Utilisation of Food in man

• Heterotrophic Nutrition or Holozoic nutrition is whereby food is taken into the mouth as a large particle and broken down so as to obtain nutrients.
• neutralization reactions happen when food is moved from the stomach to the intestines.
• Ingestion is process whereby food enters the body through the mouth.
• Digestion is the process whereby large food molecules are broken into smaller pieces so that they could be absorbed via 'villi' within the 'ileum'.
• Absorption is the process whereby small food molecules are transported from the ileum into the bloodstream due to diffusion (high concentration to low concentration).
• Assimilation is the process whereby food molecules are transported to cells of the body so that they can utilize the food molecules and carry out specific functions.
• Egestion is the process whereby all digested materials are removed from the digestive system via the anus.
• The difference between egestion and excretion is that egestion is the removal of all digested materials while excreation is the removal of metabolic waste.
• Metabolic waste is produced when cells break large molecules into smaller molecules (catabolism) or when cells convert small molecules into larger molecules (anabolism)
• metabolic waste= catabolism + anabolism
• example of metabolic waste are: urea, sodium chloride, water, carbon- dioxide, heat
• The difference between physical and chemical digestion is that physical digestion is a process whereby structures within the digestive system move to breakdown large food molecules into smaller pieces while chemical digestion is a process whereby chemicals in the digestive system break down large food molecules into smaller pieces so the enzymes can obtain food nutrients.
• Physical digestion parts: - mouth (teeth, tongue) - stomach (stomach walls, muscles)
• the teeth masticates food into smaller pieces.
• the tongue rolls the masticated food into a ball called bolus so that it can roll into the esophagus via peristalsis.
• There are 2 sets of teeth:- milk teeth/ temporary teeth and - permanent teeth
• There are 4 types of teeth: - incisors, - canines, - premolars, - molars
• incisors are broad, flat, sharp, chisel shape, one root
• incisors are used to cut food molecules.
• canines are long and pointy with one root.
• canines are used for piercing and tearing
• premolars are rough, have 2 cusps (grooves) and two roots
• premolars are used for crushing and grinding
• molars have 3 / 4 cusps and three roots
• molars are used for grinding and crushing
• children have a total of 20 teeth
• adults have a total of 32 teeth
• Dental formula: child- 2.1.2.0 (2/2 incisors, 1/1 canines, 2/2 premolars, 0/0 molars) for 1 side of the mouth up and down. (10)
• Dental formula: adult- 2.1.2.3 (2/2 incisors, 1/1 canines, 2/2 premolars, 3/3 molars) for 1 side of the mouth up and down. (16)