1. THE DIGESTIVE SYSTEM
IT’S INTESTINE TIME!!

2. bn

3. MAIN IDEA OF INTESTINES
Small intestine 
where the major events of
DIGESTION &
almost all ABSORPTION occur
Large intestine 
where WATER ABSORPTION,
vitamin production, and
FECES FORMATION occurs

5. intestine VALVES!
Valve from stomach to small intestine (S.I.)  pyloric sphincter
Valve from the S.I. to L.I. 
ileocecal valve/sphincter

6. 3 SECTIONS OF S.I.
1) **DUODENUM
2) JEJUNUM
3) ILEUM

7. MESENTERY
Layer of membrane (peritoneum) that holds the small intestine coiled together as well as to the posterior abdominal wall

8. 3 IMPORTANT FEATURES OF THE Small Intestine (S.I.):
1) CIRCULAR FOLDS  deep folds of
both the mucosa and submucosa of small intestine
(like rugae of stomach)
*increase surface area
PEYER’S PATCHES –
collections of lymphatic tissue
in submucosa; there are
more at the end of S.I. because
undigested food contains bacteria

9. 3 IMPORTANT FEATURES OF THE S.I.
2) VILLI  finger-like projections of
mucosa that
increase surface area
Contain capillary beds and
lymphatic capillaries (LACTEALS)

10. 3 IMPORTANT FEATURES OF THE S.I.
3) MICROVILLI 
very tiny projections of membrane of mucosa cells on the VILLI
** Both villi & microvilli absorb digested foods through mucosa & submucosa

11. Small Intestine Note:
** Enzymes produced by the PANCREAS and bile made by the LIVER enter the DUODENUM!!

12. Chemical Digestion & Absorption in the S.I.
Chemical digestion is completed in the small intestine due to bile as well as enzymes in the pancreatic and intestinal juices.
Approx. 90% of all ABSORPTION takes place in the S.I.! (other % in stomach & L.I.)

13. SMALL INTESTINE labeled:
First Figure/19.11 LABEL (p.472):
Duodenum
Jejunum
Ileum
Stomach
Large Intestine

14. SMALL INTESTINE labeled:
Second Figure/19.12 LABEL (p 473):
Mucosa
Submucosa
Muscularis externa
Serosa
Villus
Blood capillary
Lacteal
Simple columnar epithelium

15. THE
LARGE
INTESTINE (L.I.)

16. LARGE INTESTINE
*Is much larger in diameter but shorter in length than the small intestine
runs from the ileocecal valve to the anus

17. LARGE INTESTINE (COLON)
MAIN FUNCTIONS:
Dries out undigested food residue *absorbs water & vitamins
Eliminates residues from the body as wastes (feces)

18. 5 SECTIONS OF Large Intestine:
1) Cecum
2) Appendix
3) Colon (ascending colon, transverse
colon, descending colon, and
sigmoid colon)
4) Rectum
5) Anal Canal
ANUS – opening to exterior

19. LARGE INTESTINE (L.I.)
The outer layer of the muscularis externa is bundled into 3 bands called TENIA COLI which bunch up the colon into pouches called HAUSTRA
Tenia = flat band
Haustra = “drawer” puckered appearance

20. 2 valves in Anal Canal:
- External voluntary sphincter (skeletal muscle)
- Internal involuntary sphincter (smooth muscle)

21. Appendix Hangs from the cecum (first section of L.I.)
Sometimes bacteria can get into appendix and it becomes inflamed = appendicitis
If it broke open it would empty its contents into the abdominopelvic cavity which could be fatal

22. Important Features of L.I.
There are NO villi 
nutrient absorption into bloodstream happened in S.I.
LOTS of goblet cells in the simple columnar epithelium produce mucus (functions as lubricant)

23. BACTERIA
Bacteria live in the L.I. and break down some of the remaining nutrients which produces gas (flatulence)
FECES contain indigestible food materials, mucus, bacteria, and water

25. Digestion & Absorption in the L.I.
MECHANICAL DIGESTION in the large intestine includes:
HAUSTRAL churning or contraction of the haustra (pouches of colon) when the walls of the colon fill with chyme
PERISTALSIS (muscular contractions that propel food
MASS PERISTALSIS is a large peristaltic contraction that moves fecal material into RECTUM

26. DEFECATION REFLEX
Mass peristalsis moves indigestible materials from colon into the rectum:
Stretch receptors in the mucosa of the rectum are stimulated are the rectum is emptied
The internal involuntary sphincter opens due to a combination of pressure and parasympathetic nerve impulses

27. Chemical Digestion & Absorption in L.I.
The last small bit of digestion occurs in the L.I. by bacteria which break down any small carbohydrates, amino acids, etc.
Products of this breakdown include: gas (flatulence) as well as some vitamins

28. Chemical Digestion & Absorption in L.I.
L.I. absorbs mostly WATER and vitamins
Remember almost all absorption (including most water absorption happens in S.I.)
In the L.I. water is absorbed by osmosis

29. LARGE INTESTINE labeled:
First Figure/19.14 LABEL (p 478):
Haustra
Tenia coli
Cecum
Ileocecal sphincter
Ileum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anal canal
Anus

30. LARGE INTESTINE LABELED:
Second Figure/19.15 LABEL (p 479):
Mucosa
Submucosa
Muscularis externa
Serosa
Simple columnar epithelium

31. Accessory ORGANS Summary
PANCREAS  pancreatic enzymes that break down all 4 organic molecule groups are secreted into the duodenum

32. Accessory ORGANS Summary
LIVER 
2 main lobes which
are broken up into lobules
Produces bile which enters duodenum through the common hepatic duct
Bile breaks up fat molecules so that enzymes can digest them

33. Accessory ORGANS Summary
GALLBLADDER 
On inferior surface of liver
Stores bile when food is not being digested

34. Accessory ORGANS Summary
SALIVARY GLANDS 
*Salivary amylase
And salivary lipase
TEETH 
Mechanical digestion of food
Deciduous: first teeth/baby teeth