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Home , Extracellular digestion, Insectivore, Intracellular digestion, Lacteal, Microvillus

Feeding &

Why eat? • Macronutrients Feeding & Digestion – Energy for all our metabolic processes – Monomers to build our polymers 1. 2. Lipids 3. Protein • Micronutrients – Tiny amounts of vital elements & compounds our body cannot adequately synthesize 4. Vitamins 5. Minerals • Hydration 6. Water

Niche: role played in a FEEDING (grazer, predator, • “Eat”: Gr. -phagy; Lt. -vore , etc.)

• Your food may not Some organisms have specialized niches so as to: • increase feeding efficiency wish to be eaten! • reduce • DIET & Optimal model: Need to maximize benefits (energy/nutrients) while minimizing MORPHOLOGY costs (energy expended/risks) • FOOD CAPTURE • MECHANICAL PROCESSING Never give up!

Optimal Foraging Model Optimal Foraging Model • Morphology reflects foraging strategies • Generalist is less limited by rarity of resources • Specialist is more efficient at exploiting a specific resource Generalist

CARNIVORE elephant Optimal foraging strategies: Need to maximize benefits (energy/nutrients) INSECTIVORE while minimizing costs (energy osprey expended / risks) MYRMECOPHAGORE • Tapirs have 40x more meat, but are much harder to find and catch. Specialist So jaguars prefer .

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Bird Beaks Anteater Adaptations • Generalist & specialist bills

• Thick fur • Small eyes • Long claws in front • Long snout • Long barbed tongue • No teeth

FOOD CAPTURE SPECIALIZATIONS Fluid Feeding – Fluid Feeding • Sucking with tube – Suspension & Deposit Feeding – mosquitoes & butterflies • Lapping with brushy tongue – Grazers & Browsers – hummingbirds, fruit – : Ambush & Attraction – bees – Venoms – Tool Use & Team Efforts

Hummingbird tongue Suspension Feeding (Filter Feeding) • Filter food (plankton, small animals, organic particles) suspended in water. • http://www.youtube.com/watch?v=1wpQ8HQEkvE • Filters are hard, soft or even sticky.

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Suspension Feeding (Filter Feeding) • Barnacles: “little shrimps that glue their heads to suspension a rock and catch food with their feet” feeding in baleen whales

Right Whales — “sippers”

suspension • Skim feeding feeding in baleen whales

• Baleen is tough but flexible filter composed of the protein keratin. • The length of the baleen depends upon the feeding style of the whale

Rorquals — “gulpers” Grey Whales — “mud suckers”

• Lunge feeding

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Suspension feeding in fish — gill rakers Suspension Feeding • Raker spacing determines prey size. in extinct – If a has two similar species, they diverge in gill raker spacing. • A filters plankton in a lake – Reducing niche overlap is called resource partitioning or niche divergence.

Two species of shad

Sticky Filters Sticky Filters • Glue of webs • Mucus nets • (stinging cells) of jellyfish. – Larvaceans • Collar cells of – Spoon worms & lug worms

Giant larvacean “house”

Deposit Feeders Grazers & Browsers • : feed on decomposing particles • Grazers: feed on fast growing, abundant, short & associated deposited on/in vegetation (terrestrial grasses; aquatic turf ) sediment/soil swallow & digest organic or encrusting animals material in soil as they burrow. – Slow moving, methodical

Sea cucumber mops – Mouth-parts for cropping or scraping food close to substrate off sediment surface. – Grasses low moisture content: need water to drink • Browsers: feed on taller vegetation (leaves, bark, etc.) – More selective; more mobile to locate patches – Food moisture may be adequate – More anti-herbivore defenses (thorns, toxins, etc.)

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Grazers & Browsers Grazers & Browsers

• Grazers: feed on fast growing, abundant, short vegetation (terrestrial grasses; aquatic turf algae) or encrusting animals – Slow moving, methodical – Mouth-parts for cropping or scraping food close to substrate – Grasses low moisture content: need water to drink • Browsers: feed on taller vegetation (leaves, bark, etc.) – More selective; more mobile to locate patches – Food moisture may be adequate – More anti-herbivore defenses (thorns, toxins, etc.)

