Lecture 16

Question 1

What does GI stand for

Answer 1

The GI (Gastro-intestinal) Tract

Question 2

What are the 6 components of the GI tract and the sphincters/valces between them

Answer 2

1. Oral cavity
   — Upper esophageal sphincter
2. Esophagus
   —- Lower esophageal sphincter
3. Stomach
   — Pyloric sphincter
4. Small intestine
   —- Ileocecal valve
5. Colon (large intestine)
   — Anal sphincter
6. Rectum

Question 3

What is the purpose of muscle Sphincters and valves

Answer 3

Muscle Sphincters and valves particularly segregate functions within the tube

Question 4

What does the GI tract represent

Answer 4

Represents a vast body surface area that is exposed to external environment

Question 5

The GI tract has unique mechanisms to deal with …

Answer 5

Can sense or expel noxious substances
– Through vomit or diarrhea

Specialized populations of T cells localized to the intestinal mucosa
– Eg. peyer’s patches

Question 6

How long is the GI tract

Answer 6

About 28 feet long, folded extensively to fit in abdominal cavity

Question 7

How large is the luminal surface in the human body

Answer 7

Large luminal surface of about 200 to 400 square meters due to lots of villi and microvilli

Question 8

What is the luminal surface

Answer 8

Lumin = space within tubes, tracts, cavities and cells in body

Question 9

How long does it take meals to go through the GI tract

Answer 9

Highly variable transit time for ingested meal (total of 30-80 hours)

Question 10

What does the gut contain

Answer 10

microbiome (bacteria, ext)

–protects against pathogenic microbes that enter/reside in tract

Question 11

What coordinates the opening and closing of sphincters

Answer 11

Intrinsic (AKA enteric) nervous system

Question 12

What are the 4 processes of the GI tract

Answer 12

1. Mobility
2. Secretion
3. Digestion
4. Absorption

Question 13

What does the GI tract move

Answer 13

Ability of organisms and fluid to move and get around

Question 14

What does the GI tract secrete

Answer 14

Saliva
Antibodies
Digestive enzymes

Bile
Bicarbonate

Question 15

What does the GI tract absorb

Answer 15

Water nutrients

Question 16

What is the first phase of the GI tract

Answer 16

The Cephalic Phase of Digestion and Absorption

Question 17

What is involved in the Cephalic Phase of Digestion and Absorption

Answer 17

Chewing and mechanical absorption

Question 18

Where does the the Cephalic Phase of Digestion and Absorption begin

Answer 18

In the mouth

Question 19

What is masticiation

Answer 19

Chewing

Question 20

What controls salivary secretions

Answer 20

Salivary secretion is under autonomic control (stimulated by sympathetic and parasympathetic nervous system)

Question 21

What is the purpose of salivary secretions

Answer 21

Softens and lubricates food

Provides enzymes: amylase and some lipase (but no protein digestion)

Question 22

What are salivary secretions in response to

Answer 22

Sensory stimuli (sight, smell, taste)

Question 23

What does salivary secretion prepare the GI tract for

Answer 23

Prepares the GI tract for food processing

Question 24

What is the second phase of the GI tract

Answer 24

The Gastric Phase of Digestion and Absorption

Question 25

What occurs in The Gastric Phase of Digestion and Absorption

Answer 25

Sensory cells of the gastric mucosa increases intestinal and gland activity and relaxes sphincters in the GI Tract

Question 26

What nervous system influences the gastric phase of digestion and absorption

Answer 26

The parasympathetic nervous system (“rest and digest”)

Question 27

What is absorbed in the stomach

Answer 27

Protein and fat but not carbs

Question 28

Pepsin: what is the release stimulant and role

Answer 28

Release Stimulant: acetylcholine acid Role: Digestions protein

Question 29

Gastric lipase: what is the release stimulant and role

Answer 29

Release Stimulant: acetylcholine acid Role: Digestions fats

Question 30

What are the 4 things acetlycholine stimulates for release

Answer 30

1. Gastric acid 2. Pepsin 3. Gastric lipase 4. Gastrin

Question 31

Where does lipid digestion start

Answer 31

Started with lingo lipase in mouth - breaks down large fats such as triglycerides

Question 32

When are gastric lipases secreted

Answer 32

Gastric lipases secreted as fat moves to stomach

Question 33

When do bile salts and pancreatic lipase interact with fats

Answer 33

Once in duodenum on SI

Question 34

What is the effect of bile salts on fat

Answer 34

Bile salts cote fat droplets and causes globules to disperse, making them hydrophilic

Question 35

What is the effect of pancreatic lipase on fats

Answer 35

Pancreatic lipase present hydrolyze triglycerides into smaller components (free fatty acids and monoglycerides)

Question 36

What happens to fatty acids and monoglycerides

Answer 36

Free fatty acids and monoglycerides absorbed my SI for further processing

Question 37

What is the main contributor of digestive enzymes

Answer 37

Pancrease

Question 38

Are enzymes released from the pancreas in active or inactive form

Answer 38

Inactive - activated in select regions

Question 39

What does the gallbladder store

Answer 39

Stores bile produced in liver

Question 40

What is the importance of the small intestinal mucosa

Answer 40

Filled with villi which increase surface area to promote nutrient absorption

Question 41

What 3 things are secreted into the lumen of the SI upon the opening of the pyloric sphincter

Answer 41

1. Bicarbonate - from cells in the internal epithelium and in pancreatic secretions 2. Digestive enzymes - from the pancreas 3. Bile acids - from the liver/gallbladder

Question 42

What 2 digestive enzymes are anchored onto the luminal surface of the SI

Answer 42

Disaccharidases Amino peptidases