2. Digestion All animals are heterotrophs
Different modes of feeding evolved
Modes of feeding (structure-function) can be used as an evolutionary evidence
Compartmentalization

4. Intracellular vs. Extracellular
Intracellular- occurs within food vacuoles
E.g. food vacuoles in Paramecium, amoebocytes of sponge
Extracellular- occurs within specialized compartments
Incomplete vs. complete

5. Incomplete
A single opening is present for both entrance of food and exit of wastes
Gastrovascular cavity of Cnidarians
Gastrodermis- has specialized cells that secrete digestive enzymes
Hydrolysis of macromolecules is intracellular

6. Incomplete
Obelia sp.

7. Complete Opening of food is different from exit of waste materials
Specialized regions of the alimentary canal
Complexity varies in each phylum
Extracellular hydrolysis of food

8. Complete
Bos taurus

9. Modes of feeding Herbivore Carnivore Omnivore Dentition
Alimentary canal

10. Modes of Feeding Suspension feeders Substrate feeders Fluid feeders
Bulk feeders

11. Modes of Feeding

12. Symbiotic Relationship
Vertebrates acquired symbiotic relationship with microscopic organisms in processing food
E.g. Ruminants, Humans, termites

13. Four Main Stages of Food Processing
Ingestion
Large oral cavity
Digestion
Mechanical vs. Chemical
Absorption
Elimination

14. Digestion in Humans Primary organs of digestion
Mouth, pharynx, esophagus, stomach, small intestine, large intestine
Accessory glands of digestion
Salivary glands, pancreas, liver, gall bladder

15. Digestion in Humans Mouth- functions: ingestion and digestion
Digestion begins in the Oral Cavity
Mechanical and Chemical digestion
Salivary amylase- breaks down polysaccharide and glycogen
Saliva- also fxns as antibacterial agent and neutralizes acidity of foods

16. Pharynx Upper portion of the throat Where air and digested food meet
Digested ball (bolus) of food enters
Epiglottis- acts as a seal to prevent food from entering the air passages

17. Esophagus Upper portion- striated muscle Lower portion- smooth muscle
Connects the pharynx to the stomach
Peristalsis
Goblet cells- specialized cells that lines the esophagus
Release mucus that covers the bolus

18. Peristalsis
Wave-like motion responsible for the movement of digested food in the alimentary canal

19. Stomach Stores and digests food Cardiac sphincter- prevents backflow
Pyloric sphincter- regulates entrance of acidic chyme to the small intestine
Secretes digestive juice
Mixed with food through churning of the stomach through smooth muscle contractions

20. Stomach Chief cells- secretes pepsinogen Parietal cells- secrete HCl
HCl- disrupts the extracellular matrix of plant and animal cell
Pepsin- active form of pepsinogen
Hydrolyzes proteins
Works best in an acidic environment

21. Stomach Stomach lining is protected product- acid chyme
First, pepsinogen is only activated when secreted into the lumen due to the action of the acidic HCl (pepsinogen activation-positive feedback)
Secondly, presence of goblet cells that secrete mucus
product- acid chyme

22. Stomach

23. Small Intestine Major organ of digestion and absorption
Longest section of the alimentary canal
Divided into three sections:duodenum, jejunum, ileum
Duodenum- site of mixing of acidic chyme and other digestive juices (digestion)
Jejunum and Ileum- absorption

24. Small Intestine Carbohydrate digestion Protein Digestion
Nucleic Acid Digestion
Fatty Acid Digestion

25. Carbohydrate digestion
Starch, glycogen and other polysaccharides that were digested in the mouth is further digested
Pancreatic amylase
Maltase- splits maltose into its glucose units
Disaccharides- absorbed by intestinal epithelium

26. Protein digestion
Trypsin and Chymotrypsin- breakdown large polypeptide chain like pepsin
Dipeptidase- split small peptides
Carboxypeptidase- breakdown polypeptides in its carboxyl end
Aminopeptidase- breakdown peptidase in its nitrogenous end
Enteropeptidase- activates pancreatic enzymes

27. Protein digestion Intestinal enzymes- aminopeptidase, enteropeptidase
Pancreatic enzymes- Trypsinogen, Procarboxypeptidase, Chymotrypsinogen
Enteropeptidase- activates Trypsinogen
Trypsin- activates Procarboxypeptidase, Chymotrypsinogen

28. Nucleic Acid Digestion
Nucleases- hydrolyze nucleic acids
Exonucleases- hydrolyze nucleic acids on its terminal
Endonucleases- hydrolyze nucleic acids within
Other enzymes hydrolyze the nucleotides into its components

29. Fatty acid digestion
Bile salts- emulsify undigested fats in the duodenum
Emulsification- inc SA of fat molecules
Lipase- digests fat molecules

30. Absorption Villus- folds found in the small intestine
Microvillus- microscopic fingerlike projections that increases the absorption of materials
Each villus is connected to a capillary (BV) network and lacteals(Lymphatic system)

31. Transport of nutrients
Passive Diffusion
Active transport
Nutrients that were absorbed are transformed into what the body needs
Chylomicron- small globule that is a combination of fats, cholesterol, coated with proteins

32. Hormones that regulate digestion
Gastrin-stimulated by gastric juices
Inhibited by low pH
stimulates secretion of gastric juice
Enterogastrones- group of enzymes found in the duodenum
Cholecystokinin (CCK)- stimulated by fats and amino acids
Stimulates gall bladder to release bile
Secretin- stimulated by the acidic chyme
Stimulates pancreas to release bicarbonates
If chyme is rich in fats, it stimulates the duodenum to release other enzymes to slows down digestion in the stomach

33. Large Intestine Also called the colon
Cecum – small pouch that has different fxns
Appendix- small cecum found in man
Rectum- portion of the large intestine that temporarily stores feces
Main fxn of colon is to reabsorb water
Feces- waste that was formed after digestion
Compactness depends on water that was reabsorbed

34. Large Intestine Intestinal Bacteria- common example is E. coli
Have mutualistic relationship with host
Generate methane or hydrogen sulfide
Some produce vitamins that are needed by the body

35. Nutrition Nutritionally adequate diet composed of:
fuel (chemical energy)
organic raw materials (carbon skeletons)
essential nutrients (substances the animal cannot make)

36. Balancing the fuel Homeostatic mechanism balances the animal’s fuel
ATPs that were produced are budgeted depending on the energy requirements
Fats have the highest amount of ATP
Glucose conversion is an example of homeostatic mechanism

37. Caloric Imbalance Undernourishment Overnourishment Malnourishment
Calorie deficiency
Overnourishment
Excessive calorie intake- results to obesity
Malnourishment
Deficient in any essential nutrients

38. Essential Nutrients Essential Amino Acids Essential Fatty Acids
Vitamins
Minerals

39. Essential Amino Acids
Tryptophan, methionine, Valine, Threonine, Phenylalanine, Leucine, Isoleucine, Lysine, Histidine (infants)
Deficiency in one of these may
result into protein deficiency

40. Essential Fatty Acids
Essential Fatty Acids belong to the unsaturated fatty acid groups
An example is linoleic acid
Deficiencies are rare

41. Vitamins
Organic molecules that are required relatively in small amount
Two types:
Water-soluble
B vits, C
Fat-soluble
A, D, E, K

42. Minerals Inorganic nutrients that are required in small amounts
E.g. Calcium, Phosphorous, Sodium, etc.

43. Balance diet what enters= what leaves
It is easier to take in calories in the body than to burn it
The food pyramid serves
as a guide in the kind
of foods that should be
taken in