

The human skeleton is initially
made of cartilage but as
development progresses most of
this is replaced by bone. The
remaining cartilage exists in areas
where flexible support is needed.
Cartilage contains chondrocyte
cells surrounded by a jellylike
matrix that is made mostly of water
and fibers which combined allow
cartilage to spring back to its
original shape after being
compressed. Remember that
cartilage does not have nerves or
blood vessels which means it
depends on the surrounding dense
irregular tissue (perichondrium)
for nutrients through diffusion. This
limits the thickness of cartilage.

The 3 types of cartilage reviewed in
the previous section are used in
different location.
• Hyaline cartilage includes; 1)
articular cartilage which covers the
ends of most bones at joints; 2)
costal cartilage, which connects the
ribs to the sternum; 3) respiratory
cartilage, which reinforces air
passageways; 4) nasal cartilage,
which supports the external nose.
• Elastic cartilage: the ear and
epiglottis (flap that prevents food
from entering the lungs). This type
provides strength and
stretchability.
• Fibrocartilage: in the knee and
between the vertebrae where
strong support and resistance of
heavy pressure is required.
The axial skeleton: bones
of the skull, vertebral
column, and rib cage.
Generally these bones
protect, support, and
carry other body
structures.
 The appendicular
skeleton: bones of the
upper and lower limb
girdles and limbs. These
bones are mainly used
for locomotion.
 Beyond the classification
based on region, most
bones are classified
based on shape.

• Long Bones: bones that are longer
than they are wide (note named for
shape not size). The bones of the
limbs except the patella and the
bones of the wrist and ankle are
long bones.
• Short Bones: roughly cube shaped.
These include the bones of the wrist
and ankle.
• Sesamoid Bone: special type of
short bone that forms in a tendon.
These vary in size and number in
different individuals and while some
clearly act to alter the directional
pull of the tendon the functions of
others are not known. The most
prominent example is the patella.
• Flat Bone: These
include the sternum,
scapulae, ribs, and
most skull bones.
These bones are thin,
flattened bones that
are normally curved.
• Irregular Bones: Bones
that do not fit into the
other categories.
These include the hip
and vertebrae.





Support: create a framework that
supports tissues and cradles soft
organs.
Protection: fused skull bones,
vertebrae that surround the spinal
cord, and the rib cage all protect the
structures they contain.
Movement: Skeletal muscles that
attach to the bones by tendons use
them as levers to move the body.
Mineral Storage: Bone acts as a
reservoir for minerals (most
important being calcium and
phosphate). These minerals are
released into the blood stream as
needed which carries the minerals to
any part of the body.
Blood cell formation: Hematopoiesis
(the creation of blood cells) occurs in
the marrow cavity of certain bones.


Bones contain several types of tissues which makes
them organs
Gross Anatomy
• Bone markings: Bones are rarely smooth; instead
they have projections, depressions, and openings
that serve as the site of muscle/ligament/tendon
attachment, as joint surfaces, or as conduits for
blood vessels and nerves.
**Chart on pg 179/119 small book you need to
know**

Bone textures: The outer
layer that in dense is
called compact bone. The
inner bone is a
honeycomb of branches
called trabeculae. In living
bone the open spaces
between these branches
are filled with red and
yellow bone marrow. Red
marrow makes blood cells
while yellow marrow is a
fat reserve. This inner
layer is called spongy
bone.
• Structure of a long bone:
 Diaphysis: The shaft of the bone. The
outer layer is a thick collar of compact
bone with a center medullary cavity
which in adults is filled with yellow bone
marrow. In infants the marrow is red and
forms blood cells.
 Epiphyses: Bone ends that are normally
expanded. The outer layer is compact
bone while the inner layer in spongy
bone. The joint surface is covered with
hyaline cartilage which cushions the
bone during joint movement. Between
the diaphysis and the epiphysis there is
an epiphyseal line. This used to be a disc
of hyaline cartilage called the
epiphyseal plate that grew during
childhood to lengthen the bone.
 Periosteum: A double layer
membrane that covers the
external surface of the bone.
The outer layer called the
fibrous layer is dense
irregular connective tissue
while the inner layer called
the osteogenic layer is
composed of cells that make
(osteoblast) and break down
(osteoclast) bone. This
membrane provides
anchoring points for the
tendons and ligaments.
 Endosteum: Internal lining of
the medullary cavity
• Structures of flat,
short, and irregular
bones
 These bones have a
periosteum that
covers compact bone
which covers the
spongy bone within
and while they
contain bone marrow
there is no centralized
marrow cavity.

