Digesive system renewed

Animal Nutrition
Human Digestion

What do animals need to live?
 Animals make energy
using:
 food
 oxygen
 Animals build bodies
using:
 food for raw materials
 amino acids, sugars,
fats, nucleotides
 ATP energy for synthesis
O2
food
ATP
mitochondria

How do animals get their food?
filter feeding living in your food
fluid feeding bulk feeding

Different diets; different lives
 All animals eat other organisms
 Herbivores
 eat mainly plants
 gorillas, cows,
rabbits, snails
 Carnivores
 eat other animals
 sharks, hawks, spiders, snakes
 Omnivores
 eat animals & plants
 cockroaches, bears, raccoons, humans
 humans evolved as hunters, scavengers & gatherers

Getting & Using Food
 Ingest
 taking in food
 Digest
 mechanical digestion
 breaking up food into smaller pieces
 chemical digestion
 breaking down food into molecules small
enough to be absorbed into cells
 enzymes
 Absorb
 absorb nutrients across cell membranes
 diffusion
 active transport
 Eliminate
 undigested material passes out of body
intracellular
digestion
extracellular
digestion

Digestive systems
Everybody’s got one!

Food can be divided into six groups
according to its composition;
60%
1%
1%
5%
15%
19%
Water
Minerals
Vitamins
Proteins
Lipids
Carbohydrates
Each of these
foods should be
taken in proper
amounts for
energy production
and for the
production of
some vital
substances for
the body !!!!!

NUTRIENTS
Regulatory
Elements
Structural
Elements
Energy
Sources
LipidsCarbohydrates Proteins Minerals H2O Vitamins
Foodstuffs can be grouped according to their functions
as below;

Mouth
 Functions
 mechanical digestion
 teeth
 break up food
 chemical digestion (saliva)
 amylase enzyme
 digests starch
 mucus
 protects soft lining of digestive system
 lubricates food for easier swallowing
 buffers
 neutralizes acid to prevent tooth decay
 anti-bacterial chemicals
 kill bacteria that enter mouth with food
All that
in spit!

Swallowing (& not choking)
 Epiglottis
 flap of cartilage
 closes trachea (windpipe) when swallowing
 food travels down esophagus
 Peristalsis
 involuntary muscle contractions to move food along

 The function of the teeth is to grind the food into an easily digestible
form and to mix it with digestive secretions.
 In a mature human there are 32 teeth.
 16 of them are on the upper jaw and 16 of them are on the lower jaw.
Upper Jaw
Lower Jaw 16
16

4 are in the front and named
as incisors. (Total: 8)
2 are behind the incisors and
named as canines. (Total: 4)
4 are behind the canines and
named as premolars. (Total: 8)
6 are behind the premolars
and named as molars.
(Total: 12)
On one jaw;On one jaw;
The incisors and canines cut the food, the premolars
Adult teethAdult teeth

 Last 4 molars (=two in each
jaw bone) emerge after the
age of 20 and they are known
as wisdom teeth.
 20 of milk teeth that emerge
in the early ages are replaced
with 28 new teeth at the age
of 7. WisdomWisdom
TeethTeeth
MilkTeethofachildMilkTeethofachild

 The teeth maybe different in shape but their structures
are all same.
 A tooth is composed of 3 different parts;
The structure of a tooth: 1/5
The crown
(=the part that is seen on the gum)
The neck
(=the part in the gum)
The root
(=the part in the jawbone)

 If a cross section is studied from outside to inside 3
different layers are seen; enamel, dentine and pulp cavity.
Crown
Neck
Root
Enamel
Dentin
Gum
Pulp cavity
Nerves & blood
vessels
Periodontal fibers &
Cementum
Jawbone

 Enamel covers the crown part and it is composed of calcium
phosphorus and fluoride.
 Enamel is the hardest material in human body.
Crown
Neck
Root
Enamel
Dentin
Gum
Pulp cavity
Nerves & blood
vessels
Cementum
Jawbone

