1. Digestive System

2. Role of Digestive System
A. Prepare food for absorption and utilization by all the body cells
B. Excess food material (not absorbed) becomes feces to be eliminated
C. Ingestion vs. Digestion
1. Ingestion – process of taking food into the GI tract
2. Digestion –
a. food and fluid is broken down so the body can use them to build and nourish cells, along with providing energy
b. absorption – movement of nutrients into internal environment

3. A. Gastrointestinal (GI) Tract [aka alimentary canal] (listed in order of food pathway) mouth oropharynx pharynx esophagus stomach small intestine a. duodenum b. jejunum c. ileum large intestine a. cecum b. colon ascending colon transverse colon descending colon sigmoid colon rectum anus B. Accessory Organs salivary glands tongue teeth liver gallbladder pancreas vermiform appendix

4. Layers of the walls of the gastrointestinal (GI) tract. 1
Layers of the walls of the gastrointestinal (GI) tract (deepest) mucosasubmucosamuscularisserosa (most superficial) Tissue layers have variation in different organs

5. Mouth and Pharynx Buccal Cavity
Lips – external is skin; internal is mucous membranes
Cheeks – lined by mucous membranes; contain mucous secreting glands
Hard and Soft Palates
Hard palate – four bones
Soft palate – muscle; forms partition between mouth and nasopharynx; uvula extend from soft palate
Tongue – muscle covered by mucous membrane
mastication (chewing) and deglutition (swallowing)
papillae – surface of tongue; some contain taste buds
lingual frenulum – mucous membrane fold that anchors tong to bottom of mouth

6. Mouth and Pharynx Salivary Glands Secrete about 1L of saliva/day
Salivary amylase – enzyme in saliva that converts starch to sugar
Three pairs of glands (parotid, submandibular, sublingual)

7. Mouth and Pharynx Teeth
Anatomy
crown - covered in enamel
neck – connects crown to root
root – fits into socket in the gum
Types
Deciduous teeth (20 baby teeth)
Incisors
Canines
first molars
second molars
third molars – wisdom teeth
Permanent Teeth (32 adult teeth)
incisors
canine
premolars
Molars
Pharynx – tube through which bolus (chewed ball of food) passes when moved from mouth to esophagus (deglutition)

9. Esophagus and Stomach Esophagus Extends from pharynx to stomach
Resides in both abdominal and thoracic cavities
Peristalsis begins

10. Esophagus and Stomach Stomach Functions reservoir for food
secretes gastric juice
breaks food into small particles and mixes them with gastric juice
limited absorption
helps protect body from bacteria swallowed with food
produces gastrin – (hormone that causes the stomach to produce acid)

11. Esophagus and Stomach Stomach Sphincter Muscles Stomach wall
lower esophageal sphinter (LES)/cardiac sphincter - controls opening of esophagus into stomach
pyloric sphincter - controls opening of stomach into small intestine (duodenum)
gastric reflux – sphincter working improperly causing heartburn
Stomach wall
Gastric mucosa
Rugae – folds in lining of the stomach
gastric glands – below rugae; secrete most of gastric juice
chief cells – secrete the enzymes of gastric juice
parietal cells - secrete HCl
Zantac – reduces HCl formation in stomach
endocrine cells – secrete gastrin
Gastric muscularis – thick layer of muscle that allows stomach to contract

12. Helicobacter pylori – bacteria that causes peptic ulcers
Stomach lining replaces itself every 3 days
Chyme – liquefied food; form that food leaves the stomach
Gastroenteritis – stomach inflammation
Emesis – vomiting
35 million digestive glands in the stomach

13. Gastroesophageal Reflux

14. Gastric Ulcer

15. Small Intestine Proximal to stomach duodenumjejunumileum
Microvilli (villus) allow for absorption (increase surface area by hundreds)
Where majority of substances are absorbed
22 feet long
Food can stay here for up to 4 hours

16. Large Intestine

17. Large Intestine Proximal to small intestine
cecum ascending colontraverse colondescending colonsigmoid colon rectum
Haustra – pouchlike structures
Constipation – movement of lower colon and rectum contents at a rate slower than normal
Diverticulosis – outpouchings of intestinal wall
Colitis – inflammation of large intestine
5 feet long
Waste stays hours
Main function is water absorption in order to eliminate feces

18. Appendix and Peritoneum
Vermiform Appendix
function not fully known; but thought to provide safe place for good bacteria
appendicitis
inflammation of appendix
not common in elderly
appendectomy – surgical removal of appendix
Peritoneum
large, continuous sheet of serous membrane
parietal and visceral portions
mesentery – extension of parietal peritoneum that anchors GI tract to abdominal wall.

