消化和吸收(英文版)

1、Main processes of mammalian nutrition,Ingestion Digestion Absorption Assimilation Egestion,Digestion,Absorption,Egestion,Next,Back,Main processes of mammalian nutrition,Ingestion Digestion Absorption Assimilation Egestion,Digestion,Absorption,Egestion,Next,Back,Ingestion,is the intake of food into t

2、he alimentary canal relevant organs: teeth relevant processes: swallowing peristalsis,Next,Back,Ingestion II,is the intake of food into the alimentary canal relevant organs: teeth relevant processes: swallowing peristalsis,Back,Next,incisor,canine,premolar,molar,Digestion,is the breaking down of foo

3、d into molecules small enough to be absorbed into the body relevant organs mouth and teeth alimentary canal stomach duodenum,Back,Next,Absorption,is the movement of digested, soluble and simple molecules from the gut through the wall into the body (Contd) relevant processes diffusion active transpor

4、t relevant structures,Back,Next,Assimilation,is the uptake & utilisation of absorbed food molecules by all body cells fate of the absorbed food glucose energy production amino acids building up body materials fats energy reserve roles of liver in assimilation,Back,Next,Egestion,is the removal of und

5、igested and unwanted food materials from the alimentary canal relevant structures abnormal cases: diarrhoea constipation,Back,Next,Egestion II,is the removal of undigested and unwanted food materials from the alimentary canal relevant structures abnormal cases: diarrhoea constipation,Next,Back,Teeth

6、,structure of a tooth enamel dentine pulp cavity type dentition,Next,Back,Enamel,Dentine,Pulp Cavity,Jaw Bone,Cement,Nerve & blood vessel,Crown,Neck,Root,Teeth II,structure of a tooth enamel dentine pulp cavity type dentition,Crown,Neck,Root,Enamel,Dentine,Pulp Cavity,Jaw Bone,Cement,Nerve & blood v

7、essel,Next,Back,Enamel,outermost non-living hardest layer made up of calcium phosphate calcium fluoride organic matter,Next,Back,Dentine,middle layer hard, bone like (softer than enamel),Next,Back,Pulp Cavity,innermost layer living cells, blood vessels and nerve blood vessels: oxygen and nutrient ne

8、rves: sensitive to stimuli temperature pressure,Next,Back,Type of Teeth,Next,Back,Dentition,dental formula of a human type of teeth on one side only upper jaw lower jaw milk teeth: permanent teeth:,2120 2120,2123 2123,Next,Back,20,32,premolar,molar,canine,incisor,Tooth Decay,caused by the chemical a

9、ctions of bacteria in plaque plaque is a sticky, invisible film on the teeth surface bacteria turns sugars into acids acids dissolve the enamel and dentine,Next,Back,Tooth Decay,caused by the chemical actions of bacteria in plaque plaque is a sticky, invisible film on the teeth surface bacteria turn

10、s sugars into acids acids dissolve the enamel and dentine irritation on the nerve, cause toothache,Next,Back,How to prevent tooth decay,good brushing habits using appropriate cleaning materials avoiding sugary food having a balanced diet having regular dental check-up,Next,Back,Alimentary Canal,a tu

11、be from mouth to anus is modified into different structures digestive system = alimentary canal + associated,alimentary canal,associated glands,Next,Back,Alimentary Canal,a tube from mouth to anus is modified into different structures digestive system = alimentary canal + associated glands sequence

12、of the structures,oesophagus,stomach,duodenum,ileum,caecum,appendix,colon,rectum,anus,Salivary gland,Gastric gland,Pancreas,Liver,Intestinal gland,Next,Back,alimentary canal,associated glands,Swallowing,tongue raises pushing the bolus to the back bolus pushes the soft palate upwards epiglottis lower

13、s and covers the trachea bolus enters the oesophagus,Next,Back,Peristalsis,food is moved along the canal by rhythmic contraction and relaxation of two muscles circular muscle longitudinal muscle demonstration,Peristalsis,Next,Back,Oesophagus,Digestion II,only small molecules can pass through the wal

14、l of intestine food are usually composed of large molecules food should be digested before absorption physical methods chemical methods,Next,Back,Physical Digestion,Teeth Stomach Bile salt,by churning by emulsifying action in duodenum by,cutting,chewing,grinding,biting,tearing,Next,Back,Chemical Dig

15、estion,involved the change of the chemical structures of food e.g. this involves digestive enzymes no digestion on: water, glucose, simple sugars, minerals, vitamins,Starch,maltose,maltose,maltose,maltose,Next,Back,amylase,Mouth,saliva is a digestive juice consisting of amylase mucus water it is sli

16、ghtly alkaline,Next,Back,Stomach,cardiac sphincter action of proteases action of hydrochloric acid provide acidic medium for proteases pyloric sphincter,Next,Back,protease,Duodenum,pancreatic juice amylase, proteases, lipases bile colour, composition, no enzymatic property intestinal juice carbohydr

17、ases, proteases,Next,Back,Caecum,Colon & Rectum,no enzyme secretion in omnivores and carnivores specific function in herbivores micro-organisms cellulase weakness,Next,Back,Absorption II,take place in ileum starts at stomach / duodenum villus,Next,Back,Villus,finger like projections increase S.A./V

18、one cell thick many blood vessels central lacteal,villus,lacteal,Blood vessels,epithelium,Next,Back,Transport of absorbed food,lumen,Back,epithelium,blood capillaries,hepatic portal vein,liver,hepatic vein,vena cava,heart (general circulation),Next,Water soluble food,Fat soluble food,lumen,epitheliu

19、m,lacteal,Lymph vessel,vena cava,heart (general circulation),Assimilation II,fate of absorbed food substances glucose amino acids fats roles of liver,Next,Back,Fate of glucose,for releasing energy excess glucose will be stored as glycogen fats storage site liver muscle,Next,Back,Fate of amino acids,

20、for making new cells and tissues excess amino acids will be deaminated product: urea site of excretion: kidney,Next,Back,Fate of fats,for formation of cell membranes excess fats will be stored fats storage site adipose tissue,Next,Back,Roles of liver,regulating blood glucose level storing glycogen s

21、toring iron and vitamins breaking down excess amino acids,Next,Back,Diarrhoea,Causes: (1) bacterial infection (2) eating poisonous substances Consequences: (1) quick movement of intestine (2) food passes along the canal quickly (3) less water absorbed (4) watery faeces produced,Next,Back,Constipation,Causes: eating too less dietary fibres eating too less fresh fruit Consequences: (1) slow movement of intestine (2) food passes along the canal slowly (3) much water absorbed (4) hard, dried