Physiology of Mastication & Swallowing
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Questions and Answers

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

  • Initiates digestion of dietary lipids
  • Provides immune defense against bacteria
  • Initiates digestion of starches (correct)
  • Acts as a lubricant in the mouth
  • Which glands are primarily responsible for the production of viscous mucinous secretions?

  • Labial glands
  • Sublingual glands (correct)
  • Parotid glands
  • Submandibular glands
  • Which phase of swallowing involves the propulsion of the bolus through the esophagus?

  • Gastric phase
  • Pharyngeal phase
  • Oral phase
  • Oesophageal phase (correct)
  • What is the estimated daily saliva flow rate in a healthy individual?

    <p>1 - 2 L/day</p> Signup and view all the answers

    Which component in saliva contributes to its immune defense properties?

    <p>Lysozyme</p> Signup and view all the answers

    What is xerostomia commonly referred to as?

    <p>Dry mouth</p> Signup and view all the answers

    Which of the following statements about the parotid glands is incorrect?

    <p>They are the smallest salivary glands</p> Signup and view all the answers

    What is the result of achalasia concerning the lower esophageal sphincter?

    <p>Increased muscle tone leading to obstruction</p> Signup and view all the answers

    What main factors contribute to vomiting?

    <p>Bacterial infection and motion sickness</p> Signup and view all the answers

    What is the primary role of mucins in saliva?

    <p>Lubrication and protection</p> Signup and view all the answers

    What is the first phase of swallowing known as?

    <p>Oral phase</p> Signup and view all the answers

    During which phase of swallowing does breathing temporarily cease?

    <p>Pharyngeal phase</p> Signup and view all the answers

    What initiates the muscle contractions in the pharyngeal phase of swallowing?

    <p>Efferent signals from the deglutition center</p> Signup and view all the answers

    What type of muscle primarily composes the upper oesophageal sphincter (UES)?

    <p>Striated muscle</p> Signup and view all the answers

    Which part of the pharynx is involved in both voluntary and involuntary phases of swallowing?

    <p>Oropharynx</p> Signup and view all the answers

    Which nerve activity is primarily responsible for the tonically active state of the lower oesophageal sphincter (LES)?

    <p>Vagal cholinergic activity</p> Signup and view all the answers

    What triggers secondary peristaltic waves in the oesophagus?

    <p>Local reflex initiated by larger boluses</p> Signup and view all the answers

    Which structure closes off the trachea during the pharyngeal phase of swallowing?

    <p>Epiglottis</p> Signup and view all the answers

    What primarily composes the secretion from the oesophagus?

    <p>Mucus</p> Signup and view all the answers

    In the context of swallowing, what does the term 'degultition apnea' refer to?

    <p>Temporary cessation of breath during swallowing</p> Signup and view all the answers

    What specific role does salivary amylase play in digestion?

    <p>Begins digestion of dietary starches</p> Signup and view all the answers

    Which autonomic response is primarily responsible for increasing salivary flow?

    <p>Parasympathetic response via acetylcholine</p> Signup and view all the answers

    Which of the following best describes the relationship between salivary flow rate and electrolyte concentrations?

    <p>Higher flow rates decrease electrolyte reabsorption, increasing concentrations</p> Signup and view all the answers

    What type of reflex is stimulated by food in the mouth and is controlled by chemoreceptors?

    <p>Unconditioned salivary reflex</p> Signup and view all the answers

    What is the optimal pH for salivary amylase activity?

    <p>7.0</p> Signup and view all the answers

    Which cranial nerves are primarily involved in the autonomic regulation of salivary secretion?

    <p>VII, IX, and V</p> Signup and view all the answers

    How does sympathetic activation affect salivary secretion?

    <p>It has a limited physiological role but can increase amylase content</p> Signup and view all the answers

    What is the primary antibacterial action found in saliva that maintains oral health?

    <p>Lysozyme and IgA antibodies</p> Signup and view all the answers

    What effect does atropine, an anti-muscarinic, have on salivary secretion?

    <p>It can cause dry mouth by reducing salivation</p> Signup and view all the answers

    The mechanical process of grinding food to increase surface area for enzymatic digestion is known as?

    <p>Mastication</p> Signup and view all the answers

    What is the primary cause of dysphagia in achalasia?

