Transcript Lecture 28. Digestion in intestines

 DIGESTION IN INTESTINES
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 1,5-2,0 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: trypsinogen,
chymotrypsinogen, and
procarboxypolypeptidase.
 Trypsinogen activated by enzymes
enterokinase (produces by the mucous cells
of duodenum).
 In pancreatic juice presents proteolytic
enzymes – elastases, nucleases etc. They
hydrolyzed protein to peptides and
aminoacids.
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.
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, cholecystokininpancreasemin).
 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 cholecystokinin-pancreasemin (increase bile
formation and ejection), secretin, gastrin.
Сomposition of bile
Indexes
Duodenal (А)
Bladder (В)
Liver (С)
Color
Light-yellow
Duck-brown
Gold-yellow
15-20
30-60
Determined of
zond time
1,008-1,012
1,028-1,032
1,008-1,012
рН
7,0-7,5
6,5-7,5
7,5-8,5
Bilirubin mlmol/l
0,5-1,0
1,7-3,4
0,5-1,0
4-5
18-22
4-5
1,3-2,8
5,2-15,6
1,3-2,8
Volume, ml
Density g/сm3
Bile acids g/l
Cholesterin mlmol/l
Composition of bile:
 bilirubin,
 bile acids,
 cholesterol,
 leukocytes,
 some epitheliocytes,
 cristalls of bilirubin,
 calcium.
The role of bile
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1. Neutrolyze 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.
Large intestines
colon ascendens
colon transversum
colon descendens
colon
sigmoideum
caecum
rectum
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
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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.