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Mastication (Chewing)  To grind & break food into small parts.  Function  Facilitate swallowing  Mix food with saliva  Stimulate tastebuds that affect.

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Presentation on theme: "Mastication (Chewing)  To grind & break food into small parts.  Function  Facilitate swallowing  Mix food with saliva  Stimulate tastebuds that affect."— Presentation transcript:

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2 Mastication (Chewing)  To grind & break food into small parts.  Function  Facilitate swallowing  Mix food with saliva  Stimulate tastebuds that affect secretion of saliva, stomach & pancreas  Mechanism:  Can be done voluntary.  Most chewing is reflex in response to the present of food in mouth. Salivary Secretion  3 pairs of glands Mastication (Chewing)  To grind & break food into small parts.  Function  Facilitate swallowing  Mix food with saliva  Stimulate tastebuds that affect secretion of saliva, stomach & pancreas  Mechanism:  Can be done voluntary.  Most chewing is reflex in response to the present of food in mouth. Salivary Secretion  3 pairs of glands 2 parotids 20% Serous sec. Rich in enzymes 2 parotids 20% Serous sec. Rich in enzymes 2 submandibular 70% Mixed secretion (mucous + enzymes) 2 submandibular 70% Mixed secretion (mucous + enzymes) 2 sublingual 5% Mucous 2 sublingual 5% Mucous Buccal glands 5% Mucous Buccal glands 5% Mucous  Nerve supply: Symp. 1 st & 2 nd thoracic seg. relay in cervical ganglia Parasymp. 7 th & 9 th cranial cranial nerve facial glosso-phary.

3 Composition of Saliva:  Volume1-1.5 lit/day  pH6-7 i.e. acidic  TonicityHypotonic than plasma 99.5%Water 0.5%Solids Composition of Saliva:  Volume1-1.5 lit/day  pH6-7 i.e. acidic  TonicityHypotonic than plasma 99.5%Water 0.5%Solids Organic Mucous to lubricate food Enzymes  Ptylin (S.amylase)  Lingual lipase  Lysozymes (antibacterial) Enzymes  Ptylin (S.amylase)  Lingual lipase  Lysozymes (antibacterial) Inorganic Na & cl less than plasm. K + & HCO3 - more than plasm. Inorganic Na & cl less than plasm. K + & HCO3 - more than plasm.

4 Functions of Saliva: 1.Swallowing moisten food particles lubrication by mucous. 2.Speech help movement of tongue & lips. 3.Solvent for substance to stimulate taste bicarbonate. 4.Antibacterial due to presence of lysozymes. 5.Buffer action due to presence of bicarbonate to prevent dental caries. 6.Excretion of drugs as Hg & I2. 7.Regulation of osmolality by sensation of thirst. 8.Digestion Saliva is not essential for digestion Starch  amylase maltose Functions of Saliva: 1.Swallowing moisten food particles lubrication by mucous. 2.Speech help movement of tongue & lips. 3.Solvent for substance to stimulate taste bicarbonate. 4.Antibacterial due to presence of lysozymes. 5.Buffer action due to presence of bicarbonate to prevent dental caries. 6.Excretion of drugs as Hg & I2. 7.Regulation of osmolality by sensation of thirst. 8.Digestion Saliva is not essential for digestion Starch  amylase maltose

5 Xerostomia:  or arrested salivary secretion  Dry mouth.  Bad odor.  Dysphagia (difficult swallowing).  Dental caries.  Difficulty in speech. Mechanism of Salivary Secretion: Xerostomia:  or arrested salivary secretion  Dry mouth.  Bad odor.  Dysphagia (difficult swallowing).  Dental caries.  Difficulty in speech. Mechanism of Salivary Secretion: [1] Primary sec. = (Acini stage) contains enzymes mucous electrolytes very near to ECF [2] Secondary sec. = (Duct stage) Na+ K+ actively actively reabsorbed secreted   Na + in Saliva  K + in Saliva [2] Secondary sec. = (Duct stage) Na+ K+ actively actively reabsorbed secreted   Na + in Saliva  K + in Saliva  Na reab. > K+ secretion  -ve 70 mv. inside duct.  HCO3 - are secreted by duct into lumen.  HCO3 - is exchanged with cl-.  Duct is impermeable to H 2 O  hypotonic.  Na reab. > K+ secretion  -ve 70 mv. inside duct.  HCO3 - are secreted by duct into lumen.  HCO3 - is exchanged with cl-.  Duct is impermeable to H 2 O  hypotonic.

6 Characters of Saliva under Resting condition: Hypotonic Rich in K+ & HCO3 - Poor in Na + & cl - Characters of Saliva under Activity:  Salivary flow is rapid   time for electrolyte exchange Characters of Saliva under Activity:  Salivary flow is rapid   time for electrolyte exchange Saliva Hypotonic (closer to isotonic) Hypotonic (closer to isotonic) Less K + & HCO 3 - that of plasma High Na + & cl- but still less than plasma Aldosterone hormone:  Na+ & cl-  K+ secretion reab.  N.B.: If rate of salivary flow is rapid   K+ loss.   K+ in plasma.  Hypokalemia.  Muscle weakness & paralysis. Aldosterone hormone:  Na+ & cl-  K+ secretion reab.  N.B.: If rate of salivary flow is rapid   K+ loss.   K+ in plasma.  Hypokalemia.  Muscle weakness & paralysis.