Microscopic Anatomy:
• Inorganic calcium salts in the
matrix allow bone to have
exceptional strength while
organic collagen fibers
provide bone with some
flexibility and great tensile
strength.
• Mature bone cells
(osteocytes) exist in tiny
cavities in the matrix called
lacunae which are arranged
in concentric circles called
lamellae around a central
canal called the Haversian
canal. Together the circles
and canal make an ostean or
Haversian system.

Bone has a maze of
passageways called
conaliculi for carrying
nerves and blood
vessels which provide
the cells with nutrients
and a way to get rid of
waste that allows bone
to be well nourished in
spite of its hard matrix.
This also allows bone to
heal quickly and well.
The bone and the rest of
the body communicate
through a Volkmann’s
canal that runs into the
bone at a right angle.

Formation: With the
exception of some flat
bones, bones form by
replacing a hyaline
cartilage model formed
during the embryonic
stage in a process called
ossification. This involves
two major phases.
• The hyaline cartilage
model is covered with
bone matrix created by
bone forming cells
called osteoblasts.

The enclosed hyaline
cartilage model is
digested away making a
medullary cavity. Most
“bones” of an embryo are
converted to bone with
two execptions: the
articular cartilage that
covers bone ends which
exists for life to reduce
friction and the
epiphyseal plates which
allow bones to increase in
length through childhood.

Growth: bones grow in two
directions.
• Increase in length in
achieved by the epiphyseal
plate. New cartilage is
created on the surface of the
plate that is furthest from the
medullary cavity and on the
surface of the articular
cartilage while on the
opposite side of each
location “old” cartilage cells
are broken down and
replaced by boney matrix.
• Increase in width is achieved by osteoblasts in the periosteum
adding bone tissue while osteoclasts in the endosteum remove
bone from the inner surface. This process is called appositional
growth and is controlled by growth horomone and sex
horomones (during adolescence) until the epiphyseal plates
are completely converted to bone in the late teens.

Remodeling: 2 Aspects
• Calcium deposits in
bone are determined by
the levels in the blood.
When calcium levels are
low the parathyroid
gland releases a
hormone (PTH) that
encourages the
breakdown of bone
releasing the mineral
into the blood. When
levels are high it is
deposited into the bone
as calcium salt.
At locations where bones
need to be thicker or form
larger projections to increase
their strength where muscles
attach osteoblasts lay down a
new matrix and become
trapped within it. On the other
hand if areas of bone are not
subject to stress by muscles or
gravitational pull the bone
loses mass and atrophies.
**So the hormone released by
the parathyroid determines if
bone needs to be broken or
made and the pull of muscles
and gravity will determine
where the breakdown or
creation occurs**


Types of fractures
• Closed/Simple Fracture:
The bone breaks cleanly
but does not break the skin
• Open/Compound Fracture:
The broken bone
protrudes through the skin
• Comminuted: Bone breaks
into many pieces come in
brittle bones of elderly
• Compression: Bone is
crushed which is common
in porous bone
• Impact: Broken ends are
forced into each other
such as when you try to
catch yourself in a fall
• Spiral: Ragged break
occurs when twisting
forces are applied to the
bone such as in sports
• Greenstick: Bone does
not break all the way
through, common in the
more flexible bones of
children.

Treatment of fractures:
• Reduction is the realignment of
the broken ends of the bone. In
closed fractures the bones are
coaxed back into position. In an
open reduction surgery is
performed and then wires or
pins are used to hold the bones
in place. After reduction the
break is immobilized by a cast
or traction. Healing of a simple
fracture should take 6-8 weeks.
Large bones and bones of the
elderly take longer to heal.

Bone repair includes 4 events
• Blood vessels ruptured when a bone breaks resulting in a
blood-filled swelling called a hematoma. The bone cells
that are deprived of nutrients die
• New capillaries (granulation tissue) grow into the clotted
blood at the site of damage and dead cells are disposed
of using phagocytosis. Connective tissue cells form a
mass of repair tissue called the fibro cartilage callus that
contains cartilage matrix, bony matrix, and collagen
fibers to act as a splint closing gap.
• More osteoblast and osteoclast migrate to the site
gradually replacing the fibro cartilage with spongy bone
(bony callus)
• The bony callus is remodeled in response to stress
exerted by muscles to form a permanent “patch” at the
fracture site.
Includes the skull, vertebral column and the
thorax. It is responsible for supporting the head,
neck, trunk and protecting the brain, spinal cord
and organs of the thoracic cavity.

