1. Mastication (Chewing) Salivary Secretion
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 submandibular
70%
Mixed secretion
(mucous + enzymes)
2 sublingual 5%
Mucous
Buccal glands 5%
Mucous
Nerve supply:
Symp. 1st & 2nd thoracic seg. relay in cervical ganglia
Parasymp. 7th & 9th cranial cranial nerve facial glosso-phary.

2. K+ & HCO3- more than plasm. Mucous to lubricate food
Composition of Saliva:
Volume lit/day
pH i.e. acidic
Tonicity Hypotonic than plasma
99.5% Water
0.5% Solids
Organic
Inorganic
Na & cl less than plasm.
K+ & HCO3- more than plasm.
Mucous to lubricate food
Enzymes
Ptylin (S.amylase)
Lingual lipase
Lysozymes (antibacterial)

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

4. Na+ K+ actively actively  Na+ in Saliva  K+ in Saliva
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
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 H2O  hypotonic.

5. Saliva 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
Saliva
Hypotonic
(closer to isotonic)
Less K+ & HCO3- 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.

6. 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)

7. 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.

8. 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.

9. 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

10. is divided into The smooth muscles of G.I.T. are arranged in bundles.
Autonomous
Regulation
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

11. It is the passage of food from mouth to stomach.
Deglutition
(Swallowing)
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 phase 8-10 sec.

12. 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

13. 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.

14. Events: Palatopharyngeal folds: Soft palate (uvula): Respiration:
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.

15. Secondary Peristalsis
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.
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.

16. To protect wall of esoph. from Hcl of 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:
Only
To lubricate food
mucous
To protect wall of esoph. from Hcl of stomach
No enzymes.

17. 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.
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.