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Food ingested (Proteins (Proteins enter through the mouth and mechanical…

- - - - The stomach receives proteins as polypeptides which are long chain of amino acids and chemical digestion can occur in the stomach due to gastric pit glands that secrete enzymes for digestion
        
        Cardiac Glands below the LES
        
        Columnar Epithelial cells are found in cardiac glands to protect the epithelium from injury either mechanical or chemical
        
        Mucus gel and Alkaline fluid with Bicarb is secreted to neutralize and protect the stomach
        
        In the lower part of the stomach there are pyloric glands in the antrum
        
        From the antrum, the stomach contents move into the duodenum when the pyloric sphincter is open and gastrin moves with it
        
        duodenum has enzymes and hormones secreted into it for protein digestion
        
        The pancreas secretes proteases that are inactive into the duodenum for majority of protein digestion to occur
        
        Trypsinogen, chymotrpsinogen, procarboxypeptidase, and proelastase are the inactive forms and activated by enterkinase and then activates fellow proteases
        
        Protein absorption takes place in the small intestine and mostly in the duodenum by transporters which can absorb the amino acids and peptides that were broken down from proteins
        
        Single amino acid and peptide transporters can be found to absorb the small broken down protein molecules
        
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        Duodenal secretions
        
        Enterokinase is secreted when food is present by the duodenal mucosa which will allow proteins to become polypeptide chains that are called oligopeptides
        
        Oligopeptides can broken down by peptidases from brush border cells into peptides and amino acids for absorption
        
        Pepsinogen producing cells
        
        Mucus cells
        
        G cells which secrete gastrin for amino acids and peptides
        
        Oxyntic Glands present to secrete acid from cells
        
        Chief cells
        
        Secrete pepsinogen which will be turned into Pepsin by HCL for protein digestion by making proteins into peptides and amino acids
        
        ECL cells
        
        Secrete histamine when gastrin and Ach is present
        
        Mucous neck cells to secrete mucus
        
        Parietal/oxytinic cells
        
        Intrinsic factor made which is a glycoprotein that can adhere to vitamin B for absorption in the small intestine
        
        produces HCL from proton pump and HCO3/Cl exchanger and utilizing carbonic anhydrase
        
        HCl can be stimulated from Acetylcholine, gastrin, and histamine for activation of pepsinogen
- - - - Chemical digestion beings and ends in the small intestine
        
        The liver produces bile that the gallbladder stores and releases bile into the duodenum for the breakdown of fat
        
        bile enters the duodenum and has bile salts which emulsify lipids to increase the action of enzymes on fats, and make cholesterol and phospholipids soluble.
        
        After bile acts on lipids, pancreatic secretions act on triglycerides to break them down into fatty acids and glycerol which will then form micelles
        
        Micelles are important as they can increase transport and absorption through diffusion through brush border cells in the duodenum and jejunum
        
        micelles move into the membrane and repackage them into chylomicrons which will exit the membrane of a cell by exocytosis
        
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        fatty acids at this point can bind to proteins and prevent oil droplet formation
        
        Proteins bind with fatty acids can move products into the smooth ER and golgi for lipid digestion
        
        Unused fatty acids will be moved into the colon to be excreted through the rest of the GI tract
- - - - food now becomes bolus which will go down the esophagus, the lower esophageal sphincter will open, and carbohydrates will not be acted on in the stomach because of too acidic conditions
        
        At the bottom of the stomach, the antrum, the pyloric sphincter will open into the duodenum to allow the stomach contents to move
        
        In the small intestine, exocrine pancreas secretions are active when food is present.
        
        Duodenal secretions are important because they make different large saccharides into monosaccharides with different enzymes from brush border cells
        
        Lactase acts on lactose to make glucose and galactose
        
        Maltase acts on maltose to make glucose and glucose
        
        Sucrase acts on sucrose to make gluoce and fructose
        
        Absorption of carbohydrates take place in the small intestine and mostly in the duodenum and jejunum which have special receptors for certain monosaccharides
        
        Glucose and galactose absorbed through apical SGLT1( Na+glucose transporter) and on the basolateral side a gradient is maintained through secondary active transport from the Na/K Atpase pump. Then these molecules move out of the epithelial cells by facilitated diffusion into the ISF by a GLUT 2 transporter on the basolateral side
        
        The rest of the contents move into the colon of the large intestine when the ileocecal sphincter is opened to be excreted out of the body through the rectum and anus
        
        Fructose is moved throughout the cell only by facilitated ddiffusion and enters the apical membrane bored on GLUT-5 and exits on the basolateral side of the membrane via GLUT-2
        
        Ductal cells secrete Bicarb, secretin, and wants to neutralize acidic chyme for enzyme activity to occur
        
        Acinar cells secrete pancreatic alpha amylases to break down smaller oligosaccharides and diasaccaharides when stimulated by Ach, distension of stomach, and CCK