20. Liver Anatomical units – lobes and lobules
left lobe
right lobe – biggest section of liver
hepatic lobules – branch of hepatic vein extends through each lobule (main anat unit)
Blood flows to hepatic lobules via branches of the hepatic artery and hepatic portal vein
Common bile duct – merger of the hepatic duct and cystic duct
Produces bile
Bile salts – aid in the absorption of fats; most essential part of bile
No enzymes
Functions of liver
Detox
Bile secretion – secrete 1 pint/day
Metabolizes proteins, fats,
and carbohydrates
Misc. Info
Hepatic refers to liver
Largest gland in the body
Hepatitis – inflammation of the liver
Cirrhosis – degenerative liver
condition
Removes harmful substances from
the blood
Stores vitamins and sugars until your
body needs them

22. Gallbladder
Stores bile (holds ml bile)
Cholecystokinin (CCK) – hormone that stimulates gallbladder to release bile into duodenum (small intestine)
Secretin – stimulates release of bile
Cholelithiasis - gallstones
Cholecystectomy – surgical removal of gallbladder
Below liver
Pear shaped

23. Cholelithiasis - Gallbladder with yellow cholesterol gallstones
Cholecystectomy
Gallbladder before removal

24. Pancreas
Both endocrine and exocrine gland
Pancreatic juice secreted by exocrine acinar cells
Pancreatic cancer – form of adenocarcinoma
Breaks down sugar
Beta cells secrete insulin

25. Digestive Physiology Mechanical Digestion •Mastication •Deglutition
Oral stage – mouth to oropharynx
- voluntary control
- bolus formed
- soft palate acts as valve to prevent food from enetering nasopharynx
Pharyngeal stage – oropharynx to esophagus
- involuntary control
- epiglottis prevents bolus from entering larynx to trachea
Esophageal stage – esophagus to stomach

26. Peristalsis Segmentation
wavelike ripple of smooth muscle
ring of contraction occurs where GI wall is stretched, pushing bolus forward
stimulated by CCK – secreted by endocrine cells in presence of chyme
Segmentation
mixing movement
forward and backward movement that mechanically breaks down food and mixes it with digestive juices

27. Organ
Mechanical Process
Mouth (teeth and tongue)
Mastication
Deglutition
Pharynx
Esophagus
Peristalsis
Stomach
Churning
Small Intestine
Segmentation
Ascending and Transverse Colon
Descending Colon
Mass peristalsis
Rectum
Defecation

28. Chemical Digestion Digestive enzymes
a. extracellular, organic (protein) catalysts
b. enzyme action
1. specificity
2. optimal pH
Stomach
Jejunum
Ileum
Colon pH
3.0
7.5
3. catalyst
4. continually destroyed or eliminated, so constantly being made

29. Digestive Enzyme Action
proenzyme altered by kinase to form active enzyme
1. kinase removes prosthetic group to expose active site
2. substrate (food) binds to active site of active enzyme
3. enzyme splits substrate into components and releases them
4. enzyme can now digest new substance

30. Carbohydrate digestion
(bread, potato, rice, pasta, fruit, vegetables)
Starch and sugar are broken down by saliva, pancreatic and small intestinal juices
salivary amylase, small intestine
pancreatic juices enzymes
* starch maltose glucose (monosac)
absorbed into blood liver (stored or used)
small intestine enzymes
* sugar (sucrose) glucose + fructose
absorbed into blood
* fiber – undigestible
Cellulose cannot be broken down; eliminated in feces

31. Pepsin
Trypsin

32. Lipid Digestion
emulsification – bile breaks down fat into small droplets within the small intestine
Steatorrhea - impaired fat absorption producing large, greasy, foul-smelling stool
Fat-soluble vitamins – A, D, E, K (stored in liver and fatty tissue)
Pancreatic lipase – main fat-digesting enzyme

33. Digestive Juice
Enzyme
Substance Digested
End Product
Saliva
Salivary amylase
Starch (polysacc)
Maltose (monosacc)
Gastric Juice
Protease (pepsin)
Protein
Partially digested protein
Pancreatic Juice
Protease (trypsin)
Proteins
Peptides and a.a.
Lipase
Fats
Fatty acids, glycerol
PancreaticAmylase
Starch
(polysacc)
Intestinal
Peptidases
Peptides
a.a.
Sucrase
Sucrose
Glucose, fructose
Lactase
Lactose
Glucose, galactose
Maltase
Maltose
Glucose

34. Disorders Mumps Tooth Decay Malocclusion
GERD (gastroesophageal reflux disease)
Ulcers
Pyloric stenosis
Appendicitis
Hemorrhoids
Proctitis
Diabetes
Gastroenteritis
Anorexia
Nausea
Emesis
Diarrhea
Constipation
Malabsorption
Diverticulitis
Colitis
Irritable Bowl Syndrome
Colorectal Cancer
Hepatitis
Cirrohsis
Pancreatitis
Pancreatic cancer