DIGESTIVE GLANDS

HUMAN DIGESTIVE GLANDS

The  glands  whose secretion  help  in  the  digestion  of food  is  called  digestive  glands.  The digestive  glands  of man are classified into  two  groups,  e.g.-

i.Glands  situated  outside  the alimentary canal but  are connected  intimately  with ducts.

ii.Glands present  in  the wall of alimentary  canal.

The  glands  outside  the  alimentary  canal  are salivary  glands,  liver,  pancreas,  and the glands in  the  wall of  alimentary  wall  are gastric  glands and  some  glands of intestine.

A. Salivary  Glands:

Around  the  mouth  there  are  three  pairs  of salivary glands which are-

i. Parotid  gland: Parotid  glands  are the largest  of salivary  glands,  The  glands are  present  below each ear  and  the ducts  from  the  glands  opens  into buccal  cavity  near  the  upper  molar.

ii. Submaxillary  or Submandibular glands:  Submandibular  glands  are present  at the  posterior part of mandible and  their  ducts open  into  the buccal  cavity.

iii. Sublingual glands:  Salivary  glands are  located  below  the  tongue anteriorly.  The ducts  also open  into the  buccal  cavity.

Saliva:

The secretion  of  salivary  glands  is  called saliva.  Abont  15 litres  of  saliva  are  secreted  by the salivary  glands  each  day.  Saliva  is  a watery  (over  99-%;2f  saliva  is  water)  secretion contaiping  the  enzymes  q4livary amylase  (or  ptyaline)  and  lysozyme.  It  also  contains mucin, sodium,  potassium,  bicarbonate  and  chloride  ions.

Functions  of  saliva:

i. The water and  mucin  in  saliva  moisten,  soften,  and  lubricate  dry  food  so that  it  is  more easily  chewed and  swallowed.

ii.  The  enzyme  salivary  amylase breaks down  starch into  the  soluble  sugar  maltose.  This reaction  is  the  tirst  stage of  carbohydrate  digestion,  Food  remains  in  the  mouth for only  a few seconds  and  little  digestion occurs  here,  but  after swallowing  the  action ofsaliva  continues  for some time  in  the  stomach.  It is  finally  stopped when  the  acid  in stomach  digestive  juice penetrates  the  food  and  destroys  the amylase.

iii.  Amylase,  and  another  enzyme in  saliva  called  lysozyme,  help to  remove carbohydrate  food and  bacteria  from  between  the  teeth  and  thus  help to  prevent  tooth decay.

iv.  Saliva moistens the mouth, tongue,  and  lips,  which  facilitates  talking.  Saliva production  stops

during nervousness  or severe  illness,  making speech difficult.

v. By  dissolving  food,  saliva makes  it  possible  for  the  chemicals  within  it  to  reach  the taste buds in  the tongue.  This is  important  because taste  buds are  not stimulated  by  dry food.

vi.  Bicarbonate  in saliva acts as a buffer, which means  that  it  keeps saliva at a more or less constant  level  of weak alkalinity.  This helps  prevent  tooth  decay by reducing the strength of mouth acids  that  dissolve  tooth  enamel.  During sleep  saliva  production slows  down

considerably.

vii.  Chloride  ions  speed  up the  activity of the  enzymes.

viii. Mucin helps to  bind  food particles  together  and  lubricae  them  to  assist  swallowing.