 Right beneath the enamel dentine is present. Dentine is the
bone-like structure of the tooth.
 The pulp cavity contains the nerves and capillaries.
Crown
Neck
Root
Enamel
Dentin
Gum
Pulp cavity
Nerves & blood
vessels
Cementum
Jawbone

 The root is surrounded by periodontal fibers and a layer
of cement that fix the tooth firmly to the jawbone.
Crown
Neck
Root
Enamel
Dentin
Gum
Pulp cavity
Nerves & blood
vessels
Cementum
Jawbone

mouth
break up food
digest starch
kill germs
moisten food

 The tongue together with the teeth assist the masticated
(=chewed) food to mix with saliva in order to form a bolus.
 The taste buds on the tongue helps person to taste bitter,
sour, sweet and salty tastes.
The tongue is also studied under chapter sensory organs.
Papillae
Taste buds
TasteMolecules

 The pharynx is a cavity that is located directly behind the
mouth and at the top of the esophagus and trachea.
 The swallowed bolus passes from the pharynx into the
esophagus. The food passage into the trachea is prevented
by epiglottis.
 Swallowing
starts
voluntarily in the
mouth and
continues
through the
pharynx into the
esophagus
involuntarily.

 Esophagus resembles a pipe that is 25 cm. long and 2
cm. wide.
 It is located between pharynx and the stomach.

 The esophagus wall is composed of 3 main layers;
Outer layer Middle layer Inner layer

 Outer layer contains connective tissue and protects the esophagus.
 Middle layer contains circular muscles. Contractions and relaxations
of these muscles result in peristaltic movements. Peristaltic movements
force the food into the stomach. Reverse peristalsis causes vomiting.

Stomach
Functions
disinfect food
hydrochloric acid = pH 2
kills bacteria
food storage
can stretch to fit ~2L
food
digests protein
pepsin enzyme
But the stomach is made out of protein!
What stops the stomach from digesting itself?
mucus secreted by stomach cells protects
stomach lining

1) To store ingested food
2) To produce gastric juice for
digestion
3) To mix digestive juices and food
by physical movements
4) To carry food into the small
intestine

stomach
kills germs
break up food
digest proteins
store food
sphincter
sphincter
mouth
break up food
digest starch
kill germs
moisten food

Used to think
ulcers were
caused by stress
 tried to control with
antacids
Now know ulcers
caused by
bacterial infection
of stomach
 H. pylori bacteria
 now cure with
antibiotics
Ulcers
inflammation of
stomach
inflammation of
esophagus
Colonized by
H. pylori
Free of
H. pylori
white blood cells
cytokines
inflammatory
proteins
(CagA)
cell damaging
proteins
(VacA)
helper T cells
neutrophil cells
H. pylori

Small intestine
 Functions
 digestion
 digest carbohydrates
 amylase from pancreas
 digest proteins
 trypsin & chymotrypsin from pancreas
 digest lipids (fats)
 bile from liver & lipase from pancreas
 absorption
 nutrients move into body cells by:
diffusion
active transport
This is
where all the
work is done!

Absorption in Small Intestines
 Absorption through villi & microvilli
 finger-like projections
 increases surface area for absorption
SMALL INTESTINES
6 meters long,
but can stretch
to cover a
tennis court

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

Pancreas
 Produces digestive enzymes
 digest proteins
 trypsin, chymotrypsin
 digest starch
 amylase
 digest lipids
 lipase
 Buffers
 neutralizes
acid from
stomach
small
intestine
pancreas

stomach
kills germs
break up food
digest proteins
store food
mouth
break up food
digest starch
kill germs
moisten food
pancreas
digest all foods

Liver & Gall Bladder
 Produces bile
 breaks up fats
 gallbladder only stores bile
 that’s why you can have your gall bladder
removed
bile contains
colors from old
red blood cells
collected in liver =
iron in RBC rusts &
makes feces brown
bile contains
colors from old
red blood cells
collected in liver =
iron in RBC rusts &
makes feces brown

pancreas
digest proteins & starch
stomach
kills germs
break up food
digest proteins
store food
mouth
break up food
digest starch
kill germs
moisten food
liver
produces bile
break up fats

