Skeletal System
BONES
Internet resource site:
http://www.innerbody.com/htm/body.html
Unit Objectives
A. List five functions of bones
B. Label the main parts of a bone on a diagram of a
long bone
C. Name the two divisions of the skeletal system and
the main groups of bones in each division
D. Identify the main bones of the skeleton
E. Compare the three classifications of joints by
describing the type allowed by each
F. Describe at least four diseases of the skeletal
system
Reference
Diversified Health Occupations, 6th edition, Unit
6:4
Body Structures & Functions, 10th edition,
chapter 5
Skeletal System
The Skeletal system is
made of organs that are
called bones
THERE ARE 206
BONES IN THE ADULT
SKELETON
Bone Types
Long Bones-found in the
arms and legs
Flat Bones-examples are the
bones of the skull and the
ribs
Irregular bones-represented
by the bones of the spinal
column
Short Bones-appear cubelike
in shape such as bones of
the wrist and ankle
Parts of long bones
Definition: Long bones are
bones of the extremities
(arms & legs)
Diaphysis: shaft of long bone
that is a hollow cylinder of
hard, compact bone.
Epiphysis: at each end of the
diaphysis
Medullary canal: cavity in
diaphysis that is filled with
yellow marrow
Yellow Marrow: inside
medullary canal; mainly fat
cells
Parts of long bones
Endosteum
Membrane that lines medullary canal
Keeps the yellow marrow intact
Produces some bone growth
Red marrow
Found in certain bones such as vertebrae, ribs, sternum,
cranium, and proximal ends of humerous and femur
Produces red blood cells, platelets, and some white blood
cells
Bone marrow is important in the manufacture of blood and is
involved with the body’s immune response
Used in diagnosing blood diseases
Given as transplants to people with defective immune systems
Parts of the long bones
Periosteum
Tough membrane covering outside of bones
Contains blood and lymph vessels
Contains osteoblasts: special cells that form new bone
tissue
Necessary for bone growth, repair and nutrition
Articular cartilage
Thin layer covers the epiphysis
Acts as a shock absorber when two bones meet to
form a joint
Parts of the long bone
Spongy Bone
The medullary canal is
surrounded by
compact or hard bone.
Where less strength is
needed in the bone,
some of the hard bone
is dissolved away
leaving spongy bone
Two sections of skeleton
Axial skeleton
Forms the main trunk
of the body
Composed of the skull,
spinal column, ribs and
sternum
Two sections of skeleton
Appendicular skeleton
Forms extremities
(arms and legs)
Composed of shoulder
girdle, arm bones,
pelvic girdle, and leg
bones
Parts of the skeleton
Axial skeleton
Appendicular Skeleton
Skull
Composed of cranium and facial
bones
Collectively, there are 22 bones in
the skull
Cranium
Spherical structure that
surrounds and protects the
brain
Made of eight bones
Frontal-forms the forehead
Two Parietal-form the roof
and sides of the skull
Two temporal-house the ears
Occipital-forms the base of
the skull and contains the
foramen magnum
Ethmoid-forms the nasal
septum
Sphenoid-all other bones
connect to it (considered the
key bone of the skull)
Skull
Cranium continued
At birth, the cranium is
not solid bone
Spaces called
fontanels or “soft
spots” allow for the
enlargement of the
skull as brain growth
occurs
Fontanels are made of
membrane and
cartilage
Turn into solid bone by
about 18 months of
age
Skull
Cranial bones are thin
and slightly curved.
During infancy, these
bones are held snugly
together by an irregular
band of connective
tissue called a suture.
As a child grows, this
connective tissues
ossifies and turns into
hard bone.
