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the human skeleton
Fig. 1
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1 Vertebrates
Under a microscope you saw the difference between plant cells and animal
cells. Plant cells have cell walls whereas animal cells don’t. Plants are able
to stand upright because of this cell wall. The wood that supports a tree is
made up of very thick cell walls. If animals like mammals and insects
wouldn’t have a skeleton they would be nothing but a sac
(the skin) filled with a puddle of cells.
As we have seen in the chapter
“microscopy and cells”, there are two kinds
of skeletons. Vertebrates (gewervelden)
have bones on the inside and some
Fig. 2
invertebrates (ongewervelden), like
arthropods, have a hard external
(uitwendig) skeleton like a crab, a beetle
or a millipede. One important difference
between these skeletons is that the bones
contain living cells and the external skeleton
doesn’t. In this chapter we will discuss the
bones of the vertebrates.
In total, the human skeleton consists of
206 bones. The picture on the previous
page (Fig. 1) shows us the most important
bones and their names. The skeleton serves
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several purposes, next to supporting the
Fig. 3
body it protects important organs, it makes
movement possible and muscles are
attached to the skeleton.
In addition blood cells are produced in certain bones, like the hip bone,
sternum (borstbeen), skull (schedel), ribs, vertebrae (wervels), shoulder
blades and in the femur (opperarmbeen). Besides supporting the animal
(human) body, bones also protect our vital (van levensbelang) organs, they
produce blood cells and they make us able to move.
Questions:
1. How can some animals like jellyfish and anemones live without a skeleton?
2. Label the bones indicated in figure 3 with the correct names.
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3. The beetle and the dog in figure 2 both need to grow when they were
larvae and puppies.
The beetle needs to shed its external skeleton whereas the dog doesn’t
need to (think about the meal worms).
Explain why the beetle larva does need to shed its skeleton and the puppy
doesn’t.
4. Name three types of blood cells referred to in the text. Use an
encyclopaedia / internet.
What is the function of each type of blood cell?
5. The skeleton protects vital organs. What is or are protected by:
a the skull
b the ribcage
2 Structure of the bone
Old bones found in graves are dead, dry and brittle. But in the body, bones
are very much alive. They have their own nerves and blood vessels, and they
do various jobs, such as storing body minerals like calcium. Bones are made
of a mix of hard stuff that gives them strength and millions of living cells
which help them grow and repair themselves. In the middle of some bones is
jelly-like bone marrow, where new cells are constantly being produced for
the blood.
Calcium is an important mineral that bone cells need to stay strong so
keep drinking that low-fat milk! In the bones, a protein called collagen is
produced that makes the bones flexible. Young children have a lot of
collagen and little calcium so their bones are flexible and don’t break that
easily. Older people have less collagen and more calcium, which is why they
break their legs and hips more easily when they fall.
Collagen is also found abundantly in cartilage. Cartilage is the tissue
present e.g. in your earflap and your nose. It is also found in joints as you
will see later on is this chapter.
Questions:
6. On the food packages it should say what nutrients are present in the food
stuff and in what amounts. For next lesson make a list of food stuffs
(eten) that contain calcium and how much of it they contain.
7. Why is it important to eat or drink food with calcium?
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8. Tom broke his arm two years ago. Today his arm is as strong as ever
before. He says that this is because bones are living organs.
Explain that a bone in your arm can heal because it is alive.
Demonstration practical:
The TOA (technisch onderwijs assistent) will show you some chicken bones
that have been put in hydrochloric acid (zoutzuur) and some chicken bones
that have been burnt. Hydrochloric acid dissolves the calcium and the
burning combusts (verbrandt) the collagen.
Questions:
9. What happened to the bones that have been put in hydrochloric acid?
10. What happened to the burnt bones?
11. Explain, using these results, that little children don’t easily break their
legs.
12. Explain, using these results, that the elderly
(ouden van dagen) do break their bones
easily.
3 The spine
The spine has several special roles in the human
body. It protects the spinal cord (which connects
nerves to the brain) (see Fig. 4). Through the spinal
cord the brain communicated with all parts of the
body. The body tells the brain what they sense
(waarnemen) and the brain controls the movements.
Furthermore the spine provides the support needed to
walk upright. It also enables the torso to bend and it
supports the head.
Viewed from the side, the spine has a natural "S"
curve. This “S” curve (see figure 5) makes the spine
flexible and absorbs shocks when jumping up and
down. From top to bottom, the spine has 33
doughnut-shaped bones called vertebrae. Each
vertebra is assigned a letter and a number that
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Fig. 5
identifies its location in the spine (Fig. 5). Sandwiched between each pair of
vertebrae is a spongy cartilage, or disc (schijf) (see Fig. 4). Intervertebral
discs, as they are known, act as shock-absorbing cushions (kussens) and
make the spine flexible.
Questions:
13. Andrea has had a severe accident. She broke her back at the position of
T10 (see figure 5). Because of this she is no longer able to walk nor is
she able to feel her legs.
How can you explain this.
14. How can someone die of a broken neck?
15. Aïsha is not working today. She suffers from a hernia. She lifted a box
the wrong way and one of the cartilage discs moved from between the
vertebrae. Because of this her legs hurt.
a
In a drawing show what happened in her spine because of the
movement of the disc.
b
Explain that this movement causes the pain in her legs.
16. Peter is now 45 years old. When he was 18 he had to serve in the army.
Peter didn’t like the army because he is against violence. Still he had to
join the army, unless he was taller than 1.95 metres. Unfortunately he
was only 1.93 metres. Being a good biology student he thought of a
way... He stayed in bed for two days and was measured directly after he
got up. He was 1.96 metres tall and didn’t have to serve in the army.
What had happened to Peter during the night that made him 3 cm taller?
4 Muscles
Joints (gewrichten) occur where two
bones meet. They make the skeleton
flexible. Without them, movement
would be impossible. Muscles are also
necessary for movement: they're the
masses of tough (sterk), elastic tissue
that pull our bones when we move.
Together, our bones, muscles, and
joints (along with tendons (pezen),
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Fig. 6
ligaments (banden) and cartilage
(kraakbeen)) form our musculoskeletal
systems and enable us to do everyday
physical activities.
In your upper arm there are two muscles. In
figure 6 you can see that a muscle is attached
to the bone by tendons (Fig. 7), a tough,
Fig. 7 muscle and tendon
none flexible band of tissue. Your biceps
make your arm bend when you lift something (Fig. 6a). This muscle is
located on the topside of your upper arm. At the other side of your upper
arm we find the triceps which performs the opposite action: it straightens
the arm when it contracts (Fig. 6b). During a movement of the arm one of
the muscles contracts and the other relaxes. Two muscles that have opposite
(tegengesteld) effects are called an antagonistic pair of muscles. One is a
called flexor muscle (causes bending) the other one an extensor muscle
(causes straightening).
Questions:
17. In the text is says that antagonists contract alternately (om de beurt).
Explain that simultaneous contraction is a waste of energy.
18. In the picture (Fig. 7) you can see the location where the tendons of the
biceps are attached to the bone. The attachment of the triceps,
however, is not shown. In a drawing indicate where the triceps are
attached to the bone. Draw the humerus and the radius first.
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Fig. 8
Fig. 9
Fig. 10
5 Joints
Move the tip (phalanges) of your index
finger (wijsvinger). It can only move in one
plane (vlak). You can’t make the tip of your
finger move sideways. The movement is
limited by the type of joint that connects
the last two phalanges. This type of joint is
Fig. 11
called a hinge joint. Like a door which
hangs from hinges, it can only move in one direction (see Fig. 8).
If you try to move other joints in your body, you’ll find many hinge joints.
However, if you move your arm from your shoulder, you’ll find that you can
move it around like the rotating blades of a wind mill. This is because of a
differently constructed joint, the ball and socket joint. It allows the bones
to move in all directions (see Fig. 9).
The final joint is present in the lower arm and leg. Imagine you’re trying to
drive a screw into a wall. You can rotate your lower arm because of the
pivot joint, which allows the radius to rotate around the ulna (Fig. 10).
Figure 11 represents a hinge joint as it is present in an elbow. This joint
forms the connection between the humerus and the ulna. Both bone endings
are covered with cartilage. The cartilage protects the bones, by preventing
that they rub against each other. The synovial fluid between the bones
functions as a lubricant (smeermiddel). Around the synovial fluid is the
synovial membrane which produces the synovial fluid and keeps it inside
the joint. Together, the cartilage and the synovial fluid protect the bones
from being damaged and make sure movement goes as smoothly as possible.
Without these components the bones would come into close contact and
wear of little bits of bone every time the arm flexes or extends. Around a
joint ligaments are located, which hold the joint together. Ligaments are
tough, nonflexible tissues, in structure similar to tendons.
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Questions
19. In Fig. 1 (page 2) indicate, in red, the locations of hinge joints.
20. In Fig. 1 indicate, in blue, the locations of ball and socket joints.
21. In Fig. 1 indicate, in blue, the locations of pivot joints.
22. Make a table. In the first column present the three kinds of joints. In the
second column present the examples of questions 19 – 21. In the third
column mention the names of the two bones that form these joints
Don’t forget the titles of the columns and the main title of the table.
23. During a football match a player damaged the inside of his knee. More
precisely, he damaged his meniscus, a cartilage ring (see Fig. 12; you
don’t need to learn the parts in Fig. 12 for the test). The next day his leg
hurt when he tried to walk or even when he tried to stand on this leg.
Explain that a damaged meniscus leads to this pain (you don’t need to
study this picture for the test!!).
Fig. 12
24. Suppose your twisted your ankle outwards
(see Fig. 13).
What do you think will happen to the
ligaments?
Fig. 13
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practical bones
human
1. Above you find front legs of a horse and a lion, and the arm of a human.
a) In the limbs (ledematen) of each of these species indicated the
following bones:
- red: humerus
- blue: ulna
- green: radius
- yellow: clavicle
- brown: phalanges
b) On what part of its leg does a horse walk?
On what part does a dog walk?
And on what part a human?
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2. On your desk you’ll find two pieces of sand paper (schuurpapier).
a) Rub one piece of sand paper against the other.
What do you notice?
On your desk you’ll find two smooth glass slides and a beaker with water.
b) Rub one glass slide against the other.
What do you notice compared to a?
c) Now, do it again but with some water between the glass slides.
What do you notice?
Similarly, a joint functions better when certain components are present.
d) Which two components are meant here?
e) Explain your answer.
3. Compare the leg of a human, the leg of a bird and the leg of dinosaur.
a) Which two legs are more similar, bird and human or bird and dinosaur?
b) From what group do birds originate, mammals or dinosaurs?
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glossary with chapter “the human skeleton”:
cell walls
vertebrates
invertebrates
arthropods
external skeleton
bone marrow
calcium
collagen
cartilage
spinal cord
torso
vertebrae
spine
joints
muscles
tendons
ligaments
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biceps
triceps
to contract
antagonistic pair of muscles
flexor muscle
extensor muscle
hinge joint
ball and socket joint
pivot joint
synovial fluid
synovial membrane
cartilage
ligament
What must you know about this section?
describe the bold printed terms in your own words
functions of the skeleton
names and locations of the bones
the two substances of which bone is made and their function
the function of muscles, antagonists
three kinds of joints and their characteristics
the parts of a joint and their function
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