Presentation on Digestive System

2.  We need food for 1) energy.
2) for growth provides the substances needed
for making new cells/tissues
 3) for replacement of worn and damaged tissues

3. CARBOHYDRATES PROTEINS LIPIDS
Elements they
contain
C,H,O C,H,O,N,S C,H,O
Smaller
molecules of
which they are
made
Glucose/simple sugar Amino acids (3) fatty acids and (1)
glycerol
Solubility in H2O Monosaccharides YES
Polysaccharides NO
YES NO
Food that
contains them
Bread, cereals, deserts,
potatoes, rice, pasta,
jam, sweets, lettuce
Meat, fish, chicken, egg
white, milk, cheese,
pork, peas, beans and
cereals
Butter, oils, fat meat,
junk food, egg yolk

4. Why animals
need them
Easily available
energy (16kj/g)
Making
CELLS,ANTIBODIES
, ENZYMES; used
for ENERGY if all
the stores have run
out (17kj/g)
*Source of
ENERGY (37kj)
*LONG TERM
storage of E in fat
depots
*insulation
(adipose tissue)
*part of cell
membrane and
membrane
systems
Things to
remember
ProteinsAminoaci
ds bloodstream
build up different
proteins
(cytoplasm/enzyme
s)
aminoacids not
usedLiVERremo
val of amino group
(-NH2) 
Glycogen Stored
or OXIDIZED for E
SUGAR
GLUCOSE

6. Water functions

7. Water functions

8.  ENERGY REQUIREMENTS per day => 12000kj (=2800cal)
For *keeping our internal body processes working
*keeping our body temperature
*meeting the needs of work and activities
Balanced diet
BASAL METABOLISM 
2400 kj (574cal in 8 hours of
sleep) maintains circulation/
breathing/body temperature/
brain function/chemical
processes in liver and other
organs
8 hours asleep 2400 kj
8 hours awake (inactive) 3000 kj
8 hours physically active 6600 kj
Total 12000 kj

9. Digestion
Digestion is the breakdown of large
insoluble food molecules into small water
soluble food molecules in the digestive
system, so that they can be absorbed into
the bloodstream and carried to every cell of
the body.

10. Digestive system
 Digestive truct
 Glands
Esophagus
Stomach
Small intestines
Large intestines
Rectum and anus
Salivary glands
Liver
Gallbladder
Pancreas

11. Path of FoodMouth--chewing
Pharynx--conscious swallowing
Stomach--mechanical
and chemical breakdown
Small Intestines--
chemical digestion and absorption
Large Intestines--
resorb water, form feces
Esophagus--transport to stomach
Rectum---collect and expel feces

12. Mechanical and
chemical digestion
start in the mouth.
MOUTH
Saliva contains the enzyme amylase ( it breaks down starch into
sugar).
Saliva also contains mucus which lubricates the food and helps it
pass down the oesophagus.
Saliva lubricates
and stick the
small pieces
togetherbolus

13. SWALLOWING: Food passes from the MOUTH to the PHARYNX and into the ESOPHAGUS
1 The tongue presses UPWARDS and BACK against the roof of the mouth
2 The SOFT PALATE closes the NASAL CAVITY
3 The LARYNX cartilage is pulled upwards so that the glottis is under the back of the tongue
4 The GLOTTIS is partly closed
5 The EPIGLOTTIS shuts down to help prevent food from going down the WINDPIPE
The beginning is VOLUNTARY, once food gets to the back of the mouth  REFLEX ACTION
Chewing and
swallowing

14. Peristalsis
The oesophagus has circular muscles in the
wall. These muscles contract behind the
bolus to push it along and the muscles in
front of the food relax. This way food passes
along the oesophagus to thestomach. This
movement is known as peristalsis.
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15. Enzymes in digestion.
Enzymes are chemicals that break down
large food molecules into small food molecules.

16. STOMACH FUNCTION
Protein
breakdown-
pepsin secreted by
epithelial lining
◦ Acidic
conditions--for
pepsin to work and
to kill bacteria
–Mechanical and chemical breakdown
of food
The gastric juices contain protease enzymes (PEPSIN) and hydrochloric acid

17. STOMACH
◦ From esophagus
(cardiac orifice
or lower
esophageal
sphincter)
◦ To small
intestine (pyloric
sphincter)
Food+ GASTRIC JUICE=
CHYME

18. SALIVA + Amylase
Chewing
PERISTALSIS
Esophagus Stomach
Gastric juices: Pepsin+
Hydrochloric acid
Small Intestine-
DUODENUM
Pancreatic juice
(TRYPSIN+PANCREATIC
AMYLASE+LIPASE)+
SODIUM
HYDROGENCARBONATE
Bile
Small Intestine-
Ileum
Absorption
Liver
Assimilation of produtcs
EGESTION
KIDNEYS
LARGE INTESTINE
Colon absorbs FATTY
ACIDS, BILE SALTS;
WATER

19. INTESTINES
 Small Intestine
 Large Intestines
Reabsorption of
water
Absorption of
nutrients
Duodenum / Ileum
Cecum, colon, rectum and anal canal.
the ascending colon, the transverse colon, the descending colon,
and the sigmoid colon.

