খেলার আগেই বাংলাদেশকে সেমিফাইনালে পরাজিত ঘোষনা করলো শেওয়াগ ! দেখুন টুইটারে কি লিখেছে ?

খেলার আগেই বাংলাদেশকে সেমিফাইনালে পরাজিত ঘোষনা করলো শেওয়াগ ! দেখুন টুইটারে কি লিখেছে ?
https://www.youtube.com/watch?v=gDC5bGdhR5U

Bangladesh has already gone to semifinal ICC Champions Trophy 2017

বাংলাদেশ সেমিফাইনালে যাওয়া নিয়ে নিন্দার ঝর উঠল !! দেখুন কোন ক্রিকেট তারকা কি প্রশ্ন তুলেছে? 

https://www.youtube.com/watch?v=hBYzdC9rzc0

Gastric juice

Gastric juice

Secretion  of gastric juice  occurs  in  three  phases.  The  first  is  the  nervous  phase.  The presence  of food  in  the  buccal  cavity and its  swallowing  trigger  reflex  nerve  impulses which  pass  along  the  vagus nerve  from  the  brain  to the  stomach.  The  sight, smell, taste  and  even  the  thought  of  food  can trigger the  same  reflex.  The gastric  glands  of the stomach  are stimulated  to secrete  gastric  juice.  This  takes place  before  the food has  reached  the stomach  and therefbre  prepares it  to  receive  food.  The nervous phase of  gastrio  secretion  lasts  for approximately  one hour. The second  phase  is  the  gastric  phase which takes  place in  the  stomach.  It involves  both nervous  and  hormonal  control. stretching of the stomach  by  the  food it  contains stimulates  stretch  receptors  in  the wall of the  stomach.  These send nerve impulses  to Meissner's  plexus in  the  submucosa,  which in  turn  sends nerve  impulses  to  the gastric,glands, stimulating  the  flow  of gastric juice.  Stretching  of the stomach  and  the presence  of food also stimulates  special  endocrine  cells  in  the  mucosa  to  secrete  thehormone  gastrin. This  reaches  the gastric  glands  by way of the  bloodstream  and stimulates  them  to  produce  gastric  juice  rich in hydrochloric  acid  for about four  hours. The third  phase  is  the  intestinal  phase  which takes  place  in  the small  intestine. When acidified  chyme  enteres  and  makes contact  with  the walls of  the  duodenum,  it triggers both nervous  and  hormonal  responses.  Receptors  in  the small  intestine  are stimulated by  the presence of food,  but the  reflexes,  which  pass  through  the  brain,  inhibit secretion  of gastric  juice and slow  the  release of chyme from  the  stomach.  This prevents  too much  food being  released  into  the small intestine  at once.  In  addition,  the mucosa of the  duodenum produces two  hormones, cholecystokinin (CCK) and secretin.  (CCK may also  be known  as pancreozymin,  but  use only one  of these  names! CCK is  easier  and  more widely  used.)  The  two  hormones  are taken  in  the  bloodstream

to  the  stomach,  pancreas  and the liver.  In  the stomach  secretin inhibits  secretion of gastric  juice and CCK inhibits  stomach emptying.

Human Bile.

Human Bile

Bile is  a viscous,  greenish  yellow fluid,  sour in  taste.  It is  secreted  by hepatocytes  (liver cells)  of the liver.  Around  0.8  to  1.0 litre  of bile are produced each day  and stored  and concentrated  in  the  gall bladder. Bile  is secreted  into  the  duodenum  through  the common  bile  duct.  The hormone cholecystokinin  controlls  the  flow  of bile. Composition  of bile:  Bile is  composed  of  about  98%  water, 0.8%  bile  salts,  A.2%o bile pigments,  0.7% inorganic  salts  and 0.6% cholesterol.  Sodium  taurocholate and sodium glycocholate  are the bile  salts.  Among the inorganic  salts,  sodium  bicarbonate  is important. No  enzymes are  present in  the  bile.  Biliverdin  and  bilirubin are  main  bile pigments. The bile  pigments are  produced  in  the  liver  from  the haem  of haemoglobin  in the  process  of  the  destruction of  red blood  cells. Bile pigments have  no function and  are excretory  products. Functions of bile:  The functions of the bile  are:

i.  Emulsifies  fats  (breaks  large  fat  or  oil droplets into  an emulsion  of microscopic

droplets),  a process  that  massively  increases  the  surface  area available for fatdigesting  enzymes  to attack.

