1. Chapter 28 Structure and Function of the Gastrointestinal System
Essentials of Pathophysiology
Chapter 28 Structure and Function of the Gastrointestinal System

2. Pre lecture quiz true/false
The digestive tract is a single-layered tube.
The gastrointestinal tract is innervated by both the sympathetic and parasympathetic nervous systems.
The gastrointestinal tract is the largest endocrine organ in the body.
Each day, approximately 7000 mL of fluid is secreted into the gastrointestinal tract.
Absorption is the process of moving nutrients and other materials from the external environment of the gastrointestinal tract into the internal environment.

3. Pre lecture quiz
The __________ is a tube that connects the oropharynx with the stomach.
The small intestine, which forms the middle portion of the digestive tract, consists of three subdivisions: the duodenum, the jejunum, and the __________.
__________ movements are rhythmic propulsive movements that occur when the smooth muscle layer constricts, forming a contractile band that forces the intraluminal contents forward. 
The __________ serves as a reservoir for ingested solids and liquids. 
__________ is the process of dismantling foods into their constituent parts.
Digestion
Esophagus
Ileum
Peristaltic
stomach

4. The Job of the Bowel Food: Movement Breakdown Absorption
Keeping dangerous gut contents out of the blood
Keeping blood contents from being lost into the gut lumen

5. Sequentially number parts through which food travels1 1 2 3 8 4 7 6 9 10 5 12 11

6. Bowel and Mesenteries
Abdomen

7. Question
Tell whether the following statement is true or false. The mesentery contains the intestine’s blood supply.

8. Answer
True An extension of the visceral peritoneum, the mesentery contains blood vessels that supply oxygen and nutrients to (arteries) and eliminate CO2 and waste from (veins) the intestines.

9. Prader-Willi Syndrome
It is traditionally characterized by hypotonia, short stature, hyperphagia, obesity, behavioral issues (specifically OCD-like behaviors), small hands and feet, hypogonadism, and mild mental retardation.
Plasma ghrelin levels are extremely high
Discussion:
What are the effects of this disorder?
ghrelin a gastrointestinal hormone produced by epithelial cells lining the fundus of the stomach; appears to be a stimulant for appetite and feeding, but is also a strong stimulant of growth hormone secretion from the anterior pituitary 
Ghrelin levels increase before meals and decrease after meals. It is considered the counterpart of the hormone leptin,

10. Prader-Willi Syndrome
This is a picture of a child with Prader-Willi Syndrome, first with a small, undersized figure, then as an obese teenager later in life.

11. Scenario
A woman has a pancreatic tumor that secretes gastrin- a hormone that stimulates the secretion of gastric juice.
Question
What complication is likely to develop? Why?

12. Scenario A man cannot produce cholecystokinin. Question
What problems will this cause him?

13. Carbohydrate Digestion
Mouth: Salivary amylase
Duodenum: pancreatic amylase
Polysaccharides  disaccharides
Brush border enzymes
Disaccharides  monosaccharides
Monsaccharides absorbed into blood

14. Duodenum: pancreatic trypsinogen
Protein Digestion
Stomach: pepsinogen
Activated to pepsin by acid in stomach
Breaks proteins into polypeptides
Duodenum: pancreatic trypsinogen
Activated to trypsin in duodenum
Brush border enzymes
Breaks polypeptides into 2–3 amino acid peptides
Peptides absorbed into blood

15. Fat Digestion Duodenum: bile Emulsifies fats
Duodenum: pancreatic lipase
Breaks triglycerides into glycerol and fatty acids
Jejunum
Packages digested fats as chylomicrons
Passed to the lymph

16. Question
Digestion of which substance begins in the mouth?
Carbohydrates
Protein
Fat
All of the above

17. Answer
Carbohydrates
Carbohydrate digestion begins in the mouth with salivary amylase; protein digestion begins in the stomach with pepsinogen; fat digestion begins in the small intestine with bile and pancreatic lipase.

18. Discussion Which is the best choice to reduce fat digestion?
Suppress duodenal hormone secretion
Suppress the activity of chief cells in the stomach
Decrease intrinsic factor secretion
Block gall bladder contraction
Inactivate pancreatic lipase

19. Question
How would fat digestion be affected if bile levels decreased?
It would increase.
It would decrease.
It would have no effect—fat digestion is mainly affected by amylase.
It would have no effect—fat digestion is mainly affected by lipase.

20. Answer
It would decrease.
Bile emulsifies fat so that it can be more easily digested. Decreased amounts of bile would lead to decreased fat emulsification and decreased ability to break down/digest fats.