1. DIGESTIVE SYSTEM

2. DIGESTIVE TRACT Tube in which digestion occurs
Also called alimentary canal, gastrointestinal tract (GI)
Entire canal is about 9 meters along (30 feet) in a cadaver. Shorter in a live person

3. FUNCTIONS
Ingest food
Break down nutrients to a form that can cross plasma membranes
Absorb nutrients
Eliminate undigested parts

4. PARTS

5. ORAL CAVITY Mouth - receives food Lips (labia) protects opening
Tongue – taste buds, pushes food to back of throat fermium – a fold of mucous membrane that secures the tongue to the floor of the mouth
Roof of mouth – contains made up of: hard palate -anterior portion is bone Soft palate posterior portion is muscle

6. Parts continued
Uvula – finger-like projection that closes off nasopharynx keeps food from entering the nasal cavity
Tonsils – protects against injection

7. SALIVARY GLANDS 3 pairs secrete saliva
contains enzyme salivary amylase starts digestion of starch feel flaps under tongue and cheeks – where ducts are located
Contains substances that inhibit bacteria growth
Dissolves food chemicals so they can be tastes

8. Teeth – mechanical digestion

9. PHARYNX – region that receives food and air
Trachea – also called windpipe lies in front of esophagus
Swallowing is a reflex
Glottis – opening to the larynx
Epiglottis – spoon shaped tissue covering a piece of cartilage covers glottis so food/liquids do not enter trachea

10. ESOPHAGUS Muscular tube Connects to stomach
Remains collapsed until bolus enters
Peristalsis – rhythmic contractions that push food along digestive tract
No chemical digestion occurs

11. LAYERS OF GI TRACT
Mucosa – inner most – moist membrane that lines the lumen
Submucosa- beneath mucosa- made up of connective tissue, and lymph vessels
Muscularis external - smooth muscles
Serosa – outermost layer

12. Esophagus continued
Sphincters – muscles that encircle a tube act as valves
located at point where stomach and esophagus meet
when open – food passes into stomach
closed – keeps acid from entering esophagus

13. STOMACH Thick muscular wall Wall has deep folds called rugae
Holds 4 liters when full
Stores food
Empties in 2/6 hours
Mechanical digestion – churns and mixes food with gastric juices
pyloric sphincter connects to small intestine
Cardioesophageal sphincter – connects to esophagus

14. REGIONS OF STOMACH Fundus – expanded part of the stomach
Body – the midportion
Pylorus – terminal part of stomach

15. GASTRIC JUICES Pepsin – digests protein
HCL – hydrochloric acid pH kills bacteria breaks down connective tissue of meat activates pepsin
Mucus
Intrinsic factor – substance needed for the absorption of vitamin B12 in the small intestine

16. MUCUS Thick layer of mucus Protects stomach from HCL
Produced by goblet cells
Ulcer – open sore in wall of stomach exposed to gastric juices bacterial infection interferes with mucus production

17. STOMACH CONTINUED
Chyme – contents of stomach thick soupy liquid enters small intestines in small squirts
No absorption of food occurs in stomach
Alcohol absorption only

18. SMALL INTESTINE Major site of digestion Has small diameter
About 3 meters (9 feet) long

19. THREE PARTS OF SMALL INTESTINE
Duodenum – 1st part of small intestine
sphincter muscles control chyme entering
receives enzymes from liver and pancreas
Jejunum
Ileum – terminal part of intestine
Ends with the ileocecal valve

20. WALL OF SMALL INTESTINE
Fingerlike projections called villi
Microscopic microvilli absorb sugars and amino acids directly into blood stream
Components of fats enter smooth ER where they are rejoined and enter the lacteal (small lymphatic vessels)

21. LARGE INTESTINE 1.5 Meters Absorbs water, salts, and vitamins
Parts: cecum colon rectum

22. CECUM Lind end of large intestine
Appendix – small projection may help fight infection subject to inflammation

23. COLON
Ascending
Transverse
Descending
Sigmoid colon – enters rectum

24. RECTUM 20 cemeters Anus – opening to outside expels feces
Stretching of rectal wall sends nerve impulses to spinal cord causing relaxation of anal sphincters
Bacteria found in some feces produce vitamins that are reabsorbed by our body

25. PANCREASE Endocrine functions involves insulin and glucagon
Exocrine function involves the secretion of pancreatic juices

26. PANCREATIC JUICES Sodium bicarbonate Pancreatic amylase Trypsin Lipase
NaHCO3
Neutralizes chyme
Pancreatic amylase
Digest starch
Trypsin
Digest proteins
Lipase
Digest fats

27. LIVER Responsible for maintaining homeostasis of blood
Removes poisonous substances
Removes Fe and stores it
Removes Vitamins A,D,E and K and stores them
Makes plasma proteins to maintain osmotic pressure

28. LIVER CONTINUED Makes cholesterol and regulates amount in blood
Maintains blood glucose levels
Produces bile which emulsifies fat
Produces fact

29. GALL BLADDER Sac attached to undersurface of liver
Stores bile until needed in the duodenum
Gall stones - cholesterol comes out of bile solution forming crystals

30. Feces – more or less solid product delivered to the rectum
Resident bacteria of large intestine metabolize the remaining material
Gases are released
Methane and hydrogen sulfide produce the odor – more gas is produced when food is high in carbohydrates
Bacteria make vitamin K and some B vitamins

32. DISEASES OF THE GI TRACT
Acid reflux
Appendicitis
Cirrhosis
Colorectal cancer
Colostomy
Constipation
Diarrhea
Gallstones
Hemorrhoids
Hepatitis
Hernia
IBS
Jaundice
Lactose intolerance
Mumps
Peritonitis
Ulcer
Vomiting