MODULE 7.1 PRINCIPLES OF GI FUNCTION

Question 1

DEFINE GI-TRACT: GASTROINTESTINAL TRACT

Answer 1

• a hollow, convoluted tube that runs through the body.
• food enters the mouth and is processed in a number of ways in order to extract the necessary nutrients, electrolytes, fluids, vitamins and minerals to sustain life.

Question 2

DEFINE THE 6 SPINCTERS OF THE DIGESTIVE SYSTEM?

Answer 2

1. Upper Esophageal Sphincter. Between pharynx and esophagus.
   2- Lower Esophageal/ Cardiac. Between esophagus and stomach.
   3- Pyloric. Between stomach and duodenum.
   4- Ileocecal. Between small intestine and cecum.
   5- Internal anal.
   6- External anal

Question 3

WHAT ARE THE 2 MOST IMPORTANT ACCESSORY ORGANS FOR PROPER FUNCTIONING OF THE GI TRACT?

Answer 3

PANCREAS: secretes digestive enzymes and a bicarbonate-rich solution into the proximal region of the small intestine.
LIVER: secretes bile into the proximal region of the small intestine

Question 4

SEROSA
(wall of the duodenum)

Answer 4

the outermost connective tissue of the GI tract and is covered with thin flat epithelial cells called squamous epithelium

Question 5

MUSCULARIS EXTERNA
(wall of the duodenum)

Answer 5

contains two layers of smooth muscle: the inner circular layer and the outer longitudinal layer. Enteric neurons lie between these two muscle layers.

Question 6

SUBMUCOSA
(wall of the duodenum)

Answer 6

inward into the GI wall: made up of loose connective tissue and large blood vessels and may contain glands for secretion of contents in the GI lumen

Question 7

MUCOSA
(wall of the duodenum)

Answer 7

surrounded by the muscularis mucosae. Its made up of an epithelial cell layer and the underlying loose connective tissue called the lamina propria (which contains capillaries, enteric neurons, and immune cells like mast cells, plus a thin layer of smooth muscle called lamina muscularis mucosae. Mucosal surface area is very large. In the small intestine, villi, crypt glands, and apical microvilli drastically increase the surface area to increase the efficacy of absorption.

Question 8

MESENTERY
(cross-section of the gut)

Answer 8

surrounds the intestine and is made up of membranous tissue containing blood vessels that exchange oxygen and nutrients for carbon dioxide and waste from the intestine.

Question 9

“gut” /”bowel” refers to the?

Answer 9

INTESTINES
both terms are used for the small and large intestine.
( the gut or bowl of the gastrointestinal tract begins after pyloric sphincter and ends at the anus)

Question 10

Sort the layers of the gut from deep to superficial (i.e., from the inside out).

Answer 10

1. Lumen
2. Enterocytes
3. Mucosa
4. Mucosal Muscle
5. Submucosa
6. Circular Muscle
7. Longitudinal Muscle
8. Serosa

Question 11

Mechanical disruption?

Answer 11

-in the form of chewing and churning helps to break apart out food into manageable sizes.
1.–Mastication in the mouth (starts)
2. Churning in the stomach: helps to reduce the size of food in stomach to 2mm or less in diameter, which is necessary for stomach contents to be able to pass through the pyloric sphincter into the small intestine during a meal.

Question 12

Define Chemical Digestion?

Answer 12

-must occur before the intestinal epithelial cells can absorb them and involve 3 macronutrients

1. Lipids: mostly consumed as triglycerides, but absorption occurs only as fatty acids and monoglycerides.
2. Amino acids: consumed as proteins and large peptides but are absorbed as amino acids and small peptides.
3. Carbohydrates: consumed as starches, disaccharides and monosaccharides, et only monosaccharides can be absorbed.

Question 12

TRUE/FALSE: Carbohydrate digestion does not involve any enzyme that is secreted from the gastric mucosa.

Answer 12

TRUE: Carbohydrate digestion does not involve any enzyme that is secreted from the gastric mucosa.