Most of the bones
of the skull (except
the mandible) are
flat bones that are
firmly united by
interlocking joints
called sutures. The
cranium encloses
and protects the
brain and is
composed of eight
large flat bones.
The facial bones
hold the eyes and
the facial muscles
to change
expressions

Cranium:
• Frontal bone: The
forehead, brow ridge
and upper eye orbit
• Parietal bones: Pair of
bones that cover the
superior and lateral
areas. The suture
where they meet at
the midline of the
skull is the sagittal
suture. The one that
connects these to the
frontal bone is the
coronal suture
• Temporal bones: A pair of bones
that lie inferior to the parietal
bones and are joined to them by
the squamous suture. Important
bone markings of these bones
include:
 External auditory meatus: canal
that leads to the eardrum and
middle ear.
 Styloid process: Sharp,
needlelike projection that is
inferior to the external auditory
meatus. Place of attachment for
many neck muscles.
 Zygomatic process: Thin bridge
that joins with the cheek bone
• Mastoid process: Rough
projection that is posterior
and inferior to the external
auditory meatus that is full of
air cavities and is a place of
attachment for some neck
muscles.
• Jugular foramen: An opening
between the occipital and
temporal bones that allows
the jugular through to drain
blood from the brain.
• Carotid canal: Allows the
internal carotid artery
through to supply most of the
brain with blood.

Occipital Bone: From the
floor and back wall of the
skull. It joins the parietal
bones at the lambdoid
suture.
• Foramen magnum:
Opening that allows
the spinal cord to
connect with the brain
• Occipital condyles: On
either side of the
foramen magnum
which rest on the first
vertebra.


Sphenoid bone: Spans the
width of the skull forming part
of the floor of the cranial
cavity. At the midline is a
depression called a sella
turcica which holds the
pituitary gland in place.
Posterior to the sella turcica is
the foraman ovale which is a
large opening that allows the
cranial nerves to pass to
chewing muscles of the
sphenoid bone.
Ethmoid bone: Very
irregularly shaped bone
anterior to the sphenoid bone.
Forms the roof of the cavity
and the medial wall of the
orbits

Facial Bones:
• Maxillae: Two bones that fuse to
join the upper jaw and the hard
palate of the nose.
• Palatine Bones: Pair of bones that
form the posterior hard palate.
Failure of the fusion of theses
bones causes a cleft palate.
• Zygomatic bones: Cheek bones
that form the lateral wall of the
orbits
• Lacrimal bones: Bones on the
medial wall of the orbits that have
a groove to allow for the passage
way of tears
• Nasal bones: Form the bridge
•
•
•
•
of the nose
Vomer bone: Forms most of
the nasal septum
Inferior conchae: Project from
the lateral wall of the nasal
cavity
Mandible: Lower jaw that
holds the bottom teeth and
joins the temporal bone at the
only free moving joint of the
skull.
Hyoid bone: Only bone of the
body that does not articulate
to another bone. It is a
movable base for the tongue
and attachment point for the
neck muscles that raise and
lower the larynx when
swallowing or speaking.

Fetal Skull: There many
differences between an
infant skull and an adult
• The infants face is
small in comparison
to the cranium
• The skull itself is a
quarter of the body
length while in adults
it is an eighth of the
body length.

The bones of the skull
are not fully fused
(fibrous membranes
remain between them).
These “soft spots” are
called fontanels with
the two largest being
the anterior and
posterior fontanels. This
allows the skull to be
slightly compressed
during birth and the
brain to grown in early
infancy. They are
gradually converted to
bone and should be
fully fused by age 2.


Composed of 33 separate bones
before birth. 9 of these bones will
fuse together to form the 2 composite
bones of the sacrum and coccyx. The
other 24 single bones are divided
among region: 7 cervical vertebrae,
12 thoracic, and 5 lumbar.
The vertebrae are irregular bones
that posses a central cavity that the
spinal cord runs through. Each
vertebrae is separated by a pad of
fibrocartilage called the
intervertebral discs which cushion
the bones and absorb shock. As a
person ages these discs begin to dry
out and ligaments become weaker
which predisposes older people to
herniated discs which can cause a
numbness and pain.


