digestive system

1. Digestive system

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.

7. Action
of
Pepsin
Splits
proteins
Helps to
digest
collagen

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