1. Bioenergetics and Digestion

2. We’ll be discussing
Trends and Various Strategies Used by Organisms to Process Food
Process of Digestion in Man
Disorders of the Human Digestive System

3. Core Concepts Nutritional requirements
Animals are heterotrophs that require food for fuel, carbon skeletons, and essential nutrients.
Metabolic rate provides clues to an animal’s bioenergetic strategy.
 Evolutionary adaptations of feeding mechanisms and digestive systems
Diverse feeding adaptations have evolved among animals.
Structural adaptations of digestive systems are often associated with diet.
Symbiotic microorganisms help nourish many vertebrates.
 Overview of food processing
The four main stages of food processing are ingestion, digestion, absorption, and elimination.
Digestion occurs in specialized compartments.
The oral cavity, pharynx, and esophagus initiate food processing.
The stomach stores food and performs preliminary digestion.
The small intestine is the major organ of digestion and absorption.
Reclaiming water is a major function of the large intestine.
Hormones regulate digestion.
Nutrition and disorders of the human digestive system
A healthful diet provides both fuel and building materials.
Nutritional disorders damage health.

4. Keywords absorption alimentary canal amebocytes anorexia bile bolus
brush border
bulimia
cecum
chyme
complete digestive tract
crop
digestion
duodenum
elimination
endocytosis
enzyme
esophagus
essential nutrient
extracellular digestion
filter feeders
gallbladder
gastrovascular cavity
gizzard
heterotroph
ileum
incomplete digestive tract
ingestion
intracellular digestion
jejunum
large intestine
liver
malnutrition
microvilli
minerals
nutrition
obesity
pancreas
peptic ulcers
peristalsis
phagocytosis
pharynx
salivary glands
small intestine
sphincters
stomach
undernutrition
vesicles
villus
vitamins

6. Bioenergetics of an animal
Food
Fuel
C-skeletons
essential nutrients
ATP
resting metabolism
activity
temperature regulation
Excess for biosynthesis
85-90% of energy from food is lost as heat

7. Metabolic rates Metabolism Resting/ Basal Metabolic Rate (BMR)
Anabolism
Catabolism
Resting/ Basal Metabolic Rate (BMR)
energy/unit mass/hr
Size and relative metabolic rate are inversely proportional

8. Do plants have digestive systems?
Pitcher plant – Heliamphora nutans
Sundew– Drosera capensis
Venus fly trap– Dionaea muscipula
Carnivorous plants with primitive digestive systems
Habitats with N-poor soils
Adaptation: occasionally feed on animals
Insect traps
Glands in trap secrete digestive enzymes
Nutrients absorbed by leaves
Flypaper trap – Pinguicula gigantea

9. Evolution of digestion
Different types depending on diet and lifestyle
All must accomplish
Ingestion
Digestion
Mechanical breakdown
Chemical breakdown
Absorption
Elimination
Digestion occurs in specialized compartments

10. Intracellular digestion (evolved in single-celled protists, retained in simplest animals)
Paramecium

11. Intracellular digestion (Protists, Porifera)
SPONGES

12. Extracellular digestion
FUNGI
Sedentary heterotrophs living in or on food supply
Saprotroph/parasites
No internal cavity  release digestive enzymes
Image from

13. Extracellular and intracellular digestion Incomplete digestive system
Image from
Extracellular and intracellular digestion Incomplete digestive system
CNIDARIANS
Hydra
gastrovascular

14. Extracellular and intracellular digestion Incomplete digestive system
PLATYHELMINTHES
Planaria
Extracellular and intracellular digestion Incomplete digestive system

15. Extracellular digestion Animals with complete digestive systems
NEMATODA to VERTEBRATES
Earthworms
Extracellular digestion Animals with complete digestive systems
20 cm long with ~ 100 segments
1st – mouth
Last – anus
Eats its way through soil

16. Feeding adaptations for ingestion
Suspension-feeders
Deposit-feeders
Substrate feeders
Fluid feeders
Bulk feeders
Vertebrate dentition

17. Comparison of vertebrate digestive systems

18. Mammalian digestion General plan
Organs of the GI tract
ACCESSORY DIGESTIVE ORGANS

19. Comparison of mammalian digestive systems (Diet plays an important role in the length and structure)
Esophagus – no sphincter valve, two-way contraction of esophagus muscles
Rumen and reticulum – low partition, intermix, main fermentation <synthesis of vitamins and proteins, breakdown of fibrous feeds> vat teeming with microorganisms (before exposing to gastric juices)
Omasum – filter pump to sort food (absorption)
Abomasum – true stomach (gastric juices)