The Skeletal System
Chapter 5
Functions of Bones
Support – supports the body and
organs
 Protection – protect soft organs and
brain
 Movement – bones are the point of
attachment for skeletal muscles.
 Storage – Stores minerals, Ca and P
 Blood Cell Formation – in the
marrow.

Bones
206 bones in the adult body.
 Bones can be compact of spongy
 Can also be classified by shape:

• Long bones – limbs
• Short bones – generally cube shaped,
wrist
• Flat bones – skull, ribs and sternum
• Irregular bones – vertebrae.
Spongy vs. Compact
Long, Short, Flat, Irregular
Bone Anatomy


Diaphysis is the shaft
of the bone. Mostly
compact. Interior of
diaphysis is usually a
storage place, yellow
or red marrow for
example.
Yellow marrow is fat
storage, red is blood
production
Bone Anatomy



Epiphyses are the
ends of the bone. A
thin layer of compact
bone, enclosing an
area of spongy bone.
Spongy bone contains
red marrow
Externally, the
epiphyses is covered
by articular cartilage.
Smooth and slippery –
decreases friction in
joints.
Bone Anatomy



Bones change over time/growth.
They grow from the epiphyseal plate.
Cartilage plate that makes new bone cells
When the bone is mature, this cartilage
turns to bone and stops growing.
Bone Growth and Remodeling




Fetal skeletons are mostly cartilage and
very flexible.
As the fetus gestates these cartilage
bones go through ossification – the
process of bone formation.
A bone shell is produced around the
cartilage by osteoblasts – bone making
cells
The cartilage is digested away, leaving a
hallow core that can be filled with yellow
or red marrow.

stop
Axial vs. Appendicular

The skeleton as a whole
can be broken into two
sections.
• The Axial Skeleton includes
the skull, vertebrae, and
the bony thorax cavity.
• The Appendicular Skeleton
includes the limbs and
their attachment points.
Axial - Skull
The skull is comprised of two sets of
bones, the cranium and the facial
bones.
 The cranium encloses the brain
 Facial bones hold the eyes and are
connection points for facial muscles

Cranium


Cranium comprised
of 8 large, flat
bones.
Frontal bone
(yellow) forms the
forehead and
superior ridge of
your eye sockets.
Cranium


Behind the frontal
bone we find two
parietal bones.
They make up the
majority of the
superior and lateral
walls of the
cranium.
Cranium



Temporal bones
are inferior to the
parietal bones and
appear on the
lateral sides of the
skull.
The temporal
bones have a
number of very
important
markings.
Connection points
of your lower jaw.
Cranium



Temporal Continued.
Extermal acoustic
meatus – canal that
leads to the eardrum
Jugular foramen and
carotid canal – canals
on the inferior side of
the skull where the
veins and arteries
respectively enter the
brain cavity.
Cranium


Occipital bone
forms the posterior
and inferior floor of
the cranium.
It contains the
foramen magnum
– the canal
through which the
spinal cord enters
the cranium.

Stop
Cranium


Sphenoid bone –
butterfly shaped
bone (pink) that
forms the anterior
floor of the
cranium.
Ethmoid Bone –
Forms the roof of
the nasal cavity.
Facial Bones


Maxillae – two
bones that make
the upper jaw
(green).
The palatine
processes make up
your hard palate
(roof of your
mouth)
Facial Bones


Maxillae also
contain the
paranasal sinuses.
These cavities are
there to lighten the
skull as well as
amplify our voice,
however can
become infected –
sinusitis.
Headache and
upper jaw pain.
Facial Bones


Palatine bones
form the posterior
section of the hard
palate. If not
formed correctly
called a cleft
palate.
Zygomatic bones
form the cheeks
and eye sockets.
Facial Bones

Mandible – the
lower jaw.
Connects with the
temporal bone,
forming the only
moveable joint in
the skull.
Hyoid Bone



Hyoid Bone –
suspended above
the larynx.
Becomes the
attachment for our
tongue. Also helps
in muscle
movement of
speech.
Broken Bone?
Fetal Skull




Face is smaller.
Fontanels (soft
spots) areas where
the skull has not
fused together yet.
Made up of fibrous
membranes.
Allow for brain
growth after birth.
Solidify after 22 24 months
Pelvis Girdle


Pelvis bone makes
up our hips and
upper leg joints.
Bone shape is
different in males
and females to
allow for birth.

stop
Column Vertebral (spine)
Made up of 26 irregularly shaped
bones with ligaments and cartilage.
 Spinal cord runs through the middle
of these bones, protecting it.
 The first seven vertebrae, starting at
the base of the skull make up the
cervical Curvature. Known as C1-C7

Spine
Vertebrae 8-19 are part
of the thoracic curve.
T1-T12.
 These are followed by
the five lumbar
vertebrae L1-L5.
 The final two bones of
the spine are the
sacrum and the coccyx

Bony Thorax (Thoracic Cage)
Includes the sternum, ribs and
thoracic vertebrae making a cage for
the thoracic organs. Heart lungs etc.
 Sternum is the flat bone on the
anterior side (breastbone).
 Extreme inferior section is called
xiphoid, can be broken off during
CPR.

