The Skeletal System
• Skeleton comes from a Greek word
meaning dried up body.
• Bone appears dead and dried up, but
it is not!
• Bone is living tissue
• Newborn human has 350 bones
• Adult human has 206 bones
• Parts of the skeletal system
• Bones (skeleton)
• Joints
• Cartilages
• Ligaments (bone to bone)(tendon=bone
to muscle)
Functions of Bones
- Support of the body (framework)
- Protection of soft organs
- Serve as levers (with help from
muscles) - Storage of minerals and fats
(calcium) - Blood cell formation
Bones of the Human Body
Two basic
types of bone tissue
- Compact bone
- Dense/hard
- Spongy bone
- (Cancellous)
- Many open spaces
- Decrease wt of bone/contain
red bone marrow
Classification of Bones on the Basis of Shape
- Long bones
- Typically longer than wide
- Have a shaft with heads at
both ends - Contain mostly compact bone
- Found in legs and arms
•
Examples:
Femur, humerus
- Short bones
- Generally cube-shape and small
- Contain mostly spongy bone
- Found in wrist, ankles, and toes
•
Examples:
Carpals, tarsals
- Flat bones
- Thin and flattened
- Usually curved
- Cover organs/provide surface
for lg. muscle - Thin layers of compact bone
around a layer of spongy bone
•
Examples:
Skull, ribs, sternum
- Irregular bones
- Irregular shape
- Do not fit into other bone
classification categories
•
Example:
Vertebrae and hip
Gross Anatomy of a Bone
- Diaphysis
§
Shaft
§
Composed
of compact bone
- Epiphysis
§
Ends
of the bone
§
Composed
mostly of spongy bone
- Periosteum
§
Outside
covering of the diaphysis
§
Fibrous
connective tissue membrane
§
Serves
as an attachment for muscle
- Arteries
§
Supply
bone cells with nutrients
·
Articular cartilage
§
Covers
the external surface of the epiphyses
§
Made
of hyaline cartilage
§
Decreases
friction at joint surfaces
·
Medullary cavity
§
Cavity
of the shaft
§
Contains
yellow marrow (mostly fat) in adults
§
Contains
red marrow (for blood cell formation) in infants
Changes in the Human Skeleton
- In embryos, the skeleton is
primarily hyaline cartilage - During development, much of
this cartilage is replaced by bone - Cartilage remains in isolated
areas - Bridge of the nose
- Parts of ribs
- Joints
Bone Growth
- Epiphyseal plates allow for growth of long bone during childhood
- New cartilage is continuously
formed - Older cartilage becomes
ossified - Cartilage is broken down
- Bone replaces cartilage
- Bones are remodeled and lengthened until growth stops
- Grow longitudinally for height
- Bones grow in width to support
weight
Epiphyseal Disc
• Growth plate
• The cartilage near the epiphyseal
disc multiplies and eventually becomes ossified (turns to bone)
• As long as new cartilage continues
to form the bone continues to lengthen.
• When the growth plate hardens and
becomes ossified, growth stops
• Hormones play a big part in this
• Growth hormone stimulates growth
• Sex hormones stop growth
Bone Width
• Long after longitudinal bone growth
has stopped, bones continue to grow in thickness and width.
• Bones are continuously being
reshaped
Types of Bone Cells
- Osteocytes
- Mature bone cells
- Osteoblasts
- Bone-forming cells
- Osteoclasts
- Bone-destroying cells
- Break down bone matrix for
remodeling and release of calcium - Bone remodeling is a process by both osteoblasts and osteoclasts
Bone Remodeling
• A combined action of osteoblasts
(bone forming cells) and osteoclasts (bone destroying cells)
• Osteoblasts deposit bone on the
external bone surface
• Osteoclasts break down bone from the
inside
Bone Fractures
- A break in a bone
- Types of bone fractures
- Closed (simple) fracture –
break that does not penetrate the skin - Open (compound) fracture –
broken bone penetrates through the skin - Bone fractures are treated by reduction and immobilization
- Realignment of the bone
Dislocation of joint
• Displacement of bones at the joint
• Often caused by impact trauma to
that joint
• Can be more damaging and painful
than a fracture
• Damage to the joint capsule and
surrounding ligaments and tendons often takes much longer to heal than bone
tissue.
Repair of Bone Fractures
- Hematoma (blood-filled
swelling) is formed - Break is splinted by
fibrocartilage to form a soft callus - Blood vessels grow into the
hematoma - Fibrocartilage callus is
replaced by a bony callus - Bony callus is remodeled to
form a permanent patch
Skeletal System
Divided into two divisions
Axial skeleton ~ bones of the cranium, face, vertebral column,
and bony thorax.