 Function
 re-absorbs water
 use ~9 liters of water every day
in digestive juices
 if don’t reabsorb water
would die of dehydration
 > 90% of water re-absorbed
not enough water re-absorbed
 diarrhea
 can be fatal!
too much water re-absorbed
 constipation
 reabsorb by diffusion
Large intestines (colon)

You’ve got company!
 Living in the large intestine is a
community of helpful bacteria
 Escherichia coli: E. coli
 digest cellulose
 digests fruits & vegetables
 produce vitamins
 vitamin K & B vitamins
 BUT generate gases
 by-product of bacterial metabolism
 methane, hydrogen sulfide
 STINKY!
PEE-YOO!

 Caecum is attached vertically to the small intestine. From
caecum a projection known as appendix extends.
 The inflammation of appendix (=appendicitis) requires
surgical operation.
Appendix

stomach
kills germs
break up food
digest proteins
store food
mouth
break up food
digest starch
kill germs
moisten food
small intestines
breakdown food
- proteins
- starch
- fats
absorb nutrients
pancreas
digest proteins & carbs
liver
produces bile
break up fats
large intestines
absorb water

Appendix
Vestigial organVestigial organ

stomach
kills germs
break up food
digest proteins
store food
mouth
break up food
digest starch
kill germs
moisten food
small intestines
breakdown food
- proteins
- starch
- fats
absorb nutrients
pancreas
digest proteins & carbs
liver
produces bile
break up fats
large intestines
absorb waterappendix

Rectum
 Last section of large intestines
 eliminate feces
 what’s left over?
 undigested materials
 mainly cellulose from plants
 called roughage or fiber
 keeps everything moving & cleans out
intestines
 masses of bacteria
So don’t forget
to wash
your hands!

Different diets; different bodies
 Adaptations of herbivore vs. carnivore
 teeth
 length of digestive system
 number & size of stomachs

Teeth
 Carnivore
 sharp ripping teeth
 “canines”
 Herbivore
 wide grinding teeth
 molars
 Omnivore
 both kinds of teeth

Length of digestive system
 Herbivores & omnivores
 long digestive
systems
 harder to digest
cellulose (cell walls)
 bacteria in intestines
help
 Carnivores
 short digestive
systems
 protein easier to
digest than cellulose
appendix

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 B12 (energy production)
 kwashiorkor — protein

 Need to make sure you get enough protein
 20 amino acids to make protein
 12 amino acids humans can produce
 8 we have to eat = “essential amino acids”
 Grains (like corn) have 6 amino acids
 missing 2
 Beans (like soybean & red beans)
have 6 amino acids
 missing different 2
 mix beans & grains
for complete group of
amino acids
 rice & beans
 taco/tortilla & beans
 tofu & rice
 peanut butter & bread
Vegetarian diets

liver
pancreas
liver
Balancing Blood Sugar levels
blood sugar level
insulin
body
cells take
up sugar
from blood
liver stores
sugar
reduces
appetite
glucagon
pancreas
liver
releases
sugar
triggers
hunger
high
low
Feedback
Homeostasis

2006-2007
Don’t turn yourself
inside out…
Ask Questions!!

Feedback: Maintaining Homeostasis
 Balancing glucose levels in blood
pancreas
pancreas
insulin
liver
takes up
glucose
for storage
cells
take up
glucose
from blood
liver releases
glucose
to blood
depress
appetite
stimulate
hungerglucagon

 There are three pairs of salivary glands in the mouth;
sublingual, submaxillary and parotid glands.
 Additionally, the mucosa of the mouth produces secretions.
 Secretions of these glands form the saliva of the mouth.
 Saliva contains …
 enzyme
amylase
(=ptyalin)
 Mucus
(=it functions as a
solvent)
 Proteins
 Water
 Na++
 Ca++

