Gastrointestinal Physiology Quiz

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Questions and Answers

What is the primary role of receptive relaxation in gastric motility?

To enhance stomach capacity with minimal pressure increase (correct)

To regulate the emptying of gastric contents

To mix food with gastric juice

To promote hormone secretion in the stomach

Which phase of gastric motility involves mixing food with gastric juices?

Emptying

Storage

Filling

Mixing (correct)

What primarily regulates gastric emptying?

Hormonal control by CCK and secretin (correct)

Increased pressure in the fundus

Physical size of the food particles

Neural control from the vagus nerve

Which part of the stomach primarily acts as a reservoir?

Fundus and upper body Signup and view all the answers

Which component slows gastric emptying the most?

Fatty substances Signup and view all the answers

What is the primary function of the pyloric sphincter in the stomach?

To control the passage of chyme into the small intestine. Signup and view all the answers

Which type of cell in the gastric mucosa is responsible for secreting hydrochloric acid (HCl)?

Parietal cells Signup and view all the answers

Which substance is NOT included in gastric juice?

Insulin Signup and view all the answers

What is the role of G cells in the stomach?

Secretion of gastrin hormone Signup and view all the answers

What is the primary form of food after mixing in the stomach?

Chyme Signup and view all the answers

What primarily influences the strength of gastric contractions?

Amount of chyme in the stomach Signup and view all the answers

Which part of the stomach is most abundant in oxyntic glands?

Fundus Signup and view all the answers

What triggers feedback relaxation in the gastric system?

Chyme in the small intestine Signup and view all the answers

What protects the stomach lining from the corrosive effects of gastric acid?

Mucosal barrier Signup and view all the answers

Which factor does NOT inhibit gastric emptying?

Unneutralized acid in the stomach Signup and view all the answers

Which function is NOT associated with the stomach?

Digestion of carbohydrates Signup and view all the answers

Which response is involved in the enterogastric reflex?

Both neural and hormonal responses Signup and view all the answers

Which of the following hormones is classified as an enterogastrone?

Secretin Signup and view all the answers

Which emotions have been observed to decrease gastric motility?

Sadness and fear Signup and view all the answers

What is the effect of hypertonicity on gastric emptying?

Inhibits gastric emptying Signup and view all the answers

What is adaptive relaxation triggered by?

Stretch receptors Signup and view all the answers

What effect does the presence of food in the duodenum have on gastric emptying?

It delays gastric emptying. Signup and view all the answers

Which type of cells is responsible for secreting hydrochloric acid (HCl) in the stomach?

Parietal cells Signup and view all the answers

Which phase of gastric secretion occurs when food reaches the stomach?

Gastric phase Signup and view all the answers

What does the term 'alkaline tide' refer to?

Increase in blood pH due to HCO3- rise. Signup and view all the answers

What is the primary function of somatostatin in gastric secretion?

Inhibiting gastric acid secretion. Signup and view all the answers

Proton pump inhibitors (PPIs) primarily block which mechanism?

H/K ATPase function. Signup and view all the answers

Which hormone is secreted by S-cells in the duodenum?

Secretin Signup and view all the answers

Which type of cells secrete pepsinogen?

Chief cells Signup and view all the answers

What is one known effect of the vagus nerve related to gastric secretion?

It stimulates gastric secretion. Signup and view all the answers

Study Notes

Digestive System - The Stomach

The stomach is a J-shaped, sac-like organ located between the esophagus and small intestine.
It's divided into three sections: fundus, body, and antrum.
The stomach has three main functions:
- Storing ingested food until it can be emptied into the small intestine.
- Secreting hydrochloric acid (HCl) and enzymes that begin protein digestion.
- Mixing movements that convert pulverized food into chyme.
The pyloric sphincter is a crucial barrier between the stomach and the upper part of the small intestine.

Stomach Anatomy

Esophagus: The tube connecting the mouth to the stomach.
Gastroesophageal sphincter: Controls the passage of food from the esophagus to the stomach.
Body: Main part of the stomach.
Fundus: The upper, rounded part of the stomach.
Antrum: The lower portion of the stomach, leading to the pyloric sphincter.
Pyloric sphincter: Connects the stomach to the duodenum, regulating the release of chyme.
Pyloric gland area (PGA): The portion of the stomach that secretes gastric juice.
Oxyntic mucosa: Secretes stomach acid and digestive enzymes (chief and parietal cells); located in the body and fundus.
Smooth muscle: The muscular layer in the stomach wall responsible for mixing and emptying.
Gastric folds (rugae): Folds in the stomach mucosa that allow the stomach to expand.
Duodenum: The first part of the small intestine, following the stomach.

