Transcript Lecture 33. Digestion in oral cavity

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Digestion in oral cavity
Common characteristic of the mouth cavity digestion
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In the oral cavity take place such main processes:
1. Primary analyses of substances, which are
coming to organism – taste analyzes;
2. Reflector signals from receptor, which are
present in these area to the another organs of
digestive system, to the central nerve system –
medulla oblongata, stomach, small intestine,
pancreas;
3. Chemical processing of food;
4. Mechanical processing of food;
5. Absorption of some substances.
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Chewing of food is important, because
fruits and vegetables have cellulose
which must be broken before the food
can be utilized. In the mouth cavity
begin digestion of carbohydrates, which
help to the functional activity of
pancreas.
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When our food are in the mouth stimulate the
receptors of oral cavity; from which impulses
go to the different part of brain and return to
different part of digestion tract – stomach,
small intestine, pancreas, in which secreted
juices with enzymes
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In the mouth cavity open three pair of big
salivary glands and a lot of small buccal
glands. Submandibular and sublingual
glands consist of the cells of serum and
mucous types and secrete serous and mucus
types of saliva. Parotid glands consist of the
serum types cells and secrete serous type of
saliva.
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Small buccal glands consist of mucous types
of cells; produce mucous saliva with a big
quantity of water. Saliva necessary for our
digestion. In a mouth chewing a food by teeth
and lingual. In the mouth cavity begin
digestion of carbohydrates by alfa-amilase –
ptyalin. To secrete different types of saliva for
digestion processes – with a big quantity of
water or organic and inorganic substances.
Quantity, composition and properties of
saliva
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Quantity, composition and properties of saliva (In the
case of dream produce nearly 0,05 mL/minute, in the
normal condition – 0,5 mL/minute, in the case of
maximal secretion – near 5 mL/minute. By day
produce 0,8-1,5 L of saliva. Composition of saliva:
water, organic – alfa-amilase, lipase, phosphatase,
RNAase, DNAase, mucin, substances for protective –
lisocim, thiocianates, antibodies – and unorganic
substances – sodium, potassium, calcium, chlorites,
etc.
Mechanism of saliva forming
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In acinars' cells produce primary saliva in which
synthesis necessary amino acids, glucose, mineral
substances (for example, Ca++). In the cells of
salivary glands occur passive processes, which
provide moving of water and electrolits from blood to
the glands’ ductus (strait). In the ductus occur
reabsorption of sodium, chlorine, secretion of
potassium, HCO3–. This is the secondary saliva.
Aldosterone increase reabsorption of sodium and
secretion of potassium.
Role of saliva in vitality of human
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1. Moisten of solid food;
2. Dissolving of substances;
3. Moisten of mouth;
4. Cover food;
5. To help of swallowing;
6. Primary hydrolyzing of carbohydrates;
7. Antibacterial properties;
8. Neutralized the stomach juice.
Mechanism of saliva formation
Formation of saliva
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Conditional reactions caused by appearance
of food, it smell and other stimulus, which
are connect with food.
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Unconditional influences have parasympathetic and
sympathetic components. Parasympathetic
components beginning from receptors of tongue
and oral cavity. From its impulses pass through the
fibers of n. trigeminus, n. facialis, n. vagus, n.
glossopharyngeus, to the center of salivation.
Impulses return to saliva glands by n. facialis, n.
glossopharyngeus. Sympathetic components of
unconditional influences beginning from side cornu
of upper thoracic segments of spinal cord – Th2-Th4. Then impulses go to saliva glands through the
upper cervix sympathetic ganglion. The cortex of
big hemispheres, hypothalamus, lymbic system
regulate the salivation through these nerves.
Conditional signals, emotions may inhibit
salivation.
Influence of vegetative nerves on secretor
activity of salivary glands
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Stimulation of the parasympathetic nerve
supply causes profuse secretion of watery
saliva with a relatively low content of
organic material. Stimulation of the
sympathetic nerve supply causes profuse
secretion of saliva with small quantity of
water with a relatively big content of
organic material.
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Mediator of parasympathetic nerve system –
acetylcholine – stimulate M-cholinoreceptors of basolateral membrane and activate entrance of Ca2+ and
activate kalmodulin. These reaction caused
production of a big quantity of saliva with low
quantity of organic substances. Mediator of
sympathetic nerve system – norepinephrine –
stimulate adrenoreceptors of basolateral membrane,
activated adenilatcyclase that form cAMP. These
reaction caused production of a small quantity of
saliva which have a big quantity of organic
substances.
Swalowing