ii.  Neutralises  the  acidic  chyme from  the  stomach  and  create the  ideal  pH for  intestinal

enzymes.

iii.  Stimulates  peristalsis  (rhythmic  involuntary  muscular contractions)  in  the duodenum

and  ileum.

iv.  Allows  the  excretion  of cholesterol,  fats  and bile  pigment.

Human Digestion in stomach:

Human Digestion  in  stomach:

Mechanical digestion:  Food  from  pharynx enters the  stomach  through  the oesophagus.  Stomach  is  a bug like  organ.  Mechanical digestion  takes  place  by the churning  action  of the  stomach.  This  is  made more efficient by the fact  that  unlike  other regions  of the gut it  posseses  three  layers  of smooth  rnuscles instead  of two.  namely  the outer  longitudinal,  middle circular  and iner  oblique  layers.  Stomach  wall contains  gastric glands  which produces a iuice  collectively  known  as gastric juice.  As a result  of

mechanical  digestion  ttre  gastric  tuice  mixes  with the food  rnass.

Chemical digestion:

Approximately 2 liters of gastric  juice  are secreted  each  day. The components  of gastric iuice 

perform  the  chemical  digestion.Role  of gastric  juice  in  digestion: The  gastric juice  contains hydrochloric acid  (HCl). mucus and pepsinogen.

i. Hydrochloric  acid (HCl):  A. Kills bacteria. B. Converts  inactive  pepsinogen  into active  pepsin. C.  Makes the  stomach  contents  pH I-2.5,  ideal  for  the optimum activities  of the  stomach enzymes.  D.  Denatures  many proteins; their tertiary structure  is  altered, making them  unfold and  so easier to  digest.

ii. Mucus:  mucous  cells  protects  the stomach  lining  from  the  digestive action of  its  own secretion  and  HCl.

iii. Pepsin: Pepsin (protein breaking  enzymes  are  called  proteasei  so,  pepsin  is  a protease)  is  a powerful  endopeptidase (the  protease  that breaks bonds  between  amino acids within  proteins  thus producing  smaller  peptides  is  called endopeptidase and  that splits  off  amino  acids from proteins  i.e. polypeptides  is  called exopeptidase) enzyme:  it  breaks  specific  peptide bonds in  the  middle of  the protein chain,  turning protein molecules  into  polypeptides. The soluble protein  of  milk is caseinogen. Human  infants  digest this milk protein  with acidic  pepsin,  just  as  adults  do  (the  stomach  of ruminant mammal  secretes  a milk curdling  errzyme  called  rennin  which  clots  and  precipitates  the  soluble milk protein casein/caseinogen  into  insoluble  calcium  salt of casein  and  slows the movement of milk through the  stomach  which  is  then  digested  by pepsin;  Rennin should not  be confused  with  renin  which  also is an enzyme  produced  by  kidney).

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.

Liver

Human Liver:

Apart  from  the  skin, the liver  is  the largest  visceral organ  of the  body. It  is  also  the  largest gland  of the  body.  It  is  a deep  brown  colored  triangular  organ  situated  just  below the diaphragm  in  the  right side  of  the  stomach.  The average  weight  of the liver of  adult  man is  1500 grams. The liver consists of four  lobes.  The  right  lobe  is  the  largest.  Beneath  this lobe  the  sac  like  gall  bladder is  attached.  The bile  secreted  by the  liver is  deposited  in the gall bladder.  The bile comes  to  duodenum  through  the common  bite duct.The functional  unit hepatocyte.  Each lobule  has  a diameter of about 1 mm. Between the of the  liver  is  known  as lobule.  The cells of the  liver  is  called.lobules branches are of hepatic  artery,

hepatic  portal vein  and  bile duct.  At  the center  of  each lobule  is a branch of  the  hepatic vein which is

connected to the hepatic  artery  and hepatic  portal vein by  blood.

