Digestive system

Learning objectives zTo outline the digestive system and metabolism. zTo identify the source of energy. zTo describe the process of digestion and absorption of food. zTo describe energy conversion.

Learning objectives zTo describe the storage of energy. zTo define metabolic rate. zTo describe energy balance of human body. zTo stat the metabolic rate of the liver.

Human’s Nutrition zIngestion zDigestion zAbsorption zAssimilation zEgestion

Ingestion zThe process of food intake  Chewing : Teeth ~ Incisor, canine, premolar & molar Tongue Mouth  Swallowing

Digestion zMechanical( mastication & peristalsis) + Chemical process  solid food  smaller pieces  large molecule  smaller molecules  soluble forms  simple ones

Processes of digestion Food Mouth: teeth, saliva Oesophagus: peristalsis Stomach: gastric juice Intestine: intestinal juice Digested food

Digestion in Mouth cavity zMechanical digestion ~ chewing zChemical digestion ~ salivary amylase ( Starch  maltose) ~ lysozyme (  Pathogenic microbes) ~ Salts ( provide alkaline condition) ~ Mucus ( lubrication) zSwallowing

Digestion in stomach zMechanical ( peristalsis) zChemical ( gastric juice) ~ Pepsin (protein  polypeptides) ~ Renin ( coagulate casinogen) ~ HCl  activator  kills or inhibit bacterial growth  stimulates gastric secretion ~ Mucus ( lubrication)

Digestion in small intestine I zDuodenum (25cm) + Jejunum(2.5m) + ileum (3.6m)  Bile ~ produced by liver ~ contain no enzyme ~ Sodium bicarbonate, bile salts, bile pigments

Digestion in small intestine II  Pancreatic juice ~ produced by pancreas ~ sodium bicarbonate ~ enzymes  amylase  lipase  trysinogen  nuclease

Digestion in small intestine III  Intestinal juice ~ produced in the intestinal wall ~ alkaline mucus ~ enzymes  maltase  amylase  sucrase  peptidase  lactase

Digestion in small intestine IV zMechanical ~ the chyme is mixed with intestinal juices by intestinal movement.  Peristalsis- rhythmic contraction & relaxation of gut wall  Dividing movement

Absorption zNo absorption in mouth & oesophagus zAbsorption of alcohol & water in stomach zAbsorption in small & large intestine

Adaptation for absorption in small intestine zThin surface ~ easier to pass through zTransport vessels ~ current of blood zGreat surface area ~ numerous finger-like cilli & microvilli

Absorption via blood vessels zAmino acids. Monosaccharides, water soluble vitamins, salts & water  Carbohydrates ~ galactose >glucose >fructose ~ by active transport  Amino acids ~ by active transport  vitamins & mineral  water ~ by osmosis

Absorption via lacteal zGlycerines, fatty acids &fat soluble vitamins zAbsorbed through epithelial cell into the lymphatic ducts  superior vena cava  Heart  Different parts of body

Absorption in large intestine zWater & mineral salts  excess water, nutrients & undigested materials  faeces zOthers bacteria ~ produces Vitamin B & K as by- products  Diarrhoea & Constipation

Assimilation of food zCarbohydrate ~ mainly glucose ~ as chief energy source ~ excess glucose converted into glycogen & subcutaneous fat zAmino acids ~ synthesis protein ~ excess not stored but deaminated ~ Amino acid  urea+CO 2 zFats ~ as energy source ~ as structural substances ~ secreted as oil ~ excess stored as adipose tissues

Function of liver zRegulation ~ glucose  glycogen ~ amino acid  urea+CO 2 ~ Fat & oil  glycogen zProduction ~ Heat ~Bile ~Cholesterol ~ Red blood cells zStorage ~ blood & vitamins zElimination of hemoglobin zDetoxification zHomeostasis ~ blood clotting zDefense ~ phagocyte cells

Pancreas zIt is a mixed gland consisting of exocrine and endocrine tissues; zIt is an elongated gland lying in the loop formed by duodenum and the under surface of stomach.

Function of pancreas zExocrine secretion: ~ pancreatic juice ( amylase, maltose, trypsin) zEndocrine secretion ~ insulin: glucose in blood  glycogen in liver;   blood glucose level  lacking of insulin: Diabetes mellitus ~ glucagons: glycogen in liver  glucose in blood   blood glucose level

Balanced diet zIt is a diet contains all the essential nutrients in the correct proportion so as to provide enough energy, mineral salts and vitamins for regulation and protection.

Component of a balanced diet zCarbohydrate (55%) zLipid (<30%) zProtein (15-20%) zWater zRoughage zMineral salt and vitamin