Skull
14 facial bones
Nasal
5 bones total
2 are nasal bones that
form the bridge of your
nose
1 is the volmer bone
which forms the lower
part of the nasal septum
2 are inferior concha
bones which make up the
side walls of the nasal
cavity
Skull
Facial Bones continued
Maxilla (2)
Make up the upper jaw
Lacrimal (2)
In the inner aspect of the
eyes; contain tear ducts
Zygomatic (2)
Form the prominence of
the cheek
Palatine (2)
Form the hard palate of
the mouth
Mandible (1)
Is the lower jaw and the
only movable bone in the
face
Skull
Sinuses are air spaces in the bones of the
skull. They are lined with mucous membranes
Foramina are openings in bones that allow
nerves and blood vessels to enter or leave
the bone
Spinal Column/vertebra
The spine, or vertebral
column, is strong and
flexible.
It supports the head
and provides for the
attachment of the ribs.
The spine also encloses
the spinal cord of the
nervous system.
Spinal Column/vertebra
The spine consist of small bones called vertebrae.
Vertebrae are separated from each other by pads of
cartilage called intervertebral disks.
The disk serve as cushions between the vertebrae
and act as shock absorbers.
During our lifetime, these disk become thinner, which
is why we lose height as we age.
The vertebral column is divided into 5 sections
Spinal Column/vertebrae
1) Cervical vertebrae are located in the neck
area.
There are 7 cervical vertebrae
The atlas is the first cervical vertebrae
The atlas articulates (is jointed) with the occipital
bones of the skull
The atlas permits us to nod our head
The axis is the second cervical vertebrae
The axis is the odontoid process which forms a
pivot on which the atlas rotates; this permits us to
turn our heads
Spinal Column/vertebrae
2) Thoracic vertebrae are located in the chest area
There are 12 thoracic vertebrae
3) Lumbar vertebrae
There are 5 lumbar vertebrae
4) Sacrum
Wedge shaped vertebrae formed by 5 fused bones.
Forms the posterior pelvic girdle and serves as an
articulation point for the hips
5) Coccyx
The tailbone. It is formed by 4 four bones
Spinal Column/vertebrae
The spinal nerves enter and leave the spinal cord
through the openings (foramen) between the
vertebrae.
The spine is curved, not straight. A curved spine has
more strength than a straight one would have.
Before birth, the thoracic and sacral region are
convex curves. Once the infant learns to hold his
head up, the cervical region become concave. When
a child learns to walk, the lumbar region also
becomes concave. This completes the 4 normal
curves of the adult spine.
Spinal Column/vertebrae
A typical vertebra contains
three basic parts:
Body
foramen
processes
The large, solid part of the
vertebrae is known as
the body; the central
opening is known as the
foramen.
Spinal Column/vertebrae
Above the foramen protrude two wing like
bony structures called transverse processes.
The roof of the foramen contains the spinal
process (spine) and the articular process.
Ribs and sternum
The thoracic area of the
body is protected and
supported by thoracic
vertebrae, ribs and
sternum.
Ribs and Sternum
The sternum (breastbone) is divided into
three parts:
The upper region (manubrium)
The body
Xiphoid process which is the lower
cartilaginous part
Attached to each side of the upper region of the
sternum are the two clavicles (collar bones).
These are attached by ligaments
Ribs and sternum
Seven pairs of costal cartilages join 7 pairs of
ribs directly to the sternum.
These are known as True Ribs
The next 3 pairs are false ribs because they
are attached by costal cartilage to the
seventh rib instead of the sternum.
The last 2 pairs of ribs are floating ribs
because they are not connected to costal
cartilage nor the sternum.
Appendicular Skeleton
Includes the upper extremities: shoulder
girdles, arms, wrists, and hands
Includes the lower extremities: hip girdle,
legs, ankles, and feet.
There are 126 bones in the Appendicular
skeleton
Shoulder Girdle
Also called the pectoral
girdle
Consists of 4 bones: two
curved clavicles (collar
bones) and two triangular
scapulae (shoulder bones)
The scapulae permit the
attachment of muscles that
assist in arm movement and
serve as a place of
attachment for the arms.
The clavicles help brace the
shoulders and prevent
excessive forward motion
Arm
The bones in the arms consist of the
humerus, radius and the ulna.
The humerus is the only bone in the upper
arm.
