DIGESTIVE SYSTEM P2 L12 Flashcards
EXPLAIN THE Digestion in the duodenum
- From the stomach a prepared for further digestion chymus passes into the duodenum. Enzymes, acting here, are produced mainly in pancreatic gland (pancreas).
EXPLAIN THE Composition of pancreatic juice
- Organic compounds – the most significant of which are enzymes.
- Inorganic substances – ions, bases (mainly hydrocarbonates).
- Water
- - The quantity of pancreatic juice is up to 2.0 liters per 24 hours; its pH is 7.8-8.4. That means that pancreatic juice medium is alkaline, it is the most alkaline fluid in the body. The combination of high alkalinity with activity of pancreatic enzymes makes this juice extremely aggressive. If the intestinal mucosa is damaged, pancreatic juice is able within a few hours to form a perforation in the intestinal wall, which results in passage of digestive system contents into the abdominal cavity and development of peritonitis. Peritonitis is always a direct threat to life.
EXPLAIN THE Enzymes of pancreatic juice
- Proteases.
- Trypsin and its inactive form trypsinogen.
- Chymotrypsin and chemotrypsinogen.
- Carboxypeptidases, elastases, phospholipases and their inactive forms procarboxypeptidases, proelastases, prophospholipases.
- Nucleases, ribonucleases and others.
- Enterokinase. - Lipases.
- Amylase, maltase.
- - In the absence of food most proteases are secreted in an inactive form to prevent self-digestion of intestinal mucosa
EXPLAIN THE triggers a chain of proteases’ activation
At food a particularly large quantity of enterokinase secretes, which triggers a chain of proteases’ activation:
-enterokinaze → trypsinogen → trypsin → chemotrypsinogen → chymotrypsin → other proteases → carboxypeptidase, elastase, phospholipase.
explain the pancreatic juice enzymes :
Function
( poteases , amylase and maltase , lipase )
- Basic pancreatic proteases are trypsin and chymotrypsin, which break down internal peptide linkages
- Lipases break down fats.
- Amylase and maltase break down carbohydrates. Amylase of the pancreas is much more active than salivary amylase and is called α-amylase. It can break down polysaccharides not only into disaccharide but even into monosaccharides
- -NB!-Enzymes on fats and on carbohydrates are secreted directly in their active form because even in the absence of food they cannot damage the mucosa.
explain why Enzymes on fats and on carbohydrates are secreted directly in their active form ?
- Enzymes on fats and on carbohydrates are secreted directly in their active form because even in the absence of food they cannot damage the mucosa.
-Any cell membrane has a bilipid structure in which proteins-receptors are embedded
-Every molecule of a bilipid layer has a hydrophilic end (attaching a water molecule) and a hydrophobic (water-repulsive) end.
1-Hydrophilic ends are directed outwards, for example, they contact with external cellular environment
2-Hydrophobic ends serve as a contact place of two layers of the bilipid membrane and are directed inwards.
— Thus, each cell turns out to be covered outside with a layer of water. Lipases of digestive juices are not able to penetrate through this layer of water and therefore cannot break down the bilipid membrane layer of mucous cells. There are no carbohydrates on the outer surface of cells. That is why lipase, amylase, maltase are secreted right away in their active state.
explain why proteases are secreted in an inactive
- proteases are secreted in an inactive state and are activated only by ingestion of food. Because in the absence of food proteases would break down protein-receptors of mucous cells. Only exogenous alcohols can dissolve the outer aqueous layer of cells.
- -Therefore, excessive consumption of alcohol under the action of lipase results in destruction of bilipid layer of mucous cells in the digestive system that promotes the development of mucosal erosions which may later develop into ulcers and ulcers may develop into cancer.
- proteases are secreted in an inactive state and are activated only by ingestion of food. Because in the absence of food proteases would break down protein-receptors of mucous cells. Only exogenous alcohols can dissolve the outer aqueous layer of cells.
what is Great value in duodenal digestion
- Great value in duodenal digestion is played by bile. It is secreted by the liver. The amount of bile is up to 2.0 liters per 24 hours, its рН is 7.0 – 8.0.
Functions of the bile
- It emulsifies fats.
-Emulsification is passage of fat into a state of microscopic droplets Thus the surface area dramatically increases, thus increasing the contact area with the lipases and speed of fat breakdown.
-But emulsification is not breaking down; during emulsification fat does not lose its polymeric structure of triglycerides. - It neutralizes acidic gastric juice reaction. Pancreatic enzymes are active only in an alkaline medium.