Appendicular skeleton ~ includes the bones of the pelvic
girdles, the upper extremities and lower extremities.
The Axial Skeleton
- Forms the longitudinal part of
the body - Divided into three parts
- Skull
- Vertebral column
- Bony thorax
The Skull (28 bones) (18 names!)
- Sits on top of the vertebral
column - Two sets of bones
- Cranium (8 bones)
- Facial bones (14 bones)
- Bones are joined by sutures
- Only the mandible is attached
by a freely movable joint
The
Cranium
• Bony structure that encases and
protects the brain.
• 8 bones
• Frontal
Bone ~ forehead/upper
part of the bony structure surrounding the eyes.
• Parietal Bone (2) ~ upper sides of the head and
the roof of the cranial cavity (top of the head)
• Temporal Bones (2) ~ sides of the head, close to
ears.
• Commonly called the temples
• Includes the external auditory
meatus
•
Opening
for the ear
• Includes the zygomatic process
•
Part
of the cheekbone
• Occipital Bone ~ back and base of the cranium
• Includes the foramen magnum
•
Foramen
means hole
•
Large
hole for the brainstem/spinal cord
• Sphenoid Bone ~ forms sides of cranium and parts
of orbits of the eyes
• Butterfly shaped
• Includes Sella Turcica (Turk’s
Saddle)
•
Where
pituitary gland sits
• Ethmoid Bone ~ irregularly shaped bone located
between the eye orbits
• Major supporting bone of the nasal
cavity
• That’s it! No more cranium bones!
• 206 bones – 8 bones = 198 bones to
go…
Facial
Bones
• 14 bones
• Most of these bones come in pairs
• Only the mandible and vomer are
single bones
• Mandible ~ the lower jaw bone
• Carries the lower teeth
• The anterior portion forms the chin
• Only freely movable joint in the
skull
• Maxilla (2) ~ Upper jaw
• Two bones fused together
• Roof of the mouth
• Also form parts of the nasal cavity
and eye orbits
• Palantine Bones (2) ~ form the posterior part of the hard
palate and the floor of the nasal cavity.
• Failure of the palatine and/or
maxillary bones to fuse causes a cleft palate.
• Zygomatic Bones (2) ~ the cheekbones
• Also forms a part of the orbits of
the eyes
• Other Facial Bones
• Lacrimal Bones (2) ~ inner wall
of eye sockets
• Nasal Bones (2) ~ bridge of nose
• Vomer ~ nasal septum
• Inferior Nasal Conchae (2)
• That’s it! No more facial bones!
• 198 bones – 14 bones = 184 bones to
go…
Paranasal Sinuses
- Functions of paranasal sinuses
- Air filled cavities
- Lighten the skull
- Give resonance and
amplification to voice
The Fetal Skull
- The fetal skull is large
compared to the infants total body length - Fontanelles – fibrous membranes
connecting the cranial bones - Allow the brain
to grow - Convert to bone within 24
months after birth
The Hyoid Bone
- U shaped
- Found in the upper neck
- The only bone that does not
articulate with another bone - Serves as a moveable base for
the tongue
Middle
Ear
• 3 Tiny bones ~ transmit vibrations
• All derived from Latin words
• Malleus (hammer)
• Incus (anvil)
• Stapes (stirrup)
• Smallest bone in the body
Middle
Ear and Hyoid Bones
• That’s it!
• 184 bones – 4 bones = 180 bones to
go…
The Vertebral Column
• The backbone or spine
• Consists of 26 bones called
vertebrae
• Vertebrae separated by
intervertebral discs (act as shock absorbers)
• The spine has a normal curvature
• Each vertebrae is given a name
according to its location
• C1-C7 ~ in the neck region
• 7 cervical vertebrae
• T1-T12 ~ located in the chest region
• 12 thoracic vertebrae
• L1-L5 ~ located in the lower back
• 5 lumbar vertebrae
• Sacrum ~ curved bone of the lower
back (posterior wall of the pelvis)
• fused sacral vertebrae
• 5 vertebrae at birth
• Coccyx ~ the tailbone
• 4 vertebrae at birth
• The vertebrae become larger as the
vertebral column descends…..WHY?
• Vertebral foramen ~ opening for
spinal cord.
• What is the opening for the spinal
cord in the skull called?
• 180 bones – 26 vertebral column
bones = 154 bones to go!
