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Questions and Answers
What is one of the primary functions of saliva?
What is one of the primary functions of saliva?
Which enzyme in saliva primarily breaks down polysaccharides?
Which enzyme in saliva primarily breaks down polysaccharides?
What is the primary type of secretion produced by the sublingual glands?
What is the primary type of secretion produced by the sublingual glands?
Which type of cell produces watery, enzyme-rich secretions in the salivary glands?
Which type of cell produces watery, enzyme-rich secretions in the salivary glands?
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Which salivary gland contributes the most to saliva production?
Which salivary gland contributes the most to saliva production?
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What triggers the stimulation of salivary glands?
What triggers the stimulation of salivary glands?
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What is the primary role of salivary α-amylase in saliva?
What is the primary role of salivary α-amylase in saliva?
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Which phase of swallowing involves the movement of food from the mouth to the pharynx?
Which phase of swallowing involves the movement of food from the mouth to the pharynx?
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What condition is characterized by a decrease in saliva production?
What condition is characterized by a decrease in saliva production?
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What percentage of saliva is made up of water?
What percentage of saliva is made up of water?
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What is the maximum flow rate of saliva under stimulation?
What is the maximum flow rate of saliva under stimulation?
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Which of the following best describes achalasia?
Which of the following best describes achalasia?
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Which of these is NOT a cause of vomiting?
Which of these is NOT a cause of vomiting?
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What triggers the pharyngeal phase of swallowing?
What triggers the pharyngeal phase of swallowing?
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What occurs during the oesophageal phase of swallowing?
What occurs during the oesophageal phase of swallowing?
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Which phase of swallowing is primarily voluntary?
Which phase of swallowing is primarily voluntary?
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What is the role of the epiglottis during the pharyngeal phase?
What is the role of the epiglottis during the pharyngeal phase?
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During which region of the pharynx does the swallowing process primarily occur?
During which region of the pharynx does the swallowing process primarily occur?
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What initiates secondary peristaltic waves in the oesophagus?
What initiates secondary peristaltic waves in the oesophagus?
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What is deglutition apnea?
What is deglutition apnea?
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What type of muscle contraction primarily drives the food bolus during the oesophageal phase?
What type of muscle contraction primarily drives the food bolus during the oesophageal phase?
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What initiates the primary peristaltic contraction in the esophagus?
What initiates the primary peristaltic contraction in the esophagus?
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What is the primary function of salivary secretion during swallowing?
What is the primary function of salivary secretion during swallowing?
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What characterizes the muscle layers of the esophagus?
What characterizes the muscle layers of the esophagus?
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What role does the lower esophageal sphincter (LES) play during swallowing?
What role does the lower esophageal sphincter (LES) play during swallowing?
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In which condition is swallowing impaired due to excess tone of the LES?
In which condition is swallowing impaired due to excess tone of the LES?
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What type of muscle primarily forms the lower esophageal sphincter (LES)?
What type of muscle primarily forms the lower esophageal sphincter (LES)?
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What is a common condition associated with difficulty in swallowing in the elderly?
What is a common condition associated with difficulty in swallowing in the elderly?
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What stimulates the relaxation of the LES just before a bolus reaches it?
What stimulates the relaxation of the LES just before a bolus reaches it?
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What is the primary physiological cause of xerostomia?
What is the primary physiological cause of xerostomia?
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Which of the following conditions is NOT typically associated with xerostomia?
Which of the following conditions is NOT typically associated with xerostomia?
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What is a common cause of ptyalism during early pregnancy?
What is a common cause of ptyalism during early pregnancy?
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Which part of the nervous system is primarily responsible for saliva production?
Which part of the nervous system is primarily responsible for saliva production?
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What triggers the vomiting reflex through the pharyngeal (gag) reflex?
What triggers the vomiting reflex through the pharyngeal (gag) reflex?
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Which physiological process occurs simultaneously with vomiting?
Which physiological process occurs simultaneously with vomiting?
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What role does the chemoreceptor trigger zone (CTZ) play in the vomiting process?
What role does the chemoreceptor trigger zone (CTZ) play in the vomiting process?
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What is a common stimulus for motion sickness that can lead to vomiting?
What is a common stimulus for motion sickness that can lead to vomiting?
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Which of the following is NOT a physiological effect during the vomiting reflex?
Which of the following is NOT a physiological effect during the vomiting reflex?
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Which chemical characteristic of saliva increases during high salivary flow?
Which chemical characteristic of saliva increases during high salivary flow?
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What primarily stimulates the secretion of gastric juices in the cephalic phase?
What primarily stimulates the secretion of gastric juices in the cephalic phase?
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Which of the following is NOT a main motor function of the stomach?
Which of the following is NOT a main motor function of the stomach?
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Which cells in the stomach are primarily responsible for secreting hydrochloric acid (HCl)?
Which cells in the stomach are primarily responsible for secreting hydrochloric acid (HCl)?
