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Functions of Skeletal System

• 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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