1. Class 9 Digestive System

2. 2

3. Digestive System Functions:
Digestion
Breaking down food into usable nutrients
Absorption
Transferring nutrients into bloodstream
Excretion
Expelling out non-digestible and non-useable materials.

4. The Alimentary Canal
Continuous hollow tube extending from mouth to anus.
Mouth, pharynx, esophagus, stomach, small intestine, large intestine, anal canal 4

5. Accessory Organs
Organs that contribute to the digestive process, but are not part of the alimentary canal and the food does not travel through.
Salivary Glands, liver, gall bladder, pancreas 5

6. Four Layers 6

7. Four Layers

8. Movements of the Alimentary Canal
Peristalsis
Propels contents forward
Alternates between circular and longitudinal muscles.
Mixing Movements
Uses circular and longitudinal muscles simultaneously to cause a “mixing” or “churning” type of movement.
Mixing can be done all along the canal, but is most noticeable in the stomach.

9. The Mouth 9

10. Mouth Functions Small amount of digestion (starch/CHO) Receive food
Taste
Receive food
Moisten food and prepare for further processing

11. Salivary Glands Exocrine glands composed of mucous and serous cells
Parotid
Largest of the main glands, secretes mostly serous fluid
Submandibular
secretes equal amounts of serous and mucous fluids
Sublingual
secretes mostly mucous fluid
Saliva components:
98% water
2% - antibacterial components,
mucus,
electrolytes (Na, Ca, K, Mg),
amylase (salivary)
Salivary Amylase breaks down CHO, therefore……..
CHO DIGESTION BEGINS IN THE MOUTH 11

12. The Pharynx 12

13. Swallowing known as deglutination
allows food to pass from the mouth to the pharynx to the esophagus
can start as a “voluntary” action, but quickly becomes involuntary
“Bolus” passes along hard palate then to soft palate with tongue pushing towards oropharynx.
bolus is prevented from gaining entry into the larynx by the epiglottis

14. The Esophagus
Pierces the diaphragm through the esophageal hiatus
Circular muscles that close off before entering the stomach: cardiac sphincter ( aka gastroesophageal sphincter, lower esophageal sphincter)
Function – propel food into stomach
THERE IS NO DIGESTIVE FUNCTION 14

15. The Stomach 15

16. PROTEIN DIGESTION BEGINS IN THE STOMACH
Gastric glands
Function
Mucous cells
secretes mucous
Parietal cells
secretes HCl (acid), intrinsic factor (protein released to allow intestine to absorb vit B12)
Chief cells
secretes pepsinogen (an inactive form of pepsin). Once this mixes with HCl, it becomes pepsin and is able to breakdown protein into amino acids.
temporary storage tank for food
site for mechanical and chemical breakdown of proteins….
PROTEIN DIGESTION BEGINS IN THE STOMACH
**cells in the lining of the mucosa continuously secrete bicarbonate to protect the stomach lining from self digestion. So this, along with mucous, protects the lining.

17. 17

18. The Pancreas 18

19. Functions of the Pancreas:
Releases enzymes that digest fats, proteins, carbohydrates, and nucleic acids
Produces alkaline (basic) fluid to neutralize acidic chyme in small intestine
Produces insulin and glucagon to regulate sugar metabolism
Pancreatic juice
pancreatic amylase breaks down CHO
pancreatic lipase breaks down fats
proteinase (Trypsin) breaks down proteins
nuclease breaks down nucleic acid into nucleotides (from DNA and RNA)
* Pancreatic juice is very alkaline, which helps neutralizes the fluid and allows the intestine to absorb properly.

20. Liver 20

21. Hepatic Portal System 21

22. Liver Lobes: 2 lobes, left and right Hepatic Lobules:
cylindrical structures which are the functional units of the liver.
Contain:
hepatocytes,
bile canals and ducts,
artery (hepatic),
vein (hepatic portal on perimeter and central vein draining sinusoids into hepatic veins),
sinusoids (blood filled spaces between hepatocytes),
Kupffer cells (specialized macrophages).

24. Liver Functions Makes and secretes bile Stores some vitamins and iron
Detoxification
Stores glucose
Modifies fats so the body can use them more efficiently
Forms plasma proteins
Helps excrete by-products of RBC (bilirubin) into bile
Synthesizes urea (by-product of protein metabolism), released into blood and sent out in urine

25. Bile
Emulsify fats
Stored in the gall bladder & becomes 5x more concentrated
Produced by Hepatocytes
Pasty yellow/green substance
Contents: bilirubin, cholesterol, salts, water, sodium and potassium and sometimes small amounts of copper and other metals
About 1 liter per day is made by the liver
About 95% of all salts found in bile are reabsorbed in the body in the lower small intestine

26. The Gallbladder 26

27. The Small Intestine 27

28. Structures of the Intestinal Wall28

29. The Large Intestine 29

30. Defecation Reflex 30

31. Thank goodness!!!