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What is the main biochemical pathway involved in stimulating gastric acid secretion in the oxyntic cell?
What is the main biochemical pathway involved in stimulating gastric acid secretion in the oxyntic cell?
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What is a common cause of gastritis?
What is a common cause of gastritis?
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Which factor significantly inhibits gastric acid secretion?
Which factor significantly inhibits gastric acid secretion?
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What happens to contractions as they move toward the pyloric sphincter?
What happens to contractions as they move toward the pyloric sphincter?
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What is the primary role of the pyloric sphincter during digestion?
What is the primary role of the pyloric sphincter during digestion?
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In the fasted state, how does the stomach usually behave?
In the fasted state, how does the stomach usually behave?
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Which area of the stomach is considered the pacemaker region for electrical rhythm?
Which area of the stomach is considered the pacemaker region for electrical rhythm?
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How does increasing volume in the stomach affect pressure?
How does increasing volume in the stomach affect pressure?
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During the mixing process in the stomach, what primarily happens to the contents as contractions occur?
During the mixing process in the stomach, what primarily happens to the contents as contractions occur?
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Which neurons are responsible for relaying information between sensory and motor neurons in the enteric nervous system?
Which neurons are responsible for relaying information between sensory and motor neurons in the enteric nervous system?
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What effect does acetylcholine (ACh) have on the gastrointestinal tract when released by the parasympathetic nervous system?
What effect does acetylcholine (ACh) have on the gastrointestinal tract when released by the parasympathetic nervous system?
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Which plexus of the enteric nervous system is primarily responsible for controlling motor function?
Which plexus of the enteric nervous system is primarily responsible for controlling motor function?
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Which type of hormone action is involved in the control of the gastrointestinal tract?
Which type of hormone action is involved in the control of the gastrointestinal tract?
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What is the primary neurotransmitter released by sympathetic fibers in the GI tract?
What is the primary neurotransmitter released by sympathetic fibers in the GI tract?
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Which division of the autonomic nervous system primarily controls the upper gastrointestinal tract?
Which division of the autonomic nervous system primarily controls the upper gastrointestinal tract?
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What is the role of sensory neurons in the enteric nervous system?
What is the role of sensory neurons in the enteric nervous system?
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What is the primary function of Meissner's plexus within the enteric nervous system?
What is the primary function of Meissner's plexus within the enteric nervous system?
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What is one of the primary mechanical functions of the stomach?
What is one of the primary mechanical functions of the stomach?
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Which pathway is involved in the vagovagal reflex during receptive relaxation?
Which pathway is involved in the vagovagal reflex during receptive relaxation?
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What physiological process allows the stomach to accommodate increasing food volumes without a change in pressure?
What physiological process allows the stomach to accommodate increasing food volumes without a change in pressure?
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What happens to the stomach during the process of swallowing?
What happens to the stomach during the process of swallowing?
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What role does nitric oxide (NO) play in receptive relaxation?
What role does nitric oxide (NO) play in receptive relaxation?
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What is primarily responsible for maintaining stable pressure in the stomach as it fills?
What is primarily responsible for maintaining stable pressure in the stomach as it fills?
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What is the term used for the stomach's function as a reservoir for ingested food?
What is the term used for the stomach's function as a reservoir for ingested food?
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Which area of the stomach is primarily involved in the mixing of contents?
Which area of the stomach is primarily involved in the mixing of contents?
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What occurs beyond certain volumes of food in the stomach?
What occurs beyond certain volumes of food in the stomach?
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What triggers gastric emptying into the intestines?
What triggers gastric emptying into the intestines?
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Study Notes
Physiology of Mastication & Swallowing
- Mastication involves the mechanical breakdown of food through chewing.
- Salivation aids in hydration, lubrication, and oral hygiene, containing proteins and antimicrobial chemicals.
- Saliva consists mainly of water (~99.5%), electrolytes, and proteins, crucial for digestions such as salivary amylase and lingual lipase.
- Salivary glands:
- Parotid glands contribute ~20-25%, produce serous, watery secretions with amylase.
- Submandibular glands provide ~70-75%, have mixed serous and mucous secretions.
- Sublingual glands create ~3-5%, primarily viscous mucous.
- Saliva flow rate ranges from ~1-2 L/day, varying throughout the day.
Swallowing Phases
- Swallowing (deglutition) consists of three phases:
- Oral/Buccal: Voluntary phase where bolus is formed and pushed to the pharynx.
- Pharyngeal: Reflex phase where the bolus moves from pharynx to oesophagus, involving pressure receptors and muscular contractions.
- Oesophageal: Reflex phase transporting the bolus to the stomach through peristalsis.
Pharynx Regions
- Nasopharynx: Air conditioning pathway with lymphoid tissue; leads to Eustachian tubes.
- Oropharynx: Connects mouth and oesophagus; contains palatine tonsils.
- Laryngopharynx: Connects to larynx and oesophagus, extends to C6 vertebra.