Ribs



Humans have 12
pairs of ribs.
The first seven
pairs are called
true ribs because
they attach directly
to the sternum.
The next five either
attach indirectly or
not at all, called
false ribs.
Appendicular Skeleton



Shoulder Girdle
Clavicle – holds the
shoulder away from
the thoracic cavity
Scapula – flat bone
that extends behind
thoracic cavity and
contains the shoulder
joint.
Shoulder Girdle


Shoulder has
exceptional
movement because it
is only attached to
the axial skeleton at
one place, the
scapula can actually
slide behind the ribs.
This however allows
for easy dislocation.
Arm Bones


The upper arm is
one bone, the
humerus.
Forearm is the
radius (lateral) and
the ulna (medial)
Hand




8 carpal bones
make up the wrist.
5 metacarpals
make up the palm
Your fingers are
called the
phalanges.
They are broken
into distal,
intermediate and
proximal
phalanges.
Lower Limbs



Femur is the bone
that makes up our
thigh.
Strongest, longest,
and heaviest bone.
Trochanters –
connection points
of muscles.
Lower Leg



The lower leg is
made of two bones
Tibia is medial and
is the bone that we
call the shin.
The fibula is lateral
and smaller
Foot




Just like the hand, the
foot can be broken into
three distinct sections.
Tarsals make up your
heel and ankle
Metatarsals make up the
arch of your foot,
Phalanges make up your
toes.
Foot Arch vs. Flat Feet




There are three natural
arches to the foot.
Tendons keep this arch
in place.
The arch gives our feet
“springiness” and
allows it to absorb the
shock of walking.
Flat feet is a condition
where this arch does
not exist.
Osteoporosis





Bones do not stop changing when we are
adults.
Calcium levels and gravity take a toll on
our bones as we age.
Low calcium levels in our blood trigger
osteoclasts – bone eating cells, to digest
bone and release stored calcium.
This however can ruin the structural
integrity of the bone
Bones will get stronger or thicker when
muscles connected to them get stronger
Osteoporosis

stop
Fracture Types


Comminuted –
when the bone
breaks into many
fragments.
Occurs in severe
accidents or with
brittle bones.
Fracture Types

Compression –
bone is crushed
Fracture Types


Depressed –
Portion of bone is
pressed inward
Typical of skull
fractures
Fracture Types


Impacted – Broken
bone ends are
forced into each
other
Typically occurs
when one attempts
to break a fall with
outstretched arms
Fracture Types


Spiral – Ragged break,
usually occurs when an
excessive twisting force is
applied to a bone.
Common sports fracture
Fracture Types


Greenstick – Bone
break is
incomplete.
Common in
children whose
bones are more
flexible then
adults.
Closed vs. Open Fractures




Closed fractures do not pierce the skin
Open fractures are when bones do
protrude from the skin.
A fracture is treated with reduction – a
realignment of the bones.
Closed usually can be done with just
manipulation, open requires surgery and
bones are usually secured with pins and
plates.

stop
Fracture Repair
Once a fracture is reduced, it is
immobilized by a cast so that the
healing process can begin.
 Healing time is about 6-8 weeks
depending on the bone and the age
of the patient.

Bone Healing

When first broke, blood vessels that are
broken will leak blood into the area
forming a hematoma. Any unnourished
cells will die.
Bone Healing

The Break is splinted by fibrocartilage
callus – Capillaries invade the area
(granulation) bringing nutrients. Cartilage
forms and acts as a splint. Callus
Bone Healing

The fibrocartilage callus begins to solidify
into spongy bone. Now called the bony
callus.
Bone Healing

Over the next few months, this bony
callus is restructured to form a permanent
patch that is just as strong as the original
bone. A small callus will forever remain.
Joints
Joints occur when any two bones
come in contact. The only bone that
does not form at least one joint is
the Hyoid Bone.
 Not all joints allow for movement.
 Suture joints in the skull simply
connect different skull bones to make
a solid cranium. No Movement!

Movable Joints

Plane Joint –
Two bones can
slide or glide
past each other
to some extent.
Found in the
ankle and wrist
bones.

Stop
Movable Joints


Hinge Joint –
movement is along
one plane.
Phalanges, knees,
elbows.
Movable Joints



Saddle joints –
both bones have a
convex and
concave feature,
much like a saddle
you would put on a
horse.
Allows for larger
range of motions
Thumb
Movable Joints



Ball and Socket – a
spherical head of
one bone fits into
the round socket of
another.
Allows for
movement on
three axes
Shoulders and hips
Movable Joints


Pivot – one
rounded bone
fits into a sleeve
or ring and can
rotate.
Forearm or shin
Movable Joints


Condyloid Knuckle/egg
shaped joint.
Tend to be oval
Synovial Joint



The bones are
covered in
cartilage.
A synovial
membrane fills the
space and is filled
with fluid.
Tendons reinforce
the structure.
Joint Pain
The synovial membrane can become
inflamed. Or it could fill with too
much fluid.
 Arthritis is a general term for when
the joint is inflamed, causing pain.
 Gout – uric acid forms sharp crystals
joints which cause pain.

Joint Replacement