38 Questions
What is the primary function of retropulsion in the stomach?
To break down solid particles into smaller pieces
During which phase of gastric acid secretion is the majority of acid produced?
Gastric phase
What is the primary function of HCO3- in gastric mucus?
To neutralize H+ ions
What is the term for the process by which food is propelled back into the stomach for further breakdown?
Retropulsion
What is the pH of the stomach contents during the fasting state?
pH 1-2
What is the primary function of the mucus layer in the stomach?
To protect the stomach lining from acid and enzymes
What is the term for the complex of tubulovesicles and intracellular canaliculi in the parietal cell?
Tubulovesicle complex
What is the primary function of blood flow in the stomach?
To supply nutrients for HCl secretion and buffering via HCO3-
Which of the following salivary secretions plays a crucial role in breaking down complex carbohydrates?
Amylase
What is the primary function of the gastric mucosal barrier?
To protect the stomach lining from acid damage
Which of the following phases of acid secretion is stimulated by the sight and smell of food?
Cephalic phase
What is the primary function of pancreatic juice?
To facilitate the digestion of proteins
Which of the following hormones is released in response to the presence of acid in the duodenum?
Secretin
What is the primary function of acinar cells in the pancreas?
To produce pancreatic enzymes
Which of the following is NOT a function of saliva?
Regulating the release of gastric hormones
What is the primary function of the gastric mucosal barrier?
To protect the stomach epithelium from acid secretion
Which of the following textbooks is NOT a recommended resource for MBBS Year 1 Gastrointestinal Lectures?
Guyton and Hall Textbook of Medical Physiology
What is the role of intrinsic factor in the stomach?
It aids in the absorption of vitamin B12
What is the primary stimulant of HCl secretion by parietal cells?
All of the above
What is the structure of the glandular stomach epithelium?
Simple columnar epithelium
What is the function of surface mucous cells in the stomach?
To produce a thin film of mucous
What is the result of the structural changes in parietal cells during HCl secretion?
A marked increase in the tubulovesicular system
What is the primary component of gastric juice?
HCl
What is the location of the absorption of vitamin B12?
Ileum
What is the primary function of the CCK2 receptor in the ECL cell?
Stimulating the release of histamine
Which of the following neurotransmitters is involved in the physiological stimulation of gastric acid secretion?
ACh
What is the role of the ECL cell in the regulation of gastric acid secretion?
To produce and release histamine
Which receptor is localized on the parietal cell and involved in the regulation of gastric acid secretion?
H2
What is the primary source of gastrin in the gastric mucosa?
G cells
What is the effect of histamine on parietal cells?
Stimulating the release of HCl
What is the mechanism by which omeprazole inhibits gastric HCl secretion?
By forming a disulphide link with H+,K+-ATPase and blocking the enzyme irreversibly
What is the primary function of pancreatic juice?
To neutralize duodenal content and facilitate enzyme activity
What is the primary function of the intestinal phase of acid secretion?
To regulate the release of intestinal hormones that target acid-secreting cells
What is the composition of pancreatic juice?
Rich in HCO3- and enzymes
What is the primary function of lipase in pancreatic juice?
To hydrolyze neutral fat into glycerol and fatty acids
What is the rate of protein synthesis in the pancreas?
Highest rate of protein synthesis of any secretory tissue
What is the primary function of cholecystokinin?
To stimulate the release of pancreatic juice rich in enzymes
What is the primary function of trypsinogen in pancreatic juice?
To break down proteins into peptides
Study Notes
MBBS Year 1 Gastrointestinal Lectures
- Lectures cover the overview of the digestive system, digestion and absorption of nutrients, salivary, gastric, and pancreatic secretions, bile and biliary system, and motility of the gut.
Salivary Secretions
- Salivary glands produce saliva, which has several functions:
- Lubricates food for easy swallowing
- Aids in chewing and digestion
- Helps in oral cavity cleanliness
- Has antibacterial properties
- Salivary secretion is controlled by the nervous system and hormones.
- Factors influencing salivary secretion include:
- Parasympathetic stimulation
- Sympathetic stimulation
- Hormonal stimulation
- Reflex stimulation
Gastric Acid Secretion
- Gastric acid secretion is divided into basal (fasting) and stimulated (post-prandial) phases.
- The three phases of gastric acid secretion are:
- Cephalic phase: triggered by the sight, smell, and taste of food
- Gastric phase: stimulated by the presence of food in the stomach
- Intestinal phase: influenced by the presence of food in the small intestine
- Mucus and bicarbonate secretion create a gastric mucosal barrier, protecting the stomach from acid and enzymes.
- The stomach epithelium undergoes structural changes during HCl secretion, forming a markedly increased tubulovesicular system for proton secretion.
Gastric Mucosal Defense
- The gastric mucosal barrier consists of:
- Mucus layer
- HCO3- secretion
- Tight junctions
- This barrier protects the stomach from acid and enzymes, maintaining a neutral pH.
Pancreatic Secretion
- Pancreatic juice has a physiological function of:
- Neutralizing duodenal content
- Aiding in protein digestion
- Factors causing release of secretin and cholecystokinin include:
- Presence of acid in the duodenum
- Presence of fats in the small intestine
- These intestinal hormones modify the composition of pancreatic juice, increasing HCO3- secretion and enzyme production.
Pancreatic Juice Composition
- Pancreatic juice is composed of:
- Aqueous component rich in HCO3
- Enzyme component
- Proteolytic enzymes (trypsinogen, chymotrypsinogen, procarboxypolypeptidase, ribonuclease, deoxyribonuclease)
- Amylase (breaks down starch and glycogen)
- Lipase (hydrolyzes neutral fat into glycerol and fatty acids)
A comprehensive review of the digestive system, covering digestion, absorption, and physiology. Topics include salivary, gastric, and pancreatic secretions, bile and biliary system, and motility of the gut.
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