Transcript Digestive System 1

ACTIVITY
Can you identify these organs?
Large Intestine
Oesophagus
Small Intestine
Stomach
Can you guess the length of
the above organs?
Name of Organ
Oesophagus
Stomach
Small Intestine
Large Intestine
Entire Digestive System
Length of Organ (cm)
Name of Organ
Length of Organ (cm)
Oesophagus
~25
Stomach
~20
Small Intestine
~700
Large Intestine
~150
Entire Digestive System
~925
5 Processes of Nutrition
1)
2)
3)
4)
5)
Ingestion
Digestion
Absorption
Assimilation
Egestion
Ingestion
• The taking-in of food
Digestion
• The breaking down of large molecules
into smaller molecules
• Rely on action of digestive enzymes
Absorption
• The entrance of digested food molecules
into blood streams by diffusion or active
transport
Assimilation
• The transportation of food particles to
various parts of the body via blood
streams
Egestion
• The removal of undigested or
unabsorbed food from the body in the
form of faeces
Can you match each process
to different parts of the
alimentary canal?
• Ingestion: mouth
• Digestion: mouth,
stomach and small
intestine
• Absorption: mainly
in small intestine;
some in stomach
and large intestine
• Assimilation: all
over body
• Egestion: anus
Ingestion
Types of Teeth
Incisors
•
•
•
•
Located at front of jaws
Sharp and chisel-like edge
For cutting food into pieces
Single root embedded in jaw bone
Canines
•
•
•
•
Located next to the incisors
Sharp and pointed
For piercing and tearing food
Single root embedded in jaw bone
Premolars
• Located on the sides of jaws
• Large with a flattened top
• Cusps for crushing and
grinding food
Molars
• Located at the back of the jaws,
behind the premolars
• Larger than the premolars
• For crushing and grinding food
enamel
crown
dentine
capillary
nerve endings
cement
periodontal
membrane
gum
pulp
cavity
jaw
bone
neck
root
External Structure of a Tooth
1) Crown – the part above the gum
2) Neck – the region between the root and
the crown that is bounded by the gum
3) Root – the part embedded in the jaw
bone
Internal Structure of a Tooth
1) Enamel
- Outermost region
- Hardest region of the tooth
- 97% of it is made of calcium and magnesium
salts
- Contains no living cells
- Protects the tooth from mechanical damage
Internal Structure of a Tooth
2) Dentine (Ivory)
- Middle region of a tooth
- Bone-like substance
- 73% is inorganic matter (mainly calcium and
phosphate crystals)
- Make up the bulk of a tooth
- Contains odontoblasts, the dentine-forming
cells
Internal Structure of a Tooth
3) Pulp cavity
- Innermost region of a tooth
- Filled with living cells
- Contains blood capillaries (to supply
nutrients and oxygen to the dentine) and
nerve endings (to produce sensations of
pressure, pain and temperature)
- Blood vessels and nerves enter the tooth
through an aperture at the base of the root
Internal Structure of a Tooth
4) Cement
- Thin layer of substance covering the dentine
in the root
- Similar to bone
- Attached to a fibrous membrane called
periodontal membrane – periodontal fibres
connect the cement to the jaw bone
- These fibres anchor the tooth firmly in place
but still permit slight movement which helps
to protect the tooth from mechanical damage
What is the difference between their teeth?
I have
milk
teeth
We have
permanent
teeth
Milk Teeth vs. Permanent Teeth
• Milk teeth start to develop after birth
• Begin to show when child is about 5 months old
• Begin to shed when child is between 7 and 11
years old
• Permanent teeth are fully developed by age 17
• Permanent teeth stop growing once they are
fully developed, and cannot be replaced if
damaged
Dentition and Dental Formula
• Dentition – represents the number and
arrangement of different types of teeth
• Dental formula – a formula that shows the
number of different types of teeth on the
upper and the lower jaws
• i = incisors c = canines
pm = premolars m = molars
Dental Formula of Humans
Milk Dentition
Permanent
Dentition
Dental
Formula
i 2, c 1, m 2
2 1 2
(or 212)
212
i 2, c 1, pm 2, m 3
2 1
2 3
(or 2123)
2123
Total Number
of Teeth
(2 + 1 + 2) x 2 x 2
= 20
(2 + 1 + 2 + 3) x 2 x 2
= 32
Which of the following
is a Human skull?
Skull of Human (Omnivore)
Skull of Herbivore
Dentition of Herbivores
• Herbivores – feed on plants only
• Their dentition is adapted for cutting and
grinding grasses and plant tissues
• Diastema – a space in front of the premolars
to allow grass to be moved freely inside the
mouth
Skull of Carnivore
Dentition of Carnivores
• Carnivores – feed on animals only
• Their dentition is adapted for killing preys and
eating animal tissues (e.g. gripping, cutting
and tearing flesh, etc.)
• Carnassial teeth – the last upper premolar
and the first lower molar on each side of the
jaws. Can cut through flesh and crush bones
when the jaws move up and down