Ambush Predators • Crab & trap door , Komodo dragons, lions, Ensnare Prey etc. • Works best if animal has • Bolas spiders snag 'em, cryptic coloration. onycophorans slime 'em.

Toxins Attraction • saliva is used by & • Chemical Lures – bolas spider mimics female moth pheromone • Visual Lures – Fireflies – Snapping turtles – Angler fish

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Inject Toxins (Venom) Neurotoxins Immobilize Prey • Block neurotransmitters that control movement. • Prevent escape and/or harm to predator. • Fangs: spiders or snakes

• Stingers: wasps and scorpions

Tissue-destructive Toxins Team Efforts Digest Prey • Team up to capture larger/faster prey – social canids – lions – orcas

• Scorpions & spiders have external digestion.

• Rattlesnakes consume VERY large prey.

Tool Use Digestion • Galapagos finches, ravens, & Egyptian vultures • The (breakdown) of large food molecules • Chimps & sea otters (polymers) into small organic subunits (monomers). • The monomers may then be used for: § Metabolic fuel (cellular respiration → ATP & heat) or § Subunits to build new polymers

q Hydrolysis is catalyzed by § May be intracellular or extracellular

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Hydrolytic Enzymes Hydrolytic Enzymes • Hydrolysis reactions catalyzed by enzymes • Most plant material is largely – names end with “-ase” • Yet no animal has enzymes that can digest cellulose • Amylase: hydrolyze carbohydrates • Most depend upon • Protease: hydrolyze proteins symbioses with cellulytic protists in • Peptidase: hydrolyze their guts • In turn, the cellulytic protists depend • : hydrolyze lipids upon symbioses with bacteria to produce the actual enzymes

Intracellular Digestion

1. 2. ð food held in Protists, 3. ð vacuole fuses with sponges, filled with digestive enzymes some 4. ð food digested cnidarians 5. ð excytosis of indigestible material

Paramecium

Extracellular Digestion Internal Digestion & Food Processing

1. enzymes secreted into space 1. Ingestion (lumen of digestive tract) – Consuming food 2. ð food broken into small molecules 2. Physical disruption 3. ð absorption by cells lining the – Mastication, dissolution, denaturation, emulsification digestive tract 3. Motility 4. expulsion of indigestible material – Swallowing, peristalsis, segmentation, defecation 4. True digestion – Hydrolysis of polymers into monomers 5. Absorption – Moving nutrients from G.I. Tract into 6. Assimilation – Incorporate nutrient molecules into tissues

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Ingestion for Internal Digestion Ingestion for Internal Digestion 1. Ciliary (or flagellar) motility 1. Ciliary (or flagellar) motility 2. Oral appendages a. Ciliary b. Grasping / Sweeping 3. Protrusable / prehensile structures a. b. Jaws 4. Swallowing a. Ram / Gravity / Lunge / Suction

b. Pharyngeal / Ratcheting jaws Ctenophore irridescent comb rows [ctenes] of ciliated plates c. Lingual for both propulsion & feeding currents https://www.youtube.com/watch?v=GGFrcWD2jYA

Ingestion for Internal Digestion Ingestion for Internal Digestion 2. Oral appendages 3. Protrusable / prehensile structures a. Ciliary a. Pharynx b. Grasping / Sweeping b. Jaws

Ciliated oral tentacles of a spaghetti worm

“Mouth field” feeding appendages of a shrimp

Eversible jawed pharynx of Bloodworm Slingjaw wrasse

https://www.youtube.com/watch?v=mktMxLrU8rA https://www.youtube.com/watch?v=pDU4CQWXaNY

Ingestion for Internal Digestion Ingestion for Internal Digestion 4. Swallowing 4. Swallowing a. Ram / Gravity / Lunge / Suction b. Pharyngeal / Ratcheting jaws

