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Functions of Bones• Support – hard framework that supports and
anchors body – bones of legs act as pillars to • Protection – fused bones of the skull provide
a snug enclosure for the brain – vertebrae surround the spinal cord – rib cage protects vital organs
• Movement – skeletal muscles attach to bones by tendons and act as levers to move the body
• Storage – bone matrix (calcium, phosphorus, potassium, sodium, sulfur, magnesium, & copper) – deposits and withdrawals are constant
• Blood cell formation – hematopoiesis occurs within the marrow cavities of certain bones
Bone Markings
• Projections– Tuberosity – large, rounded projection that
may be roughened– Crest – Narrow ridge of bone– Trochanter – Very large, blunt, irregularly
shaped process (only on the femur)– Spine – sharp, slender, often pointed
projection– Process – any bony prominence
Bone Markings (ctd.)
• Projections That Help Form Joints
– Facet – smooth, nearly flat, articular surface– Condyle – rounded articular projection– Ramus – Arm-like bar of bone
• Depressions and Openings– Meatus – canal-like passageway– Sinus – Cavity within a bone filled with air and
lined with mucous membrane– Fossa – Shallow, basin-like depression in a
bone often serving as an articular surface– Fissure – Narrow, slit-like opening– Foramen – Round or oval opening through a
bone
Bone Markings (ctd.)
Bone Fractures, Development, and Degeneration
http://www.youtube.com/watch?v=Mz2UuhbtrwY
Bone Fractures
• Fracture—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
Stages in the Healing of a Bone Fracture
Figure 5.5, step 1
Hematoma
Hematomaformation
Step 1: Hematoma (blood-filled swelling) is formed
Stages in the Healing of a Bone Fracture
Figure 5.5, step 2
Hematoma
Externalcallus
Newbloodvessels
Internalcallus(fibroustissue andcartilage)
Spongybonetrabecula
Hematomaformation
Fibrocartilagecallus formation
Step 2: Break is splinted by fibrocartilage to form a callus
Stages in the Healing of a Bone Fracture
Figure 5.5, step 3
Hematoma
Externalcallus
Bonycallus ofspongybone
Newbloodvessels
Internalcallus(fibroustissue andcartilage)
Spongybonetrabecula
Hematomaformation
Fibrocartilagecallus formation
Bony callusformation
Step 3: Fibrocartilage callus is replaced by a bony callus
Stages in the Healing of a Bone Fracture
Figure 5.5, step 4
Hematoma
Externalcallus
Bonycallus ofspongybone
Healedfracture
Newbloodvessels
Internalcallus(fibroustissue andcartilage)
Spongybonetrabecula
Hematomaformation
Fibrocartilagecallus formation
Bony callusformation
Bone remodeling
Step 4: Bony callus is remodeled to form a permanent patch (spongy bone to compact bone)
Skeletal Changes Throughout Life
• Fetus– Long bones are formed of hyaline cartilage– Flat bones begin as fibrous membranes– Flat and long bone models are converted to
bone
• Birth– Fontanels remain until around age 2
Bone Growth (Ossification)
• Bones are remodeled and lengthened until growth stops– Bones are remodeled in response to two
factors• Blood calcium levels• Pull of gravity and muscles on the skeleton
– Bones grow in width (called appositional growth)
Long Bone Formation and Growth
Figure 5.4a
Bone startingto replacecartilage
Epiphysealplatecartilage
Articularcartilage
Spongybone
In a childIn a fetusIn an embryo
New boneforming
Growthin bonewidth
Growthin bonelength
Epiphysealplate cartilage
New boneforming
Bloodvessels
Hyalinecartilage
New center ofbone growth
Medullarycavity
Bone collar
Hyalinecartilagemodel
The Fetal Skull
• The fetal skull is large compared to the infant’s total body length
• Fontanels—fibrous membranes connecting the cranial bones– Allow the brain to grow– Convert to bone within 24 months (2 years)
after birth
Skeletal Changes Throughout Life
• Adolescence– Epiphyseal plates become ossified and long bone
growth ends. These plates become an Epiphyseal line and can be seen on an X-ray.
• Size of cranium in relationship to body– 2 years old—skull is larger in proportion to the
body compared to that of an adult– 8 or 9 years old—skull is near adult size and
proportion– Between ages 6 and 11, the face grows out from
the skull
Skeletal Changes Throughout Life
• Osteoporosis– Bone-thinning disease afflicting
• 50% of women over age 65 • 20% of men over age 70
– Disease makes bones fragile and bones can easily fracture
– Vertebral collapse results in kyphosis (also known as Dowager’s Hump)
– Estrogen aids in health and normal density of a female skeleton