brief summary

1. -Dimple Talukdar
25/05/2020

2.  In man , digestive system is a system of alimentary canal
and digestive glands.
 The organs of alimentary canal are- buccopharyngeal
cavity, oesophagus, stomach and intestine.
 The digestive glands are- salivary gland, gastric gland,
intestinal gland, liver and pancreas

3.  It is divided into 3 parts- vestibule, buccal cavity and pharynx.
 Vestibule is bounded externally by lips and cheeks and internally
by teeth and gums.
 Buccal cavity is the large chamber inside the mouth where
chewing take place. It is bounded by palate dorsally, ventrally by
tongue and teeth and jaws on the sides.
 Pharynx is the posterior most part of the buccopharyngeal cavity.
Pharynx opens into the oesophagus through gullet and into the
larynx through glottis.

4.  It is a long muscular tube that connects the
pharynx to the stomach.

5.  It is a J shaped thick muscular organ.
 Empty stomach possesses folds known as gastric rugae.
 Stomach is differentiated into 4 parts- cardiac, fundic,
body and pyloric.
 Cardiac stomach receives the oesophagus through cardiac
aperture.
 Fundic part is extension of the cardiac part and is filled
with air and gases.
 Body is the main part of the stomach.
 Pyloric part is further differentiated into- antrum, canal
and sphincter.

6.  Intestine is divided into large and small intestine.
 Small intestine is the longest part of the alimentary canal and lies coiled
in the abdomen.
 Small intestine is divided into 3 parts-duodenum, jejenum and ileum.
 Numerous villi are present in the ileum that increases the surface area of
absorption.
 Large intestine is shorter and wider than the small intestine. It is formed
by 3 parts-caecum, colon and rectum.
 Largest part of the large intestine is the colon.
 Colon is divided into 4 parts-ascending, transverse, descending and
sigmoid.
 The last part of the alimentary canal is the rectum. It leads into anal
canal which opens out by anus.

7.  Digestive glands secrete digestive juices for
digestion of food .
 These digestive juices contain digestive
enzymes which are of the following types-
carbohydrases, proteolytic, lipolytic and
nucleolytic.
 The digestive glands include- salivary gland,
gastric gland, liver, pancreas and intestinal
gland.

8.  Salivary glands secretes saliva that contains
digestive enzymes.
 There are 3 types of salivary glands- parotid
gland, submaxillary gland and sublingual
gland.

9.  Gastric glands secrete digestive juices that
contain digestive enzymes, HCL, mucous and
inorganic salts.
 They are of 3 types- cardiac, pyloric and
fundic.
 Fundic gland has different types of secreting
cells- chief cells, parietal cells, goblet cells
and argentaffin cells.
 Secretion of gastric juices is under hormonal
and nervous control

10.  These glands secrete intestinal juices which
is slightly alkaline.
 Intestinal glands are of 2 types- Crypt of
Leiberkuhn and Brunner’s gland.
 Crypt of Leiberkuhn has 2 types of cells –
zymogen cells and argentaffin cells
 Brunner’s gland secrete mucous and
bicarbonate to neutralize the acidic chyme.

11.  Liver is the largest digestive gland.
 Kupffer cells of the liver act as phagocytes that eat up
dead cells and bacteria.
 Hepatocyte cells of liver produces an alkaline fluid called
bile and is stored in the gall bladder.
 Bile is drained from liver by bile duct which is formed by
the joining of cystic duct from the gall bladder and hepatic
duct from different lobes of liver.
 The bile duct and the pancreatic duct join to form
hepatopancreatic duct near the duodenum.
 Liver regulates the blood sugar level by glycogenolysis and
glycogenesis.

12.  It consist of Islets of langerhans that secrete
insulin and glucagon and Acini that secretes
digestive enzymes.
 Pancreatic juice contain 4 types of enzyme-
proteolytic enzyme, pancreatic lipase, nuclease
enzymes, pancreatic amylase.
 Since pancreatic juice contain all these 4
digestive enzymes it is also called complete
digestive juice

13.  Digestion is the process in which insoluble and large molecules are
converted into soluble and smaller particles with the help of digestive
juices and enzymes .
 Digestion occurs in two processes-mechanical and chemical digestion.
 Mechanical digestion comprises of mastication (chewing) the food,
liquefaction of food by digestive juices, swallowing of the food (bolus)
and peristalsis.
 Chemical digestion is the action of enzymes on the food bolus.
 After mastication is complete, bolus is carried down through the
oesophagus by peristalsis movement, where it reaches the stomach.
 The muscular walls of the stomach churns the bolus and break into tiny
pieces.
 The bolus get mixed with HCl and other enzymes.
 The bolus is now called as chyme.

14.  Intestinal lipase- hydrolyses fats into fatty acids.
 Nucleosidase- hydrolyses nucleosides of chyme into nitrogenous base and
sugar.
 Sucrase- hydrolyses sucrose to glucose and fructose
 Maltase –hydrolyses maltose to glucose.
 Lactase- hydrolyses lactose to glucose and galactose.
 Erepsin hydrolyses all small peptides and dipeptides of chyme into amino
acids

15.  It is a process by which nutrients produced after digestion are circulated
throughout the body by blood and lymph.
 In stomach water, alcohol, simple salts, glucose are absorbed.
 Main absorption occur in the ileum of small intestine through villi.
 Absorption occurs by two process- active process and passive process.
 Water insoluble fatty acids are made soluble by bile salts through a
process called emulsification. The emulsified products form micelles
along with bile salts, phospholipids and lecithin in the intestinal lumen.
 Formation of micelle helps absorption of fatty acids and cholesterol from
intestinal lumen into epithelial cells by diffusion. In these cells many
fatty acids enter epithelial cells of intestinal mucosa resulting in the re-
synthesis of triacyl glycerides.
 Re-synthesized fats then passes into the lacteals of villi in the form of
cylomicron. The fat is carried to the receiver of the chyle and then by
the thoracic duct to left branchiocephalic vein, where it enters the
blood.

16. In this process absorbed nutrients enter into the
cells and involve in metabolic process to form bio
molecules.

17.  It is the elimination of undigested food along
with water and excess digestive enzymes.
 This undigested food is absorbed in the
colon and changed into faeces which is
temporarily stored in the rectum.
 Faeces is expelled out through the anus.