Mastication Biology Quiz

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Questions and Answers

Which anatomical structures are involved in the process of mastication?

Pharynx and tongue

Cerebral cortex and amygdala

Esophagus and stomach

Teeth and jaw muscles (correct)

What role does saliva play during mastication?

Mixes and lubricates food (correct)

Increases food temperature

Absorbs excess sugars

Breaks down food chemically

What is the primary function of the chewing reflex?

To facilitate the mechanical breakdown of food (correct)

To stimulate saliva production

To enhance taste perception

To prevent choking

Which nerve is primarily responsible for innervating the muscles involved in chewing?

Trigeminal nerve (V) Signup and view all the answers

What is the stage immediately following the dropping of the lower jaw during chewing?

Stretch reflex of the jaw muscles Signup and view all the answers

Which part of the brain is primarily involved in the swallowing reflex?

Brain stem reticular formation Signup and view all the answers

Deglutition refers to which of the following processes?

Delivery of food from the mouth to the stomach Signup and view all the answers

Which reflex is NOT typically associated with chewing?

Bowman's reflex Signup and view all the answers

What is a potential dietary restriction for edentulous patients?

Soft foods only Signup and view all the answers

Which pathway involves efferents from the pharynx and the trigeminal nerve in the swallowing reflex?

Dorsal motor nucleus pathway Signup and view all the answers

What is the role of the tensor palatini and levator palatini during the pharyngeal phase?

To elevate the soft palate Signup and view all the answers

During the pharyngeal phase, how long does respiration stop?

3/10 seconds Signup and view all the answers

What anatomical feature is formed by the contraction of the superior constrictor muscle?

Ridge of Passavant Signup and view all the answers

What mechanism primarily coordinates the contractions during the oesophageal phase?

Central and peripheral mechanisms Signup and view all the answers

Which muscle group is responsible for raising and moving the larynx during the swallowing process?

Geniohyoid and mylohyoid muscles Signup and view all the answers

Which structure prevents food from entering the trachea during swallowing?

Epiglottis Signup and view all the answers

What role does the upper esophageal sphincter (UOS) play in the swallowing process?

Closes the upper end of the esophagus Signup and view all the answers

Which nerve primarily innervates the body during the oesophageal phase?

Vagus nerve Signup and view all the answers

What is the main effect of the approximation of the palatopharyngeal folds during the pharyngeal phase?

Allows food to pass to the posterior pharynx Signup and view all the answers

What purpose does the closure of the nasopharynx serve during swallowing?

To prevent food from entering the respiratory system Signup and view all the answers

Which components form the Dorsal Vagal Complex?

Nuclei of ambiguus, tractus solitarius, and area postrema Signup and view all the answers

What is the primary function of the Dorsal Vagal Complex?

Integration of neural control for the upper gastrointestinal tract Signup and view all the answers

Which phase of swallowing involves the voluntary action of squeezing and rolling food?

Buccal stage Signup and view all the answers

What is the duration of the pharyngeal phase of swallowing?

< 1 second Signup and view all the answers

Which muscle is NOT involved in the swallowing process?

Temporalis Signup and view all the answers

Which part of the gastrointestinal tract is NOT under the control of the Dorsal Vagal Complex?

Large intestine Signup and view all the answers

What is the function of the area postrema in the Dorsal Vagal Complex?

Detecting toxins in the blood Signup and view all the answers

Which of the following best describes the oesophageal phase of swallowing?

A rapid reflexive action lasting 8-10 seconds Signup and view all the answers

Which of the following structures is primarily associated with the completion of the voluntary stage of swallowing?

Oropharynx Signup and view all the answers

What is the role of the cricothyroid muscle in swallowing?

Tensing the vocal cords during sound production Signup and view all the answers

Which of the following mechanisms aids in the opening of the Upper Oesophageal Sphincter (UOS)?

Pharyngeal peristaltic wave Signup and view all the answers

What initiates the primary peristaltic wave (OPW) in the esophagus?

Stretching of the myenteric plexus Signup and view all the answers

What physiological action does the crural portion of the diaphragm perform at the lower esophageal sphincter (LOS)?

It exerts a pinchcock action around the esophagus. Signup and view all the answers

Which of the following factors contributes to the contraction of the lower esophageal sphincter (LOS)?

Myogenic, neural, and humoral factors Signup and view all the answers

How do enteric inhibitory neurons (EIN) facilitate LOS relaxation?

By releasing VIP and NO Signup and view all the answers

Which condition is associated with defective muscle function affecting swallowing?

Myasthenia gravis Signup and view all the answers

What primarily results from the distension of the myenteric plexus after food retention?

Tertiary waves in the esophagus Signup and view all the answers

Which of the following accurately describes the role of vagal efferent fibers during swallowing?

They initiate vago-vagal reflexes due to stretching. Signup and view all the answers

What is a common finding associated with tertiary waves in the esophagus?

They indicate potential pathology. Signup and view all the answers

What factor does NOT contribute to the high resting tone of the lower esophageal sphincter?

Inhibition by the myenteric plexus Signup and view all the answers

Study Notes

Chewing

Mastication is the process of mechanically breaking down food.
Involves action of teeth: incisors for cutting, molars for grinding.
Jaw muscles are regulated by higher brain centers.
Individuals without teeth (edentulous) require a soft diet.