Pharyngeal jaws in a moray eel Disarticulation & Suction feeding by Cichlid independent action of Lunge & gravity swallowing by Blue heron https://www.youtube.com/watch?v=TbGILi8p5Y8 https://www.youtube.com/watch?v=1-p2AI9uTs0 Odontophore in a snail snake jaw bones Suction feeding by Tiger fish https://www.youtube.com/watch? https://www.youtube.com/watch?v=m2lcBaqYK1o v=HP8Ocr3KJho

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Ingestion for Internal Digestion Internal Digestion — Digestive Tracts 4. Swallowing • Epithelial tissue lining a hollow cavity (lumen) c. Lingual • Ridges & wrinkles to increase surface area for absorption • Tongue of most • Usually highly vascularized to transport absorbed materials – Intrinsic muscles — hydrostat – Extrinsic muscles — anchoring Mammalian gut

Chameleon can extend tongue >1½x body length https://www.youtube.com/watch?v=YXbgRU4k3O8

Digestive Tracts Digestive Tracts • Gastrovascular systems (blind guts) • Complete guts – indigestible material regurgitated – Mouth ⇒ Anus

Platyhelminth — Planaria Cnidarian polyp — Hydra

Digestive Tracts Digestive Tracts • Complete guts • Complete guts – Mouth ⇒ Anus – Mouth ⇒ Anus

Echinoderm seastar • Eversible cardiac • Muscular pharynx pushes food through non-muscular gut for external digestion • Free-living roundworms feed on microbes • Pyloric stomach for • Parasitic roundworms feed on host body fluids internal digestion & • No need for much specialization of gut absorption

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Digestive Tracts Digestive Tracts • Complete guts • Complete guts – Mouth ⇒ Anus – Mouth ⇒ Anus

typhlosole

intestine

Annelid • Dorsol typhlosole increases surface area adjacent to dorsal heart vessel grasshopper • Gastric ceca allow fermentation of plant material

Digestive Tracts Digestive Tracts

Insects & Vertebrates — • Gut divisions into • Anus empties into cloaca – common terminal specialized regions chamber for digestive, allows more efficient excretory & reproductive digestion & exploitation systems of more food types • Cloaca empties via vent

Internal Digestion & Food Processing Mastication — 1. Ingestion physical disruption of food particles – Consuming food 2. Physical disruption • Small particles are more easily broken down by – Mastication, dissolution, denaturation, emulsification digestive enzymes 3. Motility – Chewing ↑ Surface to Volume (S/V) Ratio of particles – Swallowing, peristalsis, segmentation, defecation ∴ ↑ exposure to enzymes 4. True digestion – Hydrolysis of polymers into monomers 5. Absorption – Moving nutrients from G.I. Tract into circulatory system 6. Assimilation – Incorporate nutrient molecules into tissues

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Gastric Mills of , ORAL MASTICATION Birds and Earthworms

• Beaks in birds, turtles, & cephalopods • Storage crop leads to grinding gizzard - a muscled sac w/ a hard lining to grind foods w/ sand, pebbles. • Teeth in vertebrates • Mandibles in • Radula in most molluscs

Human Vertebrate Digestive System • Alimentary Canal (humans: 26-foot long tube) Digestive System – Mouth – Pharynx – – gastrointestinal [G.I.] tract (“gut”) • Stomach • • • Accessory Organs – Salivary Glands – & Gall Bladder – Pancreas

Digestion Begins in Mouth Swallowing • Salivary glands – Water & mucus: moisten/lubricate food • Pharynx – Initiate swallowing reflex – Divert food bolus from respiratory tract • Esophagus – uses peristaltic action

• Salivary glands produce Amylase – Enzyme hydrolyzes – Cleans teeth • Saliva also contains mucous, buffers, antibacterials • Slug of mashed food and saliva is a Bolus

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Peristalsis Gut Motility • Peristalsis — waves of involuntary – Esophagus, stomach, small intestines • Segmentation — churning action – Stomach, small intestines • Sphincters — muscular rings that control entry/ exit – Esophageal sphincter – Pyloric sphincter – Anal sphincter Muscular action in the human gut

