GI VOPprimer

Question 1

What are the 7 functions of the alimentary canal?

Answer 1

1. Ingestion 2. Secretion 3. Mechanical digestion 4. Propulsion 5. Chemical digestion 6. Absorption 7. Excretion

Question 2

Are the contents of the alimentary canal internal or external?

Answer 2

External! Then only what we want to absorb comes to the internal part of the body.

Question 3

What are the 2 control mechanisms of the absorption of the alimentary tract?

Answer 3

The enteric nervous system and local reflexes.

Question 4

How would you describe the action potentials that occur within the alimentary canal?

Answer 4

They are auto-rhythmic and occur in bursts (multiple depolarizations right after one another).

Question 5

What are the 4 layers of the alimentary canal?

Answer 5

1. Mucosa- inner most layer, made up of stratified squamous cells in the mouth —> columnar cells within the stomach.
2. Submucosa- loose connective tissue layer, contains vessels, nerves, and lymphocytes.
3. Muscularis externa- 2 layers with circumferential (inner) and longitudinal (outer).
4. Adventitia/serosa

Question 6

What are the 2 different types of movement within the GI tract?

Answer 6

1. Peristalsis = wave of contraction posteriorly and relaxation anterior to the chyme. 2. Segmentation = lock chyme in the intestine, mix and churn its contents, allowing for absorption.

Question 7

What are the 3 main arteries that supply the abdomen and what do each of them supply?

Answer 7

1. Celiac artery 2. Superior mesenteric artery - supply small intestine and first 1/3 of the large intestine. 3. Inferior mesenteric artery - supply 2/3 of the large intestine and rectum.

Question 8

Are the arteries within the abdomen susceptible to PVD?

Answer 8

YES! Don’t forget about this!

Question 9

What is the difference between hunger and appetite?

Answer 9

Hunger is a motivational demand or drive for eating. Appetite is a desire for eating a specific food.

Question 10

What nerve controls the muscles of mastication?

Answer 10

CN V - Trigeminal N.

Question 11

What are the muscles of mastication and what roles do each of them play in eating?

Answer 11

• Buccinators and genioglossus —> positioning of food. - Pterygoids —> grinding movements - Masseters + Temporalis —> raise the jaw and bite.

Question 12

What is the mechanism of salivation?

Answer 12

Hypothalamus activates the superior salivatory nucleus within the brainstem —> stimulate the facial nerve, traveling down to the submandibular ganglion —> submandibular and sublingual glands to stimulate salivation.

Question 13

What are the 5 steps of swallowing?

Answer 13

1. Tongue pushes the food back. 2. Soft palate seals the nose from the throat. 3. Throat muscles squeeze the food down. 4. Vocal cords close to prevent choking. 5. Esophagus opens to let food down to the stomach.

Question 14

Is swallowing controlled by skeletal or smooth muscles?

Answer 14

Skeletal muscles! —> then smooth muscles take over in the esophagus to push food down.

Question 15

Where does pepsin come from and what does it do?

Answer 15

It is secreted from the glands in the wall of the stomach —> breaks down proteins within the stomach.

Question 16

What is the purpose of rugae?

Answer 16

Surface folding that increases the surface area of the stomach.

Question 17

What are haustrations?

Answer 17

Bulging of the large intestine during contraction of the teniae coli and circular muscles.

Question 18

What substances are absorbed in the large intestine?

Answer 18

Water and some vitamins.

Question 19

What gives humans the motivation to defecate?

Answer 19

Pressure within the rectum d/t build up of stool.

Question 20

What are the 2 sphincters within the rectum and anal canal, and which are under voluntary control?

Answer 20

Internal rectal sphincter — smooth mm, involuntary control. External rectal sphincter — skeletal mm, voluntary control.

Question 21

What tract within the spinal cord is responsible for allowing defecation?

Answer 21

Corticospinal tract!

Question 22

What is the role of mucus in the GI tract?

Answer 22

It is a protective substance that facilitates movement and protects the lining of the GI tract.

Question 23

What are the 4 types of glands within the GI tract?

Answer 23

1. Single cell/Goblets —> secrete mucus. 2. Pits 3. Tubular 4. Complex salivary gland

Question 24

What is saliva made of?

Answer 24

99% water, 1% digestive enzymes, mucus, IgA antibodies, and electrolytes.

Question 25

How is the amount of secretion changed with parasympathetic and sympathetic activation?

Answer 25

Parasympathetic: activated when eating —> promotes enzyme rich saliva release. Sympathetic: reduced production, and of what is released, it is mostly water.

Question 26

What do mucus neck cells secrete?

Answer 26

Mucus and bicarbonate

Question 27

What do parietal cells secrete?

Answer 27

Gastric acid (HCl) and intrinsic factor (important for Vit B12 metabolism).

Question 28

What do enterochromaffin-like cells secrete?

Answer 28

Histamine —> which stimulates acid production in the parietal cells.

Question 29

What do chief cells secrete?

Answer 29

Pepsinogen (precursor of pepsin) and gastric lipase.

Question 30

What do D cells secrete?

Answer 30

Somatostatin (which inhibits acid)

Question 31

What do G cells secrete?

Answer 31

Gastrin —> which stimulates acid production.

Question 32

What is pernicious anemia?

Answer 32

Autoimmune destruction of parietal cells in the stomach —> decreased intrinsic factor —> B12 deficiency.

Question 33

What accessory organ of the GI tract is important in sugar metabolism?

Answer 33

The pancreas!

Question 34

How does the pancreas metabolize sugar?

Answer 34

Via insulin.

Question 35

What other compounds does the pancreas help to break down? How?

Answer 35

- Proteins via the release of proteases. - Fats via the release of cholecystokinin —> activates gallbladder motion stimulation. - Acid via the release of secretin.

Question 36

What activates the pancreas to secrete all these enzymes necessary for metabolism?

Answer 36

Simulation via the vagus nerve.

Question 37

What is the name of the entrance from the pancreas to the duodenum?

Answer 37

Sphincter of Oddi.

Question 38

What organ produces bile? How does the bile get into the duodenum?

Answer 38

The liver! It secretes bile into the hepatic duct —> to the common bile duct —> through the sphincter of oddi —> duodenum.

Question 39

Where is bile stored?

Answer 39

The gallbladder!

Question 40

What is the function of bile?

Answer 40

Emulsifies fats.

Question 41

Which portion of the small intestine has the largest amount of peyer's patches?

Answer 41

The end of the ileum.

Question 42

What is the primary function of the large intestine?

Answer 42

Dehydrate stool via absorption of water.