Digestive physiology

1. MOUTH AND
SALIVARY GLANDS
Vigneswaran Ganesan M.sc.,
Assistant professor
Department of Biochemistry

2. SYNOPSIS

3. MOUTH
Oral / Buccal cavity
FUNCTIONAL ANATOMY
• Formed by cheeks, lips and palate
• Encloses the teeth, tongue and salivary glands
• Digestive juice- saliva
• Secreted by salivary glands
FUNCTIONS
Ingestion of food
Chewing the food and mixing with
saliva
Appreciating the taste of food
Transfer of food to esophagus by
swallowing
Role in speech
Expressions and social functions
MOUTH
OPENS
Anteriorly to the
exterior through lips
Posteriorly through the
Fauces into the pharynx
Fauces: opening at the back of the
mouth leading to pharynx

4. SALIVARY GLANDS- MAJOR 3
GLANDS
PAROTID GLAND
Largest
Situated at the side of the face just below
and in front of ear
20-30g
Stensen’s duct (35-40mm long)
Duct opens inside the cheek against upper 2nd molar tooth

5. SALIVARY GLANDS- MAJOR 3
GLANDS
SUBMAXILLARY /SUBMANDIBULAR GLANDS
8-10g
Medial to mandible
Wharton’s duct(40mmm long)
Duct opens at the side of frenulum of tongue
Opens by a small opening on summit of papilla called caruncula
sublingualis

6. SALIVARY GLANDS- MAJOR 3
GLANDS
SUBLINGUAL GLANDS
Smallest
Situated in mucosa at the floor of the mouth
2-3g
5- 15 small ducts called duct of rivinus
Larger duct – Bartholin duct
Drains the anterior part of the gland and opens in Caruncula
Sublingualis near the opening of submaxillary duct

7. SALIVARY GLANDS- MINOR
GLANDS
1. LINGUAL MUCOUS GLANDS
2. LINGUAL SEROUS GLANDS
3. BUCCAL GLANDS( MOLAR GLANDS)
4. LABIAL GLANDS
5. PALATAL GLANDS

8. CLASSIFICATION OF SALIVARY
GLANDS
MIXED GLANDS
• Made of serous
cells
• Secrete thin and
watery saliva
• Include parotid
gland and lingual
serous gland
MUCOUS GLANDS
• Made of mucous
cells
• Secrete thick,
viscous saliva with
high mucin content
• Lingual mucous
gland and buccal
glands and palatal
glands
SEROUS GLANDS
• Made of both
mucous and
serous cells
• Submandibular ,
sublingual and
labial glands

9. STRUCTURE AND
DUCT SYSTEM
OF SALIVARY
GLANDS
Formed by acinus or alveoli
Fine duct draining each acinus- intercalated
duct
Many intercalated ducts – intralobular duct
Few intralobular duct- interlobular duct –
form main duct
Racemose type of gland (racemose- bunch of
grapes)
Acinus – formed by small group
of cells which surround a central
globular cavity.

10. PROPERTIES AND COMPOSITION OF
SALIVA
PROPERTIES
COMPOSITION
- 99.5% water
- 0.5 solids
VOLUME = 1-1.5 LIT/DAY i.e, approx. 1ml/min
Slightly acidic ,PH =6.35-6.85
Specific gravity = 1.002-1.012
Hypotonic to plasma

11. PROPERTIES AND COMPOSITION OF
SALIVA

12. FUNCTIONS OF SALIVA
SALIVA
FUNCTIONS
DIGESTIVE
PROTECTIVE
EXCRETORY
ROLE IN
SPEECH
REGULATION
OF BODY
TEMPERATURE
REGULATION
OF WATER
BALANCE

13. REGULATION OF WATER BALANCE BY
SALIVA
.
When body water
content decreases ,
salivary secretion
decreases
Causes
dryness of
mouth
Induces
thirst
WHEN WATER IS TAKEN, IT
QUENCHES THIRST AND
RESTORES THE BODY WATER
CONTENT

14. REGULATION OF
SALIVARY
SECRETION
Nerve supply to salivary glands
Salivary glands are supplied by both
parasympathetic and sympathetic
divisions of autonomic nervous system
Regulated by nervous mechanism
Autonomic nervous system is involved
in the regulation of salivary secretion.

15. PARASYMPATHET
IC FIBERS
Parasympathetic fibers to
submandibular and sublingual gland
Motor fiber
Branch of facial nerve
Trigeminal nerve
Situated in pons of brain

16. PARASYMPATHET
IC FIBERS
Parasympathetic fibers to parotid
gland
Present in the upper part of medulla oblangata
Mandibular division of trigeminal nerve

17. PARASYMPATHET
IC FIBERS
FUNCTIONS
• Stimulation causes secretion of saliva with large
quantity of water
• Because the parasympathetic fibers activates
the acinar cells and dilate the blood vessels of
salivary glands
• Amount of organic constituents in saliva is less
• Neurotransmitter- acetyocholine

18. SYMPATHETIC
FIBERS
Preganglionic fibers Arise
from lateral horns of 1st and
2nd thoracic segment of
spinal cord
Leaves the cord through
anterior nerve roots and end
in superior cervical ganglion
of sympathetic chain
Postganglionic fibers arise
from ganglion are distributes
to salivary glands along the
nerve plexus , around the
arteries supplying the glands
FUNCTIONS
• Stimulation of fibers causes secretion of saliva
which is thick and rich in organic constituents
such as mucous
• It is because these fibers activate the acinar cells
and cause vasoconstriction
• Neurotransmitter- noradrenaline

19. REFLEX
REGULATION OF
SALIVARY
SECRETION
Salivary secretion is
regulated by nervous
mechanism through
reflex action.
Salivary reflexes are of
two types:
1. Unconditioned reflex.
2. Conditioned reflex.
CONDITIONED REFLEX
• acquired by experience and it needs previous experience
• Presence of food in the mouth is not necessary to elicit this
reflex
• stimuli for this reflex are the sight, smell, hearing or thought
of food.
UNCONDITIONED REFLEX
• inborn reflex that is present since birth
• reflex induces salivary secretion when any substance is
placed in the mouth
• It is due to the stimulation of nerve endings in the mucus
membrane of the oral cavity.

20. EFFECT OF DRUGS
AND CHEMICALS
ON SALIVARY
SECRETION
1. Substances which
increase salivary
secretion
2. Substances which
decrease salivary
secretion Substances which decrease salivary secretion
• Sympathetic depressants like ergotamine and dibenamine.
• Parasympathetic depressants like atropine and scopolamine.
• Anesthetics such as chloroform and ether stimulate the
secretion of saliva. However, deep anesthesia decreases the
secretion due to central inhibition.
Substances which increase salivary secretion
• Sympathomimetic drugs like adrenaline and ephedrine.
• Parasympathomimetic drugs like acetylcholine, pilocarpine,
muscarine and physostigmine.
• Histamine.

21. APPLIED PHYSIOLOGY

22. APPLIED PHYSIOLOGY
• Xerostomia - dry mouth (pasties or cotton
mouth)
• Drooling – uncontrolled flow of saliva outside
the mouth
• Chorda tympani syndrome – sweating while
eating
• Sjogren syndrome - an autoimmune disorder in
which the immune cells destroy exocrine
glands such as lacrimal glands and salivary
glands.