Functions of Mastication

Aids digestion by increasing surface area for enzyme action.
Mixes food with saliva and lubricates it for easier swallowing.
Prevents damage (excoriation) to the gut wall.
Facilitates food emptying and movement through the digestive tract.

Regulation of Chewing

Controlled by nuclei located in the brainstem, cerebral cortex, hypothalamus, and amygdala.
Motor branch of the trigeminal nerve (cranial nerve V) innervates the muscles of chewing.

Chewing Reflex

Initiated by the presence of food in the mouth.
This triggers a reflex inhibition of mastication muscles, causing the jaw to drop.
The jaw muscles stretch, resulting in a rebound contraction that raises the jaw.
The teeth close, compressing food against the mouth lining.
Further reflex inhibition of the mastication muscles occurs, restarting the cycle.

Deglutition (Swallowing)

A reflex action moving air, liquids, and solids from the mouth to the stomach.

Regulatory Pathways for Swallowing

Controlled by the swallowing center in the brainstem reticular formation.
Involves the nucleus ambiguus, tractus solitarius, and dorsal motor nucleus of the vagus nerve.
Afferent (sensory) nerves from the pharynx and cranial nerves V, VII, and XII carry information about the bolus.
Efferent (motor) nerves, including V, VII, IX, X, and the hypoglossal nerve, control muscle action during swallowing.

Vagal Integrative Center for the Upper GI Tract

Includes the dorsal motor nucleus of the vagus, nuclei of ambiguus, tractus solitarius, and area postrema.
Known as the dorsal vagal complex, located in the medulla oblongata.
Responsible for integrating vagal control of the esophagus, stomach, duodenum, pancreas, and gallbladder.

Muscles Involved in Swallowing

Oral/Facial muscles: Masseter, temporalis, pterygoideus (lateral & medial), tensor palatini, digastricus, stylohyoideus, facial muscles.
Pharyngeal Muscles: Palatopharyngeus, palatoglossus, levator palatini, salpingopharyngeus, superior, middle & inferior constrictors.
Laryngeal Muscles: Cricothyroideus, cricoarytenoideus, interarytenoideus.
Tongue Muscles: Geniohyoideus, thyrohyoideus (extrinsic) - posterior intrinsic tongue muscles, hypoglossus, genioglossus, styloglossus.
Esophageal Muscles: Esophageal muscles (smooth & striated)

Swallowing Stages

Voluntary: Food is moved posteriorly by the tongue and pressed against the hard palate, then soft palate into the oropharynx.
Involuntary:
- Pharyngeal Phase (< 1 second): Closure of the nasopharynx, respiration inhibited, bolus propelled through the pharynx by pharyngeal peristalsis.
- Esophageal Phase (8-10 seconds): Bolus moves from pharynx to stomach via peristalsis.

Pharyngeal Phase

Nasopharynx closure accomplished by contraction of the tensor palatini and levator palatini muscles, elevating the soft palate.
Superior constrictor muscle contraction forms the ridge of Passavant, creating a seal and initiating pharyngeal peristalsis.
Palatopharyngeal folds approximate to form a slit, allowing for passage of properly masticated food.
Larynx closure: hyoid bone is raised & moved forward by geniohyoid & mylohyoid muscles, bringing the larynx under the tongue.
Vocal cords approximate.
Epiglottis swings backward over the larynx opening to prevent food entry.

Esophageal Phase

UOS (upper esophageal sphincter) closure at the top of the esophagus.
Cricopharyngeal, or pharyngoesophageal, sphincter is a striated muscle.
A primary peristaltic wave (OPW) is initiated in the pharynx and propels the bolus distally at 4 cm/sec over 8-10 seconds.
Gravity assists bolus movement.
Secondary OPW is triggered by retained food distending the myenteric plexus.
Tertiary waves can indicate pathology.

Lower Esophageal Sphincter (LOS)

A physiological sphincter created by:
- Smooth muscle thickening at the stomach junction.
- Crural portion of the diaphragm surrounding the esophagus.
- Oblique stomach fibers form a flap valve.
LOS closes during high intragastric pressure to prevent reflux.

LOS Function

High resting tone of the UOS and LOS act as a barrier against air and gastric contents.
The esophageal body is flaccid at rest.
Sequential body contractions propel the bolus distally.
Contractions are coordinated centrally and peripherally.

LOS Contraction and Relaxation

Contraction is induced by myogenic, neural (acetylcholine), and humoral factors.
Smooth muscle contracts when stretched.
Relaxation is neurally mediated by vagal efferent fibers stimulating enteric inhibitory neurons (EIN).
EIN release vasoactive intestinal peptide (VIP) and nitric oxide (NO) to relax smooth muscle.

Esophageal Coordination and Receptive Relaxation

Vagus nerve coordinates esophageal contractions with somatic and visceral motor nerves.
Vago-vagal reflexes are triggered by esophageal body stretching.
Receptive relaxation of the stomach allows the bolus to enter and complete swallowing.

Disorders of Chewing & Swallowing

Sphincter disorders: Achalasia (LES failure to relax), Incompetent LOS ("heartburn").
Nerve Damage: Cranial nerves V, IX, X affected by conditions like poliomyelitis or encephalitis.
Muscle dysfunction: Myasthenia gravis, muscle dystrophy, diffuse esophageal spasm.
Glottis remains open: Drug-induced.

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Description

Test your knowledge on the process of mastication, its functions, and regulation in relation to the digestive system. This quiz covers the mechanics involved in chewing, the role of different teeth, and the neurological control of jaw movement.