- Food is one of the basic requirements of all the living organisms. The major components of our food are Carbohydartes,Proteins ,fats.Food provides energy and organic materials for groeth and repair of tissues.The water we take in,plays an important role in the metabolic processes and also prevents dehydration of the body.Bio-macromolecules(proteins,nucleic acids,polysaccharides and lipids)in fiod cannot be utilized by our body in their original form.They have to broken down and converted into simple substanes in the digestive system.The process of conversion of complex food substances to simple adsorbable forms is called DIGESTION..and is carried out by our digetive system by mechanical and biochemical methods.
- Various types of nutrients of food : Nutrients may be organic or inorganic in nature.The organic constituents of nutrients are Carbohydrates,lipids and protiens and vitamins,and the inorganic constituents are Minerals and Water .Carbohydrates ,lipids and proteins are Macronutrients orProximate principles of food because these constitute the energy sources for the production of heat and different organic functions.Minerals,vitamins and water are Micronutrients or Protective principles of food because although these do not provide energy,yet theur deficiencies are related to specific diseases and abnormalities in man.About 21 minerals (eg.Sodium,potassium,calcium,sulphur,phosphorus,magnesium ) or microelements (eg.Iron,iodine,manganese,cobalt,copper,molybenum ) are required in very small amount for human nutrition.
Human Digestive System
- Majority of mammals including human beings, have two sets of teeth during their life,i.e One temporary set & One permanent set. A set of Temporary set or Deciduous teeth repalced by a set of Permanent or Adult teeth. Such type of dentition is called Diphyodont.
- An adult human has 32 permanent teeth which are of 4 different types, namely incisors(I),Canine(C),premolars(PM),molars(M). Such type of dentition is called Heterodont dentition.
- The arrangement of teeth is each half of the upper and lower jaw in the order I,C,PM,M is represented by a dental formula.
- The dental formula of human beings is 2123/2123.
- Out of these 32 teeth, premolars and last molar teeth appear only once i.e are monophyodont and the remaining teeth are diphyodont.
- The hard chewing surface covering of the teeth is made up of Enamel which helps in the Mastication of food . This enamel is the hardest substance of the human body, secreted by ameloblast cell(ectodermal in origin)
Classification acc.to position
Acrodont : Teeth are attached to the free surface or submit of the jaw bone Examples: fishes amphibians and reptiles
Pleurodont: Teeth fixed to lateral surface of jaw ridge Examples fangs of snakes
Thecodont: Embedded in sockets and have well developed roots ( mammals and crocodiles)
Classification according to arrangement of enamel and dentine (more…)