Digestion in the stomach.

Functions of stomachFunctions of stomach

1. Digestive (mechanical treatment, 1. Digestive (mechanical treatment, absorption, evacuation, secretion, depo); absorption, evacuation, secretion, depo);

2. Excretor; 2. Excretor; 3. Incretor.3. Incretor.

Secretor activity of stomachSecretor activity of stomach

Production of stomach juice per day – near 2,5 Production of stomach juice per day – near 2,5 L of juice. Their main components – enzymes, L of juice. Their main components – enzymes, HCl and mucin. pH of morning saliva is HCl and mucin. pH of morning saliva is neutral, after eating – sour – 0,8-1,5.neutral, after eating – sour – 0,8-1,5.

Composition of stomach juice and their propertiesComposition of stomach juice and their properties There are 2 types of glands – the oxyntic (or There are 2 types of glands – the oxyntic (or

gastric) and the pyloric glands. The oxyntic glands gastric) and the pyloric glands. The oxyntic glands secrete hydrochloric acid, pepsinogen, intrinsic secrete hydrochloric acid, pepsinogen, intrinsic factor, and mucus. The pyloric glands secrete factor, and mucus. The pyloric glands secrete mainly mucus. The main cells (peptic or chief mainly mucus. The main cells (peptic or chief cells) produce non active enzymes (pepsinogens). cells) produce non active enzymes (pepsinogens). There are 7 pepsinogens. They hydrolyzed There are 7 pepsinogens. They hydrolyzed proteins.proteins.

Optimum pH of its activity is 1,5-2,0. Pepsinogens Optimum pH of its activity is 1,5-2,0. Pepsinogens whose activity the most in the condition of pH whose activity the most in the condition of pH 3,2-3,5 is gastrecsin. In the stomach juice 3,2-3,5 is gastrecsin. In the stomach juice produces lipase and gelatinese. HCl produce in produces lipase and gelatinese. HCl produce in parietal or oxyntic cells. pH of it secrete is near parietal or oxyntic cells. pH of it secrete is near 0,8. These processes need energy of lipids. 0,8. These processes need energy of lipids. Mechanism of it production: ClMechanism of it production: Cl-- activly activly transported in the canaliculi, Natransported in the canaliculi, Na++ – from the canal – from the canal into cytoplasm. Hinto cytoplasm. H

22O dissopciated to HO dissopciated to H++ and OH and OH--. . HH++ activly go into canaliculi in change of K activly go into canaliculi in change of K++. In . In these processes take plase Nathese processes take plase Na++,K,K++-ATPase. CO-ATPase. CO

22, , which produce in cells act with H+ and syntheses which produce in cells act with H+ and syntheses HCOHCO--. This anion go into the cell in change by Cl. This anion go into the cell in change by Cl--..

Formation of hydrochloric acidFormation of hydrochloric acidstomach

Parietal cellblood

metabolism

se

carboanhydrase

Role of the hRole of the hydrochloric acid in the ydrochloric acid in the digestiondigestion

1. To promote the swell of protein; 1. To promote the swell of protein; 2. To promote the change of pepsinogen in 2. To promote the change of pepsinogen in

pepsins; pepsins; 3. To make optimal conditions for actions 3. To make optimal conditions for actions

of pepsins; of pepsins; 4. To fulfill protective role from bacteria; 4. To fulfill protective role from bacteria; 5. To promote motor and evacuated 5. To promote motor and evacuated

functions of stomach; functions of stomach; 6. To stimulate production of duodinum 6. To stimulate production of duodinum

gormon – secretin.gormon – secretin.

Phases of stomach secretionPhases of stomach secretion Cephalic phase is caused by nervous system. It has Cephalic phase is caused by nervous system. It has

conditional and unconditional reflexes. Conditional conditional and unconditional reflexes. Conditional reactions caused by appearance of food, it smell and reactions caused by appearance of food, it smell and other stimulus, which are connect with food. other stimulus, which are connect with food. Unconditional influences is parasympathetic and Unconditional influences is parasympathetic and beginning from receptors of tongue and other beginning from receptors of tongue and other receptors of the oral cavity. From these receptors receptors of the oral cavity. From these receptors impulses pass through the fibers of n. trigeminus, n. impulses pass through the fibers of n. trigeminus, n. facialis, n. glossopharyngeus, n. vagus to the medulla facialis, n. glossopharyngeus, n. vagus to the medulla oblongata. Impulses return to stomach by n. vagus. oblongata. Impulses return to stomach by n. vagus. Except neuron influences this phase has humoral Except neuron influences this phase has humoral influences – brunch of n. vagus produce gormon influences – brunch of n. vagus produce gormon gastrin. These phase is very short.gastrin. These phase is very short.

Value of gastric juice secretionIn norm gastric juice secretion must be

NNNN

IndexesIndexes Empty Empty stomachstomach

Basal Basal secretionsecretion

Stimulated Stimulated secretionsecretion

1.1. pHpH to 3,5to 3,5 1,5-21,5-2 1,3-1,41,3-1,4

2.2. Production of common Production of common HCl, mmol/L HCl, mmol/L

10-3510-35 40-6040-60 80-10080-100

3.3. Production of free HCl, Production of free HCl, mmol/Lmmol/L

0-200-20 20-4020-40 65-8565-85

4.4. Debit of common HCl, Debit of common HCl, mmol/hourmmol/hour

to 1,5to 1,5 1,5-5,51,5-5,5 8-148-14

5.5. Debit of free HCl, Debit of free HCl, mmol/hourmmol/hour

to 1to 1 1-41-4 6,5-126,5-12

Phases of stomach secretionPhases of stomach secretion Stomach phase is depends on the quantity of food, Stomach phase is depends on the quantity of food,

which are present in stomach. It has vago-vagal which are present in stomach. It has vago-vagal reflexes (by mean of central nerves system) and reflexes (by mean of central nerves system) and local – peripheral reflexes, which are closed in local – peripheral reflexes, which are closed in stomach walls. Duration of these phase is longer stomach walls. Duration of these phase is longer and quantity of juice is much. It has humoral and quantity of juice is much. It has humoral mechanisms too (production of gastrin and mechanisms too (production of gastrin and histamin.histamin.

Intestine phaseIntestine phase: p: presence of food in the upper resence of food in the upper portion of small intestine can cause the stomach to portion of small intestine can cause the stomach to secrete small amount of gastric juice. This secrete small amount of gastric juice. This probably results of gastrin are also released by the probably results of gastrin are also released by the duodenal mucosa in response to distension or duodenal mucosa in response to distension or chemical stimuli of the same type as those that chemical stimuli of the same type as those that stimulate the stomach gastrin mechanism.stimulate the stomach gastrin mechanism.