Oesophageal Control
- Upper oesophageal sphincter (UES) opens upon swallowing; peristaltic waves move the bolus through the oesophagus.
- Secondary peristatic waves help clear lodged food, controlled by vagal and local reflexes.
- Lower oesophageal sphincter (LES) remains contracted, preventing reflux and relaxes during food passage.
Dysphagia and Achalasia
- Dysphagia indicates difficulty swallowing, often in the elderly or due to conditions like stroke or MS.
- Achalasia leads to impaired swallowing from excessive tone in the LES and weak peristalsis, causing food retention in the oesophagus.
Xerostomia and Ptyalism
- Xerostomia: Dry mouth from reduced saliva; caused by conditions like Sjögren syndrome or medications.
- Symptoms include difficulty speaking, altered taste, dental issues, and dysphagia.
- Ptyalism: Hypersalivation often linked to infections, early pregnancy, or emesis.
Vomiting (Emesis)
- A protective reflex eliminating harmful substances; triggered by various stimuli, including irritation and forceful contraction of abdominal muscles.
- Common causes include motion sickness, drugs, and psychosomatic factors.
- Vomiting involves a combination of deep inspiration, relaxation of the stomach and sphincters, and abdominal pressure increase to expel contents.
Summary Highlights
- Saliva production is primarily influenced by the parasympathetic nervous system.
- Swallowing is a complex reflex involving coordinated muscle actions of the oesophagus and sphincters.
- The vomiting reflex comprises relaxation of the GI tract and increased abdominal pressure for ejection of contents.
Learning Outcomes
- Understand nervous control of the gastrointestinal tract (GIT) and how reflexes and hormones influence gastrointestinal function.
- Recognize the initiation of slow waves and the stomach's three main motor functions: storage, mixing, and emptying.
- Identify the stomach's role in digestion, detailing gastric secretions and substances absorbed.
- Describe mediators of gastric acid secretion, pathways within oxyntic cells, and factors inhibiting secretion.
- Enumerate causes of gastritis and peptic ulcer disease.
Control of the GI Tract
- Control is managed through neural and humoral factors: intrinsic (Enteric Nervous System) and extrinsic (Autonomic Nervous System).
- Enteric Nervous System (ENS) solely resides in the GI tract and includes sensory, motor, and inter-neurons.
- Extrinsic control involves the parasympathetic (enhances activity) and sympathetic (suppress activity) nervous systems.
Enteric Nervous System (ENS)
- ENS contains sensory neurons that detect mucosal conditions, motor neurons for motility and secretion control, and inter-neurons for communication.
- Arranged in two major plexuses:
- Myenteric Plexus (Auerbach's) controls motor function.
- Submucosal Plexus (Meissner’s) regulates secretion.
Extrinsic Control of GI Tract
- Parasympathetic innervation, primarily through the vagus nerve, promotes digestion.
- Sympathetic input, via noradrenaline, reduces motility and secretions.
Gastric Motor Function
- The stomach performs three mechanical functions:
- Short-term food storage (reservoir function).
- Mixing of gastric contents.
- Emptying contents into the intestines.
Receptive Relaxation
- Triggered by swallowing, allowing the stomach to expand without increasing pressure, primarily through vagus nerve pathways.
- Enables gastric accommodation for increased volume with stable pressure.
Gastric Phases
- Cephalic Phase: Involves gastric juice secretion upon food stimuli (sight, smell, thought); gastrin release stimulates acid and enzyme secretion.
- Gastric Phase: Activated by stomach stretching, enhancing peristalsis and gastric emptying.
- Intestinal Phase: Inhibits gastric emptying through hormonal feedback (Cholecystokinin, secretin).
Gastric Juice Composition
- Secretes approximately 1,500 ml of gastric juice daily, composed of water, HCl, HCO3-, mucus, pepsin, and intrinsic factor.
- Gastric juice facilitates digestion by breaking down macromolecules.
Gastric Digestion
- Carbohydrate digestion begins in the mouth but is partially inhibited by stomach acidity.
- Lipid digestion is initiated in the stomach via gastric lipase.
- Protein digestion occurs through pepsin, activated by low pH.
Gastric Glands and Secretions
- Surface Epithelial Cells: Secrete protective thick mucus to guard against acidity.
- Pyloric Glands: Secrete gastrin (stimulates gastric acid production) and somatostatin (inhibits gastrin release).
- Oxyntic Glands: Located in fundus/body; parietal cells secrete HCl and intrinsic factor, chief cells secrete pepsinogen.
Regulation of Gastric Secretion
- Vagal stimulation enhances all gastric secretions, balancing the release of acid, pepsinogen, water, mucus, and gastrin through different cell types.
- Gastrin release is stimulated by peptides and amino acids but inhibited by high acidity (low pH).
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Description
Explore the intricate processes of mastication and swallowing through this quiz. Understand the role of salivation, the types of salivary glands, and the phases of swallowing. This quiz is essential for anyone studying human physiology.
