ch6 nutritions in human

• Process of human nutrition


  1. Food contain large complex molecules

  2. Broken down before our cells use them

  3. Cell membrane differentially permeable

  4. Large complex molecules cannot pass through

  5. Broken down to small soluble molecules

  6. Enter our cells

  7. Food molecules: structurally different form those making up our body

  8. Break them down, use small broken down molecules to build our own molecules
• Main process


  1. Ingestion: food taken in through the mouth

  2. Digestion: broken down to small soluble molecules

  3. Absorption: small soluble molecules enter our circulatory system

  4. Assimilation: absorbed food molecules taken up for metabolism

  5. Egestion: undigested and unabsorbed materials removed from the faeces
• Digestive system


  • Alimentary canal
  • Digestive glands
• Alimentary canal


  • Mouth cavity
  • Pharynx
  • Oesophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Anus
• Digestive glands


  • Salivary glands
  • Liver
  • Pancreas
• Ingestion


  1. Process of chewing food into smaller pieces: mastication

  2. Incisors: biting+cutting food, chisel shaped with sharp edges

  3. Canines: tearing flesh, pointed and curved

  4. Premolar: crushing+grinding food, broad top with cusps, 1-2 root

  5. Molar: grinding+crushing food, broad top with cusps, 2.3 roots

  6. Milk teeth, permanent teeth

  7. 2102, 2123
• Structure of tooth


  • Crown, neck, root
  • Enamel: Outermost layer of crown, Non-living, made up of calcium salts, Hardest tissue of body, Replaced by cementum
  • Dentine: Bone like substance contain large amount of calcium salts, Living tissue contain strands if cytoplasm
  • Pulp cavity: Living cells, blood vessels, nerves fibre
  • Cement: fibres pass into jawbone, fix tooth to the jawbone
• Tooth decay


  1. Healthy tooth with plaque: not painful, plaque formed in tooth, plaque consist of bacteria and food debris

  2. Decay in enamel: not painful, bacteria in plaque break down sugar into acid, acid corrode enamel and make a hole

  3. Decay in dentin: not painful, hole become larger and larger, bacteria and acids reach dentin

  4. Decay in pulp: painful, bacteria and acid reach pulp cavity, acid irritate nerves, bacterial infection result in formation of pus
• Oral care


  • Brush teeth: remove plaque and food debris
  • Use toothpaste with fluoride: strengthen enamel
  • Use dental floss: remove plaque and food debris btw food surface
  • Have dental check-ups at least once a year
  • Obtain enough vitamin D and calcium for forming stronger teeth
  • Eat less surgery and acidic food: increase chance of tooth decay
• Digestion


  1. Physical digestion: Break down into smaller pieces by physical action, Does not damage chemical structure, Increase surface area for digestive juice too act on

  2. Chemical digestion: Chemical reaction, Break down complex molecules to small soluble molecules, Digestive enzymes: Carbohydrases, lipases, proteases, Water, vitamin, minerals do not need to be digested
• Mouth cavity


  1. Chewing: mastication, catalysed saliva

  2. Saliva: Salivary amylase: breakdown starch to maltose, Mucus: stick material binds food particles together + moisten, lubricate food, Water: dissolves soluble substances so that we can taste

  3. Tongue rolls a small mass bolus, swallowed down to oesophagus through pharynx
• Peristalsis


  1. Alimentary canal: epithelium, connective tissue, circular muscle, longitudinal muscle, work together in coordinated way, Contract alternatively in wave like movement, Push the food down, Occur all along alimentary canal

  2. Digestive glands secrets mucus from walls of alimentary canal, lubricate the passage
• Stomach


  1. Churning, gastric juice

  2. Gastric juice: Pepsin: protease, Hydrochloric acid (pH2): acidic medium for action of pepsin, Mucus: protect stomach wall from being digested

