Functions of Skeletal System
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Provides support
Protects organs
Movement by working with muscle
Stores calcium
Forms blood cells— hematopoiesis
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Types of Bones
• Structure of long bones
– Diaphysis, or shaft—hollow tube of compact bone
– Medullary cavity—space inside diaphysis that
contains yellow marrow
– Epiphyses, or ends—made of spongy bone that
contains red marrow
– Articular cartilage—thin layer that covers each
epiphysis;
– Periosteum—strong membrane covering bone
– Endosteum-membrane that lines medullary cavity
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Types of Bones
• Structure of flat bones
– Thin layer of compact bone surrounding
cancellous (spongy or diploe) bone
– Spaces surrounded by boney trabeculae
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Microscopic Structure
of Bone and Cartilage
• Bone
– Spongy
• Threads called trabeculae surrounded by open
spaces
• In epiphyses
• Spaces contain red bone marrow
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Microscopic Structure
of Bone and Cartilage
• Bone: Compact
– Concentric lamella—circular layers of
calcified matrix
– Lacunae—spaces in matrix for osteocytes
– Canaliculi—passageways that connect
lacunae and allow nutrients to reach
osteocytes
– Central canal of osteon contains blood
vessel
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Bone Formation and Growth
• New bone-forming cells are osteoblasts
• Bone resorbing cells are osteoclasts
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Bone Formation and Growth
• Bone formation
– Epiphyseal plate of cartilage
between epiphyses and
diaphysis remains until skeletal
maturity
– Epiphyseal line (bone)
replaces epiphyseal plate
(cartilage) when growth ceases
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Microscopic Structure
of Bone and Cartilage
• Cartilage
– Chondrocytes located in lacunae
– Matrix is flexible gel-like substance and
lacks blood vessels
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Divisions of Skeleton
• Axial skeleton (80 bones)
– Skull
– Spine, or vertebral column
– Thorax
• Appendicular skeleton (126 bones)
– Upper extremities, including shoulder
(pectoral) girdle
– Lower extremities, including hip (pelvic) girdle
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– Spine or vertebral column
• Four normal curves
• Three abnormal curves
– Lordosis or “swayback”
– Kyphosis or “hunchback”
– Scoliosis
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Differences Between a
Man’s and a Woman’s Skeleton
• Size—male skeleton generally larger
• Shape of pelvis—male pelvis deep and
narrow; female pelvis broad and shallow
• Size of pelvic inlet—female pelvic inlet
generally wider; normally large enough
for baby’s head to pass through it
• Pubic angle—angle between pubic
bones of female generally wider
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Skeletal Disorders
• Metabolic bone diseases
– Osteoporosis
• Loss of calcified bone matrix and reduction in
number of trabeculae in spongy bone
• Bones fracture easily, especially in wrists, hips,
and vertebrae
• Treatment :
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Skeletal Disorders
• Metabolic bone diseases
– Rickets and osteomalacia—both diseases
characterized by loss of bone minerals
related to vit D
• Rickets
– Loss of bone minerals in infants and young children
before skeletal maturity
– Lack of bone rigidity causes gross skeletal changes
(bowing of legs)
– Treated with vitamin D
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Skeletal Disorders
• Metabolic bone diseases
– Rickets and osteomalacia
• Osteomalacia
– Mineral content lost from bones that have already
matured
– Increases susceptibility to fractures
– Treated with vitamin D
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Skeletal Disorders
• Metabolic bone diseases
– Paget disease (osteitis deformans)
• Faulty remodeling results in deformed bones
that fracture easily
• Cause may be genetic or triggered by viral
infections
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Skeletal Disorders
• Metabolic bone diseases
– Osteogenesis imperfecta (also called brittle
bone disease)
• Bones are brittle because of lack of organic
matrix
• Treatment may include splinting to reduce
fracture and drugs that decrease cell activity
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Skeletal Disorders
• Bone infection
– Osteomyelitis
• General term for bacterial (usually
staphylococcal) infection of bone
• Treatment involve surgery, drainage of pus,
and antibiotic
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Skeletal Disorders
• Bone fractures
– Open (compound) fractures pierce skin
and closed (simple) fractures do not
– Fracture types include complete and
incomplete, linear, transverse and oblique
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Skeletal Disorders
• Joint disorders
– Noninflammatory joint disorders—do not usually
involve inflammation of the synovial membrane;
symptoms tend to be local and not systemic
• Osteoarthritis, or degenerative joint disease (DJD)
– Most common noninflammatory disorder of movable
joints—often called “wear and tear” arthritis
– Symptoms: joint pain, morning stiffness, Bouchard nodes
(at proximal interphalangeal joints), Heberden nodes (at
distal interphalangeal joints) of the fingers
– Most common cause for partial and total hip and knee
replacements
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Skeletal Disorders
• Joint disorders
– Noninflammatory joint disorders
• Traumatic injury
– Dislocation or subluxation—articular surfaces of
bones in joint are no longer in proper contact
– Sprain—acute injury to ligaments around joints (e.g.,
whiplash type injuries)
– Strain—acute injury to any part of the
“musculotendinous unit” (muscle, tendon, junction
between the two, and attachments to bone)
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Skeletal Disorders
• Joint disorders
– Inflammatory joint disorders
• Arthritis: general name for several inflammatory
joint diseases that may be caused by infection,
injury, genetic factors, and autoimmunity
• Inflammation of the synovial membrane occurs,
often with systemic signs and symptoms
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Skeletal Disorders
• Joint disorders
– Inflammatory joint disorders
• Rheumatoid arthritis
– Systemic autoimmune disease—chronic inflammation of
synovial membrane with involvement of other tissues such as
blood vessels, eyes, heart, and lungs
– Gouty arthritis—synovial inflammation caused by gout, a
condition in which sodium urate crystals form in joints and
other tissues
– Infectious arthritis—arthritis resulting from infection by a
pathogen, as in Lyme arthritis and ehrlichiosis, caused by two
different bacteria that are transmitted to humans by tick bites
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