The document provides information about the digestive system. It discusses the organs of the digestive system including the mouth, esophagus, stomach, small intestine, large intestine, rectum and anus. It describes the functions of these organs, such as mechanical and chemical breakdown of food in the mouth, stomach and small intestine. Absorption of nutrients occurs primarily in the small intestine, while the large intestine absorbs water before waste is excreted through the rectum and anus. Glands like the liver, pancreas and salivary glands secrete enzymes and juices to aid in digestion. The six main processes of the digestive system are ingestion, digestion, absorption, assimilation, and excretion.

1. Digestive System
Or
Gastrointestinal
Or
AlimentaryTract
By : Priyanka
Research Scholar , LNIPE Gwalior

2. Digestive system
 The primary function of the digestive system is
to break down food both mechanically and by
the use of enzymes, so that it can be used by the
body for energy and cell growth and repair. It
consists of a large number of organs and
processes with the combined functions of
breaking down our food into smaller molecules
which can be used to produce energy and for
other nutritional purposes; and excreting the
waste consumed and produced by the system.

4. Organs of Digestive system
 Mouth
 Pharynx
 Esophagus
 Stomach
 Small intestine
 Large Intestine
 Rectum
 Anus

5. Mouth
 It is U shaped structure.
Vestibule: An outer part , lies between lips and
teeth.
Palate: forms the roof of mouth cavity.
Teeth: PermanentTeeth(32) andTemporary
Teeth(20).
Incisors(2) , Canine(1), Premolar(2) and Molar(3)
The set of permanent teeth is competed at the age
of 12 years.

7. Different enzymes and actions
 Amylase enzyme is present in saliva, it
converts starch into maltose.
 Pepsin, trypsin converts proteins into amino
acids.
 Lipase converts fats into fatty acids.
 Renin acts on proteins in milk

9. Salivary Glands
These are total 6 in number:
 Parotid: duct called Stenson’s duct and is
the largest gland.
 Submandibular Gland: Has a duct called
Whartson’s duct.
 Sublingual: smallest salivary gland.
Saliva: Alkaline fluid containing 99% of water
and the pH of saliva is 7.2.
 It has ptyalin enzyme which converts starch
into maltose.

10.  It is 20-25 cm long.. It lies behind the wind
pipe(trachea)
 It contains sphincters( prevents stomach acid
from back flowing into esophagus)
Deglutition: Act of swallowing: converting
food into round mass called bolus.
There is a flap called epiglottis which prevents
food from entering into windpipe.
Food travels down the esophagus through a
series of rhythmic contractions called
“Peristalisis”
Oesophagus (food pipe)

11. Stomach
It is a J- shaped organ.. It receives food from
esophagus and this secretes gastric juice.
 Goblet cells: Mucous( prevents stomach from
digesting itself)
 Parietal Cells: HCL(pH 2)
 Peptic/chief cells: Pepsinogen (inactive
protein)
 Pepsin: It is an enzyme which converts
protein into peptone.

13. Contd.
 Chyme: product of digested food in stomach.
 Pepsin of stomach, tripsin converts proteins
into peptones, polypeptide and finally into
amino acids.
 Lipase, an enzyme of pancreas convert fat
into fatty acids and glycerol.
 No absorption of food occurs in stomach
except glucose but alcohol and water can be
absorbed in stomach.

15. Small Intestine
 Part which extends from pyloric end of
stomach to ceacum.
 At an average it is of 2.4 m long.
It has three parts
 Duodenum 5 %
 Jejunum 40%
 Ileum 55%

17. Function of small intestine
 The small intestine is the part of the
intestines where 90% of the digestion and
absorption of food occurs, the other 10%
taking place in the stomach and large
intestine.The main function of the small
intestine is absorption of nutrients and
minerals from food.

18. Large Intestine
 Large intestine extends from the end of ileum to
rectum.
 It consists of Ceacum, colon and rectum.
Ceacum:The main function of the ceacum are to
absorb fluids and salts that remain after
completion of intestinal digestion.
Colon: the colon is divided into three i.e. an
ascending, a transverse and descending colon.
Rectum: The main function of the rectum is to act
as a temporary storage site for fecal matter before
it is eliminated from the body through the anal
canal.