Functions of saliva
1)It initiates carbohydrate digestion
2)It helps in detection of taste because it is a
solvent
3)It helps in formation of bolus
4)It lubricates the pharynx so that food may be
swallowed easily
5)It assists in speaking

 Gastric Juice is acidic with pH = 1-2 and capable to digest
the stomach wall.
 Gastric juice is secreted by the gastric glands in the
stomach. Gastric juice contains …
 HCl
 Pepsinogen
 rennin (=in
babies)
 a small amount
of lipase. Gastric
juice
Stomach
wall

 Self digestion is prevented by the secretion of mucus
from the gastric glands. Any damage in the gastric
mucosa results in gastritis (Inflammation of the
stomach). Gastritis may result from infection, alcohol,
or dietary changes.
Areas effected from gastritis

 Gastritis may develop in a peptic ulcer.
areas of peptic ulcer

What is the difference between
gastritis and peptic ulcer?
 Gastritis is not a single disease, it is
inflammation of the stomach lining and has
many causes from drinking too much to a
bacteria in the stomach.
 A peptic ulcer is when a sore or ulcer has
been made in the lining of the stomach by the
stomach acid.

Functions of HCI
acid in Gastric
juice

1) It converts inactive pepsinogen into active
pepsin
2) It stimulates the secretions of pancreas and
intestinal glands
3) It destroys microbes ingested with food
4) It facilitates digestion by denaturizing
proteins
Pepsinogen
(Inactive)
Pepsin
(Active)
HCl

Control of Gastric juice secretion

Food enters the
stomach
Receptors of stomach
send impulses to m.o
Medulla oblongata
send impulses via
vagus nerve
Secretory cells of
stomach secrete
hormone Gastrin
Formation of
Pepsin
Digestion of proteins and
formation of chyme
Chyme enters
duedonum
Secretory cells of
duedonum secrete
enterogastrin
Enterogastrin
inhibits the
stomach activity
Gastrin
stimulates the
secretion of HCl
and Pepsinogen
Control of Gastric juice secretion

 Bile ducts merge and form the Common hepatic duct.
 Common hepatic duct carries the bile salts into the gall
bladder for further usage.

 Approximately 600 ml. of bile is secreted from the
liver in a single day.

 Bile contains insoluble cholesterol and some other
substances.
 A reduction in the bile salts can result in the formation
of gall stones by the precipitation of cholesterol.

1) Formation and degradation of erythrocytes:
 Old erythrocytes are degraded in the liver.
 From hemoglobin bile salts and the hemoglobin of new
erythrocytes are synthesized.
 Old erythrocytes are degraded by phagocytotic activity
of Kuppfer cells.
 In early embryological development, liver functions as an
organ that produces erythrocytes.
BILEHEME
early embryological
development

2) Formation and secretion of bile:
 Bile is formed by liver cells and drain into common
hepatic duct. Common hepatic duct braches into to two
ducts. (Cystic duct and common bile duct)
 Cystic duct brings excess bile into the gall bladder and
common bile duct leads bile in the small intestine.
90% of bile salts
are absorbed
during passage
through the small
intestine.
Bile helps the
absorption of lipids
and plays a great
role in the
prevention of
bacteria production
in feces.

3) Regulation of blood sugar level:
 Excess amount of sugar in the blood is stored as
glycogen in the liver. When blood sugar level decreases
glycogen is converted into glucose and released into the
blood.
Gluc
ose
Glyco
gen
Insuli
n
Glucag
on

4) Conversion of provitamin A into vitamin A &
vitamin deposition :
 Liver converts provitamin A into vitamin A.
 On the other hand, liver stores vitamins A, D, K and
some minerals such as Fe, Cu etc.
Provitam
in A
Vitamin
A

 Liver synthesizes
12 amino acids out
of 20.
 Excess amino
acids are stored
in the form of
lipid at proper
parts of the body.
5) Regulation of
protein metabolism:

6) Urine synthesis:
After the degradation of amino acids in the cells,
poisonous ammonia (=NH3) is produced.
Ammonia is later brought to the liver to be converted
into a less poisonous substance –urine- by a process
named as ornithine cycle.
Ornithine
Arginine
Citruline
Urea
H2O H2O
H2O
NH3
CO2
NH3
Ornithine
Cycle
2NH3 CO2+ Urea H2O+

7) Plays a great role in coagulation of blood:
 In coagulation, proteins protrombin and fibrinogen are
very important. These proteins are synthesized by the
liver.
 On the other hand, heparin that prevents blood
coagulation in vessels is also synthesized by the liver.
Protrombin Thrombin
Thrombokinase
Ca++
,
Vitamin K
Fibrinogen
(Soluble)
Fibrin
(Insoluble)
Thrombocytes Clot

 Toxic substances that enter the body with food and
medicines are detoxified by the liver cells. The most
important toxic materials are H2S and H2O2. These
substances are converted into H2O and O2 by enzymatic
activity.
8) Detoxification of substances:

 The liver an organ that produces a great amount of
heat.
 The heat is distributed to other parts of the body by
blood.
9) Regulation of body temperature:
10) Immunity:
 The liver cells form lymph and also some antibodies that
are important in immunity.

.
β-cells of
the
pancreas
Normal Glucose
level
Increase in
glucose level
Conversion of glucose
into glycogen in the
liver
Affect
s
Affect
s
Insulin secretion
into blood
Insulin and Glucagon functions in the control of
blood glucose level
Decrease in glucose
level
α-cells of
the
pancreas
Glucagon is
secreted into
blood
Conversion of
glycogen into glucose

In the mouth:
In the small intestine:
(ex: sucrose,
lactose &
maltose)
from salivary
glands
+H2O Polysaccharide +Dextrin Disaccharides
Amylase
from pancreas
+H2O Dextrin Glucose
Amylase
+H2O Sucrose Glucose
Sucrase
+Fructose
from intestinal glands
+H2O Lactose Glucose
Lactase
+Galactose
+H2O Maltose Glucose
Maltase
+Glucose

 From medulla oblongata Vagus nerve caries impulses to the secretory
cells of the stomach.
 Vagus stimulates the secretion of hormone gastrin.
 Gastrin stimulates the secretion of HCl and inactive pepsinogen.
In the stomach:
Pepsinogen
(Inactive)
Pepsin
(Active)
HCl
+H2O Proteins Peptones
Additionally in
babies;
+H2O Casein Peptones
Pepsin
+Amino acids
+H2O Milk Casein
Rennin

 Chyme (=mixture of peptones, amino acids, monosaccharides, lipids,
enzymes, vitamins and minerals and water etc.) enters duodenum.
 Acidic content of chyme stimulates the secretion of hormone secretin.
 Secretin stimulates pancreas to secrete pancreatic juice.
 Pancreatic juice contains inactive enzymes trypsinogen and
chymotrypsinogen.
 On the other hand, intestinal glands secrete enterokinase. All of this
mixture (chyme + enzymes + enterokinase) is present in the intestine at
this moment.
Trypsinogen
(Inactive)
Trypsin
(Active)
Enterokinase
Chymotrypsinogen
(Inactive)
Chymotrypsin
(Active)
Enterokinase

+H2O Peptones Peptides
Trypsin
&
Chymotrypsin
+Amino acids
+H2O Peptides
Peptidase (=Erepsin)
Amino acids
from intestinal
glands
In stomach
Proteins Peptones
Amino
acids
Peptides
In duedonum In ileum & jejenum
Shortly protein synthesis is as below;

 Bile secretion from the gall bladder emulsifies the lipids and makes
their digestion easier.
 If the gall bladder is removed in a person, lipid digestion occurs harder.
from pancreas
+H2O Lipids +Glycerol Fatty acids
Lipase

from pancreas
+H2O DNA Nucleotides
DNA (ase)
+H2O RNA Nucleotides
RNA (ase)

Digesive system renewed

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