1. Digestion / Absorption
Whole goal is to break down substances into small enough units that they can enter the blood stream

2. Sphincter
A sphincter is a ring of muscle that controls the passage of material.
Relaxed = open, Contracted = closed
At the junction of esophagus and stomach is the cardiac sphincter (AKA Lower Esophageal Sphincter). Stops stomach contents from going into esophagus

3. At the junction of stomach and duodenum is the pyloric sphincter
At the junction of stomach and duodenum is the pyloric sphincter. Regulates movement of stomach contents from stomach  small intestine.
Chyme is the semifluid mass of partially digested food that is expelled from the stomach into the duodenum

5. Draw This!

6. Heart Burn
Caused by a cardiac sphincter that doesn’t tighten as it should  stomach acid into esophagus
Often happens when too much food in the stomach (overeating) or to much pressure on the stomach (obesity, pregnancy)
Certain foods act as a trigger (relaxes the sphincter or causes more acid production  smoking causes both!)

7. The Stomach Site of initial protein digestion and food storage.
Smooth muscle contractions cause ingested food to be crushed, ground, and mixed, liquefying it to form Chyme
Don’t worry about anatomy here. Want to show students there is more complexity than we are learning. Point out smooth muscle layers

8. Gastric Pits
Stomach lining contains pits which contain specialized cells

9. Gastric Pits
Stomach contains GASTRIC PITS that have GLANDS and MUCUS cells.
Glands contain:
Parietal cells – secrete HCl (hydrochloric acid)
Chief cells – secrete pepsinogen, the zymogen (inactive) form of the digestive enzyme pepsin.(Pepsinogen  Pepsin under low pH)
Pepsinogen is known as a zymogen (the inactive form of the enzyme). It is activated by the low pH in the stomach

10. Pepsin breaks down proteins into short amino acid chains
Don’t copy down diagram. To remind students that enzymes are specific (lock and key)

11. G cells – secretes gastrin, a hormone.
Gastrin stimulates the secretion of HCl and aids in stomach motility.
It’s released in response to stomach stretching or the presence of proteins in the stomach. It is inhibited by HCl in the stomach.
What kind of feedback is this??
Motility is the smooth muscle contractions in the stomach which churn the chyme and move it through the stomach. Negative feedback

13. The J-shaped stomach stores food (the semi-digested mass is called chyme), initiates the digestion of proteins, has only minimal absorption, and moves materials on to the small intestine.

14. Absorption
Some water, specific vitamins and alcohol

15. Stomach Composition
The stomach has four layers that surrounds the space called the lumen.
Mucosa
Submucosa
Muscle layer
Serosa
The stomach has folded membranes on the inside called Rugae  allows stomach to expand

16. Why doesn’t the stomach digest itself?
Mucus cells in the gastric pits secrete a thick layer of mucus which protects the walls of the stomach
also secrete bicarbonate solution which neutralizes stomach acid (acid base reaction)
Bicarbonate production less than stomach acid production (5-10 %)

17. Peptic Ulcers
One cause of peptic ulcer is bacterial infection, but some ulcers are caused by long-term use of non-steroidal anti-inflammatory agents (NSAIDs), like aspirin and ibuprofen. In a few cases, cancerous tumours in the stomach or pancreas can cause ulcers. Peptic ulcers are not caused by stress or eating spicy food.

18. Peptic Ulcer
Most commonly caused by bacterial infection  Helicobacter pylori
NSAIDS (non-steroidal anti-inflammatory drugs)  aspirin and IBProfen
Smoking
Alcohol
Genetics

19. A Very Famous Stomach! Alexis St. Martin, 1822
aXGME

20. Mechanical vs Chemical recap
Mechanical – churning of stomach
Chemical :
HCl  denatured proteins and kills ingested bacteria
Pepsin  begins protein digestion

22. Liver & Gall Bladder
Liver produces Bile  mainly water and some bile salts
Bile is stored in the Gall Bladder  the gall bladder absorbs water making the bile more concentrated
Bile releases into duodenum via bile duct

23. Bile Salts
Emulsify Fats (Emulsify - To make a suspension of small globules of one liquid in a second liquid in which the first will not mix)

24. Bile continued Mechanical digestion:
Emulsification – bile salts break down fat globules into smaller droplets so that they can be digested by enzymes.
Purpose – To increase surface area!