20. Anus
 Function.The function of the anus is to
transmit faeces from the rectum to the
external environment.

21. Assessary organ in digestion
 Liver an bile ducts
 Pancreas.

22. Liver
Liver is the largest abdominal organ and largest
gland of the body .
Hepatic lobule are the structural and functional
unit of liver
It has a mass of about 1.5kg and it produces bile
, a greenish yellow pigment made up of bile
salts as it break down old RBC’s.
 Liver cells are called lobules.

23. Contd.
 Hepatic Artery: Supplies oxygenated blood
to liver
 Hepatic veins: carry impure blood of liver
and drain into inferior vena cava.
 Bile ducts: secretion of bile is carried out by
bile ducts made up of binary calculi.
Functions of liver
Synthesis and storage of glycogen.

24. Contd.
Formation of urea
Synthesis of plasma protein.
Natural anticoagulant: Heparin
Storage of vitamin: A, D , E, K.
Bile is an alkaline fluid secreated by liver, stored
in gall bladder .. About 500-1000ml of bile is
secreated by liver per day. It contains 86% of
water , bile salts and bile pigments.

25. Pancreas(duct of Wirsung)
The pancreas is a compound elongated organ (
exocrine and endocrine).
The exocrine portion secreated an alkaline
pancreatic juice containing enzymes and the
endocrine portion secretes hormones, insulin
and glucagon.
 Amylase : starch into maltose
 Lipase: fats into fatty acids.
 Trypsin: peptones into amino acids.
 Insulin: Secreated by beta cells
 Glucagon: secreated by alpha cells

27. Digestive system Physiology
The digestive system is responsible for taking
whole food and turning them into energy and
nutrients to allow the body to function, grow,
and repair itself.The six primary processes of
the digestive system include:
 Ingestion of food
 Digestion of food into smaller pieces
 Absorption of nutrients
 Assimilation
 Excretion of wastes

28. Ingestion
The first function of the digestive system is
ingestion, or the intake of food.
The mouth is responsible for this function, as it
is the orifice through which all food enters the
body.The mouth and stomach are also
responsible for the storage of food as it is
waiting to be digested.

29. Digestion
 In human beings the digestion of food begins
in mouth itself.The salivary glands helps in
chemical digestion by secreting enzymes.The
human saliva contain an enzyme called
salivary amylase which digests the starch
present into the food.Thus the digestion of
starch begins in mouth itself.
 Then the esophagus carries food to stomach.
 The contraction and expansion movement of
walls of food pipe is called peristaltic
movement.

30. Contd.
 Now the stomach has three tubular glands.
The walls of stomach secreated gastric juice
i.e. ( HCL, the enzyme pepsin and mucus).
Due to the presence of HCL, the gastric juice
is acidic in nature. In acidic medium the
enzyme pepsin begins the digestion of
proteins present in food.Thus the protein
digestion begins in stomach and another
function of HCL is to kill bacteria which enters
the stomach by food.

31. Contd.
 The mucus helps to protect the wall from Hcl.
then the partially digested food is then goes
from the stomach to the small intestine.
 The small intestine receives the secretion
from two glands i.e. liver and pancreas . As
bile is alkaline in nature and contains salts
which helps to emulsify or break the fats
present in food. thus bile performs two
functions : makes the acidic food coming
from the stomach alkaline so that pancreatic
enzymes can act on it.

32. Contd.
Pancreas secretes pancreatic juice which
contain digestive enzymes like pancreatic
amylase, lipase and tripsin.
The walls of intestine contain glands which
secretes intestinal juice.The intestinal juice
contain a number of enzymes which
complete the digestion of complex
carbohydrates into glucose , proteins into
amino acids and glycerol.

33. Absorption
 After digestion, the molecules of food
become so small that they can pass through
the walls of small intestine which contain
blood capillaries and go into our blood.This is
called absorption the small inestine is the
main region for the absorption of digested
food.

34. Assimilation
 He blood carries the digested and dissolved
food to all the parts of the body the
assimilated food is then used by the cells for
obtaining energy.Then the digested food
which is not used by body immediately is
stored in the liver in the form of carbohydrate
called “glycogen”

35. Excretion/ Ejection /Defecation
 A part of food which we eat can not be digested
by our body.This undigested food can not be
absorbed in the small intestine .Then this food is
sent to large intestine .The walls of large
intestine absorb most of the water from that
.due to this the unabsorbed food becomes
almost solid .The large part of the large intestine
rectum stores this undigested food for sometime
and after then this undigested food is passed out
from our body through anus.The act of expelling
the faeces is called egestion or defection

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