2. Bile juice A complex green fluid produced by the liver, stored in the gall bladder, It contains no chemical enzymes but two important substances for digestion: 1. Sodium hydrogen carbonate - help to neutralize the acid chyme from the stomach and so create a more neutral pH for the enzymes of the small intestine 2. Bile salts - They emulsify fats into minute droplets - This is a physical digestion which increases the surface area for pancreatic lipase to act on

3. Pancreatic juice - for digestion and hormone (insulin) secretion 1 Mineral salts (NaHCO 3 ) - helps to neutralize the acid chyme from the stomach and to provide an optimum pH for the pancreatic enzymes to function Intralobular duct Acinar cells Cellular structure of pancreas showing intralobular ducts

4. 2. Proteases trypsinogen  trypsin enterokinase (from intestine) Proteins  peptides trypsin Chemotrypsinogen  chemotrypsin trypsin Proteins  peptides chemotrypsin Small peptides  amino acids carboxypeptidase

5. 3. Pancreatic amylase -completes the digestion of starch into maltose 4. Lipase -hydrolyses fats into fatty acids and glycerol 5. Nuclease -changes nucleic acids into nucleotides

6. Intestinal juice Brunner's glands secrete mucus and sodium hydrogen carbonate Enzymes are produced by the breakdown of cells at the tips of the villi 1. Mucus – lubricate and prevent autolysis 2. Mineral salts (NaHCO 3 ) - produced by the Brunner’s glands to neutralize the acid chyme and provide a suitable pH for intestinal enzymes

7. 3. Proteases (erepsin) - convert peptides into smaller peptides and amino acids 4. Enterokinase - activates trypsinogen into trypsin 5. Nucleotidase - converts nucleotides into pentose sugars, phosphoric acid and organic bases 6. Carbohydrases - consisting of amylase, maltase, lactase, and sucrase, etc., to complete the digestion of sugars into simple sugars

8. Lining of ileum TS of ileum showing villi

9. 15.4.5 Absorption and assimilation Absorption by diffusion and active transport Other factors: glucose & amino acids absorption seem to be linked to Na + across the epithelium; Ca ++ absorption requires vitamin D

10. A large surface area is achieved by: 1. It is very long, e.g. 6 m in man, 45 m in cattle 2. Its walls are folded to provide large internal projections 3. It has many finger-like villi 4. The epithelial cells possess microvilli (brush- border) In addition, the epithelium is only one cell thick which provides a very short distance for diffusion and active transport

13. Glucose, amino acids, vitamins, minerals & water are small enough to enter the capillaries Fatty acids, glycerol & small droplets of oil are too big and they enter the lacteal

14. Absorption of digested substances Simple sugars and amino acids go into blood capillaries which join to the hepatic portal vein going into the liver for regulation.

15. Assimilation: Simple sugars & amino acids go to the liver via the hepatic portal vein Fatty acids & glycerol recombine to form very tiny oils before going into lacteal, then through lymphatic vessels, fats enter the blood vessels for transport throughout the body

16. Liver  hepatic vein  heart  blood circulation

17. On reaching the liver, excess glucose will be converted into glycogen and stored in liver & muscles; OR changed to fat & stored under the skin Amino acids: form proteins for growth & repair; excess cannot be stored but deaminated in the liver

18. Functions of the liver 1. Stores glycogen, converting back to glucose when necessary to maintain a constant blood glucose level: glucose glycogen 2. Deamination of excess amino acids 3. Secretes bile for emulsifying fats; Provides an alkaline medium for enzymes in the small intestine

19. 4. Stores fat soluble vitamins: A, D & E Stores Fe from break down of haemoglobin & form new red blood cells 5. Synthesizes of plasma proteins

20. 15.4.6 Water reabsorption in the large intestine Most of the water drunk by man is absorbed by the small intestine Water from the digestive secretions (about 10 litres) is absorbed mainly in the ileum while the large intestine is responsible for reabsorbing the remainder

21. Bacteria in the large intestine synthesize vitamin K and is absorbed by the large intestine together with water & some minerals Excess calcium and iron salts are actively transported from the blood into the large intestine for removal with the faeces

