Lecture 16

Question 1

What does the GI tract represent?

Answer 1

a vast body surface area that is exposed to the external environment.

Question 2

What does GI Tract deal with?

Answer 2

food and potentially toxic
substances and infectious agents

Question 3

How does GI tract deal with the material it houses? What Mechanisms are used?

Answer 3

Sense and expel noxious substances
* vomit, diarrhea
* Specialized populations of T cells localized to
the intestinal mucosa
* E.g. Peyer’s patches

Question 4

name parts of GI tract / GI tube in order

Answer 4

• oral cavity
• upper esophageal sphincter
• esophagus
• lower esophageal sphincter
• stomach
• pyloric sphincter
• small intestine
• ileocecal valve
• colon (large intestine)
• anal sphincter
• rectum

Question 5

How is the GI tract segregated?

Answer 5

Muscular sphincters and valves partially
segregate function within the tube

Question 6

Length and Surface Area of GI tract

Answer 6

~28 ft. long – has to be folded extensively in abdominal cavity

• Large luminal surface area of ~200-400 m2 due to lots of villi
  / microvilli (equivalent to a tennis court)

Question 7

transit time for ingested meal

Answer 7

Highly variable, total of 30-80 hours, 5-8 hours in stomach and small intestine, Rest of time in the colon

Question 8

Higher fiber meals

Answer 8

Stay in GI system for longer

Question 9

Function of Gut Microbiome

Answer 9

protects against pathogenic microbes that enter/reside in tract. Bacteria breaks things down and has significant connection to health.

Question 10

intrinsic (enteric) nervous system function

Answer 10

to control and
coordinate the functioning of GI tract (e.g. opening and closing of
sphincters)

Question 11

GI tract Basic Processes (4)

Answer 11

Motility, Secretion, Digestion, Absorption

Question 12

Motility

Answer 12

includes peristalsis. The involuntary constriction and relaxation of the muscles of the intestine or another canal, creating wave-like movements that push the contents of the canal forward

Question 13

Secretion

Answer 13

Includes:
* Saliva, mucous
* Antibodies (IgA)
* Digestive enzymes
* Bile
* Bicarbonate

Question 14

Absorption

Answer 14

Water (large Intest.) + Nutrients (small intest.)

Question 15

The Cephalic Phase of Digestion and Absorption

Answer 15

• Chemical and mechanical digestion begins in the mouth
• Chewing (mastication)
• Secretions in response to sensory stimuli (sight, smell, taste), prepares the GI tract for food processing

Question 16

Salivary Secretion

Answer 16

• under autonomic control, stimulated by Sympathetic and Parasympathetic Nervous Systems
• Softens and lubricates food
• Provides enzymes: amylase and some lipase (but no protein digestion)

Question 17

Gastric Phase of Digestion and Absorption

Answer 17

Secretory cells of the gastric mucosa – (influence of Parasympathetic Nervous System “rest and digest”) - increases
intestinal and gland activity, and relaxes sphincter muscles in the GI tract.

Question 18

bile

Answer 18

break glycerol into backbone + fatty acid chains

Question 19

Bicarbonate

Answer 19

Homeostasis mechanism, maintains careful pH range

Question 20

secretions in response to sensory stimuli example

Answer 20

smell of baking cookies will want to make you eat more even though you just ate.

Question 21

Sympthetic Nerve

Answer 21

digest food quicker

Question 22

parasympathetic nerve

Answer 22

inhibits GI, less food break down (eg. during excersize)

Question 23

where does carb digestion begin?

Answer 23

in the mouth

Question 24

What is digested in the stomach

Answer 24

protein and fat, but not carbohydrate

Question 25

Acetylcholine

Answer 25

spikes after eating a meal to trigger release of stomach enzymes

Question 26

pepsin

Answer 26

stomach enzyme that serves to digest proteins found in ingested food

Question 27

gastric lipase

Answer 27

digestion of exogenous lipid. Triglycerides are digested to diglycerides then followed by fatty acids.

Question 28

Patient Dietary recall: identify lipids / dietary fats BREAKFAST: - Black coffee - White bread with peanut butter and honey LUNCH: - Curry chicken with basmati rice, onion, peppers, broccoli DINNER: - Veggie spring rolls - Side of stir-fried veggies EVENING SNACK: - Plain potato chips - Soda

Answer 28

White bread, peanut butter, Curry chicken (coconut milk), veggie spring rolls (pastry), stir-fried veggies (oil), potato chips

Question 29

Patient Dietary recall: identify dietary proteins BREAKFAST: - Black coffee - White bread with peanut butter and honey LUNCH: - Curry chicken with basmati rice, onion, peppers, broccoli DINNER: - Veggie spring rolls - Side of stir-fried veggies EVENING SNACK: - Plain potato chips - Soda

Answer 29

Peanut butter, curry chicken

Question 30

Fat is:

Answer 30

abundant in western diet, easier to consume than protein

Question 31

What happens in the pancreas

Answer 31

main contributor of digestive enzymes, Enzymes are released from pancreas in inactive form E.g. trypsinogen

Question 32

enzymes in small intestineare activated by

Answer 32

enterokinase in the brush border of duodenum to form trypsin – for protein digestion

Question 33

what does Gallbladder do?

Answer 33

stores bile (produced by liver) and Fat digestion

Question 34

Absorption in Small Intestine

Answer 34

Small intestinal mucosa – villi increase surface area to promote nutrient absorption

Question 35

secretion into lumen (small intestine) happens when

Answer 35

pyloric sphincter opens resulting in food (chyme) entering the upper duodenum

Question 36

Bicarbonate comes from

Answer 36

cells in the intestinal epithelium and in pancreatic secretions

Question 37

digestive enzymes come from

Answer 37

pancreas

Question 38

bile acids (fluid) come from

Answer 38

liver / gallbladder

Question 39

digestive enzymes are anchored on...

Answer 39

the luminal surface of small intestine epithelial cells

Question 40

digestive enzymes on small intestine include

Answer 40

disaccharidases and amino peptidases