Gastric juice

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Gastric juice

1. Types of Gastric gland
2. Properties.
3. Composition.
4. Secretion.
5. Factor responsible.
6. Functions.

1. Types of gastric glands : Glands depends upon the situation -

A. Fundic/ main/proper/oxyntic gland : it secrets
1. HCL
2. Mucin
3. Pepsinogen
4. Intrinsic factor

B. Cardic gland : it secrets
1. Mucin
2. Pepsinogen

C. Pylorus gland : it secrets a solution which is rich in mucus and don't contain HCL. It also secret gastrin.

Types of cell of gastric glands : 
1. Chief or peptic cell - it produce Renin, pepsin.
2. Oxyntic or parietal cells - it produce HCL.
3. Neck mucus cells - It produce Mucus, Pepsinogen.
4. Surface epithelial cells - it produce Mucus.
5. Stem cells - it produce G- cell or Daughter cell.
6. G- cells - it produce Gastrin

Naerve supply - Vagus nerve
















2. Properties : 
Volume                   - 1200 - 1500ml/day
Reaction                 - highly acidic
pH                           - 0.9 - 1.2
Specific gravity    - 1.002 - 1.004

3. Composition : 

1. Water - 99.5%

2. Solid - 0.5%...

A. Organic substances :

 a. Enzymes - 
1. Pepsin.
2. Renin.
3. Gastric lipase.
4. Gastric amylase.
5. Gelatinase.
6. Urease.

 b. Other organic substances -
1. Mucus.
2. Intrinsic factor.

 B. Inorganic substances :
1. HCL.
2. Na.
3. Ca.
4. K.
5. Cl.
6. Bicarbonate.
7. Phosphate.
8. Sulfate.

 4. Secretion : 

 Phases of gastric secretion -

 1. Cephalic phase :
- it contributes 33% of total gastric juice.
- it control by the nervous system (vagus nerve).
- it work in both condition ( conditional and unconditional)...
a. Conditional : sight, smell, thought and hearing about food.
b. Unconditional : presence of food in mouth.

 2. Gastric phase :
- it contributes 60% of total gastric juice.
- it control nervous (vagus, local nerve) and hormonal (gastrin).
- it work when bolus come in stomach.

 3. Intestinal phase : 
- it contributes 7% of total gastric juice.
- it control mainly hormonal.
- it stimulate by Gastrin.
- it inhibit by Secretin, Cholecystokinin pancreozymin, Somatostanin, Gastric inhitory peptide, Vaso active intestinal peptide.

 4. Interdigestive phase : 
- it work in between two meals.
- it work only hormonal like gastrin.
Influencing factor : alcohal and caffein.

 Mechanism of secretion of pepsinogen : pepsinogen is synthesized from amino acids in the ribosomes, ribosomes is attach with the endoplasmic reticulum in chief cells. Then pepsinogen granules are packed into zymogen granules by golgi apparatus. When zymogen granules secret in the stomach from chief cells then granules are desolved and pepsinogen is released. Then HCL act on this and convert into pepsin.

 Mechanism of seretion of HCL : CO2 present in ECF and H2O already present in parietal cell. CO2 enter into the parietal cell and combined with H2O and form H2CO3 (carbonic acid) which are the unstable compound so early break into H + HCO3.
        Nacl present in ECF and break down into Na + Cl. Then Cl enter into the canaliculus where are already present H+, then combined H+Cl and form HCL. And HCO3 move out from the cell and combined with Na and form NaHCO3 ( sodium bicarbonate).
5. Factor responsible for gastric juice : 

 1. Stimulator - Gastrin, Histamine, Vagal stimulation.

 2. Inhibitor - Secretin, Gastric inhibitory polypeptide.

 6. Functions of gastric juice :

 1. Digestive function -

 a. Pepsin : it is secret as a pepsinogen which is inactive form of this enzyme, then HCL act on this and convert into pepsin this is active form of this enzyme. Pepsin work on protein and convert into pepteose, peptone and polypeptide.

 b. Gastric lipase : it is a lipolytic enzyme and convert triglycerides into monoglyceride and fatty acids.

 c. Gelatinase : it convert gelatin into peptide.

 d. Gastric amylase : it is a very week enzyme and work on starch.

 e. Renin : it curdless milk.

 2. Haemopoietic function - intrinsic factor secret from stomach and help in the absorption of vitamin B12 . This vitamin responsible for the formation and maturation of R.B.Cs.

 3. Protective function - Gastric juice contain thick mucus which help to prevent
a. Irritation or mechanical injuty.
b. Action of pepsin.
c. Acidity of HCL.

 4. Function of HCL - 
a. It convert Pepsinogen into Pepsin.
b. It kills the bacteria.
c. It stimulate the GIT for secretion of  hormones.
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