Download 01 Digestion in oral cavity and stomach

Digestion in oral cavity and
stomach
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Digestion
Digestion: Breaking down large,
nutrient macromolecules into simpler
molecules for use by an organism.
Food enters the mouth and goes
through mechanical and chemical
changes as it passes through the
alimentary canal.
Types of Nutrients
• Micronutrients- vitamins, minerals, & water
• Macronutrients- proteins, lipids,
carbohydrates, etc…
Organs involved in digestion
Mouth
The gastrointestinal
(GI) tract involves
the stomach, small
intestine and colon.
Oesophagus
Stomach
Small intestine
Colon
Anus
Rectum
Mouth
Mastication is the action of the teeth and the jaws working
together to break food down. Food needs to be chewed to
be broken down into pieces small enough to swallow.
Breaking the food down also gives it a larger surface area
for the digestive enzymes to work on.
There are two different types of teeth in the mouth
- Incisors to tear food e.g. meat
- Molars to grind the food.
Common characteristic of the mouth cavity
digestion
• 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.
Anatomy of the Mouth and Throat
• 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.
Functions of salivary glands
• 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. 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.
• 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.
The Major Salivary Glands
Quantity, composition and properties of
saliva
• By day produce 0,8-1,5 L of saliva.
Composition of saliva:
• water,
• organic – alpha-amylase, lipase, phosphatase,
RNAase, DNAase, mucin, substances for
protective – lisocim, thiocianates, antibodies
• inorganic substances – sodium, potassium,
calcium, chlorites, etc.
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.
Influence of autonomic nerves on secretor
activity of salivary glands
• 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.
Oesophagus
• Approximately 25cm
long
• Moves food from the
throat to the stomach
– Muscle movement
called peristalsis
• If acid from the
stomach gets in here
that’s heartburn.
Peristalsis
• series of involuntary
wave-like muscle
contractions which
move food along the
digestive tract
Stomach
• Stores the food you
eat
• Chemically breaks it
down into tiny pieces
• Mixes food with
digestive juices
• Acid in the stomach
kills bacteria
Functions of stomach
• 1. Digestive (mechanical
treatment, absorption, evacuation,
secretion, storage);
• 2. Excretory;
• 3. Incretory.
mouth
break up food
digest starch
kill germs
moisten food
stomach
kills germs
break up food
digest proteins
store food
sphincter
sphincter
Secretion activity of stomach
• Production of stomach juice per day –
near 2,5 L of juice.
• Their main components – enzymes, HCl
and mucin.
• pH of morning saliva is neutral, after
eating – sour – 0,8-1,5.
Composition of stomach juice and their
properties
• There are 2 types of glands
• The oxyntic (or gastric) glands secrete
hydrochloric acid, pepsinogen, intrinsic factor,
and mucus.
• The pyloric glands secrete mainly mucus. The
main cells (peptic or chief cells) produce non
active enzymes (pepsinogens). There are 7
pepsinogens. They hydrolyzed proteins.
• Optimum pH of its activity is 1,5-2,0. Pepsinogens
whose activity the most in the condition of pH 3,2-3,5
is gastrecsin. In the stomach juice produces lipase
and gelatinize. HCl produce in parietal or oxyntic
cells. pH of it secrete is near 0,8. These processes
need energy of lipids. Mechanism of it production:
Cl- actively transported in the canaliculi, Na+ – from
the canal into cytoplasm. H2O dissociated to H+ and
OH-. H+ actively go into canaliculi in change of K+.
In these processes take place Na+,K+-ATPase. CO2,
which produce in cells act with H+ and syntheses
HCO-. This anion go into the cell in change by Cl-.
Phases of stomach secretion
• Cephalic phase is caused by nervous system. It has
conditional and unconditional reflexes. Conditional
reactions caused by appearance of food, it smell and
other stimulus, which are connect with food.
Unconditional influences is parasympathetic and
beginning from receptors of tongue and other receptors
of the oral cavity. From these receptors impulses pass
through the fibers of n. trigeminus, n. facialis, n.
glossopharyngeus, n. vagus to the medulla oblongata.
Impulses return to stomach by n. vagus. Except neuron
influences this phase has humoral influences – brunch
of n. vagus produce hormone gastrin. These phase is
very short.
Phases of stomach secretion
• Stomach phase
• is depends on the quantity of food, which are
present in stomach. It has vago-vagal reflexes
(by mean of central nerves system) and local –
peripheral reflexes, which are closed in
stomach walls. Duration of these phase is
longer and quantity of juice is much. It has
humoral mechanisms too (production of
gastrin and histamin.
Phases of stomach secretion
• Intestine phase:
• presence of food in the upper portion of small
intestine can cause the stomach to secrete
small amount of gastric juice. This probably
results of gastrin are also released by the
duodenal mucosa in response to distension or
chemical stimuli of the same type as those that
stimulate the stomach gastrin mechanism.
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In norm gastric juice secretion must be
NN
Indexes
Empty
stomach
Basal
secretion
Stimulated
secretion
1.
pH
to 3,5
1,5-2
1,3-1,4
2.
Production of common 10-35
HCl, mmol/L
40-60
80-100
3.
Production of free HCl, 0-20
mmol/L
20-40
65-85
4.
Debit of common HCl, to 1,5
mmol/hour
1,5-5,5
8-14
5.
Debit of
mmol/hour
1-4
6,5-12
free
HCl, to 1