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Dr Pradeep Kumar, Professor department of
physiology, KGMU, Lucknow
 To
understand functional significance of
gastrointestinal tract (GIT)
 Understand the structure of GIT and its
significance as functional segments
 Major intestinal secretions
 Every
cell of living system needs energy
 Unicellular organisms: Exists in the sea of
nutrients
 Can satisfy their nutritional need just by
Proteins present at the cell membrane

In multi cellular organisms, a groups of cells
converted to a tissue , to perform specific function
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A number of systems are evolved in vertebrates
including humans
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To provide nutrients to all the systems The Gastro
intestinal tract is accounted for extraction of
nutrients from the food
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The most of the food we eat are macromolecules ,
it can not cross the cell membrane easily
so it must be converted to monomers
Gastrointestinal tract is to make the food in
absorbable form by help of chewing and by the
mixing with various enzymes ,in mouth to small
intestine
Macromolecules :Food
digestive
enzymes
monomers in
small intestine
Absorption into
blood circulation
Structure of wall of the GIT
first secretion from git that encounter the food is
SALIVARY SECRETIONS

Saliva is the mixed glandular secretion which constantly
bathes the teeth and the oral mucosa

First secretion encounter the food
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It is vital for oral health
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It is constituted by the secretions of the three paired major
salivary glands; the parotid, sub mandibular and sublingual

Initiate the digestion of starch

Protects oral cavity

IgA and lysozymes
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Provide lubrication for food to make bolus
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Facilitate the taste
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Helps in speaking, swallowing, chewing

Buffer the gastric secretions reflux in to the esophagus
Parotid Is large accounts for
50% sec. of saliva
 Situated in front of ear behind
the ramus of mandible
 Gland drain in to oral cavity
opposite to second molar tooth
 Secretions are basically serous
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The submandibular gland is about half the size of the parotid gland
It lies above the mylohyoid in the floor of the mouth. It opens into the
floor of the mouth underneath the anterior part of the tongue
The sublingual is the smallest of the paired major salivary glands, being
about one fifth the size of the submandibular.
It is situated in the floor of the mouth beneath the sublingual folds of
mucous membrane.
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Water 99.55% solid 0.45%
pH 7.04
Na, K, Ca, Mg, Cl, HCO3- and phosphate
Organic substances includes
IgA, Lysozymes, albumin, glucose, lactate, urea and
ammonia etc.
Normal salivary flow rates are 0.3-0.4 ml/min when un
stimulated and 1.5-2.0 ml/min when stimulated
Approximately 0.5 – 0.6 litres of saliva is secreted per
day

The presence of saliva is vital to the maintenance of healthy hard
(teeth) and soft (mucosa) oral tissues.

Patients suffering from dry mouth can experience difficulty with
eating, swallowing, speech, the wearing of dentures, trauma to and
ulceration of the oral mucosa, taste alteration, poor oral hygiene, a
burning sensation of the mucosa, oral infections including Candida and
rapidly progressing dental caries

After radio therapy, old age and multidrug therapy
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Lippincott’s Illustrated Reviews: Physiology (2013)
Medical Physiology, UPDATED SECOND EDITION
(Walter F. Boron, MD, PhD)
BERNE & LEVY, PHYSIOLOGY, SIXTH EDITION,
UPDATED EDITION
Ganong’s Review of Medical Physiology, T W E N T Y -F O U R T H
EDITION
a) Sublingual salivary gland
b) Submandibular salivary gland
c) Parotid gland
d) Accessory salivary glands
a) Mucinous cells
b) Seromucinous cells
c) Serous cells
d) Cloudy cells
A. Alpha-amylase
B. Mucin and muramidase.
C. Bicarbonate and magnesium.
D. Protease and peptidase
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(A) saliva contains digestive enzymes.
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(B) saliva has important antiseptic action.
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(C) It is largely under hormonal control.
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(D)It exerts antibacterial action.
A. Sodium concentration increases.
B. Bicarbonate concentration decreases.
C. Chloride decreases.
D. Potassium increases.
A. Copious, protein-poor, electrolyte-rich.
B. Scant, transient protein-rich (mucin), electrolyte poor.
C. Scant, protein-poor, electrolyte-poor.
D. Copious, protein-rich (mucin), electrolyte-rich.
a) Under the palatopharyngeous muscle
b) Posterior to the mylohyoid muscle
c) Below the mylohyoid muscle
d) Above the mylohyoid
(A)Their secretion is mainly under hormonal control.
(B)The sympathetic system is the Only natural pathway for
stimulation of their secretion.
(C)Both sympathetic and parasympathetic nerves stimulate
their secretion.
D) Bradykinin decrease their blood flow rate.
(A) stimulates taste buds.
(B)Is usually followed by Mastication.
(C)Reflexively stimulates The salivary glands.
(D)All are correct.
(A)Pleasant taste sensation are not related to the reflex .
(B)Only salivatory nuclei in the brainstem need to be excited by taste
sensation without participation of suprasegmental influences.
(C)The cerebral cortex partially controls salivation.
(D) salivation could be completely interrupted in a decorticate animal
whose tongue is mechanically stimulated.
(A)Its concentration of K+ is the same as that in plasma.
(B)Its Na+&Cl- concentration are lower than those in plasma.
(C)Its osmotic pressure and PH are lower than their
corresponding values in plasma.
(D)It exerts antibacterial action.
Thank you