The curves of the spine are
divided into two groups. The
curve in the thoracic and
sacral regions are primary
because they exist before
birth. The cervical curve
develops when a baby
begins to raise its head and
the lumbar curvature
develops when baby starts to
walk. Both are secondary
curvatures.
The 3 main types of
abnormal spine curvature are
scoliosis, kyphosis, and
lordosis. These can result
from poor posture, disease,
unequal pull of muscles, or
could be congenital.

Cervical Vertebrae: Identified
as C1-C7. The first two have
specific functions so they are
different. The atlas (C1) has
no body, instead it has large
depressions that receive the
occipital condyle of the skull.
This joint allows you to nod.
The axis (C2) acts as a pivot
for rotating the atlas. The joint
between C1 and C2 allows
you to turn your head side to
side. The other typical
vertebrae have an additional
feature called a transverse
process which allows arteries
to pass through on the way to
the brain.

Thoracic vertebrae:
identifies as T1-T12
are all typical
vertebrae but there is
a facet on the
transverse process for
the ribs to articulate
and the spinous
process is long and
hook downward
causing the bone to
look like a giraffe’s
head from the side.



Lumbar vertebrae: identified as
L1-L5 they have massive block
like bodies and are the
sturdiest of the vertebrae.
Sacrum: made from five fused
vertebrae. Articulates
superiorly with the L5
vertebrae, inferiorly with the
coccyx and laterally with the
hip bones. The surface has
median sacral crests which are
the fused spinous processes of
the original vertebrae. The
sacral canal is an extension of
the vertebral canal for the
spinal cord.
Coccyx: formed by the fussion
of 3-5 irregular vertebrae. This
is the remnant of a tail.

Sternum: flat bone that forms from
the fusion of the manubrium, the
body, and the xiphoid process. The
first seven ribs attach to the
sternum and it has three important
markings:
• Jugular notch: concave upper
border of the manubrium that is
easily palpated.
• Sterna angle: place where the
manubrium and body meet at a
slight angle creating a transverse
ridge that provides a reference
for counting ribs to find the
second intercostal space to listen
to certain heart valves.
• Xiphisternal joint: point of fusion
between the sterna body and the
xiphoid process.

Ribs: there are twelve
pairs of ribs. The first
seven are called true
ribs because they
articulate to the
sternum directly. Then
there are three pairs
that articulate
indirectly and two
pairs that are called
floating ribs because
they do not articulate
at all. These five pairs
are called false ribs.
Remember all ribs
articulate to a
vertebra. The
intercostals spaces are
filled with muscle that
aids in breathing.


Clavicle/collarbone: attaches
to the sternum medially and
the scapula latterly where it
helps to form the shoulder
joint. It acts as a brace to hold
the arm away from the thorax
and helps to prevent the
dislocation of the shoulder.
Scapulae: loosely held in
place by muscles, the
shoulder blade has two
processes: the anterior
acromion process that
connects to the clavicle and
the posterior coracoid
process which anchors some
arm muscles. It also has a
glenoid cavity which is the
shallow socket that receives
the head of the arm bones.

The girdle allows the arm to have exceptionally free movement
due to
• Each girdle attaches to the axial skeleton at only one point
(clavicle to sternum)
• The loose muscle attachment of the scapula allows it to slide
with muscle movement
• The cavity is shallow and the joint is poorly reinforced by
ligaments

Humerus (arm bone): the typical long bone
that forms the arm has many distinguishing
marks. The greater and lesser tubercles
opposite the head of the bone are the
location of muscle attachment. At the
midpoint of the shaft is the deltoid
tuberosity which is where the deltoid
muscle of the shoulder articulates. The
radial groove runs down the posterior shaft
and marks the path of the radial nerve
(major nerve of the limb). At the distal end
the medial trochlea and lateral capitulum
are processes that articulate with the bones
of the forearm. Above the trochlea are two
depressions which hold the processes of
the same name of the ulna in a pliers-like
joint to allow the elbow to bend. The
anterior depression is the coronoid fossa
and the posterior is the olecranon fossa.

Forearm: the two bones of the
forearm are the radius on the
thumb side and the ulna at the
pinky. They are connected at both
ends by the radioulnar joints and
down their entire length by a
flexible interosseous membrane.
The radius articulates with the
humerus and just below the head
is the radiul tuberosity where the
tendon of the bicep attaches. The
ulna has the two processes that fit
the depressions in the humerus
and between them is the
trochlear notch.