22. 15.4.7 Elimination (Egestion) Faeces consist of indigestible food, residual material from bile, bacteria, cells sloughed off the intestinal wall and some water Mucus is secreted by the rectum for lubrication & binding faeces together Defaecation through the anus is a reflex action in baby but voluntary as baby gets older Faeces: mostly egested materials except cholesterol & bile pigments which are excretory products

23. Adaptations to particular diets Herbivorous adaptations of mammals, e.g. deer 1. A horny pad replaces the upper incisors & canines 2. Diastema - a gap to separate newly nibbled food from those chewing at the back Skull of deer

24. Dental formula of a sheep : 0033 3123 3. Cheek teeth with ridged surfaces because of differential wearing of enamel and dentine

25. 4. Jaws can move vertically & laterally - for more efficient grinding by teeth 5. Teeth have open roots - teeth grow continuously throughout life to replace wearing by constant grinding activity 6. Stomach is divided into a number of chambers with micro-organisms to secreted cellulase for the digestion of cellulose (ruminants). Regurgitation of food from stomach to mouth before passing into the remaining stomach compartments 7. The alimentary canal is relatively long because the digestion of plant material is difficult

27. Digestion of cellulose by microorganisms Micro-organisms must be kept separate from the gut so as to avoid the action of digestive enzymes, to provide long enough time for the break down of cellulose and a suitable pH for these micro- organisms In ruminants, e.g. cattle, sheep & deer - four chambers: rumen, reticulum, omasum, abomasum - food first enters the first two chambers (rumen & reticulum) to carry out extracellular digestion of cellulose by cellulase secreted by microorganisms

28. Products of digestion are either absorbed by walls of the rumen & reticulum or micro-organisms which are later digested A symbiotic relationship: - mammal gets the products of cellulose break down - Microorganisms get food supply & a warm, sheltered environment - After some hours, the ruminant regurgitates the food into the mouth and thoroughly chews it (chewing the cud)

29. When re-swallowed, food enters the omasum & abomasum ( true stomach) where the usual process of protein digestion in acid condition takes place - In rabbits and horse, the caecum & appendix are much enlarged and accommodate micro- organisms - Absorption of digested food takes place through the walls of the caecum - The yield is improved by re-swallowing of the faeces (coprophagy or refection)

30. Carnivorous adaptations of mammals Food is chiefly meat which is a more 'nutritional' than plant food. Adaptations concern modifications to the jaw & its dentition: 1. Incisors are sharp and are used for nipping & biting

31. 2. Canines are long & pointed; used for killing prey and tearing flesh from body 3. Carnassial teeth are particularly large for crushing bones 4. Teeth of upper jaw tend to overlap those of the lower jaw for slicing meat like two blades of a pair of scissors

32. 5. Jaw muscles are well developed & powerful to grip prey firmly & crushing bones 6. No lateral jaw movement which might lead to dislocation of the jaw 7. Vertical movement of the jaw is large to allow a wide gap for capturing & killing prey 8. The alimentary canal is short, i.e. meat is relatively easy to be digested

33. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores

34. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Incisors sharp, chisel-shaped for cutting or gnawing (bite until off)

35. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Incisors sharp, chisel-shaped for cutting or gnawing (bite until off) Incisors sharp, sometimes pointed, for nipping (to hold) & biting

36. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Incisors sharp, chisel-shaped for cutting or gnawing (bite until off) Incisors sharp, sometimes pointed, for nipping (to hold) & biting Upper incisors sometimes absent

37. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Incisors sharp, chisel-shaped for cutting or gnawing (bite until off) Incisors sharp, sometimes pointed, for nipping (to hold) & biting Upper incisors sometimes absent …never absent

38. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Incisors sharp, chisel-shaped for cutting or gnawing (bite until off) Incisors sharp, sometimes pointed, for nipping (to hold) & biting Upper incisors sometimes absent …never absent Canines, if present, small & incisor-like

39. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Incisors sharp, chisel-shaped for cutting or gnawing (bite until off) Incisors sharp, sometimes pointed, for nipping (to hold) & biting Upper incisors sometimes absent …never absent Canines, if present, small & incisor-like Canines long & pointed for piercing & tearing

40. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Incisors sharp, chisel-shaped for cutting or gnawing (bite until off) Incisors sharp, sometimes pointed, for nipping (to hold) & biting Upper incisors sometimes absent …never absent Canines, if present, small & incisor-like Canines long & pointed for piercing & tearing Diastema present

41. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Incisors sharp, chisel-shaped for cutting or gnawing (bite until off) Incisors sharp, sometimes pointed, for nipping (to hold) & biting Upper incisors sometimes absent …never absent Canines, if present, small & incisor-like Canines long & pointed for piercing & tearing Diastema present…absent

42. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Incisors sharp, chisel-shaped for cutting or gnawing (bite until off) Incisors sharp, sometimes pointed, for nipping (to hold) & biting Upper incisors sometimes absent …never absent Canines, if present, small & incisor-like Canines long & pointed for piercing & tearing Diastema present…absent Molars & premolars flattened with ridges of enamel for grinding food

43. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Incisors sharp, chisel-shaped for cutting or gnawing (bite until off) Incisors sharp, sometimes pointed, for nipping (to hold) & biting Upper incisors sometimes absent …never absent Canines, if present, small & incisor-like Canines long & pointed for piercing & tearing Diastema present…absent Molars & premolars flattened with ridges of enamel for grinding food …have pointed cusps for shearing food

44. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Carnassial teeth absent

45. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Carnassial teeth absentCarnassial teeth: last upper premolars & first molars

46. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Carnassial teeth absentCarnassial teeth: last upper premolars & first molars Open pulp cavity for continuous teeth growth to compensate for wearing

47. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Carnassial teeth absentCarnassial teeth: last upper premolars & first molars Open pulp cavity for continuous teeth growth to compensate for wearing Closed cavity with no growth when grow to full size

48. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Carnassial teeth absentCarnassial teeth: last upper premolars & first molars Open pulp cavity for continuous teeth growth to compensate for wearing Closed cavity with no growth when grow to full size Teeth of upper jaw meet those of lower jaw end on to allow grinding of food

49. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Carnassial teeth absentCarnassial teeth: last upper premolars & first molars Open pulp cavity for continuous teeth growth to compensate for wearing Closed cavity with no growth when grow to full size Teeth of upper jaw meet those of lower jaw end on to allow grinding of food Teeth of upper jaw slide past outside of lower jaw: shear food

50. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Carnassial teeth absentCarnassial teeth: last upper premolars & first molars Open pulp cavity for continuous teeth growth to compensate for wearing Closed cavity with no growth when grow to full size Teeth of upper jaw meet those of lower jaw end on to allow grinding of food Teeth of upper jaw slide past outside of lower jaw: shear food Lateral movement of lower jaw aids grinding of food

51. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Carnassial teeth absentCarnassial teeth: last upper premolars & first molars Open pulp cavity for continuous teeth growth to compensate for wearing Closed cavity with no growth when grow to full size Teeth of upper jaw meet those of lower jaw end on to allow grinding of food Teeth of upper jaw slide past outside of lower jaw: shear food Lateral movement of lower jaw aids grinding of food No such movement to avoid dislocation of the lower jaw

52. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Jaw muscles relatively small

53. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Jaw muscles relatively small….relatively large

54. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Jaw muscles relatively small….relatively large Less well developed processes for muscle attachment

55. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Jaw muscles relatively small….relatively large Less well developed processes for muscle attachment Well developed ….

56. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Jaw muscles relatively small….relatively large Less well developed processes for muscle attachment Well developed …. Specialized stomach/caecum & appendix to accommodate symbiotic cellulose digesting micro-organisms

57. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Jaw muscles relatively small….relatively large Less well developed processes for muscle attachment Well developed …. Specialized stomach/caecum & appendix to accommodate symbiotic cellulose digesting micro-organisms No such adaptation; Caecum & appendix small

58. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Jaw muscles relatively small….relatively large Less well developed processes for muscle attachment Well developed …. Specialized stomach/caecum & appendix to accommodate symbiotic cellulose digesting micro-organisms No such adaptation; Caecum & appendix small Relatively long alimentary canal

