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Classification 2 types of bone (osseous) tissue –Compact – dense, looks smooth –Spongy – needlelike pieces, lots of space Divided into 4 groups based on shape –(1)Long bones Shaft with head at both ends Compact All limbs except wrist and ankles
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Chapter 5 Skeletal System
Skeletal system: bones, joints, cartilages, ligaments
2 divisions: Axial and Appendicular
Bones – 206Functions
• Support/framework• Protection• Movement• Storage – minerals (calcium and
phosphorus), fats in internal cavities• Blood cell formation – hematopoiesis – in
marrow
Classification• 2 types of bone (osseous) tissue
– Compact – dense, looks smooth– Spongy – needlelike pieces, lots of space
• Divided into 4 groups based on shape– (1)Long bones
• Shaft with head at both ends
• Compact• All limbs except wrist
and ankles
– (2)Short bones• Cube-shaped• Spongy• Ankles and wrists• Sesamoid – form in tendons
– ex. patella– (3)Flat bones
• Thin, flat, curved• Compact layered around spongy• Skull, ribs, sternum
– (4)Irregular bones• Don’t fit into other three• Vertebrae, hip bones
Long Bone Structure• Diaphysis – shaft
– Compact bone– Periosteum – protective connective
membrane– Perforating (Sharpey’s) fibers
connect membrane and bone• Epiphyses – ends
– Thin compact layer around spongy– Covered by articular cartilage –
decreases friction– In adults: epiphyseal line – bony
tissue– In kids: epiphyseal plate – cartilage –
causes lengthwise growth
• Cavity– Yellow marrow (medullary cavity)
• In adults• Fat deposits
– Red marrow• In kids• Blood cell formation• In adults this marrow
is in spongy, flat bones
Bone Markings
• Where muscles, tendons, ligaments attach or where vessels and nerves pass– 2 types: projections (processes) and
depressions (cavities)
Microscopic Anatomy• Osteocytes – mature bone cells• Found in cavities called lacunae• Lacunae form circles (lamellae) around a central
canal (Haversian canal) which carries blood vessels and nerves
• Osteon (Haversian system) – each complex• Canaliculi – canals that come off central canal
and lead to lacunae• Perforating (Volkmann’s) canals – run at right
angles to shafts
Formation, growth, & remodeling• Ossification – bone formation
– 2 steps• Hyaline cartilage model is covered with bone matrix by
osteoblasts (bone forming cells)• Cartilage is broken down and leaves the medullary cavity
• By birth only cartilage regions left are:– Articular cartilage – covers ends – stays for life– Epiphyseal plates – area of longitudinal growth
• New cartilage is added on surface away from medullary cavity
• Cartilage closest to cavity is broken down and replaced by bone
• Appositional growth – diameter increase– Osteoblasts in periosteum add bone to external
diaphysis• Growth controlled by growth hormone and sec
hormones• Bones remodel (change) because of:
– Calcium levels in blood• Decrease in calcium – PTH released – activates osteoclasts
which break down bone to release calcium• Increase in calcium – hypercalcemia – calcium deposits form
– Pull of gravity and muscles• Causes bones to become thicker and form projections for
attachment
Fractures• Closed (simple) fractures – clean break –
under skin• Open (compound) fractures – ends pierce
skin• Reduction – realignment
• Closed – placed/coaxed by hands• Open – surgery
• Repair– Hematoma forms– Break splinted by a fibrocartilage callus– Bony callus forms – replaces cartilage– Bone remodeling
• Types– Comminuted –
many fragments – common in older people
– Compression – crushed
– Depression – pressed inward – skull fracture
– Impacted – ends forced into each other – falls
– Spiral – twisting forces – sports
– Greenstick – partial break – kids
Other Disorders• Sprain – tendon/ligament
damage• Arthritis
– Osteoarthritis (OA) – aka “wear and tear arthritis”
– Rheumatoid arthritis (RA) – autoimmune – body’s immune system is attacking itself
– Gouty arthritis – gout – uric acid builds up and is deposited in joints
• Osteoporosis – bone thinning
Joints
• aka articulations• Functions
– Hold bones together– Allow movement
• 2 ways to classify– (1)Function – amount of movement
• Synarthroses – immovable• Amphiarthroses – slightly movable• Diarthroses – freely movable
– (2)Structurally • Fibrous
–Joined by fibrous tissue–Synarthroses –Ex. skull sutures
• Cartilaginous–Joined by cartilage–Most amphiarthroses–Ex. pubic symphysis, intervertebral joints–A few synarthroses – epiphyeal plates,
btw ribs and sternum
• Synovial– Separated by a joint cavity w/
synovial fluid– Found in limbs– 4 features
» Articular cartilage over ends
» Fibrous articular capsule» Joint cavity – enclosed by
capsule» Contains synovial fluid» Reinforcing ligaments
– May have bursae (fluid filled sacs) or a tendon sheath (completely wraps tendons in high friction areas)
• Synovial joint types – based of shape– Plane – gliding – flat surfaces
– wrist – nonaxial– Hinge – uniaxial – elbow, knee,
fingers– Pivot – uniaxial – radioulnar
joint, atlas and axis
– Condyloid – biaxial – side/side and back/forth• Btw metacarpals and phalanges
– Saddle – biaxial – carpometacarpal of thumb – twiddling
– Ball and socket – multiaxial – shoulder, hip