Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Fundamentals of Physiology PM1A > GI Tract > Flashcards

GI Tract Flashcards

1
Q

What are the 4 layers of the GI

A

Mucosa
Submucosa
Muscularis externa
Serosa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

3 layers of the mucosa

A

1-mucous membrane - layer of epithelial cells that protect gut from abrasion, secrete substances, enteroendocrine cells that release hormones into lamina prioria & capillaries

2- lamina propria- connective tissues, contains blood capillaries and lymph vessels

3- musularis mucosa- thin layer of smooth muscle, controls folding of mucosa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is sub mucosa

A

Contains blood and lymph vessels - a deep boundary- neurons are organised to form intrinsic or submucosal plexus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is muscularis externa

A

Smooth muscle cells of the outer layer that run longitudinally, inner layer has circular arrangement

Produce waves of contraction (peristalsis or segmentation)

Myenteric plexus is located between thick and thin muscles

This network of neurons is connected to the submucosal plexus to form the ENS

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is serosa?

A

Loose connective tissue and membrane that protects the Tract when it moves

Forms a visceral (inner) peritoneum and is continuous with the parietal (outer) peritoneum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

4 major activities of the GI tract

A

1 motility
2 secretions
3 digestion
4 absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How does the enteric nervous system receive input ?

A

1- from the autonomic nervous system (but can work independently)

2- from mechano-chemo receptors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How does enteric ns send input ?

A

To smooth muscles, secretory& endocrine cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the 2 neuromodulators in GI tract

A

Acetylcholine

Noradrenaline

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Role of acetylcholine?

A
  • Contraction of smooth muscle in the wall
  • relaxation of sphincters
  • increased salivary, gastric and pancreatic secretion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Role of noradrenaline?

A
  • relaxation of smooth muscle in wall
  • contraction of sphincters
  • increased salivary secretion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The role of saliva?

A

1- dilute, buffer and lubricate ingested food (very hypotonic, high K+ and bicarbonate) low Na and Cl

2- initial digestion of starches and lipids - eg
Amylase: enzyme in saliva and pancreatic fluid that converts starch and glycogen to simple sugars

Lingual lipase- digestive enzyme breaks down fatty acids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Role of the oesophagus

A

No absorptive or digestive function- just conveys bolus to stomach by secreting mucus to promote movement ie peristalsis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Functions of the stomach

A

The temporary storage of food - digests food chemically & mechanically

Also secretes enzymes for digestion and protection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Anatomy of the stomach

A

fundus, cardia, body and Antrum

3 layers of muscle of varied thickness eg thicker where contractions are needed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is gastric motility (2 types)

A

1 receipting relaxation

2 mixing and digestion

17
Q

What is receipting relaxation?

A

Orad region receives food bolus - temporary storage

18
Q

What is mixing and digestion of gastric motility?

A

The caudad region has a thick muscular wall

Vigorous contraction from body to pylorus area - mix food and water with gastric secretory products (=chyme )

  • grinding food to enhance digestion
  • retropulsion
19
Q

How is HCl secreted?

A

By parietal cells (oxyntic cells), predominantly in fundus and body of stomach

20
Q

What is functions of HCl (5)

A

1- acidify gastric content to pH 1-2

2- breakdown of connective tissue and muscle fibres of ingested meat

3- activate pepsinogens

4- optimal conditions for activity of pepsins

5- defence mechanism against micro organisms that may cause infection

21
Q

What substances alter HCl secretion?

A

Histamine
Acetylcholine
Gastrin

22
Q

How does histamine alter HCl secretion

A

It is released by enterochromaffin like ECL walls.

Paracrine regulation of parietaL cells - activates H2 receptors and increases HCl secretion

23
Q

How does acetylcholine alter HCl secretion

A

From the vagus nerve - neurocrine regulation of parietal cells
Activates h3 receptors to increase HCl secretion

They also have an indirect effect as they stimulate the release of histamine

24
Q

How does acetylcholine have an indirect effect on HCl secretion

A

Stimulates release of histamine

25
Q

How does Gastrin alter HCl secretion

A

It is secreted by G cells into circulation and has endocrine regulation of parietal cells-

Activates.CCKB receptors
Increases HCl secretion

26
Q

What is the endocrine, paracrine & neurocrine regulation of HCl secretion

A

Endocrine- Gastrin
Paracrine- histamine
Neurocrine- acetylcholine

27
Q

What phases does regulation of gastric secretion occur ?

A

1 cephalic
2 gastric
3 intestinal

28
Q

Overview of cephalic phase

A

Stimuli involved in parasympathetic in brain - sight smell or taste of food stimulates the phase

Involves- Ach, Gastrin releasing peptide, histamine (secrete HCl), Gastrin (these stimulate parietal cells to secrete HCl)

29
Q

Overview of gastric phase

A

The stimulus is food or fluid in stomach - the distention of stomach and digestion of food

Ie- the arrival of food in the stomach initiates the phase and accelerates gastric secretion in response to chemical stimuli and distention

Involves- mechanoreceptors (stretch), ENS reflex, peptones, Gastrin hormone

30
Q

Overview of intestinal phase

A

Involves responses to products of protein digestion (chyme) in duodenum

Involves- enterogastric reflex, CCK, GIP

Then secretin

31
Q

What inhibits Gastrin and thus HCl and how?

A

Somatostatin in response to low pH

-Directly inhibits via parietal cells
Indirectly inhibits by inhibiting ECL and histamine secretion, and inhibits G cells

32
Q

How is churning and mixing motion slowed in the intestinal phase??

A

Enterogastric reflex (stimulated by chemoreceptors in response to chyme) inhibits the myenteric plexus

33
Q

What does the presence of lipids and carbs in chyme do? (Intestinal phase)

A

Stimulates the production of cholescysokinin CCK and gastric inhibitory peptide (ie glucose dependent immunotropic peptide) in duodenum

34
Q

How is secretin released? (Intestinal p)

A

Decrease in pH due to acidity of chyme stimulates production of secretin by S cells

35
Q

What does secretin , GIP & CCK do?

A

Secretin inhibits Gastrin and thus HCl release

GIP and CCK inhibit secretions of chief cells, parietal cells, G cells and overall peristalsis in stomach

36
Q

What are the 5 major actions of CCK?

A

1- contraction of gall bladder and ejection of bile
2- secretion of pancreatic enzymes
3- secretion of bicarbonate
4- trophic effects on exocrine pancrease&gall bladder
5- inhibition of gastric emptying

37
Q

What does gastric inhibitory peptide do? (Hormone)

A

Stimulates insulin secretion

Inhibits gastric H+ secretion

38
Q

What does secretin do (hormone)

A

Secreted by enteric endocrine S cells

Fundamentals of Physiology PM1A (23 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions