The great Serengeti migration: A quest for minerals anphys-opener-04-0.jpg

Digestive system Functions Organs

Organs of alimentary canal Figure 23.2

Month Esophagus Stomach Small intestine Large intestine Accessory organs Salivary glands, liver, pancreas, gall bladder Figure 23.1

Digestive tracts of various vertebrates

Digestive tracts of invertebrates and vertebrates

Figure 4.1 The composition of the adult human body anphys-fig-04-01-0.jpg

Nutrition Proteins Lipids Carbohydrates Vitamins and minerals

Figure 4.2 Amino acid chemistry (Part 1) anphys-fig-04-02-1.jpg

Figure 4.2 Amino acid chemistry (Part 2) anphys-fig-04-02-2.jpg

Figure 4.3 Fatty acids and triacylglycerols (Part 1) anphys-fig-04-03-1.jpg

Figure 4.3 Fatty acids and triacylglycerols (Part 2) anphys-fig-04-03-2.jpg

Figure 4.4 Carbohydrate chemistry anphys-fig-04-04-0.jpg

Figure 4.5 Vitamin structures anphys-fig-04-05-0.jpg

Examples of feeding adaptations Food chains

Figure 4.6 Some species feed by targeting and subduing individual food items (Part 1) anphys-fig-04-06-1.jpg

Figure 4.7 Specialization of a vertebrate feeding apparatus anphys-fig-04-07-0.jpg

Dentition

Figure 4.8 Specialization of an invertebrate feeding apparatus (Part 1) anphys-fig-04-08-1.jpg

Figure 4.8 Specialization of an invertebrate feeding apparatus (Part 2) anphys-fig-04-08-2.jpg

Figure 4.10 The feeding apparatus of a baleen whale anphys-fig-04-10-0.jpg

Figure 4.12 Reef-building corals of warm waters need light because they are symbiotic with algae (2) anphys-fig-04-12-2.jpg

Figure 4.9 Short food chains deplete energy less than long food chains do anphys-fig-04-09-0.jpg

Digestive systems of insects and crustaceans Crustaceans’ digestive system is separate from the excretory system Insects– the Malpighian tubules – excretory system is connected at the junction of the midgut and hindgut

Figure 4.16 The digestive systems of two types of arthropods: insects and crustaceans anphys-fig-04-16-0.jpg

Figure 23.1

Contractions of the stomach churn chyme. Stomach (continued) Contractions of the stomach churn chyme. Mix chyme with gastric secretions. Push food into intestine. Insert fig. 18.5

Each villus is a fold in the mucosa. Small Intestine Each villus is a fold in the mucosa. Covered with columnar epithelial cells interspersed with goblet cells. Epithelial cells at the tips of villi are exfoliated and replaced by mitosis in crypt of Lieberkuhn. Lamina propria contain lymphocytes, capillaries, and central lacteal. Insert fig. 18.12

Histology of the Alimentary Canal Figure 23.6

Sensors of the GI tract– regulatory mechanisms Mechanoreceptors and chemoreceptors involved Located in the walls of the tract organs Sensors respond to Stretching Osmolarity pH Presence of substrates and end-products

Regulatory mechanisms (2) Receptors initiate reflexes Activate of inhibit glands that secrete digestive juices Stimulate smooth muscle of GI tract Move food along the tract Mix lumen content

Peristalsis and Segmentation Figure 23.3

Adaptation associated with animal’s diet Microbe-assisted digestion –animals in hydrothermal vents-trophosomes Dentition/mouth parts Length of digestive tract Herbivores Carnivores Omnivores Sharks Birds

Microbe-dependent digestion Digestion assisted by microbes

Animals maintain symbiosis with three categories of microbes Heterotrophic microbes Organic compounds of external origin Autotrophic microbes Synthesize organic molecules from inorganic precursors Chemosynthetic Photosynthetic

Figure 4.13 Hydrothermal-vent worms are symbiotic with chemoautotrophic bacteria (Part 1) anphys-fig-04-13-1.jpg

Hydrothermal-vent worms Symbiotic with chemoautotrophic bacteria- trophosomes Worms have not mouth, gut, or anus Food comes from sulfur-oxidizing chemoautotrophic bacteria Organic molecules from bacteria meets nutritional needs Vents- source of H2S

Hydrothermal-vent worms Symbiotic with chemoautotrophic bacteria- trophosomes Worms have not mouth, gut, or anus Food comes from sulfur-oxidizing chemoautotrophic bacteria Organic molecules from bacteria meets nutritional needs Vents- source of H2S

Figure 4.13 Hydrothermal-vent worms are symbiotic with chemoautotrophic bacteria (Part 2) anphys-fig-04-13-2.jpg

Comparison of the digestive tracts of carnivores and herbivores Carnivores- foregut digestion Herbivores Hindgut Foregut

Figure 4.14 The digestive tract of ruminants (Part 1) anphys-fig-04-14-1.jpg

Rumen – first chamber/fermentation occurs Stomach of ruminants Several chambers Rumen – first chamber/fermentation occurs Regurgitate fermenting materials from the rumen into mouth Further grinding and reswallow From rumen reticulum omasum abomasum (true stomach)

Functions of microbes in ruminants Synthesize B vitamins, essential amino acids Fermentative breakdown of compounds that animals cannot digest– cellulose Recycle waste nitrogen from animal metabolism Make ammonia so other microbes can use it as nitrogen source

Figure 4.14 The digestive tract of ruminants (Part 2) anphys-fig-04-14-2.jpg

Figure 4.15 The digestive tracts of two hindgut fermenters anphys-fig-04-15-0.jpg

Hind and midgut fermenters Enlarged cecum/colon Rabbits, horses, zebras, rhinos, apes, elephants Break down of cellulose and carbohydrates Forms short-chain fatty acid B vitamins- not utilized, lost in feces Coprophagy– rabbits eat special soft feces

A comparison of the digestive tracts of a carnivore (coyote) and a herbivore (koala)

Digestion and absorption Digestive enzymes in 3 spatial contexts Intraluminal enzymes Membrane-associated enzymes Intracellular enzymes

Intracellular and extracellular digestion Intraluminal and membrane-associated enzymes are responsible for extracellular digestion Intracellular enzymes are responsible for intracellular digestion Advantages and disadvantages of intra- and extracellular digestions?

Figure 4.17 The stomach of a clam (Part 2) anphys-fig-04-17-2.jpg

Carbohydrate digestion   Organ Substrate Enzyme End product(s)   Oral cavity Starch Sal1vary amylase Maltose Stomach Amylase denatured Lumen of intestine Undigested polysaccharides Pancreatic amylase Brush border of small intestine Disaacharides: maltose Sucrose Lactose Maltase Sucrase Lactase Monosaccharides

Figure 4.19 Absorption of monosaccharides in the vertebrate midgut (Part 2) anphys-fig-04-19-2.jpg

Protein digestion Organ Substrate Enzyme End product(s) Stomach   Organ Substrate Enzyme End product(s)   Stomach Polypeptides Pepsinogen +HCl = pepsin Smaller peptides Lumen of intestine Trypsinogen, chymotrypsinogen (inactive enzymes released from the pancreas, transported to duodenum via pancreatic duct. These enzymes are activated by enterokinase from small intestine to trypsin and chymotrypsin Smaller polypeptides Aminopeptidase, carboxypeptidase Amino acids Brush border of small intestine Dipeptides Dipeptidase

Figure 4.18 The digestion of a short protein by three pancreatic peptidases anphys-fig-04-18-0.jpg

Fat digestion Organ Substrate Enzyme End product(s) Oral cavity   Fat digestion Organ Substrate Enzyme End product(s)   Oral cavity No enzyme to digest fat Stomach Lumen of intestine Fat globules Bile salt from gallbladder lipase Emulsified fat Glycerol, fatty acids Brush border of small intestine

Chemical Digestion: Fats Figure 23.35

Figure 4.19 Absorption of monosaccharides in the vertebrate midgut (Part 1) anphys-fig-04-19-1.jpg

Chemical Digestion: Carbohydrates Carbohydrates absorption: via cotransport with Na+, and facilitated diffusion Enter the capillary bed in the villi Transported to the liver via the hepatic portal vein

Chemical Digestion: Proteins Absorption: similar to carbohydrates Enzymes used: pepsin in the stomach Enzymes acting in the small intestine

Chemical Digestion: Fats Absorption: Diffusion into intestinal cells where they: Combine with proteins and extrude chylomicrons Enter lacteals and are transported to systemic circulation via lymph

Coordination of digestion– neural and endocrine control Controls of digestive activity Extrinsic Central nervous system and autonomic nervous system Intrinsic Hormone-producing cells in stomach and small intestine Distributed via blood and interstitial fluid to target cells

Endocrine control Gastrin Secretin CCK GIP Where? When? Why? How?

Figure 4.20 GI function after a meal is coordinated in part by hormones secreted by cells in the gut anphys-fig-04-20-0.jpg