26. Check your understanding
What is the function of the 2 sphincters in the stomach
What role does each cell in the gastric pit play?
Describe the chemical digestion that occurs in the stomach
What is the main purpose of bile salts. Explain.

27. Other Liver Functions Regulate blood glucose levels (stores glycogen)
Breakdown and synthesis of lipids and fats
Protein breakdown and amino acid synthesis
Stores vitamins (A, B12, D) and iron
Breaks down hormones, antibiotics, and other toxic substances (detoxifier)
Breaks down the by-products of RBC recycling
Note** these are main functions. Liver is thought to do about 500 separate functions
Removes effect of poison

28. Gall Stones
Crystalline mass formed from bile pigments, cholesterol, and calcium salts.
Cause severe pain and blockage of bile duct

29. gallstone - A small, hard object, in the shape of a pebble, that sometimes forms in the gallbladder or bile duct; composed of cholesterol, bile pigments and calcium salts

31. Liver Cirrhosis
Most commonly caused by alcohol, hepatits B, hepatits C, and fatty liver disease.
Gradual build up of scar tissue that replaces normal tissue
Leads to liver failure

32. Ethyl alcohol is toxic to the liver

33. Healthy Liver

34. Liver cirrhosis
Note extensive scarring

35. Chronic alcoholism will typically lead to damage of the liver characterized by scarring. The damaged liver often turns an orange color. This damage of the liver is called “cirrhosis”.
Cirrhosis of the liver

36. Jaundice
One of the by-products of RBC destruction is bilirubin (yellow color)
The liver filters out bilirubin from blood, and excretes in bile.
If liver is failing, or bile duct is blocked, bilirubin builds up in body, causing jaundice  a yellowing of skin and whites of eyes.

39. Gastrointestinal Disorder Project
So now that you know (almost) a lot about the normal functioning of the digestive system, it’s time to investigate some disorders!

40. Plagiarism Source all the materials you use!
In University if caught plagiarizing you will automatically receive a zero on the assignment with the potential of receiving a failing grade in the course or a suspension from the University!

41. http://www.youtube.com/watch?v=yQHx9 WEfT-Y&safe=active

42. Small Intestine Small Intestine is 7 meters in length
Three parts to small intestine:
Duodenum – first cm Area of most digestion.
Jejunum
Ileum

43. When chyme enters the small intestine it stimulates the release of secretin and cholecystokinin by the duodenum walls.
Secretin regulates pH  inhibits gastric HCl production and stimulates bicarbonate ion secretion (pancreas) Cholecystokinin causes release of bile (gall bladder) and digestive enzymes (pancreas).

44. Pancreas
Secretes pancreatic juice into the duodenum

46. Pancreatic juice contains:
Bicarbonate –
changes pH of chyme from highly acidic (pH 2) to weakly basic (pH 8)
Important pH for pancreatic enzymes to function

47. Enzymes
lipase - breaks down triglycerides into fatty acids and glycerol.

48. Protease – to digest proteins
Amylase – to digest carbohydrates

49. Insulin
Glucagon
Regulation of
blood glucose levels

50. Check your understanding!
What accessory gland produces a secretion with no digestive enzymes?
What kinds of foods are broken down by the pancreas?
Most enzymes are secreted as zymogens (inactive), why do you think that is?

51. Check your understanding!
Explain two functions of pancreatic fluid.
Someone recently has had a cholecystectomy, a surgical procedure to remove his gall bladder. Now he must take medication to prevent diarrhea. Why would the removal of the gall bladder cause diarrhea?

52. Mesentery Tissue that supports the intestinal tract.
A double layer of connective tissue in which blood vessels, nerves, lymphatics and other structures are contained.

53. Thin walls of small intestine with blood supply.
Mesentery

55. The intestines are held in place by a pair of membranes called the mesenteries (1). The mesenteric arteries run between these parallel membranes, and give rise to a vast number of tiny arteries (2) that take blood to the jejunum and ileum. These in turn break up into the thousands of arterioles that supply the villi and help to absorb food.
Near the base of the mesenteries is a row of white, fatty-looking bumps. These are lymph nodes on the lymph ducts that drain the lacteals. Since you take so much foreign material into your gut, it makes sense that you should have a strong line of defense against any invading microorganisms that might escape the digestive processes.

