Download Digestive system

DIGESTIVE
SYSTEM
• The function of the system
• The structure and function of each
organ
• Specialized cells/tissues in each organ
YEAR 8 BODY SYSTEMS
Let’s think about digestion!
Umm…?
Do you know
which organs
make up our
digestive
system?
Do you know the
pathway that
food takes on
its way through?
Umm…?
Do you know
what the
purpose of
digestion is?
Structures of
the digestive system
Gall
bladder
We’re
needed
too!
Salivary
glands
Large
intestine
Stomach
Mouth
Digestive
System
Small
intestine
Pancreas
Oesophagus
Rectum
Liver
Pathway through
the digestive system
Salivary
glands
Mouth
Don’t
forget
us!
Stomach
Oesophagus
Liver
Small intestine
Pancreas
Gall bladder
Large intestine
Rectum
/Anus
Purpose of
the digestive system
 To break down large food molecules that we have
consumed into smaller molecules
 The smaller molecules are needed so that:
We can get them through the lining of the
intestine and into our blood stream
2) We can use them to build our own larger molecules
1)
Fun facts about
the digestive system
 We eat about 500kg of food per year.
 We produce 1.7L of saliva each day.
 In the mouth, food is either cooled or warmed to a
more suitable temperature.
 The oesophagus is approximately 25cm long.
 Muscles contract in waves to move the
food down the oesophagus. This means that
food would get to a person's stomach,
even if they were standing on their head.
Fun facts about
the digestive system
 In an average person, it takes 8 seconds for food to
travel down the food pipe, 3-5 hours in small intestine
and 3-4 days in the large intestine.
 The human body takes 6hrs to digest a high fat meal
and takes 2hrs for a carbohydrate meal.
 Every day 11.5L of digested food,
liquids and digestive juices flow
through the digestive system,
but only 100mls is lost in faeces.
The digestive system
 Anus
 Appendix
 Gall bladder
 Large intestine
 Liver
 Mouth
 Oesophagus
 Pancreas
 Rectum
 Salivary glands
 Small intestine
 Stomach
Can you label this diagram?
The digestive system
Mouth
Salivary glands
Liver
Oesophagus
Stomach
Gall bladder
Small intestine
Appendix
Rectum
Pancreas
Large intestine
Anus
Let’s start at
the very beginning…
 What do we need to begin digestion?
o Mandible (jaw)
o Teeth
─ These structures facilitate mechanical digestion.
─ The food is physically broken into smaller pieces by
our teeth which are attached and moved by to our
jaw.
 Saliva
 Tongue
 Taste buds
Let’s start at
the very beginning…
 Saliva begins the process of chemical digestion, as well
as providing moisture that will help your food begin to
break down.
 Chemical digestion involves enzymes. These are special
chemicals that help chemical reactions occur at a faster
rate.
 Saliva contains salivary amylase –
an enzyme that helps the larger
carbohydrate molecules (eg. starch)
break down into smaller sugars
(eg. maltose).
Let’s start at
the very beginning…
Salivary
amylase
Starch
Starch
Starch
Maltose
Starch
Maltose
Does temperature affect enzymes?
Investigation 4.10
 Copy and complete the results table on p152 into your
books.
 Complete the activity.
 Answer the discussion questions on p152 below the task.
The oesophagus
 Food is now chewed and moisturized by saliva and is
pushed back by the tongue.
 We swallow, and the food goes into the oesophageus.
 The muscles that surround this tube contract to push
the food into the stomach.
 These contractions are called
peristalsis and they are
powerful enough to allow us to
swallow even if lying down
— or upside down.
The stomach
 A temporary food storage area.
 It can expand to hold 2-4Ls of food.
 Muscle movements in the stomach wall mix the
food with gastric juice.
 Gastric juice contains enzymes which help to break down
proteins.
 The stomach also contains dilute hydrochloric acid,
which kills germs and provides a suitable environment
for protein digestion.
o eg. the enzyme pepsin for protein breakdown works best in very
acidic conditions
The small intestine
 A tube about 6m long.
 Food moves through it by peristalsis.
 It makes more enzymes to complete digestion.
 Here, nutrients are absorbed into your bloodstream.
 The blood then carries the nutrients to all of the cells
of your body, where they will be used to make our own
large molecules.
 The pancreas, liver and gall bladder are
all connected to the small intestine.
The small intestine
...zoomed in!
 The small intestine is lined by tiny finger-like
projections called villi.
 The outer layer of cells lining each villi (called epithelial
cells) are covered in similar structures called microvilli
The small intestine
...zoomed in!
Why do you think
thatthe
thesurface
small
They increase
needs
area intestine
across which
the the
villi andcan
microvilli?
small intestine
absorb
nutrients.
It means that the organ
can do its job faster and
more efficiently.
The pancreas
 Makes pancreatic juice, which is basic or alkaline so it
neutralises the stomach acid.
Gastric juice
(HCl in stomach)
Pancreatic juice
 The pancreas also makes enzymes that
break down proteins, fats and
carbohydrates.
The liver
 The largest internal organ.
 It makes bile, which breaks down
fats
 It also controls blood sugar
 It destroys poisons and toxins
– like alcohol!
 It also stores vitamin A, vitamin D and iron.
The liver
The gall bladder
 Bile made in the liver is stored here.
 The bile is used to break up fats into droplets small
enough to be transported to the rest of the body.
 This bile can sometimes form stones and cause severe
pain. In this case, the individual
would need to reduce their intake
of fat, and possibly have to
have their gall bladder
removed.
The large intestine
 The large intestine is also known as the colon.
 Undigested material passes into the large intestine and
moves along by peristalsis.
 The large intestine absorbs
water, salts, vitamins and
any remaining sugars so that
they can be reused by the
body.
 The colon sits in an upside-down
U-shape across your belly
The appendix
 This organ is attached to the
large intestine.
 It used to be involved in digesting
woody stems and other plant
materials back in the day...
 But now it plays no part in digestion in humans.
 However, it is believed to play a role in fighting some
diseases.
The rectum and anus
 Rectum:
o The final part of the large intestine.
o This is where the faeces are stored.
 Anus:
o
The faeces pass through here
when you go to the toilet.
What can go wrong?
 Heartburn
 Crohn’s disease
 Inflammatory bowel
 Diverticulosis
disease
 Irritable bowel
syndrome
 Appendicitis
 Constipation
 Gallstones
 Haemorrhoids
 Pancreatitis
 Peptic ulcer
What do you do now?
 Watch the video on the next
slide (also on eBook) and
answer the worksheet
Answer the
following
worksheet
 SQ8 p157
 SQ8 p153
 Q1, 5, 6, 8
 Q1, 2, 4, 11
 SQ8 Student workbook:
 Worksheet 4.6