What is MASTICATION Cutting of food substances into

What is MASTICATION?

Cutting of food substances into small particles and grinding them into a soft bolus is known as mastication

Significance of mastication: mastication FBreakdown of foodstuffs into smaller particles FMixing of saliva with food substances thoroughly FLubrication and moistening of dry food by saliva FAppreciation of taste of the food

Muscles of mastication Center- Medulla and Cerebral cortex Mandibular division of v cranial nerve

What is DEGLUTITION ?

Deglutition is a process by which chewed food in emptied from the mouth into the stomach

Stages of deglutition ØORAL STAGE ØPHARYNGEAL STAGE ØESOPHAGEAL STAGE

ORAL STAGE ØVoluntary stage ØBolus passes through oral cavity into the pharynx

Movements of Oral stage ØOnce the bolus is formed it is projected on to the back of the tongue ØThe tongue is elevated and pressed against the hard palate. ØSoft palate is elevated.

ØThe bolus is propelled into pharynx ØThe forceful contraction of tongue against the palate produces a positive pressure in the posterior part of the oral cavity

PHARYNGEAL STAGE Øinvoluntary stage ØBolus is pushed from pharynx into esophagus

v BACK INTO THE MOUTH v UPWARDS INTO NASOPHARYNX v FORWARDS INTO LARYNX v. ENTRANCE OF BOLUS INTO ESOPHAGUS

BACK INTO THE MOUTH Ø The position of tongue against palate Ø High intraoral pressure developed by the movement of the tongue

UPWARDS INTO NASOPHARYNX Ø Upward movement of soft palate

FORWARDS INTO LARYNX Ø Approximation of the vocal cords Ø Forward and upward movement of larynx Ø Epiglottis swing backwards over the superior opening of the larynx Ø Temporary arrest of breathing

ENTRANCE OF BOLUS INTO ESOPHAGUS Ø Upward movement of larynx – stretches the opening of esophagus Ø Upper esophageal sphincter relaxes Ø Entire muscle of pharynx contracts

ESOPHAGEAL STAGE Ø involuntary stage Ø The function of the esophagus is to transport the bolus from the esophagus to the stomach

v. Primary peristaltic contractions v. Secondary peristaltic contractions

Primary Oesophageal peristalsisØ It is the continuation of the peristaltic wave that is produced in the pharynx by the contraction of the superior pharyngeal constrictor Ø Its function is to propel the food through the esophagus to the stomach Ø The vagus controls the esophageal peristalsis through the myentric plexus

Ø If the primary peristaltic wave fails to evacuate the food bolus, then the secondary peristaltic wave arises by. Vago- vagal reflux

Difference b/w 10 and 20 peristalsis Primary: • Initiated by swallowing and begins when the food passes into Oesophagus from Pharynx. • Coordinated by vagal fibers from the swallowing centre. Secondary: • Initiated by the presence of food in Oesophagus after the primary peristalsis is complete and is due to the mechanical or irritant receptor stimulation. • Coordinated by intrinsic nervous system of Oesophagus.

OESOPHAGEAL PERISTALSIS

1. Pharyngo- eesophageal sphincter : - formed by the tonic contraction of the cricopharyngeus muscle - It is normally closed except during the deglutition - It prevents the entry of air from the mouth into the esophagus § 2. Gastro- esophageal sphincter

DEGLUTITION REFLEX Sensory receptors- Tonsillar pillars, posterior pharyngeal wall, soft palate, epiglottis Afferent – V, IX, X cranial nerves Deglutition center- Located in the floor of the IV ventricle near the resipiratory center in the medulla Efferent - V, VII, IX, X, XII, cranial nerves Effectors – Pharyngeal musculature and tongue

APPLIED PHYSIOLOGY

BUCCAL STAGE Ø Painful inflammatory process involving the mouth and the tongue Ø Paralysis of the tongue Ø Congenital anomaly of lips, tongue and palate

Pharyngeal stage Ø Acute pharyngitis Ø Tonsilitis Ø Carcinoma of the larynx or thyroid

Oesophageal stage Ø Diffuse spasm of the esophagus Ø Carcinoma of the esophagus Ø Achalasia cardia Ø GERD- Heart burn

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