Stomach • Distensible: stores swallowed food pending further processing. Sealed by sphincters at either end. • Mucosa wrinkled to form rugae that increase surface area • Highly motile. Regulates rate of passage to intestines. • Many leading to gastric glands secreting gastric juice • Masticated food + digestive juices Gastric Juice: A. Goblet cells ➠ alkaline mucus = chyme • Helps protect mucosa from auto-digestion. • Acid in gastric juice B. Parietal cells ➠ hydrochloric acid [HCl] ➠ pH < 2 disinfects the chyme • Disinfects chyme; denatures protein C. Chief cells ➠ pepsinogen ( a weak protease) • Auto-hydrolyzes to form pepsin (stronger protease) D. Other cells produce hormones

Protein Digestion Regulation of Gastric Activity Begins in the Stomach

1. Acid denatures protein in the chyme – Unfolded protein structure more vulnerable to hydrolysis 2. Pepsin hydrolyzes polypeptides into • Gastric and motility stimulated oligopeptide fragments by parasympathetic neurons, intrinsic stretch reflex, gastrin hormone, and 3. Digestion and amino acids in chyme (positive feedback absorption completed in amplification). small intestines • Inhibited by stretch reflex and hormones from intestines, or chyme pH <1.5.

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Digestion Completed in Small Intestine Visceral Digestive Accessory Glands • Chyme enters via the pyloric sphincter. • First segment = : from accessory glands enter via common duct. • First 40% = duodenum + : most digestion and absorption of macro- & micronutrients. • Final 60% = : most absorption/reabsorption of water and salts.

Liver: the biochemistry lab Liver to Gall Bladder: Bile Salts: Emulsifier • Liver produces bile salts & pigments. • Bile is stored & released by Gall Bladder into Small Intestine. • Emulsify: Bile salts break large fat globs into small droplets (detergent action).

Fatty chyme entering the duodenum Cystic duct Common hepatic duct

Gallbladder 3CCK stimulates of wall to contract

4 Bile passes down the Common bile duct 1Chyme with cystic duct and common fat enters bile duct to duodenum duodenum 5 Hepatopancreatic Pancreatic duct sphincter relaxes and bile enters duodenum

2Cells from the intestinal mucosa • Exocrine component — Acini: secrete the hormone cholecystokinin (CCK) – Secrete pancreatic juice. into the bloodstream Pancreas • Bicarbonate to neutralize acid chyme Duodenum Hormonal signals released into • Suite of hydrolytic enzymes bloodstream • Endocrine component — Islets: Bloodstream Stimulation of effector organ – Secrete insulin and glucagon.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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Small Intestine

Absorption enhanced by large surface area & high vascularization: • Lining wrinkled into ridges (plicae) and finger-like protrusions (villi). Pancreas • Surface of mucosal epithelia cells wrinkled into microvilii (brush border). • Core of each villus bears dense capillary beds surrounding a central lacteal • Endocrine component — Islets: (). – Secrete insulin and glucagon. • Capillaries carry absorbed substances to the hepatic portal vein and then to the liver. Lacteal transports to central veins and general circulation.

Small digestion Intestine salivary & pancreatic amylase

Brush Border of microvilli

undigestible

brush border enzymes Microvillus

Carbohydrate Digestion — Summary Protein Digestion — Summary 1. Hydrolysis of (poly-) starts 1. Proteins are denatured by gastric acid in stomach. with salivary amylase. 2. Hydrolysis of exposed polypeptides starts with pepsin in gastric • Minor significance — amylase denatured by gastric acid. juice under acidic pH. 2. Pancreatic amylase in duodenum & jejunum 3. Pancreatic proteases & peptidases, plus brush border hydrolyzes polysaccharides into maltose & maltriose. peptidases in duodenum & jejunum hydrolyze poly-/ oligopeptides into tri-/dipeptides & amino acids. 3. Brush border enzymes hydrolyze tri-/ 4. Brush border transporters absorb tri-/dipeptides & amino into . acids into mucosal epithelia. Intracellular peptidases 4. Brush border transporters absorb monosaccharides hydrolyze tri-/dipeptides into amino acids. Amino acids by active cotransport into hepatic portal vein. absorbed into hepatic portal vein. 5. Insulin dependent: amino acids taken up by liver for 5. Insulin dependent: monosaccharides taken up by liver gluconeogenesis, or circulate as substrate for protein synthesis for glycogenesis, or circulate as energy substrate for glycolysis or lipogenesis.