Functions of Liver:

Liver's  function  is  extensive.  Different  types  of biochemical  reactions take  place liver,  so  it  is  alscl called  the  organic laboratory  or  chemical  workshop.  Some functions  of  liver  are as follows:

Storage  functions:

ii.  Storage  of glycogen: Glucose is  taken  to  the  liver  in  the  hepatic  portal vein.  If the concentration  of glucose  in  the blood  rises  above  0.1%  by weight, the  excess  is converted  to  glycogen  under  the control  of insulin,  a honnone  produced by  the pancreas.  The conversion  of slucose  to glycogen  is 

called  glycogenesis.

ii. The production  and  storage  of  bile: The liver produces  bile  salts and  adds  to them the  bile  pigment bilirubin  from  the  breakdown  of red  bloocl  cells. With  sodiumchloride  and sodium  hydrogen carbonate, cholesterol  and  water,  this  forms  the  greenyellow  fluid  known  as bile. Upto  1 dm3 of bile may  be produced  daily.  It  is temporarily  stored in  the  gall  bladder  before  being discharged  in  the gall hladder. It  is used  to emulsify  fats  before  their  digestion  by  lipase  in  the  duodenum.

iii. Storage  of vitamins:  The  liver  r,vill  store  a flumber  of  vitarnins  which  can later  be released if deficient  in  the  diet.  It  stores  mainly the  tat-soluble  vitamins  A, D, E and K, although  the  water 

soluble  vitamin B and  C can  also stored.

iv.  Storage  of  minerals: The  liver stores  minerals, e.g. iron,,  potassium,  copper  and zrflc. It  is  the liver's stores of these minerals,  along  with  vitamins,  w'hich makes  it  such  l nutritious  food.

v. Storage of  blood:  The liver,  with its  vast  complex  of blood  vessels,  forms  a large store  of blood with a capacity of up to 1500  cm3. In  the  event of haemorrhage, constriction  of these  vessels  forces blood  into the  general circulation to  raplace  that lost  and so helps  to  maintain  blood pressure.  In stressful  situations,  adrenaline also causes  constriction  of these vessels,  creating  a rise  in  blood pressure.

Metabolic  functions:

Carbohydrate  metabolism:  Liver performs  the  following  metabolic  functions related  to  carbohydrate 

metabolism:

A. When the level  of blood  sugar (glucose)  falls  below  its  normal  level,  the glycogen isreconverted  into glucose,  a process called  glycogenolysis, under the  control  of hormone  adrenaline  (produced  by the adrenal glands)  and  hormone glucagon (produced  by the  pancreas).

B. Muscles  also  break  down  glycogen  if  it needs  glucose  for  its  own respiration,  in  which case  the glycogen is  converted  to  glucose phosphate,,  but is  then  converted  to pyruvate (glycolysis)  which is used  to  produce ATP  during  aerobic  or  anaerobic  respiration. Lactic  acid (lactate)  produced  by anaerobic  respiration  in  skeletal  muscle can be converted  later  into  glucose  and  hence  glycogen  in  the liver.

C. When the  demand  for  glucose  has exhausted the  glycogen  store  in  the  liver,  glucose can  be synthesised  from non-carbohydrate sources  by the  process  called gluconeogenesis.

D. Carbohydrate  in  the  body which  can  not be used  or stored  as  glycogen  is converted into  fats  and  stored.

ii.  Fat  metabolism:  The liver performs  the  following  functions  ralated  to fat  metabolism:

A. The  liver  can break  down fats  into  fatty acids and  glycerol  for  respiration if  glucose  is in  short supply. Fatty acids  are coverted  to acetyl groups  which  combine  with coenzyme  A to  form  acetyl coenzyme  A. This enters  Kreb's  cycle  for oxidation and produce  energy.