    <p>Weak oesophageal peristalsis</p> Signup and view all the answers

    Which of the following contributes to xerostomia?

    <p>Sjogren Syndrome</p> Signup and view all the answers

    How does the vomiting reflex primarily increase intra-abdominal pressure?

    <p>Contraction of the diaphragm</p> Signup and view all the answers

    Which phase of swallowing involves the relaxation of the upper esophageal sphincter (UES)?

    <p>Pharyngeal phase</p> Signup and view all the answers

    What condition is characterized by hypersalivation and can occur during early pregnancy?

    <p>Ptyalism</p> Signup and view all the answers

    Which neurotransmitter is primarily involved in the regulation of saliva production?

    <p>Acetylcholine</p> Signup and view all the answers

    Which factor contributes to vomiting due to irritation in the gastrointestinal tract?

    <p>Motion sickness</p> Signup and view all the answers

    What is a common complication associated with xerostomia?

    <p>Dental caries</p> Signup and view all the answers

    Which process is primarily involved in the initial mechanical breakdown of food?

    <p>Chewing</p> Signup and view all the answers

    What role does the medulla play in the vomiting reflex?

    <p>Integrates input from various receptors</p> Signup and view all the answers

    This describes the chemical nature of mucins—they are proteins with carbohydrate (sugar) side chains attached.

    <p>Glycoproteins:</p> Signup and view all the answers

    This describes their function—mucins act as ..........in the body, helping to protect and moisten tissues, particularly in mucus secretions.

    <p>Lubricant</p> Signup and view all the answers

    PNS ach recptorter for slivia production is

    <p>M3</p> Signup and view all the answers

    salivary centre in brainstem coordinates responses

    <p>cranial nerves VII, IX, and V.</p> Signup and view all the answers

    what can cuase a dray mouth?

    <p>atropine</p> Signup and view all the answers

    Sympathetic more complex, but limited physiological role α-AR activation what effect does it have?

    <p>increase flow</p> Signup and view all the answers

    The laryngopharynx extends from the hyoid bone to the larynx.coresposens to c6

    <p>c6</p> Signup and view all the answers

    The contraction of the palatal muscle pulls the soft palate over the nasopharynx

    <p>nasopharynx</p> Signup and view all the answers

    Pharyngeal muscles pull the

    <p>epiglottis to close off the trachea</p> Signup and view all the answers

    what phase prevent the inhlation of food

    <p>deglutition apnea</p> Signup and view all the answers

    Oesophageal Phase Controled by

    <p>vagal and intrinsic reflexes</p> Signup and view all the answers

    Secondary Peristaltic Contraction is initiated by stimulation of [blank].

    <p>receptors within the esophagus</p> Signup and view all the answers

    Primary Peristaltic Contraction: Initiated by [blank].

    <p>swallowing</p> Signup and view all the answers

    Two types of peristaltic contractions in the esophagus are both controlled by the [blank].

    <p>vagus nerve (cranial nerve X) and intrinsic reflexes</p> Signup and view all the answers

    The esophagus, like the rest of the GI tract, has two muscle layers—_______ and _______.

    <p>circular, longitudinal</p> Signup and view all the answers

    The two places in the gut where striated muscle occurs are the esophagus and the _______.

    <p>pharynx</p> Signup and view all the answers

    Circular Muscle Layer: This layer of smooth muscle fibers runs around the circumference of the GI tract. Contraction of these fibers narrows the lumen (the interior space) of the tract, which helps in pushing the contents forward. This type of muscle is referred to as [blank].

    <p>smooth</p> Signup and view all the answers

    Longitudinal Muscle Layer: This layer of smooth muscle fibers runs along the length of the GI tract. Contraction of these fibers shortens the tract, aiding in moving the contents along and facilitating [blank] (the wave-like movement of food).

    <p>peristalsis</p> Signup and view all the answers

    Lower esophageal sphincter contraction. Tonically active muscle prevents reflux through [blank].

    <p>vagal cholinergic activity.</p> Signup and view all the answers

    les xrelaexes preioier to food passage due to ................ that inhibit smooth muscle

    <p>VIP and NO by vagus nerve</p> Signup and view all the answers

    _________ is a condition characterized by the increased tone and inability to relax of the lower esophageal sphincter (LES), which impairs the normal passage of food into the stomach.

