Download Composition and properties of pancreatic juice

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Physiology of digestion.
Normal Physiology
AS. Tolokova T.I.
Common characteristic of the mouth
cavity digestion
• 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.
• 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. 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
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.
Quantity, composition and
properties of saliva
• 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.
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Mechanism of saliva
forming
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.
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Role of saliva in vitality
of human
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.
Formation of saliva
• 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-Th-4. 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
• 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.
• Mediator of parasympathetic nerve
system – acetylcholine – stimulate Mcholinoreceptors
of
baso-lateral
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
Functions of stomach
• 1. Digestive (mechanical treatment,
absorption, evacuation, secretion,
depo);
• 2. Excretor;
• 3. Incretor.
Secretor 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) and the pyloric
glands. The oxyntic 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
gelatinese. 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- activly
transported in the canaliculi, Na+ – from the
canal into cytoplasm. H2O dissopciated to H+
and OH-. H+ activly go into canaliculi in
change of K+. In these processes take plase
Na+,K+-ATPase. CO2, which produce in cells
act with H+ and syntheses HCO-. This anion
go into the cell in change by Cl-.
Formation of
hydrochloric acid
stomach
Parietal cell
blood
metabolism
carboanhydrase
se
Role of the hydrochloric acid
in the digestion
• 1. To promote the swell of protein;
• 2. To promote the change of pepsinogen in
pepsins;
• 3. To make optimal conditions for actions of
pepsins;
• 4. To fulfill protective role from bacteria;
• 5. To promote motor and evacuated functions
of stomach;
• 6. To stimulate production of duodinum
gormon – secretin.
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
gormon gastrin. These phase is very short.
• Value of gastric juice secretion
• In norm gastric juice secretion must be
N
N
Indexes
Empty
stomach
Basal
secretion
Stimulated
secretion
1.
pH
to 3,5
1,5-2
1,3-1,4
2.
Production
common
mmol/L
40-60
80-100
3.
Production of free 0-20
HCl, mmol/L
20-40
65-85
4.
Debit of common to 1,5
HCl, mmol/hour
1,5-5,5
8-14
5.
Debit of free HCl, to 1
mmol/hour
1-4
6,5-12
of 10-35
HCl,
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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.
• 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.
Role of pancreas in the digestive system
• There are two secretor functions of
pancreas – external and internal. The
external secretor function of pancreas
means that exsogenic cells of pancreas
and ducts cells produce pancreatic
juice. It helps to hydrolyzed protein to
peptides
and
amino
acids,
carbohydrates to monosaccharides,
lipids to the fat acids and glycerin. It
neutralizes acidic chymus, which come
from stomach.
• Internal secretor function of pancreas
is production of hormones (insulin,
glucagons, somatostatin).
Composition and properties of
pancreatic juice
Quantity of pancreatic juice per day is 1,52,0 L. Reaction of it – pH = 8,0-8,5. It
consists of a big quantity of hydro
carbonates. It has near 10 % of protein –
enzymes, which are act on protein, lipids
and carbohydrates. According to that
there are 3 groups of enzymes:
proteolytic
•
lipolytic
•
amilolytic
Proteolytic enzymes
• Proteolytic enzymes secreted in the inactive
enzymatically form. The more important of them
are trypsinogen, chymotrypsinogen, and
procarboxypolypeptidase. Trypsinogen activated
by enzymes enterokinase (produces by the mucous
cells of duodenum).
• After activation tripsinogen has name – tripsin.
This enzyme is very active. It also activates
chemotripsinogen to form chemotripsin, and
procarboxypolypeptidase is activated to the form
carboxypolypeptidase in a similar manner.
• In pancreatic juice presents proteolytic enzymes –
elastases, nucleases etc. They hydrolyzed protein
to peptides and aminoacids.
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Lipolytic and amylolytic
enzymes
The main enzymes for fat digestion (lipolytic
enzymes) are pancreatic lipase, which is capable of
hydrolyzing neutral fat into fatty acids and
monoglycerides; cholesterol esterase, which causes
hydrolysis of cholesterol esters; and phospholipase,
which splits fatty acids from phospholipids.
