Podcast
Questions and Answers
What does the pylorus do in the stomach?
What does the pylorus do in the stomach?
The stomach only has two layers of smooth muscle in its muscularis layer.
The stomach only has two layers of smooth muscle in its muscularis layer.
False
Name one type of cell in the gastric glands and its function.
Name one type of cell in the gastric glands and its function.
Parietal cells, which secrete hydrochloric acid.
Gastric juice is produced by the secretion of zymogenic cells, parietal cells, and ______ cells.
Gastric juice is produced by the secretion of zymogenic cells, parietal cells, and ______ cells.
Signup and view all the answers
Match the following components of gastric juice with their functions:
Match the following components of gastric juice with their functions:
Signup and view all the answers
Which of the following substances are secreted by the gastric glands in response to parasympathetic stimulation from the vagus nerves?
Which of the following substances are secreted by the gastric glands in response to parasympathetic stimulation from the vagus nerves?
Signup and view all the answers
The intestinal phase is responsible for the secretion of large amounts of gastric juice.
The intestinal phase is responsible for the secretion of large amounts of gastric juice.
Signup and view all the answers
What effect do emotions such as anger and fear have on digestion?
What effect do emotions such as anger and fear have on digestion?
Signup and view all the answers
The three phases of gastric secretion regulation are the cephalic phase, gastric phase, and ________ phase.
The three phases of gastric secretion regulation are the cephalic phase, gastric phase, and ________ phase.
Signup and view all the answers
Match the following hormones with their functions related to gastric secretion:
Match the following hormones with their functions related to gastric secretion:
Signup and view all the answers
Which of the following hormones inhibits gastric emptying?
Which of the following hormones inhibits gastric emptying?
Signup and view all the answers
The pancreas produces primarily digestive hormones.
The pancreas produces primarily digestive hormones.
Signup and view all the answers
What is the primary function of pancreatic lipase?
What is the primary function of pancreatic lipase?
Signup and view all the answers
The liver manufactures bile salts for the __________ and absorption of fats.
The liver manufactures bile salts for the __________ and absorption of fats.
Signup and view all the answers
Match the following pancreatic enzymes with their functions:
Match the following pancreatic enzymes with their functions:
Signup and view all the answers
What is the pH range of pancreatic juice?
What is the pH range of pancreatic juice?
Signup and view all the answers
What is the role of cholecystokinin (CCK) in pancreatic secretion?
What is the role of cholecystokinin (CCK) in pancreatic secretion?
Signup and view all the answers
What is the primary enzyme responsible for protein digestion in the stomach?
What is the primary enzyme responsible for protein digestion in the stomach?
Signup and view all the answers
Gastric lipase is most effective at a pH of 2 to 3.
Gastric lipase is most effective at a pH of 2 to 3.
Signup and view all the answers
What is the primary role of mucus in the stomach?
What is the primary role of mucus in the stomach?
Signup and view all the answers
The main substance that gastric contents are reduced to is called ______.
The main substance that gastric contents are reduced to is called ______.
Signup and view all the answers
Which factor does NOT stimulate gastric emptying?
Which factor does NOT stimulate gastric emptying?
Signup and view all the answers
Match the substances to their roles in digestion:
Match the substances to their roles in digestion:
Signup and view all the answers
Food typically spends more time in the stomach if it is rich in carbohydrates.
Food typically spends more time in the stomach if it is rich in carbohydrates.
Signup and view all the answers
What is the function of the pyloric sphincter during digestion?
What is the function of the pyloric sphincter during digestion?
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 stomach wall has the same four basic layers as the rest of the GI tract, with modifications.
- The mucosa forms folds called rugae when empty.
- Simple columnar epithelium lines the mucosa, containing gastric pits that extend into the lamina propria.
- Gastric glands are located within these pits.
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 three layers of smooth muscle: an outer longitudinal layer, a middle circular layer, and an inner oblique layer.
- This multi-layered arrangement allows for a variety of contractions to churn food.
- This churning mixes food with gastric juice, breaking it into smaller particles before sending it to the duodenum.