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Absorption/Assimilation of Lipids Lipid Digestion — Summary 1. & oils are emulsified by bile salts (detergent) in duodenum & jejunum . 2. Pancreatic in duodenum & jejunum hydrolyze into & fatty acids. 3. Monoglycerides & fatty acids, plus , coalesce with bile salts to form micelles. 4. Brush border transporters absorb micelles into mucosal Insert fig. 18.36 epithelia. Intracellular liposynthases condense monoglycerides & fatty acids into new triglycerides. Triglycerides & cholesterol are bound to carrier proteins to form . 5. are absorbed into the lacteal and systemic circulation. Lipoprotein-lipase of vessel endothelia releases fatty acids & glycerol for tissue lipogenesis.

LDLs are Lousy; HDLs are Healthy

Large Intestine Digestion Overview • Final water absorption • Compaction, storage, & excretion of feces – 1/3 bacteria by weight (some make K & B vitamins). – Brown color from bile pigments of RBC breakdown.

Carnivores Have Short Tracts Ruminant herbivores Herbivores Have Long Tracts • Masticated vegetation swallowed into rumen – First of four stomach chambers • Plant material much harder to digest. • Cultures of microbes digest the cellulose and other complex – Aided by cellulytic protists & bacteria carbohydrates – Occasionally regurgitate and rechew cud to aid process • Microbial populations actual food – Pass to other chambers and intestines for digestion & absorption

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Ruminants re-chew a cud. Non-ruminant herbivores Rabbits and other juvenile non-ruminants • Cellulytic protists & bacteria in – Enlarged region of large intestine right after junction with small intestine re-chew by coprophagy • Plant carbs metabolized by microbes into free fatty acids (FFA) • FFAs can be absorbed by large intestine

Digestion in the Horse Purina Mills — Omolene University Non-ruminant herbivores • Similar solution in herbivorous reptiles • Cellulytic protists & bacteria in enlarged colon – Stomach=30% of total gut; colon=60% • Plant carbs metabolized by microbes into volatile free fatty acids (FFA) – FFAs can be absorbed by large intestine • BUT, cellulytic microbes require warm temperatures! – ∴ ectothermic herbivorous reptiles are limited to tropics & deserts

http://www.youtube.com/watch?v=maWXVKI-gq4

Green iguana Green sea turtle

Lengthening Intestine WHAT HAPPENS TO IT ALL? to Meet Metabolic Demands

• House wrens lengthen 22% in winter • lactating • All eat more too

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WHAT HAPPENS TO IT ALL? Fate of Chemical Energy • Stored as – blood sugars – liver & muscle glycogen – body fat • Stored energy used for – 1) metabolism – 2) growth – many insects don't feed as adults – 3) reproduction

Regulation of Energy Metabolism Malnutrition: • Energy reserves: "the cellular imbalance between supply of nutrients – Molecules that and energy and the body's can be oxidized for demand for them to ensure energy are derived growth, maintenance, and specific functions.” from storage molecules — World Health Organization (glycogen, protein, and fat). Stages of malnutrition caused by excessive or • Circulating substrates: Insert fig. 19.2 inadequate intake of – Molecules absorbed nutrients. through small intestine Modified from Olson RE: "Pharmacology of nutrients and carried to the cell and nutritional disease," in for use in cell Principles of Pharmacology, respiration. edited by PL Munson. New York, Munson, Chapman, and Hall, 1995; in Merck Manual of Diagnosis and Therapy, 2004.

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