Stomach Mucosa

The stomach lining is composed of a simple columnar epithelium.
Gastric pits: Indentations in the stomach lining.
Gastric glands: Located at the base of the gastric pits.
Surface mucous cells: Secrete mucus to protect the stomach lining from the acidic digestive juices.
Mucous neck cells: Secrete mucus, but their mucus is alkaline.
Parietal cells: Secrete hydrochloric acid (HCl) and intrinsic factor.
Chief cells: Secrete pepsinogen, an inactive enzyme precursor converted to pepsin in the presence of HCl.
Enteroendocrine cells: Secrete hormones like gastrin. Different glands contain different populations of these cells (e.g. cardiac glands, pyloric glands, oxyntic glands)

Gastric Juice Contents

HCl
Pepsinogen
Electrolytes
Intrinsic factor
Mucus (mucus gel layer)

Gastric Mucosal Barrier

Protects the stomach lining from HCl damage.
The luminal membranes of the gastric cells are impermeable to H+.
The cells are tightly joined by junctions.
A mucus coating protects the mucosa.
Prevents the acid from damaging the stomach.

Gastric Motility

Functions:
- Serve as a reservoir
- Breaks food into smaller particles and mixes it with gastric juice
- Empties gastric contents at a controlled rate
Four aspects:
- Filling (involves receptive relaxation – fundus)
- Storage
- Mixing (takes place in the antrum)
- Emptying (largely controlled by factors in the duodenum)
Different regions have different types of contractions (tonic or phasic).
The reservoir part (fundus and upper body) has tonic contractions, while the antral pump ( lower body and antrum) has phasic contractions.

Factors Influencing Gastric Emptying (from duodenum perspective)

Fat: Delay emptying due to fat digestion/absorption being primarily in the duodenum.
Acid: Unneutralized acid in the duodenum inhibits further emptying.
Hypertonicity: High osmolarity in the duodenum inhibits emptying.
Distension: Too much chyme in the duodenum inhibits further emptying.

Gastric Emptying and Mixing

Gastric contents can remain unmixed for about one hour in the stomach. Liquids empty faster than solids, and fats take longer to empty than liquids.
Mixing happens in the antrum via retropulsion (tossing chyme back into the stomach for further mixing).
A peristaltic contraction from the fundus pushes chyme toward the opening of the pyloric sphincter and into the duodenum.
A portion of the chyme can get tossed back into the stomach if the pyloric sphincter is closed.

Regulation of Gastric Acid Secretion (stomach perspective)

Gastrin: Released by G cells in response to food presence & stimulates parietal cell & ECL secretion.
Histamine: Released by ECL cells, stimulates parietal cells.
ACh (acetylcholine): Stimulates parietal cells via vagal nerves (Cephalic and Gastric phase) and potentially enteric nerves, enhances HCl secretion.

Control of Pyloric Sphincter

Hormones (CCK, Secretin, Gastrin, GIP) promote constriction.
Sympathetic innervation.

Phases of Gastric Secretion

Cephalic phase: Increased secretion of acid and pepsinogen before food reaches the stomach (e.g. smell, taste conditioning).
Gastric phase: Food reaching the stomach triggers secretion of gastric juices, particularly in response to protein presence.
Intestinal phase: Helps shut off gastric juice flow once chyme moves into small intestine.

Disorders of Gastric Emptying

Gastroparesis: Delayed emptying of the stomach.

Types Of Cells Of The Stomach

Parietal cells: Secrete HCl, intrinsic factor
Chief cells: Secrete pepsinogen
Mucus neck cells: Secrete mucus
G Cells: Gastrin
D Cells: Somatostatin
ECL cells: Histamine

Additional factors

Emotions (sadness, fear decrease gastric motility, anger, aggression increase, intense pain inhibits motility)
Presence of food & acid in the duodenum delays gastric emptying

Conclusion

This provides an overview of the stomach's structure, function, and regulation. Further study into specific mechanisms and regulatory pathways is recommended.

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Description

Test your knowledge on gastric motility and its phases with this quiz. Explore concepts such as receptive relaxation, gastric emptying regulation, and the stomach's role as a reservoir. Perfect for students in physiology or medical courses.