Textbook Question
Describe the role of these cells found in gastric glands: parietal, chief, mucous neck, and enteroendocrine.
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Ch. 23 The Digestive System
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732
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Table of contents
- Ch. 1 The Human Body: An Orientation25
- Ch. 2 Chemistry Comes Alive24
- Ch. 3 Cells: The Living Units24
- Ch. 4 Tissue: The Living Fabric19
- Ch. 5 The Integumentary System12
- Ch. 6 Bones and Skeletal Tissues19
- Ch. 7 The Skeleton14
- Ch. 8 Joints7
- Ch. 9 Muscles and Muscle Tissue26
- Ch. 10 The Muscular System25
- Ch. 11 Fundamentals of the Nervous System and Nervous Tissue23
- Ch. 12 The Central Nervous System25
- Ch. 13 The Peripheral Nervous System and Reflex Activity30
- Ch. 14 The Autonomic Nervous System16
- Ch. 15 The Special Senses26
- Ch. 16 The Endocrine System26
- Ch. 17 Blood27
- Ch. 18 The Cardiovascular System: The Heart25
- Ch. 19 The Cardiovascular System: Blood Vessels27
- Ch. 20 The Lymphatic System and Lymphoid Organs and Tissues16
- Ch. 21 The Immune System: Innate and Adaptive Body Defenses27
- Ch. 22 The Respiratory System21
- Ch. 23 The Digestive System31
- Ch. 24 Nutrition, Metabolism, and Energy Balance26
- Ch. 25 The Urinary System26
- Ch. 26 Fluid, Electrolyte, and Acid-Base Balance24
- Ch. 27 The Reproductive System24
- Ch. 28 Pregnancy and Human Development25
- Ch. 29 Heredity11
Hoehn, Haynes, Abbott12th EditionMarieb Human Anatomy & PhysiologyISBN: 9780138242732Not the one you use?Change textbook
Chapter 23, Problem 23
Describe the regulation of the cephalic, gastric, and intestinal phases of gastric secretion.
Verified step by step guidance1
Begin by understanding that gastric secretion is regulated in three overlapping phases: the cephalic, gastric, and intestinal phases, each triggered by different stimuli and involving neural and hormonal controls.
For the cephalic phase, explain that it is initiated by the sight, smell, taste, or thought of food, which activates the brain (specifically the hypothalamus and medulla oblongata). This leads to parasympathetic stimulation via the vagus nerve, promoting secretion of gastric juices even before food enters the stomach.
In the gastric phase, describe how the presence of food in the stomach stimulates gastric secretion. This occurs through two main mechanisms: distension of the stomach wall activating stretch receptors and chemical stimuli (like peptides and amino acids) activating chemoreceptors. These signals enhance secretion of gastric acid (HCl) and enzymes, primarily through local reflexes and release of the hormone gastrin from G cells.
For the intestinal phase, explain that it begins when chyme enters the small intestine. Initially, this phase can stimulate gastric secretion via intestinal gastrin release, but predominantly it inhibits gastric secretion to regulate the rate of stomach emptying. This inhibition is mediated by hormones such as secretin, cholecystokinin (CCK), and gastric inhibitory peptide (GIP), as well as neural reflexes that reduce gastric motility and secretion.
Summarize by noting that these phases work together to optimize digestion: the cephalic phase prepares the stomach, the gastric phase maximizes secretion in response to food presence, and the intestinal phase modulates secretion to coordinate digestion and absorption in the intestines.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Cephalic Phase of Gastric Secretion
The cephalic phase is the earliest phase of gastric secretion, triggered by the sight, smell, taste, or thought of food. It involves neural mechanisms, primarily the vagus nerve, which stimulates gastric glands to secrete acid and enzymes in preparation for digestion.
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Gastric Phase of Gastric Secretion
The gastric phase begins when food enters the stomach, causing distension and chemical stimulation. This phase involves both neural reflexes and hormonal signals, such as gastrin release, which enhance acid and enzyme secretion to aid in food breakdown.
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Intestinal Phase of Gastric Secretion
The intestinal phase occurs when chyme enters the small intestine, regulating gastric secretion through inhibitory signals. Hormones like secretin and cholecystokinin reduce acid production to prevent excessive acidity and coordinate digestion and nutrient absorption.
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Related Practice
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a. What is the relationship between the cystic, common hepatic, bile, and pancreatic ducts?
b. What is the point of fusion of the bile and pancreatic ducts called?
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Explain why fatty stools result from the absence of bile or pancreatic juice.
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