It is the second largest bone in the body
The upper end of the humerus has a smooth,
round surface called the head, which
articulates with the scapula.
Arm
The forearm consists of
two bones, the radius
and the ulna
The radius is the bone
that runs up the thumb
side of the forearm.
Its name derives from
the fact that it can
rotate around the ulna.
This allows the hand to
rotate freely and with
great flexibility
Arm
The ulna is the largest bone in the forearm.
It is far more limited than the radius
At its upper end, it produces a projection
called the olecranon process, forming the
elbow
The olecranon process is known as the
“funny bone”.
The olecranon process articulates with the
humerus
Hand
The hand is a
remarkable piece of
skeletal engineering
Contains more bones
per size than any other
part of the body
Collectively, the hand
has 27 bones
Hand
Wrist bones (carpals)
Consist of eight small bones arranged in two
rows held together by ligaments
There is only slight lateral movement of the
carpals
Hand
The hand consist of two parts: the palmer
surface and the fingers
The palmer surface had 5 metacarpal bones
The fingers have 14 phalanges (singular,
phalanx)
Each finger has three phalanges except for
the thumb which only has two
There are hinge joints between each phalanx,
allowing the fingers to be bent easily
The thumb is the most flexible finger.
Pelvic Girdle
Made up of two os
coxae (coxal or hip
bones)
Join with sacrum on the
dorsal part of the body
Join together at a joint
called the symphysis
pubis
Serves as an area of
attachment for the
bones and muscles of
the legs
Pelvic Girdle
Each os coxa made of
three bones that are
fused or joined
Ilium
Ischium
Pubis
The female pelvis is
much wider than the
male pelvis for
childbirth
Pelvic Girdle
Contains two recessed areas or sockets
called acetabulums that provide for
attachment of bones of the leg
Obturator foramen
Opening between the Ischium and pubis
Allows for passage of nerves and blood
vessels to and from the legs
Legs
Femur-thigh bone
Longest & strongest
bone in the body
Patella-kneecap
Flat, triangular bone
found in front of the knee
joint
Tibia-long supporting bone
of lower leg medial surface
Fibula-smaller bone of the
lower leg, lateral surface
Ankle & Foot
Tarsals
7 bones in ankle
Calcaneous is the heel
bone and the largest of
the ankle bones
Metatarsals
5 bones forming the
instep (arch) of the foot
Phalanges
14 bones on each foot
Form the toes
Joints
Defined as areas where
two or more bones join
together
Ligaments: connective
tissue bands that hold
long bones together
Joints (articulations)
Joints
Arthroscopy:
examination of a joint
using arthroscope with
fiber optic lens. Most
knee injuries are treated
with arthroscopy
Joints
Three main types of joints:
1) Diarthroses (comprise most of the joints)
Freely moveable
Ball-and-socket joints of the shoulder & hip
Hinge joints of the elbow and knee
Pivot joints of the radius and ulna, atlas and axis
Gliding joints of the vertebrae
2) Amphiarthroses
Slightly moveable
Ex: attachment of ribs to the spine & the symphysis pubis
3)Synarthroses
Immoveable
Example is the cranium; the suture is an immovable skull
joint
Joints
When two movable
bones meet at a joint,
their surfaces do not
touch one another
Movable joints
(diarthroses) tend to
have the same structure
consisting of 3 main
parts:
Articular cartilage
A bursa (joint capsule)
A synovial joint cavity
Diseases and abnormal conditions
Arthritis
Group of diseases involving inflammation of
the joints
Two main types: Osteoarthritis and
rheumatoid arthritis
Osteoarthritis
Chronic disease that occurs with aging
Symptoms: joint pain, stiffness, aching, limited
range of motion (ROM)
Treatment: rest, heat/cold applications, ASA,
NSAIDs, steroids, special exercises
Diseases and abnormal conditions
Rheumatoid Arthritis
Chronic inflammatory disease of connective
tissue and joints, results in permanent
deformity and immobility
Three times more common in women
Often begins between ages of 35-45
Treatment: Rest and prescribed exercise,
medications and surgery to replace joint
Diseases and abnormal conditions
Ricketts
Usually found in children
Caused by lack of vitamin D
Bones become soft due to lack of calcification,
causing deformities such as bowlegs.