B. The  liver  converts  excess carbohydrate  to fat.

C. Removes  cholesterol  from  the  blood and  breaking  it  down  or, when necessary, synthesising  it.

D. Desaturation of  fats:  Fats are stored in  the  body  in  saturated  form. This means  that they  cannot
take  any  more  hydrogen into their  composition.  Before  saturated  fats  can be used  by  the tissues  ofthe body,  the  hydrogen  must  be removed,  and this  occurs  in the  liver. The resultant  unsaturated fats  can be used  to provide .

iii. Protein metabolism: The liver  performs the  following  important  functions  related to proteion metabolism:

A. Formation  of urea:  Amino  acids  are taken  to the  liver  in  the  hepatic  portal  vein. Those  that are in excess of  the  body's  needs  cannot be stored. The nitrogen-containing part of the amino  acids is removed and changed  to  urea. The  process  is  sometimes referred  to as deamination.

B. Transamination:  The  systhesis  of  amino  acids  by the transfer  of amino  group  from an amino acid to another  organic  acid is  called  transamination.  Transamination  is  the means of producing  amino  acids which  are  deficient  in  the  diet. The essential  amino acids  (8  in  number: valine,  isoleucine,  leucine, lysine,  methionine,  phenylalanine, tryptophan,  threonine)  can not  be synthesised by  transamination  in  the live  and  must be  obtained  from  the  diet.

C. Plasma protein  production:  Plasma  proteins,  albumin,  globulin,  fibrinogen and prothrombin  are vital components  of  plasma  and  the  majority of thern  are  synthesised from  amino  acids  ion  the liver.

iv.  Formation  and  breakdown  of red  blood  cells:  The  fetus relies solely on the liver  for the  production of red blood  cells.  In an  adult,  this  role  is  transferred  to  the  bone malTow.

v. Breakdown  of haemoglobin  of red  blood cells: The  adult  liver,  however,  continues to  break  down red  blood cells  at the  end of their  120-day  life  span. The phagocytic macrophage  cells  that  is,  Kupffer cells  lining  the sinusoids  carry  out this  breakdor.vn.The  haemoglobin  they  contain  is broken  clown  into haem  and  globin.  Globin  is  the protein  part of  the  molecule  and is  broken  down to  its  individual amino  acids. The iron  is  removed  from  haem and  the remaining  part of the  molecule  forms  a green pigment  called  biliverdin  which  is  converted  to  bilirubin,  yellow in  colour and  a component  of  bile. The accumulation  of bilirubin  in  the blood is  a symptom  of liver disease and produces a yellowing  of the skin,  a condition  known  as  jaudice. The iron  is  either  stored in  the liver  cells as a compound  called ferritin  or used  in  ttie formation  of  new  red  blood  cells by  the  bone  maffow. The liver  produces haematinic principle,  a substance  needed  in  the  formation  of red blood  celis.Vitamin  Bn deficiency results  in  pernicious  anaemia.

xi.Hormone  breakdown:  To  varying degrees,  the  liver  breaks  down all  hormones. Some, such  as testosterone, are rapidly  broken down  whereas otheres,  like  insulin,  are destroyed more  slowly.

xii.Detoxification:  The  liver  is  ideally  situated  to  remove,  or render  harmless, toxic material absorbed by the  intestines.  Foreign  organisms  or material are  ingested  by the Kupffer  cells  while  toxic  chemicals are made safe  by chemical  conversions within hepatocytes. Alcohol  and nicotine  are two  substances dealt with  in  this  way.

xiii.Production of heat: The liver,  with its considerabie  metabolic  activity,  can  be used to  produce  heat in  order  to  comb  at a fall  in  body temperature.  This reaction,  triggered by  the hypothalamus,  is  in  response  to  adrenaline,  thyroxine  and nervous stimulaion. Whether the  liver's  activities  produce excess  heat  under  ordinary circumstances  is a matter  of some  debate.

xiv.Cholesterol  Production:  The liver  produces  cholesterol  and  production  of cholesterol  is  the  begining  of the  sysnthesis  of other  steroid  molecules.The  major source  of  cholesterol  is the diet, and
many  dairy  products  are  rich  in  cholesterol  or fatty acids from  whichcholesterol  can be  systhesised.