The Bony Thorax (Thoracic Cage)
- The chest region
- Forms a cage to protect major
organs - Composed of sternum, ribs and
thoracic vertebrae. - Sternum ~ breastbone.
- Dagger-shaped bone located
along the midline of the anterior chest. - Ribs ~ 12 pairs of ribs attach
posteriorly to the thoracic vertebrae - True ribs ~ first 7 pair
- False ribs ~ last 5 pairs
That is it for the axial skeleton!
• 154 bones – 24 ribs -1 sternum = 129
bones to go!!!
The Appendicular Skeleton
- Limbs (appendages)
- Pectoral (shoulder) girdle
- Pelvic girdle
The Pectoral (Shoulder) Girdle
- Composed of two bones
- Clavicle – collarbone
- Scapula – shoulder blade
- These bones allow the upper
limb to have exceptionally free movement
Bones of the Upper Limb
- The arm is formed by a single
bone - Humerus
- Head of humerus allows for
rotation - The forearm has two bones
- Ulna
- Radius
Radius
• Radius ~ locate
on the lateral or thumb side when the palm of the hand is facing forward.
Ulna
• Ulna~ the longer of the two forearm bones.
• Located on the medial or little
finger side of the forearm.
Bones of the Upper Limb
- The hand
- Carpals – wrist
- Metacarpals – palm
- Phalanges – fingers
Bones of the Pelvic Girdle
- Composed of two coxal bones
(hip bones) - Composed of three pair of
fused bones - Ilium
- Ischium
- Pubis
- The total weight of the upper
body rests on the pelvis - Protects several organs
- Reproductive organs
- Urinary bladder
- Part of the large intestine
Bones of the Lower Limbs
- The thigh has one bone
- Femur – thigh bone
- Patella ~ knee cap
- Triangular bone located within
a tendon that passes over the knee. - The leg has two bones
- Tibia ~ shin bone
- larger
- Fibula
- Long and thin
- The foot
- Tarsal (7)– ankle
- Metatarsals (5)– sole/instep
- Phalanges (14) – toes
Joints
- Articulations of bones
- Functions of joints
- Hold bones together
- Provide flexibility
- Ways joints are classified
- By their function
- By their structure
Functional Classification of Joints
- Synarthroses – immovable joints
- Amphiarthroses – slightly
moveable joints - Diarthroses – freely moveable
joints
Structural Classification of Joints
- Fibrous joints
- Generally immovable
- Cartilaginous joints
- Immovable or slightly moveable
- Synovial joints
- Freely moveable
Fibrous Joints
- Bones united by fibrous tissue
– synarthrosis or largely immovable.
Cartilaginous Joints – mostly amphiarthrosis
- Bones connected by cartilage
- Examples
- Pubic
symphysis - Intervertebral
joints
Synovial Joints
- Articulating bones are
separated by a joint cavity - Synovial fluid is found in the
joint cavity - Reinforced by ligaments
- 6 Types of Synovial Joints
Hinge
joint
·
Movement
is like two boards joined together by a hinge
·
Movement
in one direction
·
Elbow,
knees, fingers
Ball and
Socket Joint
·
When
ball-shaped end of one bone fits into the cup-shaped socket of another
·
Bones
can move in many directions
·
Shoulder,
hip
Pivot
Joint
·
Allows
for rotation around the length of a bone.
·
Allows
only for rotation
·
Head
(side to side “no” action)
·
Forearm
joints (palms) supination/pronation
Saddle
Joint
·
When
the surfaces of both articulation bones are saddle-shaped
·
Concave/convex
·
Thumb
·
Wide
range of motion
Gliding
Joint
·
Interaction
of flat surfaces of articulating bones
·
Limited
but complex movement
·
Wrist,
ankle
Condyloid
Joint
·
Oval-shaped
articular surface of one bone fits into the oval-shaped depression of another
·
Mandible,
knuckles
Inflammatory Conditions Associated with Joints
- Bursitis – inflammation of a
bursa usually caused by a blow or friction - Tendonitis – inflammation of
tendon sheaths - Arthritis – inflammatory or degenerative
diseases of joints - Over 100 different types
- The most widespread crippling
disease in the United States
Clinical Forms of Arthritis
- Osteoarthritis
- Most common chronic arthritis
- Probably related to normal
aging processes - Rheumatoid arthritis
- An autoimmune disease – the immune
system attacks the joints - Symptoms begin with bilateral
inflammation of certain joints - Often leads to deformities
- Gouty Arthritis
- Inflammation of joints is
caused by a deposition of urate crystals from the blood - Can usually be controlled with
diet - Red meat and wine are high in
uric acid.