Preventable with sufficient quantities of
calcium, Vitamin D, and sunlight
Diseases and abnormal conditions
Fractures
Involve a crack or break
in the bone
Types of fractures
1) Greenstick
Bone is bent and
splits causing a crack or
incomplete break
Common in
children
Fractures
2) Simple
Complete break with no damage to skin
3) Compound
Break in bone that ruptures through skin
Increased risk of infection
4) Comminuted
Bone is broken into many pieces (shattered)
Fractures
Reductions
Process by which bone is put back into proper
alignment
Closed reduction: position bone in alignment,
usually with traction or force, and apply cast or
splint to maintain position
Open reduction: surgical repair of bone, and,
at times, insertion of pins, plates, rods and
other devices. AKA ORIF (open reduction
internal fixation)
Diseases and abnormal conditions
Dislocation
Bone is forcibly displaced from a joint
Reduced and immobilized with splint, traction, or cast
Sprain
Twisting action tears ligaments at a joint
Common sites are wrists and ankles
Symptoms: pain, swelling, discoloration, limited
movement
Treatment: rest & elevation; Immobilization with elastic
bandage or splint; Cold applications
Diseases and abnormal conditions
Strains
Overstretching or tearing of muscle
Diseases and abnormal conditions
Osteomyelitis
Inflammation of bone usually caused by a
pathogen
Symptoms: pain at site, swelling, chills, fever
Treatment is antibiotics (usually IV) for
infection
Diseases and abnormal conditions
Osteoporosis
Affect 25 million Americans, 80% which are
women
Etiology
Deficiency of hormones, especially estrogen if
female (By age 55, the average postmenopausal
woman has lost 35% of her bone mass)
Prolonged lack of calcium in diet
Sedentary lifestyle
Osteoporosis con’t
Loss of calcium and phosphate causes bones
to become porous, brittle, and prone to
fracture
Treatment
Increased intake of calcium and Vitamin D
Exercise
Medications to increase bone mass
Estrogen replacement
Diseases and abnormal conditions
Abnormal curvatures of the spinal column
Kyphosis: “Hunchback” or rounded bowing of
the back at the thoracic area
Scoliosis: Side to side or lateral curvature of
the spine
Lordosis: “swayback” or abnormal inward
curvature of the lumbar vertebrae
Diseases and abnormal conditions
Osteosarcoma
Bone cancer
May occur in younger people
The most common site of affliction is just
above the knee
Functions of bones
1. Framework: support body’s muscles, fat, and skin
2. Protection: surround vital organs to protect them
Examples: Skull that surrounds the brain and the ribs
that protect the heart and lungs
3. Movement and anchorage of muscles.
4. Produce blood cells: produce red & white blood
cells and platelets, a process called hemopoiesis or
hematopoiesis
5. Mineral Storage: stores most of the calcium supply
of body. Also stores phosphorus
Bone Formation
Bones consist of microscopic cells called
osteocytes. An osteocyte is a mature bone
cell
Embryo skeleton starts as osteoblasts, then
change to cartilage.
Ossification (bone replaces cartilage) starts at
8 weeks
Infant’s bones are very soft and pliable
because of incomplete ossification at birth
(Fontanels are an example of this)
Motions
Joints can move in may
directions
Flexion: Brings two
bones closer together
which decreases the
angle between the two
bones
Extension: increasing
the angle between two
bones which results in a
straightening motion
Motions
Abduction
The movement of an
extremity away from
the midline
Adduction
The movement of an
extremity towards the
midline
Motions
Pronation
The forearm turns the
hand so the palm is
downward or backward
Supination
The palm is forward or
upward
Motions
Circumduction
Includes flexion,
extension, abduction,
and adduction
Rotation
Movement allows the
bone to move around
one central axis