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Questions and Answers
What is the primary function of salivary α-amylase?
What is the primary function of salivary α-amylase?
- Digestion of triglycerides
- Bacteria-static activity
- Digestion of carbohydrates (correct)
- Lubrication of the oral cavity
Which of the following substances is responsible for neutralizing gastric acid in the digestive system?
Which of the following substances is responsible for neutralizing gastric acid in the digestive system?
- Zymogen
- Sodium bicarbonate (correct)
- Mucins
- Haptocorrin
What role does Haptocorrin play in digestion?
What role does Haptocorrin play in digestion?
- Responsible for fat digestion
- Binds vitamin B12 in the lumen (correct)
- Facilitates starch digestion
- Inhibits bacterial growth
Which of the following is not produced by the exocrine pancreas?
Which of the following is not produced by the exocrine pancreas?
Which type of lipase is involved in triglyceride digestion in the oral cavity?
Which type of lipase is involved in triglyceride digestion in the oral cavity?
What is the primary purpose of the brush border membrane in the GI tract?
What is the primary purpose of the brush border membrane in the GI tract?
Which types of cells are primarily responsible for modifying the fluid and ion secretions in the salivary glands and pancreas?
Which types of cells are primarily responsible for modifying the fluid and ion secretions in the salivary glands and pancreas?
Which type of secretion is primarily produced by acinar cells?
Which type of secretion is primarily produced by acinar cells?
What percentage of saliva is produced by the three major salivary glands?
What percentage of saliva is produced by the three major salivary glands?
Which of the following components is NOT typically found in saliva?
Which of the following components is NOT typically found in saliva?
Which function is NOT associated with saliva?
Which function is NOT associated with saliva?
Which gland contributes 5% of saliva production?
Which gland contributes 5% of saliva production?
What type of fluid do acinar cells primarily secrete?
What type of fluid do acinar cells primarily secrete?
What is the primary effect of chyme progression from the stomach to the intestine?
What is the primary effect of chyme progression from the stomach to the intestine?
Which process is indicated as leading to an alkaline load in the blood?
Which process is indicated as leading to an alkaline load in the blood?
What is the role of bicarbonate (HCO3-) in the intestinal lumen?
What is the role of bicarbonate (HCO3-) in the intestinal lumen?
What can be inferred about the blood during vomiting?
What can be inferred about the blood during vomiting?
Which of the following statements is true regarding the acid-base status in the stomach and intestine?
Which of the following statements is true regarding the acid-base status in the stomach and intestine?
In which area does the highest secretion of HCO3- likely occur during digestion?
In which area does the highest secretion of HCO3- likely occur during digestion?
What happens to the pH of the blood as acidic chyme moves into the intestine?
What happens to the pH of the blood as acidic chyme moves into the intestine?
Which of the following describes the effect of vomiting on the intestinal bicarbonate levels?
Which of the following describes the effect of vomiting on the intestinal bicarbonate levels?
What is the function of apical membrane hydrolases?
What is the function of apical membrane hydrolases?
Which condition can result from lactase deficiency?
Which condition can result from lactase deficiency?
What type of molecules do enzymes on the luminal surface of the small intestine reduce?
What type of molecules do enzymes on the luminal surface of the small intestine reduce?
What is a consequence of increased luminal osmolality due to lactase deficiency?
What is a consequence of increased luminal osmolality due to lactase deficiency?
Which of the following best describes the digestive process on the enterocyte surface?
Which of the following best describes the digestive process on the enterocyte surface?
What is the primary product of the enzymatic digestion of lactose?
What is the primary product of the enzymatic digestion of lactose?
What effects can watery diarrhea have on the digestive system?
What effects can watery diarrhea have on the digestive system?
How do brush border enzymes aid in digestion?
How do brush border enzymes aid in digestion?
What is the primary function of glutaminase in the metabolism of glutamine?
What is the primary function of glutaminase in the metabolism of glutamine?
What percentage of dietary fats supply daily calories according to the provided information?
What percentage of dietary fats supply daily calories according to the provided information?
What is the energy yield per gram of lipid compared to carbohydrates?
What is the energy yield per gram of lipid compared to carbohydrates?
Which mechanism is involved in the epithelial transport of amino acids?
Which mechanism is involved in the epithelial transport of amino acids?
What is the significance of the futile detoxification cycle involving urea?
What is the significance of the futile detoxification cycle involving urea?
How much dietary fat is typically ingested per day?
How much dietary fat is typically ingested per day?
What are the primary transporters for dipeptides in the intestinal epithelial cells?
What are the primary transporters for dipeptides in the intestinal epithelial cells?
Which of the following statements is true regarding amino acid absorption at the end of the jejunum?
Which of the following statements is true regarding amino acid absorption at the end of the jejunum?
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Study Notes
The Digestive Tract
- A large surface area is needed for absorption in the gastrointestinal (GI) tract.
- The brush border membrane aids in absorption.
Secretions
- Secretions from salivary and pancreatic glands are essential for digestion and absorption.
Saliva
- 95% of saliva is produced by three major salivary glands.
- 5% of saliva is produced by lingual (tongue) glands.
- Saliva composition:
- Salt
- Water
- Proteins
- Mucins
- Salivary α-amylase
- Begins starch digestion
- Destroyed in stomach acid
- Lingual lipase and salivary lipase
- Begin triglyceride digestion
- Lysozyme, secretory IgA, lactoferrin
- Bacterial static or cidal activities
- Haptocorrin
- Vitamin B12 luminal chaperone
Pancreas
- 85% of the pancreas is dedicated to exocrine function (remaining 15% is endocrine)
- Secretes:
- NaHCO3 (sodium bicarbonate)
- Neutralizes gastric acid
- Zymogens
- Inactive precursors of enzymes crucial for digestion
- NaHCO3 (sodium bicarbonate)
Acid/Base Neutralization in the Gut
- The stomach secretes H+ into the lumen and HCO3- into the blood.
- The intestine secretes HCO3- into the lumen and H+ into the blood.
- The progression of chyme (food) from the stomach to the intestine results in neutralization of pH in the lumen and blood.
Acid/Base with Vomiting
- Vomiting can cause a heavy alkaline load in the blood.
- The stomach secretes H+ into the vomit and HCO3- into the blood.
- The intestine secretes HCO3- into the lumen and H+ into blood.
Apical Membrane Hydrolases
- Also known as brush border enzymes
- Digest nutrients directly on the surface of absorbing epithelial cells
Enterocyte Surface Digestion of CHO
- Enzymes on the luminal (apical) surface of the small intestinal epithelium reduce the variety of molecules available for absorption.
- Lactase deficiency can lead to osmotic diarrhea.
Lactose Intolerance
- Lactase deficiency prevents the breakdown of lactose into glucose and galactose.
- This leads to an increase in luminal osmolality.
- Water accumulates in the lumen, causing distension.
- Enhanced peristalsis results in watery diarrhea.
Epithelial Transport of Amino Acids
- Amino acids are primarily absorbed in the jejunum.
- Dipeptides are transported by the PEPT1 transporter.
- Amino acids are transported by multiple transporters.
Lipid Digestion
- Dietary fats provide roughly 40% of daily calories.
- We ingest about 100 grams of lipids per day.
- Almost all lipids are triglycerides.
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