Transcript The Digestive System

Do now!
In pairs can you discuss
what a “balanced diet” is?
Bunny suicide #4
Last lesson
• Components of a balanced diet
What did you eat yesterday?
• Stick in the sheet “What food contains”
• Put the title “What I ate yesterday” in your books
• Think carefully and write a list of everything you
ate and drank yesterday. Include quantities.
• Read pages 6 and 7 of your book.
• Write 3 sentences explaining if you had a balanced
diet yesterday (or not!)
The digestive
system
Today’s lesson
A long tube!
We can think of the digestive system as if it
were a long tube
Breaking up of food
During its journey down the tube, food is
gradually broken down into smaller parts
until it can be absorbed by the blood. This is
called digestion.
The journey begins in the mouth
Ingestion
Putting food into the mouth is called
ingestion (feeding).
Teeth
The incisors help us to bite the food into
large chunks the food
Teeth
The molars help to grind the food into even
smaller pieces.
Saliva
Salivary glands produce saliva which makes
the food moist and easier to swallow
Saliva
Saliva also contains enzymes, which are
chemicals which break down the food
chemically.
Gullet/oesophagus/food pipe
The gullet is a tube with a muscular wall
that squeezes the food into the stomach
Gullet/oesophagus/food pipe
To show that this is true you can try
drinking water whilst standing on your
head!
Gullet/oesophagus/food pipe
It takes around 10 seconds for food to travel
from the mouth to the stomach
Stomach
The stomach is a stretchy muscular bag
which mixes the food with hydrochloric
acid and pepsin, an enzyme which helps to
digest protein molecules
Stomach
The stomach churns the
food for about 2 – 4 hours
Small intestine
The stomach squirts food into the small
intestine.
Small intestine
Here food is mixed with digestive juices
from the liver and pancreas.
Small intestine
Bile from the liver breaks up fat.
Small intestine
Pancreatic juice neutralises the stomach
acid and contains enzymes that digest
carbohydrates, proteins and fats.
(small intestine)
Small intestine
As food passes
along the long tube
of the small
intestine, its
molecules become
small enough to be
absorbed into the
blood through the
intestine walls.
Surface area
The lining of the small intestine has a large
surface area to help this to happen.
villi
Small intestine
The small intestine is about 6.5 metres long
and food spends up to 6 hours here.
Large intestine
The large intestine absorbs water from what
remains of the food.
Large intestine
Semi-solid (if you’re lucky!) faeces are
formed after 12-36 hours in the large
intestine.
Rectum
Faeces are stored in the rectum until there is
a convenient moment to get rid of them!
Anus
They exit through your anus. This is called
egestion.
Peristalsis
Throughout its journey, the food is squeezed
down the digestive system by muscular
walls in a process called peristalsis.
Role play?!
Draw the sentence!