digestive enzymes and hormones
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DIGESTIVE ENZYMES AND DIGESTIVE ENZYMES AND HORMONES
Jessica C. Largado
Camille Lee R. Mananggit
Functions of SecretoryGlands
1. Secretion of digestive enzymes
2. Production of mucus
Lubrication
Protection of alimentary tract Protection of alimentary tract
A. SALIVARY SECRETION
Saliva-mixed secretion of salivary glands
MAIN SALIVARY GLANDSMAIN SALIVARY GLANDS
1. Parotid
2. Submaxillary or Mandibular
3. sublingual
Sublingual gland
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. Cardiac Gland
-secrete mucus
2. Fundic gland
-gastric/oxyntic gland-gastric/oxyntic gland
Types of Glands
-has five types of cells
1. parietal cells-secrete HCl
2. chief cells or peptic cells-secrete pepsinogenpepsinogen
3.mucous cells-secrete mucus
4. endocrine D cells-secrete somatostatin
5. entero-chromaffin-like cells-histamine
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
1. Gastrin
-from G cells
-stimulated by
protein products inprotein products in
the stomach
Stimulation of Acid Secretion
2. Acetylcholine
-released from cholinergic neurons
-stimulates acid production in the same way as gastrin
3. 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
Stomach secretes acids at mealtime
Antrum contents approaches Ph 2.0
D cells secrete somatostatin
Inhibition of gastrin & histamine release
Inhibition of acid production
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
mucusmucus
2. Enterocytes – secrete
water and electrolytes
Stimulation of Acid Secretion
Brunner’s Gland
-duodenal gland
-secrete large amount of alkaline mucus in response toresponse to
1. tactile or irritating stimuli
2. vagal stimulation
3. GI hormone-secretin
Stimulation of Acid Secretion
Digestive Enzymes
1. Peptidase-split small peptides into AA
2. Four enzymes that split disaccharide into monosaccharide
a. sucrase
b. maltaseb. maltase
c. isomaltase
d. lactase
3. Intestinal lipase-split neutral fats into glycerol and FA
HorMones
1. Gastrin- stimulates gastric glands to secrete pepsinogen and hydrochloric acid
-presence of peptides and amino acids in gastric lumenin gastric lumen
2. 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. Cholecystokinin- stimulates the release of digestive enzymes in the pancreas
-emptying of bile in the gall bladder
-presence of fatty acids and amino -presence of fatty acids and amino acids in the small intestine
4. Gastric Inhibitory Peptide- decrease the stomach churning
-slowing the emptying of the stomach
-presence of fat and glucose in small intestine
HorMones
5. Motilin- increase the migrating myoelecticcomponent of gastrointestinal motility
-secretion is associated with fasting
6. Ghrelin- appears to be a strong stimulant for 6. 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. Endocrine-hormone secreting
2. Exocrine- enzyme and bicarbonate secreting partsparts
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 membranesb. active zymogen -do not attack membranes
eg. Lipase, amylase
Secretion of Pancreatic Enzymes
2. Proteolytic enzymes
1. trypsin
2. chymotrypsin
3. carboxypeptidase3. carboxypeptidase
4. ribonucleases
5. deoxyribonuclease
Regulations of Pancreatic Secretion
1. Nervous Regulation
2. Hormonal Regulation
1. Cholecystokinin (CCK)
2. Secretin2. Secretin
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