  3. Creamy liquid called Chyme

  4. Pyloric sphincter release food little at a time to duodenum
• Small intestine


  1. Emulsification by bile, catalysed by pancreatic juice, enzymes on small intestinal wall

  2. Digestion of food completed in duodenum and ileum

  3. Chyme enters, various secretions released, contraction of muscles in intestinal wall to help mix with digestive juices

  4. Bile: Bile salts: emulsify lipids, Bile pigments: waste products

  5. Pancreatic juice: Pancreatic amylase: carbohydrases, Protease: protien to peptide to amino acid, Sodium hydrogencarbonate: neutralise acidic chyme

  6. Intestinal juice: Slightly alkaline, Contains water, mucus, sodium hydrogencarbonate, Carbohydrases: disaccharides to monosaccharides, Protease: peptide to amino acids
• Absorption


  1. Most food molecules absorbed in small intestine in ileum

  2. Small intestine: very long, 7m in adults, allows sufficient time for complete digestion and absorption

  3. Wall: Circular muscle, Longitudinal muscle, Inner wall highly folded, increase surface area for absorption

  4. Villi: Finger like projection, Lymph vessel called lacteal surrounded by network of capillaries

  5. Epithelium: One cell thick, Cell membrane has a large number of microvilli called brush borders

  6. Absorbed from lumen to capillaries and lacteals through epithelium, By diffusion, osmosis, active transport

  7. Water and Water soluable: Monosaccharides, amino acids, minerals, water soluble vitamins

  8. Lipids and lipid soluble: Fatty acid + glycerol, enter epithelium of willi, recombine to fine lipid droplets, Lipid soluble vitamins, absorbed into lymph
• Adaption of small intestine for absorption

  • Long: Sufficient time to complete digestion + absorption, Inner wall highly folded, Epithelium one cell thick, Lacteal + network of capillaries in villi, Peristalsis
• Absorption in large intestine

  Remains of food moved by peristalsis, Remains of water, minerals, vitamins, absorbed inside blood in colon, Faeces
• pancreatic enzymes are secreted by the pancreas to further breakdown carbohydrates, fats, and proteins.
• hydrochloric acid breaks down proteins into amino acids
• The liver produces bile which helps break down fats during digestion.
• Bile is stored in the gallbladder until needed.
• the stomach is the organ that secretes gastric juice, which contains hydrochloric acid (HCl) to break down food.
• Enzymes produced by the small intestine continue breaking down carbohydrates, fats, and proteins.
• the stomach secretes hydrochloric acid which helps break down proteins into amino acids.
• enzymes such as trypsin, chymotrypsin, carboxypeptidase, and elastase are involved in protein digestion.
• Bacteria in the gut produce enzymes that aid in the digestion of complex carbohydrates.
• lipase is an enzyme that breaks down fat into fatty acids and glycerol.
• Pepsinogen is converted to pepsin in the stomach.
• Trypsinogen is converted to trypsin in the duodenum.
• Vitamins are organic compounds required in small amounts for normal metabolism.
• Vitamins are organic compounds required in small amounts for normal body function.
• Pancreatic enzymes are secreted from the pancreas and enter the duodenum through the pancreatic duct.
• Water-soluble vitamins dissolve in water and include B complex vitamins and Vitamin C.
• Enzymes produced by bacteria in the gut can also contribute to the fermentation process, producing short-chain fatty acids as a result.
• Human digestive system


  1. Mouth cavity

  2. Oesophagus

  3. Stomach

  4. Small intestine

  5. Large intestine

  6. Anus

  
• Mouth cavity


  • Food is chewed to increase the surface area for digestive juices
• Oesophagus


  • Food is pushed down by peristalsis
• Stomach


  • Digestion of proteins begins
• Small intestine


  • Digestion of carbohydrates and lipids is completed
  • Digested food substances and most of the water are absorbed

  
• Large intestine


  • Most of the remaining water is absorbed
  • Faeces are passed out of the body