Ch.6 Nutrition in Human

• Plants make food by themselves - autotrophic nutrition. They are called autotrophs.
• Organisms that can't make their own food - heterotrophic nutrition. They are called heterotrophs.
• There are three types of heterotrophic nutrition, Holozoic nutrition, Saprophytic nutrition, Parasitic nutrition.
• Holozoic : take in complex food and digest inside

  Saprophytic : breakdown food outside & abosrb soluble nutrients (Fungi & bacteria)

  Parasitic : live inside of a body & obtain food from them
• Human take in food which is large and complex molecules. They need to be broke down before use them.
• Food molecules are different from the molecule we need. Therefore, we need to break them down and make up our own molecules.
• Five steps of process of nutrients : Ingestion, Digestion, Absorption, Assimilation, Egestion.
• Digestive system consists of alimentary canal and digestive glands.
• Alimentary canal : mouth cavity, oesophagus, stomach, small intestine, large intestine, anus.
• Digestive glands : salivary glands, liver, pancreas.
• Four types of teeth : Incisors, Canines, Molar, Premolars
• Incisors : one-root, chisel-shaped, biting and cutting food.
• Canine : one root, pointed and curve, tearing flesh
• Premolars : broad top, one/two root(s), crushing and grinding food
• Molars : broad top , two/three tops, crushing and grinding food
• there are two types of teeth - permanent teeth and milk teeth
• dental formula of milk teeth : 2102/2102
• Dental formula of permanent teeth : 2123/2123.
• Enamel : outermost layer, non-living(only)(made of calcium salts), hardeest tissue, replace by cementum and connect the peridontal membrane.
• Dentine : bone-like, made of calcium salts, living tissue
• Pulp cavity : living cells, blood vessels(supply oxygen & nutrients), nerve fibre(detect temperature & pressure)
• Physical digestion is the process of breaking down large molecules into smaller ones. It doesn't change the chemical strucutre but increase the surface area.
• Chemical digestion involves chemical reaction-breaking down large, complex food molecules into small, soluble molecules. (using carbohydrates, Lipases, Proteases)
• Mouth cavity : Chewing and saliva (Chem)

  Stomach : Churning and Gastric juice (Chem)

  Small intestine : Emulsification (bile) and pancreatic juice (chem) and intestinal wall (chem)
• Salivary glands : breakdown of starch to maltose

  Mucus : helps bind fod particles, moisten and lubricates -> more easy to chew and swallowed

  Water : dissolves soluble substances -> taste food
• Swallowing : tongue raise, soft palate move up (prevent entering nasal cavity), larynx rises -> epiglottis covers
• Peristalsis is the process of moving food from the oesophagus to the rectum.
• The wall of the alimentary canal consists of four layers: the innermost epithelium, a layer of connective tissue and two layers of muscles: circular and longitudinal.
• The muscle fibres in the two layers of muscles are arranged in different ways.
• These muscles work together in a coordinated way to push the food along the alimentary canal.
• Longitudinal muscles have fibres arranged along the length of the tube, while circular muscles have fibres arranged in rings around the tube.
• Faeces are brown in colour because of the presence of bile pigments.
• Faeces are temporarily stored in the rectum.
• The process of expelling faeces from the body is called egestion or defaecation.
• When the sphincter relaxes and the muscles of the rectum contract, faeces are pushed out through the anus.
• At the anus, there is a ring of muscles called the anal sphincter.
• Faeces are semi-solid waste containing dietary fibre, bacteria, secretions from the alimentary canal, dead cells from the intestinal wall and a small amount of water.
• The oesophagus contracts alternatively to produce a wave-like movement to push the food down to the stomach, a process known as peristalsis.
• Behind the bolus, Circular muscles contract and longitudinal muscles relax, causing the lumen to become smaller, squeezing the food forward.
• In front of the bolus, Circular muscles relax and longitudinal muscles contract, causing the lumen to become larger, allowing the food to slide through the lumen from the pharynx to the oesophagus.