Biology *1080 Lecture 16

Question 1

What is the GI tract?

Answer 1

Aids to digest and absorb ingested nutrients, and to excrete waste products of digestion.

Question 2

What does the GI tract consist of?

Answer 2

Oral cavity, esophagus, stomach, small intestine, colon and rectum

Question 3

What does the GI system do?

Answer 3

It “sees” not only our food, but toxic substances and infectious agents

Question 4

How does the GI tract deal with toxic substances?

Answer 4

Vomit and Diarrhea

T-cells localized in the intestinal mucosa

Question 5

How long is the GI tract?

Answer 5

28 ft and folded extensively in the abdominal cavity

Question 6

Why is the SA large in the GI tract?

Answer 6

Due to lots of villi/microvilli (finger-like projections)

Question 7

What is the variable transit time for ingested meal?

Answer 7

30-80 hours

Question 8

What stays longer in the GI tract?

Answer 8

Fibre, where as carbs go quicker through GI tract

Question 9

What does the GI tract house?

Answer 9

Gut microbiome (bacteria) to protect against pathogenic microbes that enter/reside in the tract (breakdown of indigestible food)

Question 10

What is the GI tract controlled by?

Answer 10

Intrinsic nervous system - opening and closing of sphincters

Question 11

Motility in GI tract

Answer 11

Peristalsis (involuntary) - constriction and relaxation of the muscles in the GI tract

Question 12

Secretion in GI tract

Answer 12

Saliva, mucous

Antibodies (protect against antigens)

Digestive enzymes

Bile (breaks down fatty acid)

Bicarbonate (glycerine and three fatty acids)

Question 13

Digestion in GI tract

Answer 13

Break down of food

Question 14

Absorption in GI tract

Answer 14

Water (large intestine)

Nutrients (small intestine)

Question 15

What is the cephalic phase of digestion and absorption?

Answer 15

Secretions initiated by the sight, smell, thought or taste of food (related to the head)

Question 16

Mechanical digestion

Answer 16

Physically breaking down (i.e, chewing)

Question 17

What are the three glands in your mouth?

Answer 17

Parotid Gland

Sublingual Gland

Submandibular Gland

Question 18

What is salivary secretion under control by?

Answer 18

Autonomic control (stimulated by sympathetic and parasympathetic nervous system)

Question 19

What does salivary secretion do?

Answer 19

Softens and Lubricates food

Provides enzymes such as amylase (breaks down carbs/starches) and lipase (lipid break down)

Question 20

What is the influence of the parasympathetic system on digestion?

Answer 20

“Rest and digest” - increases intestinal and gland activity, and relaxes sphincter muscles in the GI tract

Question 21

What do parietal cells secrete?

Answer 21

Gastric Acid

Intrinsic Factor

Question 22

What stimulates parietal cell secretion?

Answer 22

Acetylcholine

Question 23

What do chief cells secrete?

Answer 23

Pepsin

Gastric Lipase

Question 24

What stimulates chief cells secretion?

Answer 24

Acetylcholine

Question 25

What is the function of secretion from chief cells?

Answer 25

Digests proteins and fats

Question 26

What do G cells secrete?

Answer 26

Gastrin

Question 27

What stimulates G-cell secretion

Answer 27

Acetylcholine

Question 28

What does not get digested in the stomach?

Answer 28

Carbohydrates (remember amylase is not found in stomach)

Question 29

What is the main contributor of digestive enzymes?

Answer 29

Pancreas

Question 30

What are enzymes related from the pancreas in the form of?

Answer 30

Trypsinogen (inactive)

Question 31

Where is trypsinogen activated in?

Answer 31

In the small intestine by enterokinase in the brush border of duodenum to form trypsin (protein digestion)

Question 32

What does the Gallbladder store?

Answer 32

Bile - fat digestion

Question 33

Where is bile produced from?

Answer 33

Liver

Question 34

What are the three main parts of the small intestine in order?

Answer 34

Duodenum, jejunum, ileum

Question 35

What is the benefits of small intestine mucosa (villi) ?

Answer 35

Villi increase surface area to promote nutrient absorption

Question 36

What are the secretions into the lumen of the small intestine upon the opening of the pyloric sphincter?

Answer 36

Bicarbonate Digestive Enzymes (from pancreas) Bile Acids (from liver/gal bladder)

Question 37

What are the digestive enzymes anchored on the luminal surface?

Answer 37

Disaccharides (carbs) Amino peptidases (proteins)

Question 38

What happens to people who have celiac disease?

Answer 38

The vili in their small intestine become flatten (decrease in SA) A decreased SA causes a decrease in nutrient absorption resulting in many nutrient deficiencies