Gastric Juice
- Gastric juice is a mixture of secretions from zymogenic cells, parietal cells, and mucous cells.
- Daily production of gastric juice is approximately 2500 ml.
Composition of Gastric Juice
- Gastric juice contains various cations (e.g., Na+, K+, Mg2+, H+) and anions (e.g., Cl-, HPO42-, SO42-).
- It also contains pepsin (I-III), gelatinase, mucus, intrinsic factor, water, and hydrochloric acid.
- Hydrochloric acid converts pepsinogen to pepsin, essential for protein digestion, along with killing ingested bacteria and aiding protein digestion.
- Intrinsic factor is essential for vitamin B12 absorption.
Regulation of Gastric Secretion
- Gastric secretion is regulated by both nervous and hormonal mechanisms.
- Parasympathetic stimulation from nuclei in the medulla travels via the vagus nerve to stimulate gastric glands.
- Emotions like anger and fear can slow down digestion by stimulating the sympathetic nervous system.
Cephalic, Gastric , and Intestinal Phases
- Gastric secretion is regulated in three phases (Cephalic, Gastric, and Intestinal).
- The Cephalic phase involves sight, smell, or taste of food triggering the medulla to stimulate gastric glands.
- The Gastric phase involves food stretching the stomach, stimulating acid and gastrin release, and increasing gastric motility.
- The Intestinal phase involves partially digested proteins in the duodenum triggering the release of enterogastrin, which further regulates secretion.
Inhibition of Gastric Secretion
- Presence of acid, partially digested proteins, irritation of the duodenum mucose, presence of fats, and other substances, also inhibit gastric secretion.
- Hormones such as secretin, CCK, and GIP also slow down or inhibit the gastric juice secretion by inhibiting sympathetic stimulation.
Mechanical Digestion
- The stomach mixes food with gastric juice through mixing waves (peristaltic movements)
- This process reduces food to a thin liquid called chyme.
Chemical Digestion
- The primary chemical activity of the stomach is protein digestion by pepsin.
- The acidic environment (pH 2) is optimum for pepsin to function.
- Pepsin breaks down certain peptide bonds between amino acids in proteins.
- The zymogenic cells secrete pepsinogen, which is converted to pepsin by hydrochloric acid from parietal cells.
- Mucus protects the stomach lining from digestion by pepsin.
- Gastric lipase is present in the stomach for fats.
- Infants secrete rennin which acts on milk casein.
Regulation of Gastric Emptying
- Gastric emptying is stimulated by nerve impulses in response to distension and the release of stomach gastrin, as well as food types
- The rate of emptying is influenced by the type of food.
- The stomach empties contents into the duodenum within 2-6 hours after ingestion.
- Carbohydrates remain in the stomach the shortest time, followed by protein and fat.
- Stomach emptying is inhibited by the enterogastric reflex and hormones (secretin, CCK, and GIP).
The Small Intestine
- The mucosa contains intestinal glands (crypts of Lieberkühn) that secrete intestinal juice.
- Duodenal glands secrete alkaline mucus.
- Mucus protects the wall of the small intestine from acidity.
- Goblet cells add additional mucus.
- Solitary and Peyer's patches increase immunity.
Intestinal Juice
- A clear yellow fluid; about 2-3 litres per day.
- pH is 7.6, with water and mucus.
Absorption in the Small Intestine
- Digested nutrients are absorbed from the alimentary canal into the blood and lymph.
- This process, called absorption, accounts for approximately 90% in the small intestine.
The Large Intestine
- The large intestine completes the absorption process.
- It also manufactures certain vitamins (by bacteria), forms feces, and expels the feces.
- Bacteria in the large intestine break down remaining carbohydrates;
- forming gases as a result.
- It absorbs water, salts, and some electrolytes.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the intricate structure and function of the stomach in this informative quiz. Delve into the anatomy of various parts such as the cardia, fundus, body, and pylorus, as well as the types of gastric glands and their secretions. Test your knowledge on the stomach's muscular layers and linings.