Pancreas

Human Pancreas:

Pancreas is  an irregularly  shaped, pink  colored  gland.  It  is  located  in  the bend  of  the duodenal loop.  lt  is  a compound  gland,  dual  firnction  exocrine  and endocrine.  The exocrine  part  make up  99  percent  of the  glandular tissue  of pancreas.  They  secrete digestive  juice  called  pancreatic juice.  This  fluid  contains  water,  some  salts,  sodium hydrogen carbonate and  a mixture  of about 15 enzymes. The  pancreatic juice  passes  into the  duodenum  through  pancreatic  duct  which  joins the  common  bile  duct .The  endocrine  structures  are called  islets  of  Langerhans  which produce two  hormones insulin  and  glucagon.

Function:  Pancreatic juice  plays  important  role  in  digestion  and  the  hormones  controls

the carbohydrate  metabolism.

lntestinal Gland

Human lntestinal  Gland

The  mucosa of  small intestine  possesses  numerous finger-like  projections  called villi (sing.villus). At the base of  the  villi  the epithelium  folds  in places  to form  narrow  tubes.  These tubes are called  crypts  of Lieberkuhn  (fig.  3.5). In  the crypts  of Lieberkuhn  there present  a kind  of cell called Paneth  cetl.  In  the  duodenum there  in  addition  rounded  Brunner's  gland.

Cells  of  the  intestinal  mucosa, are subjected to  considerable wear  and are constantly undergoing replacement.  Cells  deep  in  the crlpt of  Lieberkuhn  divide  rapidly and  migrate up the villus.  The cells reach  the tip  of the villus  in  about two days.  there they  shed,  along with their  membrane enzymes, into the  lumen  at the  rate  of some  17 billion  a day  along length  of the intestine. Before they  are  shed, however, these  cells  differentiate into absorptive  cells  that  transports nutrients into  the network  of  blood and  lymph  vessels, once  digestion is  completed.  The  average  life  of these  cells  is  about 5 days.

Functions:

i. The  epithelial  cells  of villi produce  membrane enzyme which  helps in  digestion.

ii. The  cells  of  the  crypts secrete  intestinal  juice,  a slightly  alkaline  fluid  which contains

water  and  mucus and  helps to  increase  the volume  of fluid  in  the  gut.

iii. Paneth  cells  secrete  lysozyme,  the  bacterial  enzyme  which  kills  bacteria.

iv. Goblet cells  secrete  mucus.  which  protects  the  intestinal  wall.

v. Bru,,ner's  glands  secrete mucus which  als, r'oiects  the  intestinal  rvall.

Gastric Gland:

Human Gastric  Gland:

The  deep tubular  glands of the stomach wall are called  gastric  gland .Collectively  the  secretion  of the  gastric glands is  called  gastric juice. Approxirnately  2 liters  of gastric  juice are secreted  each  day.  There arc  4 kinds off cells  found  in the  gland.  Each  type  of cell produces  a specific secretion  which  are as.

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i.  Oxyntic  cell  (:Parietal  cell): Produces  Hydrochloric

acid  (HCl):

Function:

a. It  is  a strclng  bacteriocide  and kills bacteria.

b.  Converts  inactive  pepsinogen  into active  pepsin.

c.  Denatures  proteins  and  helps  to soften tough   connective  tissue  in  meat.

ii.  Mucous cells:  Secretes  mucus.

Fuction:  Mucus  protects  the stomach  lining  from  the digestive action  of its own secretion  and HCl.

iii. Argentaffine cells:  Secretes  gastric  intrinsic  factor.

Function: Helps  in  the absorption  of vitamin  B12.

iv.  Chief cells  (also  called  zymogen  cells,  peptic  cells): These  cells  secrete pepsinogen.  Hydrochloric  acid converts  pepsinogen  into  active  pepsin. Pepsin then helps in  digestion.