Hand:
• Carpal: two irregular rows
of four bones that make
up the wrist or carpus that
are held together tightly
by ligaments.
• Metacarpals: make up the
palm of the hand and are
number from the thumb
as 1-5.
• Phalanges: each finger
has three phalanges
(proximal, middle, and
distal) while the thumb
has two (proximal and
distal)



The coxal bones (hip bones) are
attached securely to the axial
skeleton and the socket that
receives the thigh bone is deep
and heavily reinforced by
ligaments.
Supporting the weight of the
entire upper body and
protecting the reproductive
organs, the bladder, and the
lower parts of the large
intestines are two main functions
of the pelvis.
The coxal bone is formed by the
fusion of three bones: the ilium,
ischium, and pubis.
• Ilium: connects to the sacrum
and forms the upper flaring
part of the hip.
• Ischium: the “sit down” bone
supports the bodies weight
when sitting. The ischium has
a tuberosity which forms the
majority of the base, a spine
that narrows the pelvic outlet,
and the greater sciatic notch
which allows the sciatic nerve
and blood vessels passage to
the thigh.
• Pubis: the most
anterior part of the
coxal bone. The two
pubis bones fuse to
for the cartilaginous
joint called the pubic
symphysis.
• All three bones fuse
to form the
acetabulum which
receives the head of
the thigh bone.

The pelvic bones of the male and female have structural
differences to allow for child birth. The inlet is more circular,
the pelvis is shallower, the iliac flare is more lateral, the sacram
is shorter and less curved, the ischial spines are shorter, and
the pubic arch is more rounded in a female.

Femur (thigh): the
strongest and heaviest
bone of the body. The
head of the femur
articulates securely with
the acetabulum of the
pelvis. The neck of the
femur is thinner and a
common fracture site in
the elderly. The femur
slants medially so that
the knee is in line with
the bodies center of
gravity.

Leg: the tibia and fibula
which are connected
along their lengths by
an interosseous
membrane form the
leg. The tibia (shin
bone) is larger and
more medial. The tibial
tuberosity is the site of
attachment for the
patellar (knee cap)
ligament.

Foot: supports the bodies weight
and acts as a lever that allows the
body to move forward. The foot
has three types of bones.
• Tarsuls: the seven bones that
create the posterior half of the
foot. Most body weight is
carried by the calcaneus (heel
bone) and the talus (ankle).
• Metatarsuls: five bones that
form the sole of the foot.
• Phalanges: the fourteen bones
that make up the toes. The
large toe contains two (distal
and proximal) while the other
toes contain three (distal,
middle, and proximal).
Function: hold bones
together securely while
also allowing mobility.
 Functional types of joints:
• Synarthroses:
immovable joint such
as those of the cranium.
• Amphiarthroses:
slightly moveable joint
such as the spine.
• Diarthroses: freely
movable joints such as
those of the limbs.


Structural classification of joints:
• Fibrous joints: bones are
united by fibrous tissue such
as the sutures of the skull.
• Cartilaginous joints: bones
are connected by cartilage.
Slightly movable joints that
fall into this category are the
pubic symphysis and the
interverbral joints. The
immovable examples include
the cartilage that attaches the
true ribs to the sternum and
the cartilage found in the
epiphyseal plates of the
growing long bones.
• Synovial joints: the bones are
separated by a fluid filled cavity.
All of these joints have articular
cartilage that covers the end of the
bones, the joint is enclosed by a
sleeve of fibrous connective tissue,
a cavity that contains synovial fluid,
and reinforcing ligaments. These
joints can be further classified
based on shape
 Plane joint: articulating surfaces
are flat and the joint is able to
slide but not rotate (nonaxial)
such as the joints between the
bones of the wrist.
 Hinge joints: one bone fits
into the “trough” of another
bone. Angular movement
within one plane is allowed
such as the elbow and the
joints of the phalanges.
 Pivot joint aka gliding
joints: the bones fit
together like a hinge point
but are only allowed to
rotate along the long axis.
The best example is the
joint between the bones of
the lower leg.
 Condyloid joints aka ellipsoid
joint: allows movement side to side
and back to front but no rotation
around the long axis such as the
joints of the knuckles.
 Saddle joints: both bones are
saddle shaped. This joint allows
essentially the same movement as
the condyloid joint with the best
example being the joint between
the carpal and metacarpal of the
thumb (twiddle your thumbs)
 Ball and socket: allows movement
on all axes such as the shoulder
and hip.