Digestive Systems
Heterotrophs need food!! Filter feeders-Suspension feeder Substrate feeders Fluid feeders Bulk feeder
What type of Food? Macronutrients (elements): Needed in large quantity….Can you name some? Micronutrients (elements): Can you name some?
Intracellular vs. Extracellular Digestion Intracellular: Food taken into cells by phagocytosis with digestive enzymes being secreted into the phagocytic vesicles Ex: Extracellular: digestion in the lumen (opening) of digestive system; nutrients are transferred to the blood or body fluid Ex:
One opening primitive digestive systems Planaria
Simple Tube Digestive Systems Nematode
Compartmentalized Digestive System Horse
Digestion: Mechanical Oral Cavity food torn my mouth to increase surface area Movement by tongue Stomach Smooth muscles of stomach contract to mix food with gastric juices Wave like contractions
Digestion Oral Cavity (carbohydrate digestion only) Pharynx Esophogus Salivary glands secrete salivary amylase Mucous helps to moisten food Pharynx Esophogus No digestion or absorption occurs Stomach (protein digestion only) Chief cells secrete pepsinogen Goblet cells secrete mucus Perietal cells secrete HCl Mixture of food and gastric juices called acid chyme
More Digestion Small Intestine Mucosa cells secrete Peptidases (proteases) Glycosidases Lactase Pancreas secretes into Duodenum of Small Intestine Sodium bicarbonate Lipase Amylase Trypsin Gall Bladder Secretes bile through bile duct
Digestion and Absorption In mammals, absorption of nutrients occurs in the small intestine
Villi of small intestine
Absorption Small Intestine Large Intestine Villi and microvilli absorb nutrients and transport into blood vessels and lymph Jejunum and illeum Large Intestine Main function is absorption of water, minerals and important vitamins Synthesis of vitamin K also takes place
Hormones regulate digestion Gastrin: stimulates HCl secretion in the stomach Secretin: stimulates pancreas to secrete bicarbonate Cholecystokinin (CCK) stimulates contractions of the gall bladder Insulin: lowers blood sugar Many gut hormones also in brain: CCK induces feeling of satiety (feeling full)