Ø Pharynx It is a channel for both air and food. The upper parts
connect with the nose and mouth, lower parts with the larynx leading to the oesophagus for swallowing.
At the distal end of glottis,
epiglottis and reflexes controlled
by the brain which prevents food
from being swallowed by the wrong way. If
food enters into the larynx
coughing reflexes expels inhaled particles.
Ø
Oesophagus
It is a thick walled tube consisting longitudinal and circular
muscle fibres which runs between the pharynx
and stomach. The wall of
oesophagus is lined with mucous membrane
which secretes mucous (acts a s lubricant for passage of food) o
Peristaltic movements
Swallowing is a voluntary
action where oesophagus is involuntary
because inside it will show contractions and relaxation (works as their
wish) producing wave like movements known as peristaltic movements.
Note: No enzymes are present in this and the role is just
transferring the food to the stomach.
Ø Stomach
It is a elastic sac
that forms the widest part of the digestive tract and food is churned by the muscles and mixes with the secretion. The important parts of stomach are
§ Serosa: Outer membrane of the stomach.
§ Sub mucosa: Composed of loose connective tissues.
§ Mucosa: Inner membrane containing mucous substance, enzymes ,harmones
and acid.
o
Muscles in Stomach
These are circular,
longitudinal and oblique layer of the smooth muscles. The oesophagus which
joins the stomach known as oesophageal
sphincter which helps to control the entry of food. At the exit of the
stomach pyloric sphincter is present
which opens and closes to allow food to move into the duodenum.
o
Acid(Hcl) in Stomach
The contents of the stomach are acidic due to the presence
of HCL(PH:2) which helps in killing the bacteria present in the
food and also destroys the structure of
proteins hence enzymes can digest them easily
o
Enzymes in Stomach
A substance produced
by a living organism that acts as a catalyst to bring about a specific
biochemical reaction known as enzymes.
§
Pepsin
and Lipase
·
Pepsin
Proteins ---> Peptones
+ Polypeptides
·
Lipase
Fats---> Fatty acids + Glycerol
Pepsin
↓inactive
Pepsinogen
↓ Acid
Pepsin
Ø Parts beside the stomach
o
Liver – Largest organ
It is a wadge shaped located in the upper right hand side of the
abdominal cavity, brown in colour producing bile. The cells present in the l
Liver known as Hepatocytes.Bile reaches the duodenum through a
bile duct.
·
Bile Juice
It is a mixed colour of yellow and golden brown , thick
and sticky in nature without any enzymes. It constitutes
§ Water : 86%
§ Bile pigments: Bilurubin and Biliverdin.
§ Bile salts: Sodium cholate and Sodium deoxycholate.
·
Bile Salts
These salts help in changing the fats into the smaller
particles known as emulsification.
It is very important in the distribution of lipids and absorption of fatty
acids.
When bile duct is blocked, it mixes with the blood and
circulates around the body. Due to this eye and skin becomes yellow, known as JAUNDICE.
o
Gall bladder
It is a pear shaped
dark colored sac lying behind the liver which helps to store the bile juice temporarily.
o
Pancreas
It is an elongated part lying behind the stomach and
partly with the curved of the duodenum. It secretes the juice containing enzymes
which breaks down the carbohydrates,
fats and proteins. These enzymes secretes into the duct that conveys to the
pancreatic duct which transports the enzymes to the duodenum.
o
Functions
·
Glucagon: Raises the level of glucose (sugar) in
the blood.
·
Insulin: Stimulates cells to use
glucose.
·
Somatostatin: May regulate the
secretion of glucagon’s and insulin.
o
The Islets of
Langerhans, known as "islets," are clusters of cells scattered
throughout the pancreas. Ø Intestine
o
Small intestine
It is a narrow and tubular part occupying the central and
lower part of the abdominal cavity. It is composed of:
§ Duodenum: It is the shortest, widest and flexible part of the intestine
forming U or C shaped area and
receives the pancreatic juice.
§ Jejenum: It is the middle part lying between duodenum and ileum which
is soft and long.
§ Ileum: It is the longest part which helps to absorb the nutrients
from the digested food passed along from other two parts and opens into the caecum.
o
Absorption in Intestine
The transportation of products of digestion from the
intestine into the blood known as absorption.
The intestinal wall has a number of finger like
projections Villi(Villus) helps in
absorption by increasing the surface area.Thedigested product first absorbed
into the villi from there into the body.
 
o
Large intestine
It is a short and widest bent tube which absorbs water and
discharges undigested food. It is composed of:
§ Caecum: It is the proximal part where ileum opens consisting a pouch
like structure which ends in a tubular region known as vermiform appendix.
§ Colon: It converts chyme into
faeces for excretion. During this process colon converts water from the chime changes
it from liquid to solid form. It also synthesizes
vitamins K and B and gases like hydrogen, carbondioxide,
hydrogen sulphide and methane.
§ Rectum: It is the final secretion of the intestine. Normally it is
empty except before defecation i.e.,
partly faeces into the rectum by the wave movements.
§ Anus: It is lined with vertical vertical ridges known as anal columns with two flat sheets of
muscles in the wall of the anal canal. The sphincters
(internal and external) act like valves and relax during defecation.
……………………….………..THE END………………………………………
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