Physiology of Mastication & Swallowing

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Questions and Answers

What is one of the primary functions of saliva?

To lubricate ingested food (correct)

To absorb nutrients directly

To stimulate appetite

To aid in the digestion of proteins

Which enzyme in saliva primarily breaks down polysaccharides?

Pepsin

Lingual lipase

Trypsin

Salivary amylase (correct)

What is the primary type of secretion produced by the sublingual glands?

Mucus and serous in equal amounts

Saline solution

Viscous mucinous secretions (correct)

Serous watery secretions

Which type of cell produces watery, enzyme-rich secretions in the salivary glands?

Serous cells Signup and view all the answers

Which salivary gland contributes the most to saliva production?

Submandibular gland Signup and view all the answers

What triggers the stimulation of salivary glands?

Chemo and mechanoreceptors Signup and view all the answers

What is the primary role of salivary α-amylase in saliva?

Initiate digestion of starches Signup and view all the answers

Which phase of swallowing involves the movement of food from the mouth to the pharynx?

Oral phase Signup and view all the answers

What condition is characterized by a decrease in saliva production?

Xerostomia Signup and view all the answers

What percentage of saliva is made up of water?

99.5% Signup and view all the answers

What is the maximum flow rate of saliva under stimulation?

5 ml/min Signup and view all the answers

Which of the following best describes achalasia?

Inability of the lower oesophageal sphincter to relax Signup and view all the answers

Which of these is NOT a cause of vomiting?

Increased salivation Signup and view all the answers

What triggers the pharyngeal phase of swallowing?

Pressure receptors in the pharynx Signup and view all the answers

What occurs during the oesophageal phase of swallowing?

Contraction of the upper esophageal sphincter Signup and view all the answers

Which phase of swallowing is primarily voluntary?

Oral phase Signup and view all the answers

What is the role of the epiglottis during the pharyngeal phase?

To close off the trachea Signup and view all the answers

During which region of the pharynx does the swallowing process primarily occur?

Oropharynx Signup and view all the answers

What initiates secondary peristaltic waves in the oesophagus?

Stretch receptors activated by a lodged bolus Signup and view all the answers

What is deglutition apnea?

The inhibition of breathing during swallowing Signup and view all the answers

What type of muscle contraction primarily drives the food bolus during the oesophageal phase?

Involuntary Signup and view all the answers

What initiates the primary peristaltic contraction in the esophagus?

Swallowing Signup and view all the answers

What is the primary function of salivary secretion during swallowing?

To increase lubrication for food movement Signup and view all the answers

What characterizes the muscle layers of the esophagus?

Striated muscle in two segments Signup and view all the answers

What role does the lower esophageal sphincter (LES) play during swallowing?

It relaxes just before the bolus arrives Signup and view all the answers

In which condition is swallowing impaired due to excess tone of the LES?

Achalasia Signup and view all the answers

What type of muscle primarily forms the lower esophageal sphincter (LES)?

Circular smooth muscle Signup and view all the answers

What is a common condition associated with difficulty in swallowing in the elderly?

Dysphagia Signup and view all the answers

What stimulates the relaxation of the LES just before a bolus reaches it?

Vasoactive intestinal peptides and nitric oxide Signup and view all the answers

What is the primary physiological cause of xerostomia?

Decreased salivary gland function Signup and view all the answers

Which of the following conditions is NOT typically associated with xerostomia?

Hypersalivation Signup and view all the answers

What is a common cause of ptyalism during early pregnancy?

Gastro-oesophageal reflux Signup and view all the answers

Which part of the nervous system is primarily responsible for saliva production?

Parasympathetic nervous system Signup and view all the answers

What triggers the vomiting reflex through the pharyngeal (gag) reflex?

Irritation of the throat Signup and view all the answers

Which physiological process occurs simultaneously with vomiting?

Closure of the glottis Signup and view all the answers

What role does the chemoreceptor trigger zone (CTZ) play in the vomiting process?