56. Adhesions often form following abdominal surgery or after an abdominal infection (peritonitis).

58. Peritonitis can also follow a penetrating abdominal injury.

59. Made up of three parts:
Duodenum
Jejunum
Ileum
Small Intestine

62. Segmentation
Smooth muscle contractions in both directions that mix and further break down contents of small intestine (chyme)
Is this mechanical or chemical digestion?

63. Absorption The small intestine absorbs the majority of nutrients
such as
The breakdown products of
Carbohydrates
Protein
Fats
Vitamins
by active and passive mechanisms

64. Intestinal villi

66. Each villus contains blood capillaries and a lymph capillary (lacteal)
Each villus contains blood capillaries and a lymph capillary (lacteal). Each villus is covered with microvilli.

67. Villi – tiny, finger-like projections on the walls of the small intestine
Microvilli – “brush border”  further increases surface area

68. Within villi structures are blood vessels that carry the absorbed nutrients to the rest of the body
Also contain in the villi are structures called lacteal, which absorbs fats to be delivered into the bloodstream

69. The Colon (AKA large intestine)

70. Main Functions of the Large Intestine
Water absorption
Absorption of vitamins produced by bacteria
Mass movements (defecation) – removes undigested food

71. Chemical Digestion
Indigestible food matter (e.g. cellulose) is digested by enteric bacteria (ex. E. Coli) that thrive in the large intestine.
These bacteria produce vitamin K and some B vitamins.

72. Appendix Vestigial organ  has lost function but retained structure
However, some scientists now think it does serve a function stores good bacteria to help repopulate gut after infection.

73. These wax models of human anatomy were made in the 19th century to help train doctors. They are now seen in the medical wing of this great museum in Vienna, (Wien).

74. Endoscopic view of appendix
Cecum

75. Rectum Connected to the sigmoid colon of the large intestine
Damp Mass of indigestible food remaining in large intestine is called FECES.
Temporarily stores feces before elimination (egestion)

76. Anus
The ending portion of the gastrointestinal tract in which feces (undigested food matter) leaves the body
Anal sphincter controls opening of anus.

77. Bowel Movement
Receptors in the walls of the large intestine give the central nervous system (brain) signals when a bowel movement is needed.
Some substances stimulate the bowel movements like caffeine.

78. Defecation to eliminate feces.

79. Summary

80. Digestion Time Summary
Digestion takes different lengths of time depending on the food being consumed. For healthy adults, it's usually between 24 and 72 hours.
Mouth (20 sec)
Starch is digested to maltose by carbohydrase / amylase.
Esophagus (10 sec)
Muscles squeeze food along the canal.
Stomach (2-6 hours)
Gastric juice mixes food when stomach churns.
Small intestine (5 hours)
Intestinal juice contains enzymes that complete the digestion process.
Large intestine and anus (min of 24 hours)
Undigested food reaches the large intestine
Lots of water is removed and taken back into the body

81. Washing your hands is essential
Washing your hands is essential! (Return to regular notes booklet for this)
Bacteria
Food poisoning
Parasites
Worms (Tapeworms)
* All can be transferred
through the mouth!

83. The Bacteria in your Gut?
Good, bad or ugly?
Good √
E.coli helps you digest food that you could not digest otherwise.
Bad √
 The bacteria that help you out, also produce flatulence as a by-product. Gas is a normal part of digestion.
Ugly √
 Some bacteria cause food poisoning, resulting in severe stomach cramps, vomiting and diarrhea.

85. More important stuff...
Our bodies make two hormones that contribute to homeostasis.
GASTRIN: Releases gastric juice (HCl) and relaxes gastric sphincter.
SECRETIN: Help release bicarbonate ions that neutralize HCl.
Our pancreas also helps with homeostasis in regulating blood glucose.

87. Insulin and Glucagon in Digestive System
Two hormones secreted by pancreas.
Work with liver to control level of glucose in body (blood).
Insulin released after meal  allows cells to become permeable to glucose.
Excess glucose stored by liver as glycogen.
Can change back to glucose if blood glucose becomes too low  Glucagon