7 Control of Salivary Secretion:  Under nervous control Only why there is No hormonal control  The hormonal control needs  Time, while food in mouth  Stay for very short time Basal Secretion of Saliva:  Continuous & spontaneous.  Occurs even in absence of stimuli.  Is due to parasymp. Tone  Control of secretion  Unconditioned reflex (simple)  Conditioned reflex (acquired) Control of Salivary Secretion:  Under nervous control Only why there is No hormonal control  The hormonal control needs  Time, while food in mouth  Stay for very short time Basal Secretion of Saliva:  Continuous & spontaneous.  Occurs even in absence of stimuli.  Is due to parasymp. Tone  Control of secretion  Unconditioned reflex (simple)  Conditioned reflex (acquired)

8 Unconditioned reflex:  Food in mouth stimulate  Chemoreceptors  Pressure receptors  Afferent 7, 9, 10 cranial nerves.  Centre M.O.  Efferent 7 & 9 cranial nerves.  Response   salivary secretion.  N.B.: During dental procedures, salivary secretion is  due to stimulation of pressure receptors. Unconditioned reflex:  Food in mouth stimulate  Chemoreceptors  Pressure receptors  Afferent 7, 9, 10 cranial nerves.  Centre M.O.  Efferent 7 & 9 cranial nerves.  Response   salivary secretion.  N.B.: During dental procedures, salivary secretion is  due to stimulation of pressure receptors.

9 Conditioned Reflex (Acquired):  Before food enters mouth.  Sight, smell, odor, hearing thinking.  Centre: Cerebral cortex  +++ superior & inferior Salivary nuclei   Afferent: 7th & 9th cranial nerves  Response:  Salivary secretion  This reflex needs previous experience.  Removal of cortex  Loss of Cond. Re. Conditioned Reflex (Acquired):  Before food enters mouth.  Sight, smell, odor, hearing thinking.  Centre: Cerebral cortex  +++ superior & inferior Salivary nuclei   Afferent: 7th & 9th cranial nerves  Response:  Salivary secretion  This reflex needs previous experience.  Removal of cortex  Loss of Cond. Re.

10 Role of Autonomic Nerves:  Cause dry mouth during stress  Rich in mucous  Rich in enzymes  Small volume  High volume (  water)  Concentrated  True secretion  Visicid  Dominant role Symp. Parasymp.  N.B.: VIP is cotransmitter with ac. ch.  VIP  V.D not blocked by atropine  N.B.: VIP is cotransmitter with ac. ch.  VIP  V.D not blocked by atropine

11  The smooth muscles of G.I.T. are arranged in bundles.  They are electrically connected with one another through gap junctions that allow low-resistance movement of ions from one cell to the next.  So, each muscle layer functions as functional a syncytium.  The pace maker cells of G.I.T smooth muscle are present in the circular muscle layer.  These cells are called:  Interstitial cells of Cajal  These Cajal cells are self excitable like SA-node  Electrical activity of G.I.T is divided into  The smooth muscles of G.I.T. are arranged in bundles.  They are electrically connected with one another through gap junctions that allow low-resistance movement of ions from one cell to the next.  So, each muscle layer functions as functional a syncytium.  The pace maker cells of G.I.T smooth muscle are present in the circular muscle layer.  These cells are called:  Interstitial cells of Cajal  These Cajal cells are self excitable like SA-node  Electrical activity of G.I.T is divided into Basic electric rhythm = Slow wave potential = Resting membrane potential Basic electric rhythm = Slow wave potential = Resting membrane potential

12  It is the passage of food from mouth to stomach.  Started: Voluntary (Buccal phase)  Completed: Involuntary (Pharyngeal & oesoph.)  Controlled by: Deglutition Centre in M.O.  Involves 3 phases  Buccal (oral) 1 sec.  Pharyngeal phase 2 sec.  Oesophageal phase8-10 sec.  It is the passage of food from mouth to stomach.  Started: Voluntary (Buccal phase)  Completed: Involuntary (Pharyngeal & oesoph.)  Controlled by: Deglutition Centre in M.O.  Involves 3 phases  Buccal (oral) 1 sec.  Pharyngeal phase 2 sec.  Oesophageal phase8-10 sec.