It detects toxins and drugs in the blood. Signup and view all the answers

What is a common stimulus for motion sickness that can lead to vomiting?

Changes in visual perception Signup and view all the answers

Which of the following is NOT a physiological effect during the vomiting reflex?

Increased intrathoracic pressure Signup and view all the answers

Which chemical characteristic of saliva increases during high salivary flow?

Increased concentration of components Signup and view all the answers

What primarily stimulates the secretion of gastric juices in the cephalic phase?

The thought, sight, smell, and taste of food Signup and view all the answers

Which of the following is NOT a main motor function of the stomach?

Absorption of nutrients Signup and view all the answers

Which cells in the stomach are primarily responsible for secreting hydrochloric acid (HCl)?

Parietal cells Signup and view all the answers

What is the main biochemical pathway involved in stimulating gastric acid secretion in the oxyntic cell?

Histamine receptor activation Signup and view all the answers

What is a common cause of gastritis?

Helicobacter pylori infection Signup and view all the answers

Which factor significantly inhibits gastric acid secretion?

Release of somatostatin Signup and view all the answers

What happens to contractions as they move toward the pyloric sphincter?

They increase in force and speed Signup and view all the answers

What is the primary role of the pyloric sphincter during digestion?

To regulate the outflow of chyme into the small intestine Signup and view all the answers

In the fasted state, how does the stomach usually behave?

It remains quiescent but can respond to stimuli Signup and view all the answers

Which area of the stomach is considered the pacemaker region for electrical rhythm?

Proximal stomach or orad Signup and view all the answers

How does increasing volume in the stomach affect pressure?

Pressure remains constant Signup and view all the answers

During the mixing process in the stomach, what primarily happens to the contents as contractions occur?

Most contents are pushed back for the next wave Signup and view all the answers

Which neurons are responsible for relaying information between sensory and motor neurons in the enteric nervous system?

Inter-neurons Signup and view all the answers

What effect does acetylcholine (ACh) have on the gastrointestinal tract when released by the parasympathetic nervous system?

Increases motility and secretions Signup and view all the answers

Which plexus of the enteric nervous system is primarily responsible for controlling motor function?

Auerbach's plexus Signup and view all the answers

Which type of hormone action is involved in the control of the gastrointestinal tract?

Both intrinsic and extrinsic actions Signup and view all the answers

What is the primary neurotransmitter released by sympathetic fibers in the GI tract?

Noradrenaline Signup and view all the answers

Which division of the autonomic nervous system primarily controls the upper gastrointestinal tract?

Parasympathetic nervous system Signup and view all the answers

What is the role of sensory neurons in the enteric nervous system?

They receive information from the mucosa. Signup and view all the answers

What is the primary function of Meissner's plexus within the enteric nervous system?

Control of mucosal secretions Signup and view all the answers

What is one of the primary mechanical functions of the stomach?

Mixing of contents Signup and view all the answers

Which pathway is involved in the vagovagal reflex during receptive relaxation?

Vagus nerve Signup and view all the answers

What physiological process allows the stomach to accommodate increasing food volumes without a change in pressure?

Enteric nervous system control Signup and view all the answers

What happens to the stomach during the process of swallowing?

Relaxation of the lower oesophagus Signup and view all the answers

What role does nitric oxide (NO) play in receptive relaxation?

Facilitates relaxation of muscles Signup and view all the answers

What is primarily responsible for maintaining stable pressure in the stomach as it fills?

Receptive relaxation Signup and view all the answers

What is the term used for the stomach's function as a reservoir for ingested food?

Reservoir function Signup and view all the answers

Which area of the stomach is primarily involved in the mixing of contents?

Antrum Signup and view all the answers

What occurs beyond certain volumes of food in the stomach?

Marked increase in pressure Signup and view all the answers

What triggers gastric emptying into the intestines?

Increased muscle contractions in the antrum Signup and view all the answers

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.