Question 12

Salivary Glands
(Digestive Enzyme Location)

Answer 12

• release enzymes to begin the chemical digestion of carbohydrates and lipids.
  ENZYMES/TARGETS
  Amylase/Starch
  Lipase/Triglycerides

Question 13

Stomach
(Digestive Enzyme Location)

Answer 13

ENZYMES/TARGETS
Pepsin/Proteins
Lipase/ Triglycerides

Question 14

PANCREAS
(Digestive Enzyme Location)

Answer 14

ENZYMES/TARGETS
Amylase/Starch
LipaseColipase/Triglycerides
Phospholipase/Phospholipid
Trypsin/Peptides
Chymotrypsin/Peptides

Question 15

INTESTINE
(Digestive Enzyme Location)

Answer 15

ENZYMES/TARGETS

Enterokinase / ACTIVATES TRYPSIN
Disaccharidases/ COMPLEX SUGARS
Dipeptidases/ PEPTIDES

Question 16

IS RESPONSIBLE FOR ACTIVATING LUMINAL PANCREATIC ZYMOGENS?

Answer 16

TRYPSIN

Question 17

TRUE/FALSE: CHYMOTRYPSIN PREFENTIALLY CLEAVES AT AMINO ACID RESIDUES WITH POSITIVELY CHARGED SIDE CHAINS.

Answer 17

False: This is a characteristic of trypsin. Chymotrypsin preferentially cleaves at aromatic side chains.

Question 18

Breaks down phospholipids?

Answer 18

Phospholipase

Question 19

Breaks down starch?

Answer 19

Amylase

Question 20

Breaks down proteins?

Answer 20

Pepsin

Question 21

Breaks down triglycerides?

Answer 21

Lipase

Question 22

ENTEROCYTES
(wall of the colon-large intestine)

Answer 22

are the surface absorptive cells of the intestine.

Question 23

GOBLET CELLS
(wall of the colon-large intestine)

Answer 23

secrete mucus and are the second most abundant epithelial cell.

Question 24

ENTERIC ENDOCRINE CELL
(wall of the colon-large intestine)

Answer 24

secrete a variety of products, like cholecystokinin, secretin, and peptide.

Question 25

ENDOCRINES
(involved during digestion)

Answer 25

-(Hormones)
- All GI hormones are peptides
- Released into blood ® act on distant target cell

Question 26

PARACRINES
(involved during digestion)

Answer 26

• Some are peptides (somatostatin), some are not
  (histamine)
• Endocrine cells release ® diffuse to target cells
• Can act on endocrine cells (+ or –)

Question 27

Neurocrines
(involved during digestion)

Answer 27

-(neurotransmitters)
Some are peptides (VIP), some are not (ACh, NE)
- Nerves release ® diffuse to target cells

Question 28

Upper Esophageal Sphincter

Answer 28

Known as the high-pressure zone: this sphincter is to protect against reflux of food into the airways as well as prevent entry of air into the digestive tract

Question 29

Lower Esophageal Sphincter

Answer 29

a ring of muscle fibers that acts as a valve to prevent stomach contents from flowing back up into the esophagus. separates the esophagus from the stomach.

Question 30

Pyloric Sphincter

Answer 30

muscular valve that controls the flow of food from the stomach to the small intestine. (chime :small digested food)

Question 31

Ileocecal. Sphincter

Answer 31

a muscle valve that controls the flow of digested food from the small intestine to the large intestine

Question 32

Internal anal Sphincter

Answer 32

a ring of involuntary smooth muscle located at the end of the rectum, forming the inner part of the anal canal, and plays a crucial role in maintaining fecal continence by generating resting pressure to prevent stool leakage; essentially, it’s the muscle that keeps the anus closed without conscious effort.

Question 33

External anal Sphincter

Answer 33

a large, circular, voluntary muscle that surrounds the anal canal and is responsible for keeping stool in the anal canal until you’re ready to defecate: