Series 8
17
Without a skeleton the human body would be
a soft mass of flesh, unable to stand up or to
move. Our 206 bones form the framework for
our flesh, work with muscles to help us move
and also protect our organs. Our skeletons
have some amazing properties and abilities
that make it both strong, yet flexible and able
to do things you might not expect.
frontal bone
parietal bone
temporal bone
zygomatic arch
mandible
skeleton
THE
clavicle
The skull is made up of 22 bones, of these 21 are fused into place and only the
jawbone moves. The skull protects the brain and houses the delicate organs of
the ear and eyes. In a baby the bones of the skull are not fully formed, they are
joined instead by membranes called fontanelles. This allows the baby’s skull to
be compacted to fit through the birth canal. The bones eventually fuse together
at 12 to 18 months. Inside the skull are spaces filled with air called sinuses,
these help lighten the skull and also help amplify the voice.
ribs
Throughout history the image of the skeleton has been
used to frighten and sometimes amuse us. Bones without
the skin on them have a way of reminding us of death
and have been used as a symbol for death for centuries.
Ancient sorcerors or magic makers often used bones
in rituals. Traditional Aboriginal kadaitja men pointed
specially prepared human or emu bones at people to steal
their life essence.
One well known image of Death is that of a skeleton in a
black black robes wielding a scythe. But not all skeletal
images are meant to frighten us. During their Dia de los
Muertos, or Day of the Dead, the Mexicans paraded festive
looking images of skeletons to honour their dead. The
procession is led by images of Mictecacihuatl, the Aztec
goddess of the underworld who is depicted with a skull
face and exposed rib cage.
A sculpture
of skeletons
“wrestling”
exhibited at
a theatre in
Mexico City’s
Zocalo main
square in
2007
humerus
ILIUM OF PELVIS
(Hipbone)
ULNA
RADIUS
Spine
The ribcage protects the heart
and lungs. It is made up of
twelve sets of flat curving bones
that join to the thoracic vertebrae
(bones of the spine). The ribs are
joined together at the sternum
at the front and the upper most
ten ribs are connected to the
sternum with flexible cartilage
to enable the rib cage to expand
when a person breathes.
The backbone or spine is made up of 24
main bones: 7 cervical (neck), 12 thoracic
(chest) and 5 lumbar (lower back). At the
base of the spine there are 5 bones fused
as one known as the sacral bones, and
between 3 and 5 fused caudal vertebrae
(the coccyx). Between each of the
vertebrae are discs made of cartilage. The
spine is not straight but curves in an sshape when seen from the side. The discs
and the curve make the spine flexible and
help it to absorb shocks. Jutting out from
each of the vertebrae are bits of bone
known as processes that provide anchor
points for the muscles. Running down the
middle of the spine is the spinal chord,
which connects the nerves of the body
with the brain.
Joints
COCCYX
ISCHIUM
METACARPALS
(Palm bones)
PUBIC BONE
Digging bones
After death bones last longer than the soft tissues in
the human body. In countries where space for burials is
limited graves are often dug up, or taken from a tomb,
after a certain time and the bones put into an ossuary. An
ossuary is either a stone box that might hold more than
one member of the same family or in some cases it is a
tomb where many bones are stacked.
Ribs
SACRUM
SHAFT OF FEMUR (Thighbone)
PATELLA (Kneecap)
1
Broken
bone
2
Tuesday 11.30am on
callus
3
Skull
scapula
sternum
Scarey skeletons
How bones heal
PHALANGES
(Finger bones)
There are many different kinds
of joints in the body. Ball and
socket joints, like the shoulder
and hip, allow limbs to move in
many directions. Condyloid joints
are like ball and socket joints
but with less movement, like
the knee joint. hinge joints (the
elbows) allow movement back
and forward, pivot joints allow
limited rotating movement (the
neck). Saddle joints have two
interlocking bones shaped like
saddles, the only example of this
kind of joint is the thumb. Gliding
joints, where two flat surfaces rub
against each other, in the wrists
and feet allow them to flex.
regrown
blood vessels
blood
clot
As strong as bones are sometimes they can break. One of the most
remarkable things about bones is that they can heal after being
broken. 1. When the bone breaks it causes bleeding. Within about
six hours the blood forms a clot, sealing off the broken blood
vessels, and new bone begins to grow. Cells in the periosteum
start to divide to cover the broken area and form a seal.