    <p>Achalasia</p> Signup and view all the answers

    Vomiting (Emetic) Center: Located in the __________ of the brainstem.

    <p>medulla oblongata</p> Signup and view all the answers

    The area postrema of the brainstem contains the [blank] Trigger Zone, which detects chemical signals in the blood and CSF.

    <p>Chemoreceptor</p> Signup and view all the answers

    In the context of vomiting, peripheral nerves transmit signals from the gastrointestinal tract via afferent nerves to the [blank].

    <p>vomiting center</p> Signup and view all the answers

    Emotional and sensory inputs processed by the [blank] influence the vomiting center. This includes memory and anticipatory responses.

    <p>Higher Cortical Centers</p> Signup and view all the answers

    The inner ear's vestibular apparatus sends motion-related signals to the brain when there's a discrepancy in sensory information regarding [blank].

    <p>balance</p> Signup and view all the answers

    What is the role of the salivary center in the brainstem during the vomiting reflex, and why is increased salivation important?

    <p>The salivary center stimulates the production of saliva to neutralize stomach acid and protect oral tissues during vomiting.</p> Signup and view all the answers

    The emetic center is located in the [blank] and its primary function is to coordinate the [blank] reflex.

    <p>medulla oblongata, vomiting</p> Signup and view all the answers

    During vomiting, the respiratory center interacts with the emetic center to typically [blank] breathing patterns.

    <p>decrease</p> Signup and view all the answers

    The [blank] reflex involves deep inspiration, closure of the glottis, relaxation of the stomach, LES, oesophagus, and UES, along with contraction of abdominal muscles and diaphragm to force gastric contents upwards.

    <p>vomiting</p> Signup and view all the answers

    Vomiting Reflex • Deep inspiration and closure of _______ – elevation of soft palate and uvula • Relaxation of stomach, LES, oesophagus and UES • Contraction of abdominal muscles and diaphragm • Increases intra-abdominal pressure forcing gastric contents upwards – against gravity

    <p>the glottis</p> Signup and view all the answers

    Vomiting Reflex: Deep inspiration and closure of the glottis – elevation of soft palate and uvula; Relaxation of stomach, LES, oesophagus and UES; __________; Increases intra-abdominal pressure forcing gastric contents upwards against gravity.

    <p>Contraction of abdominal muscles and diaphragm</p> Signup and view all the answers

    The vomiting reflex involves deep inspiration and closure of the glottis, elevation of the soft palate and uvula, relaxation of the stomach, LES, oesophagus, and UES, contraction of abdominal muscles and diaphragm, and increases in [blank].

    <p>intra-abdominal pressure forcing gastric contents upwards against gravity</p> Signup and view all the answers

    Study Notes

    Saliva

    • Major salivary glands: Parotid (~20-25%), Submandibular (~70-75%), and Sublingual (~3-5%).
    • Parotid glands produce serous watery secretions rich in amylase; located anterior to the ear.
    • Submandibular glands are major glands producing a mix of serous (watery) and mucous (thicker) secretions, resulting in intermediate secretion.
    • Sublingual glands mainly produce viscous mucinous secretions; smallest and located under the tongue.hick mucinous fluid

    Composition of Saliva

    • Typical saliva production: 1-2 L/day, varies with stimuli; basal flow ~0.5 ml/min, max ~5 ml/min.
    • Composition: ~99.5% water, ~0.5% electrolytes (Na+, K+, HCO3-, Cl-) and proteins (α-amylase, lingual lipase, mucins, IgA, lysozyme).
    • Saliva is hypotonic to plasma, with lower sodium and chloride, but higher potassium and bicarbonate concentrations.in have a ph range of 6-8

    Regulation of Salivation

    • Salivation controlled by autonomic nervous system; parasympathetic activation (ACh) increases salivation.

    • Simple reflex triggered by food in the mouth via chemoreceptors and pressure receptors.

    • Conditioned reflex occurs from learned experiences (thinking/smelling food).

    • Salivary centre in brainstem coordinates responses via cranial nerves VII, IX, and V.

