GIT secretion
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Saliva, gastric juice, pancreatic juice, hepatic bile, and gallbladder bile are the five major gastrointestinal secretions. Each secretion has a distinct pH, color, composition, producing glands, functions, regulatory mechanisms, and conditions that increase or decrease their production. Saliva aids digestion and protects the oral cavity. Gastric juice contains acids and enzymes to break down food in the stomach. Pancreatic juice and hepatic bile neutralize stomach acids and aid fat digestion. Gallbladder bile emulsifies lipids and neutralizes acid in the small intestine. The secretions are regulated by neural, hormonal, digestive, and physiological factors.
GIT secretion
- 1. GIT Secretions summarization By: Olla BaEissa Secretion saliva Gastric juice Pancreatic juice Hepatic bile Gall bladder bile Amount 1.0 –1.5 L / day 2-3 L / day 1500 ml/ day 500 ml/ day PH pH – 6.8 – 7.2 pH is 1-3 (highly acidic) pH – 7.8 – 8.4 (alkaline ) pH 7.8 – 8.6 color is golden yellow pH 7.0 – 7.4 color is dark green Composition 99.5 % water & 0.5% others includes: Electrolytes, glycoproteins (mucins), antibodies, Enzymes, Lysozyme, Lactoferrin, kallikrein 97 – 99 % water contains inorganic salts, & Others organic components include: mucin, digestive enzymes and hormones. - Water solution of enzymes & electrolytes (primarily HCO3–) - water, bile salts, neutral fats, phospholipids and electrolytes, & Cholesterol and bile pigments from the breakdown of hemoglobin. The glands produce it - the parotid, - the submandibular - the sublingual glands. - Enteroendocrine cells - Chief cells: pepsinogen - Parietal cells: HCl & IF - mucus neck cells: mucus - Pancreas (exocrine secretion) - liver hepatocytes Functions 3- Stimulate taste buds 4- contain IgA 5- Contain Lysozyme and Lactoferrin to protect the mouth from excess bacteria. 6- contain Proline rich proteins to protect tooth enamel 7- Buffering 8- neutralizes gastric acid 9- reduces heart burn 10- Initiate digestion of carbohydrates by salivary amylase 1- Lubricating the mouth and mucus for protection of oral mucosa, mastication & swallowing. 2- Moistening – speech - secrete hormones that regulate stomach functions, peristalsis, and secretions. - initiate digestion of proteins - convers hormons - chemical digestion - provides optimal pH - destroys some bacteria - Stops carbohydrate digestion - secrete a mucus protect the epithelium from chemical insults. - secrete a mucus that coats and lubricates the gastric surface - Neutralizes acidic chyme - Provides optimal pH for pancreatic enzymes in digestion - important for digestion and absorption of fats & fat-soluble vitamins in the small intestine. - Many waste products, including bilirubin, are eliminated from the body by secretion into bile. - acts to some extent as a surfactant - helping to emulsify the lipids in food. - neutralizing any excess stomach acid in the duodenum.
- 2. Regulation of Secretion Sympathetic and parasympathetic are stimulatory 1- Sympathetic and parasympathetic 2- hormonal regulation 1- hormonal regulation CCK & Secretin 1- hormonal regulation choleretics and cholagogues Conditions where saliva is more Chewing, Taste, Smell Conditioned reflex, Nausea Conditions where saliva is less Sleep, Fatigue, Dehydration, fear