13 1.Buccal phase (Oral phase):  Voluntary lasts for 1 sec.  Passage of food from mouth to phary. by contraction of myelohyoid muscle.  The bolus is on the dorsum of tongue  The tip of tongue is in contact to hard palate.  Tongue moves upward & backwards  To push bolus into pharynx.  We can stop deglutition in this buccal phase (bec. it voluntary). 1.Buccal phase (Oral phase):  Voluntary lasts for 1 sec.  Passage of food from mouth to phary. by contraction of myelohyoid muscle.  The bolus is on the dorsum of tongue  The tip of tongue is in contact to hard palate.  Tongue moves upward & backwards  To push bolus into pharynx.  We can stop deglutition in this buccal phase (bec. it voluntary). Hard palate Bolus Tongue

14 2.Pharyngeal phase:  Involuntary lasts 2 sec.  Passage of food from pharynx to oesoph.  When bolus is at oropharyngeal junction  It stimulates: Pressure receptors  Afferent: 5 & 9 cranial nerves.  Centre: Deglutition centre in M.O.  Efferent: 5, 9, 10 & 12 cranial n. 2.Pharyngeal phase:  Involuntary lasts 2 sec.  Passage of food from pharynx to oesoph.  When bolus is at oropharyngeal junction  It stimulates: Pressure receptors  Afferent: 5 & 9 cranial nerves.  Centre: Deglutition centre in M.O.  Efferent: 5, 9, 10 & 12 cranial n.

15 Events: Palatopharyngeal folds:  Approximate to prevent passage of large bolus into pharynx. Soft palate (uvula):  Moves upwards to close posterior nasal cavity to prevent food entrance into nasal cavity. Respiration:  Is inhibited  i.e. reflex apnea for 2 sec. Vocal cords:  Approximated. Larynx:  Moves upwards & anterior to be covered by epiglottis.  Anterior movement will open upper oesoph. sphincter. Pharyngeal muscles:  Fast pharyngeal peristalsis to  intrapharyngeal pressure to move bolus into oesophagus.  It is Primary Peristalsis. Upper oesophageal sphincter:  Is relaxed by the anterior movement of larynx. Events: Palatopharyngeal folds:  Approximate to prevent passage of large bolus into pharynx. Soft palate (uvula):  Moves upwards to close posterior nasal cavity to prevent food entrance into nasal cavity. Respiration:  Is inhibited  i.e. reflex apnea for 2 sec. Vocal cords:  Approximated. Larynx:  Moves upwards & anterior to be covered by epiglottis.  Anterior movement will open upper oesoph. sphincter. Pharyngeal muscles:  Fast pharyngeal peristalsis to  intrapharyngeal pressure to move bolus into oesophagus.  It is Primary Peristalsis. Upper oesophageal sphincter:  Is relaxed by the anterior movement of larynx.

16 3.Oesophageal phase:  Involuntary.  Passage of food from oesophagus into stomach.  2 types of peristalsis. 3.Oesophageal phase:  Involuntary.  Passage of food from oesophagus into stomach.  2 types of peristalsis. Primary Peristalsis Secondary Peristalsis  Continuation of peristaltic wave initiated in pharynx.  Takes 8-10 sec.  Occurs with each swallowing  Controlled by swallowing centre in M.O.  Continuation of peristaltic wave initiated in pharynx.  Takes 8-10 sec.  Occurs with each swallowing  Controlled by swallowing centre in M.O.  If food is remained in oesoph. wall.  Food attached to oesph. wall will stimulate.  Pressure receptors   Local reflex from oesophageal myenteric plexus   Very strong Powerful peristalsis to push food till reached to stomach.  Sec. peristalsis occurs when primary fails to move food into stomach.  If food is remained in oesoph. wall.  Food attached to oesph. wall will stimulate.  Pressure receptors   Local reflex from oesophageal myenteric plexus   Very strong Powerful peristalsis to push food till reached to stomach.  Sec. peristalsis occurs when primary fails to move food into stomach.

17 Lower esophageal sphincter LES:  Formed of circular muscle.  It is Tonically contracted to prevent reflux of Hcl from stomach into oesoph.  When peristalsis reaches lower end of esophagus, LES is relaxed to allow bolus to pass into stomach. Lower esophageal sphincter LES:  Formed of circular muscle.  It is Tonically contracted to prevent reflux of Hcl from stomach into oesoph.  When peristalsis reaches lower end of esophagus, LES is relaxed to allow bolus to pass into stomach. Esophageal secretion: No enzymes. Only To lubricate food mucous To protect wall of esoph. from Hcl of stomach

18 Motor disorders of esophagus: (1) Achalasia (2) LES incompetence  Failure of relaxation of LES. Due to:  Damage of myenteric plexus.  Accumulation of food in esophagus.  Distension of esoph. Treatment:  Antispasmotics to relax sphincter  Surgical myotomy to dilate sphincter.  Failure of relaxation of LES. Due to:  Damage of myenteric plexus.  Accumulation of food in esophagus.  Distension of esoph. Treatment:  Antispasmotics to relax sphincter  Surgical myotomy to dilate sphincter.  If LES is incompetent Hcl reflux from stomach to esoph.  Heart burn.  If LES is incompetent Hcl reflux from stomach to esoph.  Heart burn. (3) Dysphagia:  i.e. difficulty in swallowing  Ex.  Myasthenia gravis  Paralysis of 5, 9, 10 cranial nerves.  i.e. difficulty in swallowing  Ex.  Myasthenia gravis  Paralysis of 5, 9, 10 cranial nerves.


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