59. Comparison of herbivorous and carnivorous adaptations in mammals HerbivoresCarnivores Jaw muscles relatively small….relatively large Less well developed processes for muscle attachment Well developed …. Specialized stomach/caecum & appendix to accommodate symbiotic cellulose digesting micro-organisms No such adaptation; Caecum & appendix small Relatively long alimentary canal …short alimentary canal

60. TABLE 15.5. SUMMARY OF DIGESTION - see p.297 of text book 15.5 Nervous and hormonal control of secretions - not required in syllabus Carnivorous plants All carnivorous plants are autotrophic but live in soils which are deficient in nitrogen, in cold places with slow decomposition of humus, or in places where leaching is common. Parasites Endoparasites: parasites live inside host’s body Ectoparasites: parasites live outside host’s body

61. Parasites show some or all of the following features: They 1 have agents for penetration of the host 2 have a means of attachment to the host 3 have protection against the host’s immune responses 4 show degeneration of unnecessary organs 5 produce many eggs, seeds or spores 6 have a vector or intermediate host 7 produce resistant stages to overcome the period away from host

62. rostellum hook sucker immature proglottis Tapeworm 1. Structure of a tapeworm flat, long, ribbon like, with many ( 1000 ) segments head with hooks & suckers for attachment onto the host’s intestinal wall each segment contains both male & female reproductive organs (bisexual) for self-fertilization 2. Life cycle Primary host - man; Secondary host - pig, for dispersal & infection

63. 3. Adaptation of tapeworm to the parasitic mode of life in the ileum hooks & suckers for attaching itself onto the intestinal wall of host reproductive organs are well developed; bisexual for self-fertilization numerous eggs are produced to increase the chances of survival of the species

64. no digestive system is needed; absorption of digested food by diffusion through the body surface which is long & flattened to increase the surface area for absorption of digested food can undergo anaerobic (no O 2 ) respiration in the intestine body is covered by a thick cuticle and secretes anti-enzymes to protect itself against the digestive juice of host

65. 4. Effect on host host loses weight & becomes weak because tapeworm absorbs his digested food hooks & suckers damage the intestinal wall of host 5. Means to get rid of tapeworm take in drugs pork should be inspected by government before selling; pork should be thoroughly cooked before eating good sewage system so that pigs do not get in contact with human faeces

66. Saprophytes saprophytes obtain food from dead organic matter, e.g. bacteria and fungi Mucor is a bread mould (fungus) which depends on bread for food; hyphae: filaments mycelium: colony of filaments

67. Nutrition - hyphae go into bread; produce digestive enzymes to break down complex organic substances in bread into simple soluble compounds for absorption Extracellular digestion: digestion outside the cell Importance of saprophytism: dead organisms are broken down to recycle materials

68. Symbionts Examples of symbiosis: 1. Lichen - an association between an alga and a fungus Alga receives protection, anchorage, water and minerals from the fungus Fungus receives food made by the alga through photosynthesis

69. 2. Hydra-Chlorella symbiosis Chlorella (unicellular green algae) in endoderm of hydra. They photosynthesize and make maltose for hydra. Endosymbiosis: inside the cells of the partner

70. 3. Mycorrhizas - an association between roots of higher plants with fungi Fungus receives carbohydrates from plant Higher plant receives inorganic nutrients from fungus Root of pine tree Hyphae of fungus

71. Gut symbionts Protozoans and bacteria living in the gut receive food and protection. They synthesize their own vitamins, especially vitamins K & B, and any excess is made available to the host animal.

72. In termites, protozoans producing cellulase which is essential for the digestion of wood. Many herbivorous mammals have an enlarged caecum and appendix to hold large masses of plant tissue which is digested by the cellulase secreted by these symbionts. In ruminants, the rumen houses a great variety of symbionts than the caecum and they can achieve a more complete breakdown of cellulose. Further more, these symbionts provide a source of protein when they die and pass into the gut.

73. Symbiosis and the nitrogen cycle Nitrogen fixation by leguminous plants in their root nodules provides about 100 million tonnes of nitrogen per year. This association provides bacteria with carbon source and plants with nitrate.