Digestive System PPT

1. Animal Digestion
Gazelle and Python

2. How do animals get their food?
filter (suspension) feeding substrate feeding
fluid feeding bulk feeding

3. Eating a balanced diet
 What happens if an animal’s diet is
missing an essential nutrient?
 deficiency diseases
 scurvy — vitamin C (collagen production)
 rickets — vitamin D (calcium absorption)
 blindness — vitamin A (retinol production)
 anemia — vitamin B (energy production)
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4. Digestion System Diversity
Intracellular Digestion Extracellular Digestion
• food particles engulfed • the breakdown of food
by phagocytosis particles outside of
• food vacuoles fuse cells
with lysosomes • occurs in
containing hydrolytic compartments that
enzymes are continuous with
• Example: sponges the outside of the
animal’s body
• Examples: hydra,
worms, insects,
humans
intracellular
digestion

5. Digestive System Diversity
Animals, such as hydra,
with simple body plans
have a single opening
pouch called the
gastrovascular
cavity that functions
in both digestion and
distribution of
nutrients.
extracellular
digestion

6. Digestive System Diversity
More complex animals, such as
humans, have a digestive
tube, the alimentary canal,
with two openings, a mouth
and an anus.
Everybody’s got one!

7. Digestive
mouth stomach
break up food Organ Review kills germs
moisten food break up food
digest starch digest proteins
kill germs store food
liver
produces bile
- stored in gall bladder
break up fats small intestines
breakdown food
pancreas - proteins
produces enzymes to - starch
digest proteins & carbs - fats
absorb nutrients
large intestines
absorb water

8. Maintaining Homeostasis
• Interactions between certain organs
help to regulate homeostasis.
• Example:
• After stomach mechanically breaks
down food, enzymes are produced by
the stomach and small intestine to
chemically digest them into nutrients.
• These nutrients are absorbed by the
small intestine and eventually delivered
to cells.

9. Maintaining Homeostasis:
Ooooooh!
Stomach Zymogen!
• Functions
 disinfect
food
HCl = pH 2
 kills
bacteria
 breaks apart cells
 Components of HCl are
produced by parietal cells
 chemical
digestion
Example: pepsin
 enzyme breaks down proteins
 chief cells secrete pepsinogen
 activated by HCl
But the stomach is made out of protein!
What stops the stomach from digesting itself?
mucus secreted by stomach cells protects
stomach lining

10. Maintaining Homeostasis:
Small intestine
 Function
 chemical digestion
digestive enzymes
 absorption through villi & microvilli:
 finger-like projections
 increase surface area for absorption
 over 6 meters!
 small intestine has huge surface area = 300m 2
(~size of tennis court)
 most nutrients are absorbed across the
epithelium of the small intestine
 Structure
 3 sections
 duodenum = most digestion
 jejunum = absorption of nutrients & water
 ileum = absorption of nutrients & water

11. Duodenum
 1st section of small intestines
 acidfood from stomach mixes with
digestive juices from accessory glands:
 pancreas
 liver
 gall bladder

12. Accessory Organ:
Pancreas
 Digestive enzymes
 peptidases
 trypsin
 trypsinogen
 chymotrypsin
 chimotrypsinogen small intestines
 carboxypeptidase
 procarboxypeptidase
• pancreatic amylase
 Buffers
 reduces acidity
 alkaline solution rich in
bicarbonate (HCO3-)
 buffers acidity of material from
stomach Explain how this is a
molecular example of
structure-function theme.

13. Accessory Organ: Liver
 Digestive System Functions
 produces bile
 bile contains bile salts
o stored in gallbladder until needed
o break up and absorb fats in the duodenum
 act like detergents to breakup fats
Circulatory System
Connection
bile contains
colors from old
red blood cells
collected in liver =
iron in RBC rusts &
makes feces brown

14. Evolutionary Adaptations of
Vertebrate Digestive Systems
 specializationin teeth
 length of digestive system
 number & size of stomachs

15. Digesting cellulose
 How well you digest cellulose
governs life strategy of herbivores
starch
cellulose
bond between the sugars governs digestibility

16. Cow
can digest cellulose well;
no need to eat
supplemental sugars
Gorilla
can NOT digest cellulose
well; must supplement with
sugar source, like fruit

17. Mutualistic Adaptations
 How can cows digest cellulose efficiently?
 symbiotic bacteria in stomachs help digest cellulose-
rich meals caprohagy ruminant
 rabbit vs. cow adaptation: eat feces vs. chew cud
Ruminants
additional
mechanical
digestion by
chewing food
multiple times
after mixing it
with enzymes

18. Maintaining Homeostasis through Feedback
Example: Regulation of Blood Sugar
insulin
body liver stores reduces
cells take glucose as appetite
pancreas up glucose glycogen
from blood
high
liver
blood glucose level
(90 mg/100 mL blood)
low
liver
triggers releases
hunger glucose pancreas
Is this a negative or
positive feedback
liver glucagon system?

19. Homeostatic Imbalance
Diabetes mellitus
• caused by a deficiency of insulin or a
decreased response to insulin
• marked by elevated blood glucose
levels