what is digestion?its steps,parts of digestive system and absorption of fat,carbohydrates and proteins etc?

2. Digestion is the breakdown
of large, complex organic
molecules into smaller
components that can be
used by the body.
Molecules need to be small
enough to diffuse across
plasma membranes.

5. Steps of digestion
 Ingestion – this is the consumption of or taking in
of nutrients.
 Digestion – the chemical breakdown of large
organic molecules into smaller components by
enzymes.
 Absorption – the transport or delivery of
digested nutrients to body tissues.
 Assimilation-the conversion of absorbed food
into the substance of the body.
 Egestion – the elimination of food waste
materials from the body.

7. Esophagus
Approximately 10” long
Functions include:
1.Secrete mucus
2.Moves food from the throat to
the stomach using muscle
movement called peristalsis
If acid from the stomach gets in
here that’s heartburn.

10. STOMACH
J-shaped muscular bag that stores the
food you eat, breaks it down into tiny
pieces.
Mixes food with digestive juices that
contain enzymes to break down
proteins and lipids.
Acid in the stomach kills bacteria.
Food found in the stomach is called
chyme.

12. Small intestines are roughly
7 meters long
Lining of intestine walls has
finger-like projections
called villi, to increase
surface area.
The villi are covered in
microvilli which further
increases surface area for
absorption.

13. SMALL INTESTINE
The majority of chemical
digestion occurs in the first
of three sections of the
small intestine known as the
duodenum.
This section also contains an
opening from the bile duct
and pancreatic duct through
which bile and pancreatic
enzymes enter the small
intestine

14. Small Intestine
 Food enters the small
intestine as a semi-
solid mixture known as
chyme. The chyme is
acidic due to the HCl in
the stomach so it
needs to be
neutralized.
 The presence of chyme
in the small intestine
triggers the conversion
of prosecretin into
secretin which is
absorbed into the blood
stream and carried to
the pancreas

15. Large intestine
About 5 feet long
Accepts what small
intestines don’t absorb
Rectum (short term
storage which holds
feces before it is
expelled).

16. ANUS
 Thehuman anus is the
external opening of the
rectum.Its closure is controlled
by sphincter muscles. Feces are
expelled from the body through
the anus during the act of
defecation, the primary
function of the anus.

17. Accessory Organs
• Salivary gland
• Liver
• gall bladder
• pancreas

18. Salivary glands
parotid glands - produce a
serous, watery secretion.
submaxillary (mandibular)
glands - produce a mixed
serous and mucous secretion.
sublingual glands - secrete a
saliva that is predominantly
mucous in character.

19. Liver
 The liver is a large
accessory organ of the
digestive system that is
constantly producing a
fluid known as bile.
 Bile is stored in the gall
bladder until it is needed
in the small intestine.

20. Liver and Gall Bladder
 The presence of lipids in the
small intestine trigger the
release of the hormone
cholecystokinin (CCK) which
triggers the release of bile
from the gall bladder.
 Bile contains bile salts that
emulsifies fats which means it
breaks them into smaller
droplets so they can be
digested.

25. Pancreas
 The pancreas is an accessory
organ of the digestive
system. It releases
chemicals to aid in
digestion.
 Secretin will stimulate the
pancreas to release a
solution containing
bicarbonate ion into the
small intestine where it will
neutralize the acidic chyme
and raise the pH from 2.5 to
9.0. This inactivates the
pepsin.

26. Pancreas and Carbohydrates
 Amylase enzymes are
released from the
pancreas that break large
carbohydrate chains into
small chains called
disaccharides.
 Then the small intestine
releases disaccharide
enzymes which break
those small chains into
individual sugars.

27. Pancreas & Proteins
 Trypsinogen, a protein-
digesting enzyme is released
into the small intestine where
it is convertes into trypsin and
it breaks down large protein
chains into smaller chains.
 The final step in protein
digestion occurs with the
release of erepsins from the
pancreas and they break the
smaller chains into individual
amino acids.

30. ABSORPTION OF MATERIAL
The passage of digested food from the digestive tract into
the tissue or into the blood and lymph is called
abosrption.

31. Structure of the Villus
 Each villus contains a
capillary network along
with a lacteal.
 End products of protein
and carbohydrate
digestion enter the
capillary network.
 End products of fat
digestion are absorbed
into the lacteal. The
lacteal is a vessel of the
lymphatic system.

35. THANK
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