      Autonomic Control of Secretion

      • Parasympathetic (ACh) is dominant response

      – hence dry mouth with anti-muscarinics such as atropine • Increases salivary flow rate

      – increased flow rate decreases electrolyte reabsorption along the duct so salivary

      electrolyte concentrations increase – and blood flow via vasodilatation

      • Sympathetic more complex, but limited physiological role

      – α-AR activation seems to increase flow (may be related to resistance in duct)

      – β-AR activation increases amylase content

    Functions of Saliva

    • Initiates digestion, principally of starches, but minimal digestion occurs.
    • Lubricates food aiding in swallowing and taste bud stimulation.
    • Contributes to oral hygiene through buffering (bicarbonate) and antibacterial actions (IgA, lysozyme).

    Mastication

    • Begins mechanical breakdown of food, increasing surface area for salivary enzymes.
    • Saliva mixes with food to form a bolus, facilitating swallowing.
    • Taste stimulation leads to reflex increase in gastric and salivary secretions in preparation for food.

    Phases of Swallowing (Deglutition)

    • Three phases: oral (voluntary), pharyngeal (reflex), and esophageal (reflex).
    • Oral phase involves rolling bolus from mouth to pharynx.
    • Pharyngeal phase triggers pressure receptors, activating swallowing reflex; epiglottis closes off the trachea.
    • Esophageal phase features peristaltic waves moving bolus from UES to LES.

    The pharynx serves as a common pathway for the respiratory and gastrointestinal tracts and consists of three regions.

    • The nasopharynx conditions inspired air and houses lymphoid tissue (adenoid tonsils) and openings to the eustachian tubes.
    • The oropharynx directs food to the esophagus and contains palatine tonsils.
    • The laryngopharynx extends from the hyoid bone to the larynx.coresposens to c6

    Pharyngeal Phase Control:

    As the bolus enters the pharynx, it triggers involuntary pressure receptors that send afferent signals to the deglutition center in the medulla oblongata and pons, initiating muscular contractions.

    The contraction of the palatal muscle pulls the soft palate over the nasopharynx. Pharyngeal muscles pull the epiglottis to close off the trachea while moving the bolus downwards, lasting approximately 1 second during which breathing is inhibited (deglutition apnea).

    Oesophageal Phase Control: The upper oesophageal sphincter (UES) contracts and primary peristaltic waves push the bolus through the esophagus. Secondary waves help clear any lodged bolus. Oesophageal muscle layers consist of circular and longitudinal muscles with variations along its length, and UES and LES are formed by thickened striated or circular smooth muscle. Controlled by vagal and intrinsic reflexes, peristaltic contractions facilitate swallowing.

    Lower Esophageal Sphincter (LES)

    • Tonically active muscle prevents reflux through vagal cholinergic activity.
    • relaexes preioier to food passage due to vip and no by vagle that inhipite smooth muscle
    • decartion is entrily mucse amiing to lubrcat and prtect from acide ensymes

    Swallowing Complications

    • Conditions affecting striated muscles (e.g., stroke, muscular diseases) can impair swallowing.
    • Dysphagia (difficulty swallowing) frequently occurs in the elderly and is exacerbated in achalasia due to excessive LES tone.

    Xerostomia and Ptyalism

    • Xerostomia (dry mouth) can stem from medical conditions like Sjögren Syndrome, dehydration, anxiety, or medications.
    • Associated issues include speech difficulties, dental problems, and increased risk of oral infections.
    • Ptyalism (hypersalivation) may be caused by infections, pregnancy, or associated with nausea and emesis.

    Vomiting (Emesis)

    • A defense mechanism to expel harmful substances; involves complex pathways activating the vomiting centre in the medulla.
    • Common triggers include irritation, motion sickness, raised intracranial pressure, and psychological factors.
    • Vomiting involves deep inspiration, gastric relaxation, and abdominal contraction leading to expulsion of contents.

    Summary Insights

    • Saliva production primarily regulated by PNS; has low Na+ and Cl- and high K+ and HCO3- concentrations.
    • Swallowing process is a highly coordinated reflex involving muscular contractions and relaxation.
    • Vomiting reflex includes GI tract relaxation and an increase in intra-abdominal pressure, forcing expulsion.

    Additional Study Resources

    • Textbooks on gastrointestinal physiology for further reading.
    • Educational videos on swallowing mechanisms may provide illustrative understanding.

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    Description

    Test your knowledge on the composition and functions of saliva with this quiz. Explore the roles of salivary α-amylase, glands responsible for mucinous secretions, and phases of swallowing. Additionally, learn about saliva flow rates and its immune defense properties.

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