• Lipolytic enzymes ejected in active (pancreatic lipase,
muntinase) and inactive conditions (prophospholipase
A).
• The pancreatic digestive enzyme for carbohydrates
(amilolytic
enzyme)
is
alpha-amylase,
which
hydrolyzes starches, glykogen, and most other
carbohydrates
(except
cellulose)
to
form
disaccharides and a few trisaccharides.
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Regulation of pancreas secretion
There are 3 phases of pancreatic
secretion:
cephalic,
stomach
and
intestine.
• The 1 stage caused by nervous influences.
N. vagus realizes this effect by helps of
conditioned and unconditioned reflexes.
Secretion begins after 1-2 minutes of
food. Juice consists of enzymes, small
quantity of water and ions. Sympathetic
influences have a trophy role.
• During the 2 phase there are two kinds of
influences: nervous and humoral (gastrin
from stomach).
• The 3 phase caused by chyme contents.
The main is humoral factors (secretin,
cholecystokinin-pancreasemin).
• Secretin stimulates production of a big
quantity of juice with a high concentration
of hydrocarbonates and a small quantity
of enzymes in ducts cells. CKP stimulates
production of a less quantity of juice with
a big concentration of enzymes in acinars
cells.
• Secretion of pancreatic juice stimulates
also
by
vaso-intestinal
polypeptide,
serotonine, insulin, bombesin, sustantio P
calcium ions, and salts of bile acids.
• Secretion of pancreatic juice inhibits by
glukagon, calcitonin, somatostatin. During
dreams, hart physical and mental activity,
pain secretion inhibits too.
Bile production and bile
secretoin
Secretion of bile occur all time and increase by
influences of bile acids, cholecystokininpancreasemin, secretin.
• Bile secretion in the duodenum depends from
take food (minerals water, HCl, fatty acids
increase bile formation).
• It depends of nervus vagus (increase bile
formation) and humoral influences –
concentration
of
cholecystokininpancreasemin (increase bile formation and
ejection), secretin, gastrin.
Composition of bile:
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bilirubin,
bile acids,
cholesterol,
leukocytes,
some epitheliocytes,
cristalls of bilirubin,
calcium.
The role of bile
• 1. Neutralize the stomach acid;
• 2. Inhibit the act of stomach proteases;
• 3. Increase the activity of pancreatic lipase;
• 4. Emulsificates the lipids by help of bile
acids actions;
• 5. Bile acids help stabilizing of emulsion;
• 6. Increase the absorption of fatty acids,
carrotin, vitamins K, D, E;
• 7. Increase tone and motor function of
intestines (more duodenum and large
intestine);
• 8. Decrease the activity of intestine micro
flora;
• 9. Take place of enzymes fixation on the
intestines surface.
Composition and properties of
intestine juice
• Composition of intestine juice:
• mucine, enzymes – peptidase, saccharase,
maltase, lactase, lipase, phosphatase,
nuclease; immunoglobulins; ions; leukocytes;
epitheliocytes (200 g per day).
• pH of intestine juice is 7,5-8,0; production
per day – near 1,8-2,5 L.
• Functions:
ending hydrolyses of all
nutritive substances; protective of mucus
wall; support of chyme in fluid condition;
formed of base reaction of intestine
contents.
Increase secretion: parasympathetic
nerves, secretine, and glucagons.
Digestion in the large
intestine
• Composition of intestine juice: mucus,
epithelial cells, and small quantity of
enzymes (peptidase, lipase, nuclease,
phosphatase).
Functions:
protective from mechanical,
• chemical irritations;
• formed of base reaction of intestine
contents.
Role of the micro flora
of large intestine
• 1. Ending decompose of all nutritive substances,
which are do not digested in small intestines.
• 2. Synthesis of some vitamins – of B group,
vitamin K.
• 3. Take place in metabolic processes.
• 4. Stimulates absorption of water and amino
acids.
• 5. Inactivate enzymes of small intestines.
• 6. Forms normal reaction in large intestine.
• 7. Decompose organic substances of chyme.
• 8. Have protective role to the pathogenic
microorganisms.