Gastro II

Question 1

What is the role of non-GIT hormones in hormonal GIT regulation? Give an example.

Answer 1

They can influence the growth and development of GIT. For example, growth hormone or thyroid hormone.

Question 2

Where do GIT hormones (in general) exert their area of influence?

Answer 2

They can either influence activities outside the GIT or inside the GIT.

Question 3

Give an example of a GIT hormone that influences activities outside the GIT and how it does so.

Answer 3

Ghrelin is released by glands in the stomach when you’ve been fasting for a long time. This will travel via the bloodstream to the hypothalamic feeding center in the brain. The effect is to stimulate hunger and increase appetite.

Question 4

What hormone has the opposite effects to Ghrelin?

Answer 4

Leptin - it induces satiety and decreases appetite.

Question 5

What is the effect of Leptin? Where is it produced (is it a GIT hormone)?

Answer 5

Leptin is produced by fat cells after overeating (it is not a GIT hormone). It will induce satiety in the hypothalamus and decrease appetite.

Question 6

Hormonal regulation of GIT activity occurs via the […] system, which is located in the […]

Answer 6

Hormonal regulation of GIT activity occurs via the diffuse endocrine system, which is located in the mucosa

Question 7

What are the 5 most important GI hormones?

Answer 7

Gastrin, CCK, secretin, GIP, VIP

Question 8

GIT regulatory hormones are mostly of the type […]

Answer 8

Peptides

Question 9

What is the typical path of GIT regulatory hormones produced in the GIT?

Answer 9

1. Released into hepatic portal vein
2. Goes to liver
3. Goes to heart
4. Travels through systemic circulation
5. Reaches target cells

Question 10

Why do GIT hormones pass through the liver before reaching the circulation?

Answer 10

Because the blood that they’re being carried in will have toxins from what we’ve ingested. We don’t want these in the bloodstream, so the liver filters them.

Question 11

Do GIT regulatory hormones have one or multiple targets?

Answer 11

They can have multiple targets that can be excitatory or inhibitory.

Question 12

GIT hormones can interact with […]

Answer 12

one another and with neurotransmitters

Question 13

The propulsion of food in the GIT is driven by what force(s)?

Answer 13

It is mainly driven by gradients in pressure. Variations in resistance are normally insignificant.

Question 14

How are gradients in pressure generated for propulsion in the GIT?

Answer 14

By coordinated contractions of muscular elements in the GIT wall. These contractions can be segmentation or peristalsis.

Question 15

What is the difference between segmentation and peristalsis? What do they have in common?

Answer 15

Similarity: they are both generated by circular muscles.

Segmentation = rings of circular muscle are contacting at alternating points in the GIT. This movement is good for mixing.

Peristalsis = circular muscle is contracting in a wave that propagates one after the next. This pushes contents forward.

Question 16

What is responsible for the lack of resistance in propulsion?

Answer 16

The presence of (5) sphincters at the start and end of the esophagus, stomach, small intestine, and anus.

Question 17

What is the cause of gastric reflux?

Answer 17

If the sphincter at the start of the stomach stays open when it’s not supposed to, acidic stomachs contents will come into the esophagus and damage it.

Question 18

What are the 3 phases of deglutition? Which are voluntary?

Answer 18

Oral, pharyngeal, and esophageal. Only the oral phase is voluntary.

Question 19

What is the function of the pharynx?

Answer 19

Conveys food from the mouth to the esophagus through deglutition.

Question 20

What is the function of the esophagus? What must occur for this function to be possible?

Answer 20

Transports food into the stomach. This requires the relaxation of the UES and LES

Question 21

What happens during the oral phase of deglutition to the:
a) Bolus
b) Soft palate
c) Lips

Answer 21

a) When we choose to swallow, the bolus moves to the anterior of the mouth and then goes down to the pharynx.
b) The soft palate will close off once the bolus is in the throat to push it down.
c) The lips will remain closed.

Question 22

What concludes the oral phase of deglutition?

Answer 22

When the bolus arrives at the pharynx

Question 23

The oral phase of deglutition is controlled by what body part? Explain how.

Answer 23

The cortical and medullary centers of the brain. The idea to swallow (since it’s voluntary) originates in the cortical center, and this signals to the deglutition center in the medulla to trigger reflexes that will drive the rest of the deglutition process.

Question 24

The reflexes involved in the oral phase of deglutition are coordinated by the […] in the […]

Answer 24

deglutition center in the medulla oblongata

Question 25

The ability to initiate the oral phase of deglutition comes from the […]

Answer 25

cortex

Question 26

Stroke patients often have difficulty […]. Explain why.

Answer 26

Stroke patients often have difficulty swallowing because it’s a brainstem driven process that’s very complex. This can be very problematic because our food often contains bacteria. If it gets aspirated into the lungs, it can lead to lung infections.

Question 27

What is particular about the pharynx with regards to deglutition?

Answer 27

It is the place where the respiratory and digestive tracts cross.

Question 28

Explain what happens in the pharyngeal phase of deglutition.

Answer 28

As soon as the bolus is in the pharynx, it will stretch it. This will contribute to reflexes created by the deglutition center. As the bolus is there, it will press on the epiglottis, which can move to block the trachea. By blocking the trachea by moving the epiglottis, this is one way to protect the airways.

However, this is not the only way. There’s also a reflexive contraction of the vocal cords and the closure of the glottis, which protect the lower airways.

Question 29

What are the 4 steps of the pharyngeal phase of deglutition?

Answer 29

1. Passages to nose, mouth, and trachea are blocked
2. Apnea
3. UES relaxes
4. Pharynx muscles contract
   The contraction of pharynx muscles will move the food into the esophagus.