- It dissolves fat hydrolysis products.
- It promotes their absorption.
- It activates enzyme of the pancreas and the intestines.
Not only enterokinase but the bile as well activates pancreatic enzymes. - It stimulates motor and secretory activity of the intestines.
- It activates bile-forming (choleresis) and bile secretion (cholekinesis).
- It has a bacteriostatic effect
- It facilitates absorption of fat-soluble vitamins.
explain Digestion in the small intestine and in the large intestine
- small intestine : food enters the small intestine, which length is up to 5 m. Digestion in the small intestine does not fundamentally differ from that in the duodenum. Everything is digested. That is why we do not discuss it in detail.
- large intestine: The final part of the digestive tract is the colon. Only 5% of digestion takes place in the large intestine. Here mainly water absorption takes place. Complete breaking down of food is due to enzymes which passed with the chymus from previous digestive parts. Here food left-over contains a large number of toxic products which have not undergone absorption in the upper intestine
what is Ilya Mechnikov discovers
- offered to resect a larger part of the colon upon the delivery of a child. This position was, of course, wrong. Because, in spite of low intensity of digestion and high concentrations of toxins
Classification of colonic microflora
1- Symbiontic:
- 1Lactic,
- 2bifidum bacteria,
- 3 bacteroids
- Symbiosis is a mutually beneficial coexistence, close collaboration, joint vital activity of two different species of living creatures.
2-Potentially pathogenic:
- 1 Escherichia coli,
- 2 streptococci,
- 3 staphylococci,
- 4 sporeforming anaerobes
- There is no pathogenic microflora in a normal intestine. Pathogenic microflora is, for example, vibrio cholera or dysenteric amoeba. In the norm here they are not met.
- potentially pathogenic microflora has a negative influence on the macroorganism and under certain conditions can cause inflammation, ulcers, such devastating disorders as cancer, sepsis. But in the norm the value of symbiontic microflora is significantly greater than the risks from the presence of potentially pathogenic microflora.
explain the Value of symbiontic microflora
1- It suppresses potentially pathogenic microflora.: It occupies the spatial and food substrate, not allowing potentially pathogenic flora to multiply intensively. In addition, it carries out a biochemical suppression – secretes a variety of bacteriostatic substances
2-It immunizes the macroorganism : . Symbiontic flora is foreign for the macroorganism which fights against it, shows its immune responses.
3-It digests cellulose: . In human digestive system no enzymes are secreted for dietary fibres – a raw carbohydrate which in large quantities contains in vegetables, brown bread.
4-It produces vitamin K. : Food contains extremely low quantities of this vitamin. It is necessary for the synthesis of haemostatic enzymes (which stop bleeding) as well as for absorption of Ca2+. Calcium, in its turn, provides many vital processes in the body. It is enough to recall its role in polarizing and depolarizing processes of excitable tissues, especially cardiomyocytes
explain the Theories of hunger and thirst
-Hunger describes those sensations that promote attainment of minimal energy needs while thirst represents sensations that promote attainment of minimal hydration needs
– we can describes what if the body rich in energy or poor in energy or full only by looking at the hormon
level in the body bcs these hormons will send a signal to the part in the brain that’s reasonable for detramaining that we are hungry or not which is the ( hypothalamus )
—-there is 3 hormones’ will be produced to control the hunger and thirst.
- glucose :
1- in rich of energy body the will release a hormon that called insulin
for storing the rich amount of the glucose and block the receptor of the hypothalamus therefor inhibiting the body of taking more energy bcs is already rich in energy
2- in the poor of energy body the insulin will not be produced , so there is nothing will block the receptor of the hypothalamus and inhibit the hunger
-lipids
1-in rich of energy body the will release a hormon that called leptin
for storing the rich amount of the glucose and block the receptor of the hypothalamus therefor inhibiting the body of taking more energy bcs is already rich in energy
2-in the poor of energy body the leptin will not be produced , so there is nothing will block the receptor of the hypothalamus and inhibit the hunger
-Ghrelin (stomach hormon or hunger hormon )
1- its only produced with small amounts in stomach when the stomach is empty
to send a signal to the hypothalamus that’s the body poor in energy
Composation of gastric juice
- The quantity of gastric juice is up to 2,0 liters per 24 hours. its composed of 4 substance 1- water 2-HCL 3-Mucus 4-Enzymes : 4.1-Pepsin, its inactive form – pepsinogen; 4.2-Gastricsin, a variety of pepsin; 4.3-Chemosin (rennin) 4.4-Gelatinase; 4.5-Lipase
