Digestion in Mouth

Human Digestion  in  Mouth

Mechanical digestion: Mouth cavity  is  the  chamber  just  inside  the  mouth  in  which  food  is  chewed. During cher,ving  the  muscular tongue  moves food  around  the  mouth  and  mixes  and  moistens it with saliva. The  tongue  posseses  taste  buds  that contain  receptors  sensitive  to  sweet, salty,  sour  and bitter sunstances.  A simple  (inborn)  or conditioned  (learned)  reflex results in  stimulation  of  the  salivary glands to  secrete  saliva.  The eye  and  the  olfactory  (smell) receptors  in  the  nose  are  also  important receptors  in  triggering  reflexes that  bring  about salivation.

Chemical digestion: Digestion of food  begins  immediately  after the  ingestion.  But little  is  digested  in  the
mouth, because  food  remains  in  the  mouth for  a short  time.  In  the  mouth, the  food  is  also mixed with saliva  (  about  1.5 dm3  of saliva produced daily)  produced  by three  pairs  of salivary glands whose ducts
lead  into  the  mouth.

Role of saliva  in  digestion:
i. Water  and  mucin of saliva  lubricates  and  softens  the  food.
ii.  Lysozyme  helps to kill  bacteria.
iii.  The salivary  amylase  (:ptyaline)  acts  on  cooked  starch (starches  are  long  polymers of  glucose) and begins to  break  it  first  down into  shorter polysaccharides,  and  then  to the  disaccharide  maltose.  The action  of  amylase  continues in  the  stomach  until it is destroyed by the  hydrochloric  acid  of  stomach.
iv.  Among  the  mineral  salts  the  chloride  ion  speedup  the  activity of the  enzyme. Eventually  the semisolid,  partially  digested food  particles are stuck  together  and  moulded into  a bolus (or pellet) by  the tongue,  which  then pushes  it towards  the  pharynx.