Mucus : saves the stomach lining from the destructive action of HCL. • Bolus is now called Chyme. • Pyloric Sphincter : Chyme when passes from stomach to small intestine has to pass through a muscular sphincter called Pyloric sphincter.
- 9. Small Intestine Responsible for the complete digestion of all macromolecules and absorption of • Glucose • Fatty acids • Amino acids
- 10. Parts of small intestine. 1. Duodenum 2. Jejunum 3. Ileum
- 11. Duodenum • First U shaped part • Around 30 cm in length • Enzymes are secreted into duodenum from pancreas and gall bladder. • It is lined by folds of tissue called Villi. Villi contains microvilli. • This increases the surface area for absorption of nutrients.
- 12. Jejunum • Around 2.5 m long • Its role is absorption of nutrients ILEUM • Around 3m long. • Has fewer villi and microvilli than other parts • Responsible for pushing the waste materials into large intestine.
- 13. Functions of small intestine • 90% of digestion and absorption occur here • Digestion of proteins - with the help of trypsin and chymotrypsin secreted from pancreas • Digestion of fat -with the help of lipases • Digestion of carbohydrates -with the help of pancreatic amylases • Absorption of almost all nutrients.
- 14. Large intestine Parts 1. Caecum 2. Colon – ascending colon - Transverse colon - Descending colon - Sigmoid colon 3. Rectum 1. – ascending colon - Transverse colon - Descending colon - Sigmoid colon
- 15. • Caecum - first part - looks like a pouch - Passes digested matter from small intestine to colon • Colon major part of large intestine it has 4 parts – ascending colon - Transverse colon - Descending colon - Sigmoid colon
- 16. • Rectum Final part of large intestine Left over waste collects here Emptied through anus
- 17. Functions of large intestine • Absorption of water • Absorption of vitamins • Reduce acidity • Protects from infections: prevents harmful bacteria from reentering body • Produce antibodies to boost immunity
- 18. Accessory organs of digestive system • Liver • Gall bladder • Pancreas
- 19. Liver Functions • It secretes bile • Breaks down old red blood cells • Metabolism of fats,proteins and carbohydrates • Hemopoesis in fetus • Synthesis if glucose • Storage of glycogen,aminoacids and Vit B12,Aand D
- 20. Gall bladder • Storage of bile • Bile emulsifies fat in digested food • Assists in absorption of fat
- 21. Pancreas • Secretes a number of different enzymes into small intestine • Role in digestion of carbohydrates, fats and proteins. • It neutralizes HCL from stomach and changes the PH of small intestine to alkaline