The nutrition function: the digestive system.

1. THE NUTRITION FUNCTION I.
The digestive system.

2. The nutrition function.
 Taking in of nutrients (found in food) which are
organic substances and mineral ions, containing
raw materials or energy for growth and tissue
repair, absorbing and assimilating them.
 In multicellular organisms, several systems take
part in this function.
 Digestive system.
 Respiratory system.
 Circulatory system.
 Excretory system.
Intimately interlinked.
Endocrine and nervous
system also participate.

3. Digestive System Processes.
 Ingestion : Intake of food into the body through
mouth.
 Digestion: The process of break-down of
large, insoluble food molecules into small, water
soluble molecules using mechanical and chemical
processes.
 Absorption : The process of passing digested food
molecules across the wall of the intestine into the
blood or lymph.
 Assimilation : The movement of digested food
molecules into the cells of the body where they are
used, becoming part of the cells.
 Egestion : Passing out of undigested food, in
the form of faeces, through the anus.

4. Digestion
Mechanical
Chew
Tear
Grind
Mash
Mix
Chemical
Carbohydrates
Lipids
Protein
s
(physical)
Enzymatic reactions to
improve digestion of

5. Digestive System Organization
• Gastrointestinal
tract.
• Accessory glands.

6. Digestive System Organization
• Gastrointestinal
tract.
– Direct link/path between
organs, 8m.
– Shape varies.
– Secrete mucus (ˈmjuːkəs) or
digestive juices.
– Structures
• Mouth
• Pharynx
• Esophagus
• Stomach
• Small intestine
• Large Intestine
• Rectum

7. Digestive System Organization.
 Gastrointestinal
tract.
 Accessory organs.
 Not part of the path of
food, but play a critical
role.
 Include:
 Salivary glands,
 liver, gall bladder, and
 pancreas

10. Mouth
 Epiglottis is a
flap-like
structure at the
back of the
throat that
closes over the
trachea
preventing the
bolus from
 CHEWING: Teeth mechanically break down food into
small pieces.
 SALIVATION: Tongue mixes food with saliva (contains
amylase (ˈæmɪleɪz), which helps break down starch).
 SWALLOWING: the tongue push the bolus towards the
pharynx.

11.  Saliva (səˈlaɪvə) is a
watery liquid released
by salivary glands.
 Starts digestion of
starch molecules:
AMYLASE
(ˈæmɪˌleɪz).
 Destroys some
bacteria:
LYSOZYME
(ˈlaɪsəˌzaɪm).
 Eases the bolus into

14. PHARYNX
 It is a common passageway for air and food.
It participates in swallowing
(ˈpælɪt)
(ɛpɪˈɡlɒtɪs)
(ɪˈsɑfəgəs)

15. Esophagus
 Approximately 20-
25cm long
 Functions include:
1.Secretes mucus
2.Moves food from the
throat to the stomach
using muscle
movement called
peristalsis
(pɛrɪˈstælsɪs)
 If acid from the
stomach gets in here
that’s heartburn
(cardia at the entering
of the stomach stops

17. Stomach
 J-shaped muscular bag that stores the food
you eat, and digests it.
 Mixes food with digestive juices that
contain enzymes to break down proteins
(pepsine) and lipids.
 HYDROCHLORIC ACID in the stomach
kills bacteria, and supports enzyme’s work.
 It absorbs water, alcohol and some drugs.
 Food in the stomach is called chyme
(kaɪm), once it has mixed with gastric
juices.
The stomach takes around 4 hours to do it’s
job on the food, depending on what kinds
of food are digested.

18. cardia
paɪˈlɔːrəs
ˈkɑːdɪə
djuːəʊˈdiːnəm

19. Small Intestine
 Small intestines are roughly 7
meters long, finishing in the
ileocecal valve.
 Intestine walls have finger-like
projections called villi, to increase
surface area.
 The villi are covered in microvilli
which further increases surface

21. Small Intestine
 Nutrients from the food pass into the bloodstream through
the small intestine walls.
 Establishes an optimal pH for
enzymes.
 Secretes digestive enzymes.
 Absorbs:
 80% ingested water.
 Vitamins.
 Minerals.
 Carbohydrates.
 Proteins.
 Lipids.

22.  When the chyme mixes with intestinal
juices, and secretions from liver and
pancreas, it transforms into chyle (kaɪl).
 The first part of
intestine
(duodenum)
receives
following
secretions.
 Pancreatic juice
from pancreas.
 Bile juice from
liver.

23. Liver
 Directly affects digestion by
producing bile
 Bile helps digest fat.
• Filters out toxins and waste including
drugs and alcohol.
 Bile does not contains any enzymes.
 Bile contains bile salts which acts on
fats.
 Bile salts break fats up into smaller fat
droplets which can be more easily
digested by lipase.23

24. Gallbladder
 Stores bile from the
liver, releases it into
the small intestine.
 Bile is realeased
through the ampulla of
Vader.
 Fatty diets can cause
gallstones.

25. Pancreas
 Produces digestive
enzymes to digest
fats, carbohydrates
and proteins.
 Regulates blood sugar
by producing insulin, a
hormone.
 Pancreatic juice also
neutralizes the acid
liquid from the
stomach.

26.  After digestion, simpler molecules are obtained:
 Monosaccharides.
 Glycerol and fatty acids.
 Amino acids.
 Those nutrients are absorbed through the small
intestine inner layer. Capillaries collect them.

27. Large Intestine
 About 1’5 m long.
 Accepts what small intestines
don’t absorb.
 Functions
 Bacterial digestion
 Ferment carbohydrates
 Protein breakdown
Absorbs more water.
 Concentrates wastes.

28. Large Intestine
 Portions of the large intestine,
 ascending,
 transverse,
 descending,
 sigmoid, and
 Rectum.
The rectum is the short term storage which holds
feces before it is expelled).

29. https://www.youtube.com/watch?v=8YXKklSxW30

30. Write the name of each colored organ:
 Green:
 Red:
 Pink:
 Brown:
 Purple:
 Green:
 Yellow:

31. How’d you do?
 Green: Esophagus
 Red: Stomach
 Pink: Small Intestine
 Brown: Large Intestine
 Purple: Liver
 Green: Gall Bladder
 Yellow: Pancreas

32. References and Links
 Inner body: http://www.innerbody.com/
 Your Digestive System and How It Works
 Digestive system diagram comes from this site
 The Real Deal on the Digestive System
 Pancreas: Introduction and Index
 Your Gross and Cool Body - Digestive System