20. Small Intestine:
Modifications for absorption
dense capillary
network
Digested food passes
to the blood to be
taken to the liver and
then distributed round
the body
Microvilli:
Increases surface
area  the larger
the surface, the
faster the
absorption
thin epithelium
increases contact,
fluids can pass
easily to reach the
capillaries
Length
It gives plenty of
time for digestion
to be completed
and for digested
food to be
absorbed

21. *They work in stages and different parts of the canal  e.g: starch  MALTOSE  GLUCOSE (SALIVA/PANCREAS)
protein  PEPTIDE  Amino acid (AA) (STOMACH)
 Fats  LIPASE  GLYCEROL+ FATTY ACIDS
*TYPES: 1) CARBOHYDRASES  digest CH e.g  AMYLASE => MALTOSE  MALTASE => GLUCOSE
2) LIPASES  digest FATS into=> fatty acids and glycerol
3) PROTEASES  digest proteins into POLIPEPTIDES => Amino acid (AA)
*

22. PROTEASES are produced in an inactive form + MUCUS
* PEPSIN is produced as PEPSINOGEN and becomes PEPSIN when it
encounters HYDROCHLORIC ACID
* TRYPSIN is produced as TRYPINOGEN and becomes TRYPSIN when it
encounters ENTEROKINASE (produced by duodenum lining)
BRAIN
nerve impulses
GASTRIN  when food reaches
the stomach, circulates in the
blood to maintain the gastric
secretion
SECRETIN
stimulates secretion of
ENTEROKINASE and SODIUM
HYDROCARBONATE

24. INGESTION
DIGESTION
ASSIMILATION
ABSORPTION
EGESTION
D
U
O
D
E
N
U
M
I
L
E
U
M
AMYLASE
Salivary/pancreatic
PEPSIN
TRIPSIN
BILE salts
LIPASE
MALTOSE
PEPTIDES
MALTOSE
GLUCOSE
AA

25. ILEUM ABSORPTION
GLUCOSE and AA  Epithelial cells =>Capillaries =>VEINS =>HEPATIC
PORTAL VEIN => LIVER => BLOOD CIRCULATION
GLYCEROL+ FATTY ACIDS  LACTEALS => Lymphatic system =>
bloodstream
HOW  water/alcohol => OSMOSIS
Amino acids/ salts/sugars =>ACTIVE TRANSPORT
FAT soluble VITAMINS =>ACTIVE TRANSPORT (+fat droplet)
WATER soluble VITAMINS => DIFFUSION
CALCIUM IONS => need VITAMIN D => ACTIVE TRANSPORT

26. ASSIMILATION : uptake and use of
food
STORAGE
GLUCOSE  ENERGY from respiration *GLYCOGEN in LIVER (Short
term storage) and MUSCLE
*FAT  fat depots
FATS  to form some cell structures (membranes)
or as a source of ENERGY *LONG-TERM STORAGE
 FAT DEPOTS
ADIPOSE TISSUE
(round kidneys/under skin)
AMINO ACIDS  build up proteins forming
tissues/enzymes *NOT STORED in the
body DEAMINATED (-NH2)

27. redish-brown organ which lies beneath the
diaphram and overlaps the stomach partially
ALL THE BLOOD FROM THE BLOOD
VESSELS OF THE ALIMENTARY CANAL
PASSES THROUGH THE LIVER, ADJUSTING
ITS COMPOSITION BEFORE JOINING
GENERAL CIRCULATION
Functions: 1) REGULATION OF BLOOD SUGAR: removes excess glucose and stores it as
GLYCOGEN (normal level 80/150mg) or from GLYCOGEN to GLUCOSE maintaining
HOMEOSTASIS (internal environment within narrow limits) and the composition of the
BODY FLUIDS
2) PRODUCTION OF BILE  BILIRUBIN
pigment from breakdown of haemoglobin .
BILE contains bile salts (for digestion of fats)
3)STORAGE OF IRON
4)DEAMINATION  conversion of useless AA to glycogen
removing the amino group (-NH2)Ammonia (poisonous)
UREA excreted by the KIDNEYS
5) MANUFACTURE OF PLASMA PROTEINS
6) DETOXIFICATION  ALCOHOL/MEDICINES
7) STORAGE OF VITAMINS A AND D

28. PART OF
CANAL
JUICE SECRETED ENZYMES SUBSTANCE PRODUCT OTHER
SUBSTANC
ES IN THE
JUICES
FUNCTION OF THE
OTHER
SUBSTANCES
MOUTH Saliva amylase starch maltose
- -
PHARYNX
- - - - - -
STOMACH Gastric juice Pepsin proteins Poly
peptides
Hydro
chloric
acid
Gives acidity
for the pepsin
to work
Kills bacteria
DUODENUM *pancreatic
juice
Amylase
Lipase
trypsin
Starch
Fats
Proteins and
Polypeptides
Maltose
Fatty acids/
glycerol
Sodium
hydrogen
carbonate
Neutralises
acidity of chyme
Makes the
environment
alkaline
* Bile (liver) Bile salts
&pigments
Emulsify fats
Excretory
product
ILEUM - Maltase
Sucrase
Lactase
Peptidase
Lipase
Maltose
Sucrose
Lactose
Polypeptides
Emulsify fats
Glucose
Glucose &
Fructose
Galactose&
Glucose
Aminoacids
Fatty acids/
glycerol