Human Anatomy: The Stomach

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Questions and Answers

Which of the following cells secrete hydrochloric acid?

Zymogenic (peptic) cells

Parietal (oxyntic) cells (correct)

Enteroendocrine cells

Mucous cells

The pylorus is the large central portion of the stomach.

False

What are the two main functions of hydrochloric acid found in gastric juice?

kills bacteria and aids protein digestion

The large folds in the stomach mucosa are called __________.

rugae Signup and view all the answers

Match the following components of gastric juice with their functions:

Pepsinogen = Converts to the enzyme pepsin Mucus = Protects stomach lining Gastrin = Stimulates gastric acid secretion Hydrochloric Acid = Kills ingested bacteria and aids protein digestion Signup and view all the answers

Which of the following substances is secreted by gastric glands in response to food stimuli?

Pepsinogen Signup and view all the answers

Emotions such as anger and fear can accelerate digestion in the stomach.

False Signup and view all the answers

What are the three phases of gastric secretion regulation?

Cephalic Phase, Gastric Phase, Intestinal Phase Signup and view all the answers

The hormonal substances secreted by the intestinal mucosa that inhibit gastric secretion include __________.

Secretin, Cholecystokinin, Gastric inhibiting peptide (GIP) Signup and view all the answers

Match the following hormones with their functions:

Secretin = Stimulates bile secretion from the liver Cholecystokinin (CCK) = Stimulates secretion of digestive enzymes from the pancreas Gastric inhibiting peptide (GIP) = Inhibits gastric secretion and decreases GIT motility Stomach gastrin = Stimulates gastric glands to secrete gastric juice Signup and view all the answers

What is the primary role of pepsin in the stomach?

To initiate protein digestion Signup and view all the answers

Rennin is important for the digestion of carbohydrates in the stomach.

False Signup and view all the answers

What substance is secreted by the parietal cells that activates pepsinogen?

Hydrochloric acid Signup and view all the answers

Gastric emptying is stimulated by nerve impulses in response to __________.

distension Signup and view all the answers

Match the following components of gastric digestion with their roles:

Pepsin = Digestion of proteins Gastric lipase = Splitting butterfat in milk Rennin = Coagulating casein Gastrin = Stimulating gastric emptying Signup and view all the answers

Study Notes

The Stomach

The cardia surrounds the lower esophageal sphincter.
The fundus is the rounded portion above and to the left of the cardia.
The body is the large, central portion of the stomach.
The pylorus is the narrow inferior region that connects to the duodenum via the pyloric sphincter.

The Stomach Linings

The mucosa forms folds called rugae when the stomach is empty.
The mucosa is simple columnar epithelium with pits that extend into the lamina propria.
The pits in the mucosa are gastric glands.

Gastric Glands

Gastric glands contain several types of secreting cells:
- Zymogenic (peptic) cells secrete pepsinogen (a precursor to pepsin).
- Parietal (oxyntic) cells secrete hydrochloric acid and intrinsic factor.
- Mucous cells secrete mucus.
- Enteroendocrine cells secrete stomach gastrin.

The Muscularis

The stomach muscularis has 3 layers of smooth muscle:
- An outer longitudinal layer.
- A middle circular layer.
- An inner oblique layer.
This arrangement allows the stomach to churn food, mix it with gastric juice, and pass it into the duodenum.

Gastric Juice

Gastric juice is a collection of secretions from several cell types.
Zymogenic (peptic) cells secrete enzymes, like pepsin.
Parietal cells secrete HCl.
Mucous cells secrete mucus.
2500ml of gastric juice is produced daily.

Composition of Gastric Juice

Gastric juice contains various cations (Na+, K+, Mg2+, H+) and anions (Cl-, HPO42-, SO42-).
It also includes enzymes like pepsin I-III and gelatinase.
Intrinsic factor is involved in vitamin B12 absorption.
Water is present in the gastric juice.
Hydrochloric acid is crucial for converting pepsinogen to pepsin.

