Chapter 14: The Digestive System

Transcription

1 Chapter 14: The Digestive System

2 Digestive system consists of Muscular tube (digestive tract) alimentary canal Accessory organs teeth, tongue, glandular organs

3 6 essential activities Ingestion Propulsion Mechanical digestion Chemical digestion Absorption Defecation

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5 Histology of the Digestive Tract mucosa primarily surface epithelium lining of tract after esophagus, simple columnar submucosa connective tissue muscularis externa smooth muscle serosa innermost layer (closest to viscera)

6 Alimentary Canal Wall Structure

7 Peristalsis

8 Process begins in the mouth What type of epithelial tissue is found here? Is there any digestion in the mouth?

9 Digestion begins in the mouth

10 Salivary Glands parotid glands submandibular glands sublingual glands saliva binds food into bolus contains salivary amylase digests starches

11 Salivary Glands

12 Teeth begin to process food

13 After chewing food in the mouth Food enters the esophagus What is the function of the esophagus? What type of epithelial tissue is found here?

14 Esophagus is hollow tube

15 From the esophagus food enters the stomach What are the functions of the stomach? What type of epithelial tissue is found here? What else is unique to the histology of the stomach?

16 Stomach

17 Stomach simple columnar epithelium produces mucous gastric glands contain cells that secrete gastric juices: pepsinogens digest proteins HCl activates enzymes mucous protects stomach wall gastrin digestive hormone

18 Gastric Pits

19 Does digestion occur in the stomach? Absorption? Carbohydrates Proteins

20 Small Intestine major function: responsible for 90% of absorption divided into three regions duodenum jejunum ileum

21 Histology of the Small Intestine Lining forms large folds called plica epithelial tissue projections called intestinal villi all the cells have microvilli villus contains a lacteal contains nerve and blood vessels

22 Small Intestine Structure

23 Small Intestine purpose of villi, microvilli and circular folds?

24 Pancreas primarily an exocrine gland triggered release by secretin alkaline mixture of enzymes, water, and ions travels in pancreatic duct, joins the common bile duct

25 Pancreas

26 Pancreatic Enzymes pancreatic amylase starch digestion trypsin, chymotrypsin, carboxypeptidase protein digestion lipases fat digestion nucleases nucleic acid digestion

27 Liver each lobe divided into lobules cells called hepatocytes produces and secrete bile

28 Liver

29 Liver Functions Metabolic regulation Hematological regulation Bile production

30 Metabolic Functions all blood from digestive system flows through liver liver regulates blood contents of glucose lipids amino acids

31 Liver s role in glucose regulation if levels drop, glycogen reserves in liver provide more glucose for blood glycogenolysis - break down glycogen also gluconeogenesis - form glucose from fats & proteins if levels rise, glucose is stored as glycogen glycogenesis - form glycogen from glucose

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33 Liver s role in lipid metabolism regulates circulating levels of triglycerides, fatty acids, and cholesterol if levels decline, lipid stores are released HDL: transport cholesterol from body cells to liver LDL: transport cholesterol to body cells

34 Liver s role in amino acid metabolism? removes excess amino acids from the bloodstream what happens to these amino acids?

35 Other metabolic functions of the liver Removal of waste products Vitamin storage Mineral storage Drug inactivation

36 Bile produced by liver release triggered by secretin bile salts emuslify lipids

37 Gall bladder Major functions: bile storage bile modification

38 What regulates release of bile? CCK (cholecsystokinin) released from the duodenum triggered by the entry of foods high in fats into the duodenum

39 The last part..large intestine General functions Reabsorption of water Absorption of vitamins made by bacteria Storage of fecal material

40 Anatomy of large intestine

41 Digestion and Absorption

42 Chemical Digestion What is chemical digestion? Why is chemical digestion important? What types of organic compounds are digested? Where does chemical digestion occur?

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45 What is needed for these reactions? Enzymes What are some examples? Where are they found?

46 Where does most absorption occur? SI active transport capillary beds to liver via hepatic portal vein lipids & fats absorbed by diffusion

47 Absorption in Large Intestine bacteria produce vitamin K & some Bs