Published on March 9, 2014
DIGESTIVE ENZYMES AND HORMONES Jessica C. Largado Camille Lee R. Mananggit
Functions of Secretory Glands 1. 2. Secretion of digestive enzymes Production of mucus Lubrication Protection of alimentary tract
A. SALIVARY SECRETION Saliva-mixed secretion of salivary glands MAIN SALIVARY GLANDS Parotid 1. Submaxillary or Mandibular 2. sublingual 3.
Major Types of Secretion 1. Serous secretion- ptyalin or salivary amylase -starch splitting enzyme
Major Types of Secretion 2. Mucus secretion- mucus -for lubrication
B. GASTRIC SECRETION Components: 1. pepsinogen-active form of pepsin -protein digestion 2. mucus- lubricated ingested food -protects mucosa 3. HCO3- protects mucosa against acid and pepsin 4. Intrinsic factor- absorption of Vit B12 5. Rennin- milk coagulation 6. Gastric lipase- hydrolyze fats
Types of Glands 1. 2. Cardiac Gland -secrete mucus Fundic gland -gastric/oxyntic gland
Types of Glands -has five types of cells 1. parietal cells-secrete HCl 2. chief cells or peptic cells-secrete pepsinogen 3.mucous cells-secrete mucus 4. endocrine D cells-secrete somatostatin 5. entero-chromaffin-like cellshistamine
Types of Glands 3. Pyloric gland-has G cells
Types of Glands Cardiac gland Fundic gland
Types of Glands Pyloric gland
Types of Glands
Types of Glands
Stimulation of Acid Secretion Gastrin -from G cells -stimulated by protein products in the stomach 1.
Stimulation of Acid Secretion 2. 3. Acetylcholine -released from cholinergic neurons -stimulates acid production in the same way as gastrin Histamine -released from ECL cells -directly contacts the parietal cells
INHIBITION OF ACID SECRETION Stomach secretes acids at mealtime Antrum contents approaches Ph 2.0 D cells secrete somatostatin Inhibition of gastrin & histamine release Inhibition of acid production
C. Secretion of the Small Intestine 1. Crypt of Lieberkuhn -secrete enterokinase and amylase -has two types of cells 1.Goblet cells - secrete mucus 2. Enterocytes – secrete water and electrolytes
Stimulation of Acid Secretion Brunner’s Gland -duodenal gland -secrete large amount of alkaline mucus in response to 1. tactile or irritating stimuli 2. vagal stimulation 3. GI hormone-secretin
Stimulation of Acid Secretion
Digestive Enzymes 1. 2. Peptidase-split small peptides into AA Four enzymes that split disaccharide into monosaccharide a. sucrase b. maltase c. isomaltase d. lactase 3. Intestinal lipase-split neutral fats into glycerol and FA
HorMones 1. 2. Gastrin- stimulates gastric glands to secrete pepsinogen and hydrochloric acid -presence of peptides and amino acids in gastric lumen Secretin- signals the secretion of sodium bicarbonate in the pancreas -stimulates bile secretion in the liver -acidic pH in the lumen of small intestine
HorMones 3. 4. Cholecystokinin- stimulates the release of digestive enzymes in the pancreas -emptying of bile in the gall bladder -presence of fatty acids and amino acids in the small intestine Gastric Inhibitory Peptide- decrease the stomach churning -slowing the emptying of the stomach -presence of fat and glucose in small intestine
HorMones 5. 6. Motilin- increase the migrating myoelectic component of gastrointestinal motility -secretion is associated with fasting Ghrelin- appears to be a strong stimulant for appetite and feeding -secretion peaks prior to feeding and diminishes with gastric filling
D. EXOCRINE PANCREAS 1. 2. Endocrine-hormone secreting Exocrine- enzyme and bicarbonate secreting parts
Secretion of Sodium Bicarbonate Carbon dioxide combines with water through carbonic anhydrase to form carbonic acid Carbonic acid dissociates into bicarbonate (actively transported into lumen) and hydrogen Hydrogen ion exchanged for sodium ion Sodium ion diffuses into lumen Sodium and bicarbonate attract water, forming bicarbonate solution
Secretion of Pancreatic Enzymes 1. Zymogen granules a. inactive zymogen -attack membranes eg. Proteases b. active zymogen -do not attack membranes eg. Lipase, amylase
Secretion of Pancreatic Enzymes 2. Proteolytic enzymes 1. trypsin 2. chymotrypsin 3. carboxypeptidase 4. ribonucleases 5. deoxyribonuclease
Regulations of Pancreatic Secretion 1. 2. Nervous Regulation Hormonal Regulation Cholecystokinin (CCK) 1. 2. Secretin
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