Regulation of Gastric Secretion

Gastric secretion is regulated by both nervous and hormonal mechanisms.
Parasympathetic impulses stimulate gastric secretion.
Several hormones also regulate gastric secretion. Emotions (like anger, fear, and anxiety) slow digestion through the sympathetic nervous system.
Gastric secretion has cephalic, gastric, and intestinal phases.

Cephalic Phase

Sight, smell, and taste of food trigger the cephalic phase.
Signals from the cerebral cortex or hypothalamus travel to the medulla.
The medulla sends impulses via the vagus nerve to the gastric glands, stimulating gastric secretions.

Gastric Phase

Distension of the stomach initiates the gastric phase.
Receptors detect the presence of proteins and alcohol and stimulate the production of stomach gastrin.
Stomach gastrin increases gastric juice production and the motility of the digestive tract.
Pyloric mucosa responds to protein and alcohol, releasing stomach gastrin and regulating the chyme flow.

Intestinal Phase

Partially digested proteins entering the duodenum trigger the release of enterogastric gastrin.
This phase regulates gastric secretion through nerve signals and the release of hormones like secretin, CCK, and GIP.
The duodenum's distension, the presence of acid, protein, and fats cause inhibition of gastric secretions.

Hormonal Inhibition of Gastric Secretion

Intestinal mucosa secretes hormones that inhibit gastric secretion and decrease motility.
Secretin, CCK, and GIP inhibit gastric secretion.

Digestion in the Stomach

Mechanical digestion occurs via mixing waves, breaking food into smaller pieces.
Chemical digestion involves the activation of pepsinogen to pepsin and the beginning of protein digestion.

Chemical Digestion

Pepsin is the main enzyme for protein digestion, working best in the acidic environment of the stomach (pH 2).
Pepsinogen is converted to pepsin by HCl. Mucus protects stomach lining from pepsin.
Gastric lipase is another enzyme present in the stomach, crucial for the limited fat digestion. Rennin helps in milk digestion in infants.

Regulation of Gastric Emptying

Gastric emptying is regulated by nerve impulses in response to stomach distension and hormone release (stomach gastrin).
Different food types (e.g., carbohydrates, proteins, fats) have varying emptying speeds.
Stimulation: distension of the stomach, and products within the stomach like proteins and alcohol.
Inhibition: the enterogastric reflex, the presence of chime within the duodenum (fatty acids, highly acidic, hyper/hypotonic), hormones like secretin, CCK, and GIP.

Pancreas, Liver, and Gallbladder

The pancreas is a gland with both endocrine and exocrine functions. Pancreatic juice contains enzymes for carbohydrate, protein, and fat digestion. Bicarbonate ions raise the pH to neutralize gastric acid for optimal enzyme action.
The liver produces bile, which emulsifies fats, and performs many other important functions concerning metabolism, storage and detoxification..
The gallbladder stores and concentrates bile until needed by the small intestine.

Intestinal Juice

A clear yellow fluid is secreted by the small intestine's glands.
Contains water, mucus, and other substances.

Passage of Digested Nutrients

Absorption occurs through the villi and microvilli in the small intestine.
Methods of absorption include diffusion, facilitated diffusion, osmosis, and active transport.

The Large Intestine

The large intestine completes absorption and forms feces.
Bacteria in the large intestine aid in the digestion of some remaining nutrients via fermentation.
Vitamins and electrolytes are reabsorbed.
Water is absorbed.

Defecation

Mass peristaltic movements push feces toward the rectum.
The external anal sphincter controls the defecation process by allowing or preventing the expulsion of feces.

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Description

This quiz covers the anatomy and physiology of the stomach, including its structure, the roles of its various linings, and the functions of gastric glands. Test your knowledge on the stomach's components like the cardia, fundus, body, and pylorus, along with the types of cells involved in digestion.