2. After about three or four weeks the periosteum has covered
the broken section and the clot has formed into a soft fibrous
mass called a callus. 3. Osteoblasts within the callus transform
the soft tissue into spongy bone, joining the broken bone together. This
normally bulges out around the area of the break. Three to four months after
the break occurred compact bone has formed, the bulge is remodelled and
osteoclasts absorb dead bone fragments.
An X-ray of a
broken arm
Did you know?
X-rays
n Most people only see bones from dead animals that have
been left out in the sun that are usually dry and brittle. But
when they are inside the body bones are actually moist and
more flexible.
Because bones are more dense than the flesh and organs
of the body it is possible to see them by sending x-rays or
waves of radiation (invisible to the human eye) through
the body and recording the shadows cast by the bones
as images on either a photographic plate or some other
device sensitive to the radiation. This method of creating
pictures of a living person’s skeleton was discovered by
Wilhelm Roentgen in 1895.
n The bones that make up the ear are not counted as part of
the skull although they do sit inside a cavity in the skull. The
ear contains the smallest bone in the body the incus (anvil).
The teeth, which are made of dentine and enamel, are also not
considered bones.
n Men and women both have twelve sets of ribs despite a
persistant myth that men have one rib less. This belief was
inspired by the biblical story that God used one of the first man
Adam’s ribs to create Eve, the first woman.
One of the earliest
known X-rays.
Taken in public by
inventor Wilhelm
Konrad Roentgen
in 1896, it shows a
woman’s hand.
n The female pelvis has a wider opening (pelvic inlet) than
that of a male to allow space for a baby to squeeze through
during childbirth. That is how people are able to tell whether an
unidentified skeleton is that of a male or female.
CARPAL BONES
spongy
bone
Appendicular bones
The skeleton is divided into two parts: the 80 axial bones - skull,
ribs and spine - and the 126 appendicular bones - shoulders,
arms, hands, pelvis, legs and feet. It is called appendicular
because it appends hangs off the axial skeleton. The appendicular
bones include the largest bone in the body the femur or upper leg
bone. Ball and socket joints connect the arms to the shoulders
and the legs to the pelvis, giving them a greater range of
movement than any other bones in the body.
SPONGY
BONE
Ossuary in Grand Meteoron monastery, containing the
skulls of past monks, at Meteora, Greece
PICTURE: Andrew Bain
TIBIA (Shinbone)
FIBULA (Calf bone)
COMPACT
BONE
BLOOD
VESSEL
TALUS
BONE
MARROW
TARSALS (Ankle bones)
PERIOSTEUM
METATARSALS (Foot bones)
PHALANGES (Toe bones)
Bone structure
Bone is made up of calcium phosphate, collagen
fibres and cells that maintain the structure of the
bones. Covering the bones, except at the joints, is
a thin yet tough membrane called the periosteum.
This layer has nerves, to warn of damage, and blood
vessels to supply the bone cells or osteocytes. On the
inner layer of the periosteum are osteoblasts, these
are the cells that create new bone.
Under the periosteum is the most dense layer of
bone known as compact or cortical bone. Within
this cortical bone are structures called osteons,
cylindrical units of hard bone with hollow channels
for blood vessels and small spaces called lacunae
containing osteocytes.
In the middle of the bone there is tissue called
spongy or cancellous bone. It is not actually soft
and spongy like the name suggests but made up
of hard struts that provide strength but make the
bones less heavy. In the middle of the spongy bone
is the marrow along with some blood vessels. The
red marrow produces blood cells while the yellow
marrow is mostly for storing fats.
Find out more
Sources and further study:
It’s True! Your Bones Are Stronger Than Concrete
by Diana Lawrenson (Allen & Unwin)
e.explore Human Body by Richard Walker (DK)
Encyclopaedia of the Human Body by Richard Walker (DK)
The Human Body (BBC DVD)
Howstuffworks How Broken Bones Heal http://health.
howstuffworks.com/heal-broken-bones1.htm
Encyclopaedia Britannica
Editor: TROY LENNON Artwork: MARIO LENDVAI
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