HUMAN SKELETON

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HUMAN SKELETON

• AN ENDOSKELETON

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FUNCTIONS OF THE SKELETON

• SUPPORT
• MOVEMENT
• PROTECTION
• MINERAL RESERVE
• HEMATOPOIESIS

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BONE CLASSIFICATION

• LONG BONES
• SHORT BONES
• FLAT BONES
• IRREGULAR BONES
• SESAMOID BONES

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LONG BONES

• HUMERUS
• RADIUS
• ULNA
• FEMUR
• TIBIA
• FIBULA
• PHALANGES

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SHORT BONES

• CARPALS
• TARSALS
• SESAMOID BONES

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SESAMOID BONES

• SHORT BONES EMBEDDED IN TENDONS
• PATELLA

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FLAT BONES

• CALVARIUM
• RIBS
• STERNUM

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IRREGULAR BONES

• ETHMOID
• SPHENOID
• VERTEBRAE
• SCAPULA
• PELVIC BONES

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LONG BONE STRUCTURE

• DIAPHYSIS
• EPIPHYSES
• MEDULLARY CAVITY
• ENDOSTEUM
• PERISOTEUM

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PERIOSTEUM
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SHARPEYS FIBERS
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ENDOSTEUM
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YELLOW BONE MARROW
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RED BONE MARROW
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SPONGY BONE
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SPONGY BONE
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COMPACT BONE
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STRUCTURE OF COMPACT BONE
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EPIPHYSEAL LINE
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EPIPHYSEAL PLATE
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EPIPHYSEAL PLATE
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FLAT BONE STRUCTURE
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HISTOLOGY OF BONE
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BONE MATRIX

• 35 PERCENT ORGANIC COLLAGEN PROTEOGLYCANS
• 65 PERCENT INORGANIC HYDROXYAPATITE

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TYPES OF BONE CELLS

• OSTEOBLASTS
• OSTEOCYTES
• OSTEOCLASTS

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OSTEOBLASTS

• EXTENSIVE ENDOPLASMIC RETICULUM
• LOTS OF RIBOSOMES
• PRODUCE COLLAGEN AND PROTEOGLYCANS
• PRODUCE HYDROXYAPATITE
• PRECURSORS

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FUNCTION OF OSTEOBLASTS

• OSSIFICATION OR OSTEOGENESIS

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OSTEOCYTES

• FORMED WHEN OSTEOBLASTS ARE SURROUNDED BY MATRIX
• MAINTAIN MATRIX AROUND THEMSELVES
• LACUNAE
• CANLICULI

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OSTEOCLASTS
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OSTEOCLASTS

• LARGE CELLS
• MULTINUCLEATE
• RUFFLED BORDER
• PUMP HYDROGEN IONS AND ENZYMES INTO MATRIX

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RESORPTION OF BONE

• OSTEOCLAST PRIMARILY RESPONSIBLE
• OSTEOBLAST ASSIST

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WHERE DO BONE CELLS COME FROM

• MESENCHYMAL CELLS
• STEM CELLS
• OSTEOPROGENITOR CELLS
• OSTEOCLASTS HAVE A DIFFERENT ORIGIN

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ORGANIZATION OF BONY TISSUE

• WOVEN VS LAMELLAR CANCELLOUS VS COMPACT

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CANCELLOUS BONE

• INTERCONNECTING RODS OR PLATES
• TRABECULAE
• SPONGY BONE

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COMPACT BONE

• DENSER
• FEWER SPACES
• OSTEONS
• CENTRAL CANAL
• PERFORATING CANALS

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HOW DOES BONE DEVELOP

• INTRAMEMBRANOUS VS ENDOCHONDRAL OSSIFICATION

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INTRAMEMBRANOUS OSSIFICATION
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MESENCHYMAL MEMBRANE FORMATION BEGINS ABOUT 5TH
WEEK GESTATION
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OSSIFICATION BEGINS AT ABOUT 8TH WEEK GESTATION
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IS COMPLETED BY ABOUT TWO YEARS OF AGE
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BONES FORMED BY INTRAMEMBRANOUS OSSIFICATION

• SKULL BONES
• MANDIBLE
• PARTS OF CLAVICLES

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RED BONE MARROW
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ENDOCHONDRAL OSSIFICATION
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CARTILAGE FORMATION BEGINS AT ABOUT THE FOURTH
WEEK OF GESTATION
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OSSIFICATION BEGINS AT ABOUT 8 WEEKS OF GESTATION
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SOME MAY NOT BEGIN OSSIFICATION UNTIL LATER
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BONES FORMED BY ENDOCHONDRAL OSSIFICATION

• FEMUR
• HUMERUS
• ETC

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BONE GROWTH

• APPOSITIONAL GROWTH

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ROLE OF THE EPIPHYSEAL PLATE IN BONE GROWTH

• ZONE OF RESTING CARTILAGE
• ZONE OF PROLIFERATION
• ZONE OF HYPERTROPHY
• ZONE OF DIFFERENTIATION

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ZONE OF RESTING CARTILAGE
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ZONE OF PROLIFERATION
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ZONE OF HYPERTROPHY
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ZONE OF DIFFERENTIATION
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HOW THE ARTICULAR CARTILAGE GROWS

• SIMILAR TO PROCESS IN EPIPHYSEAL PLATE
• COLUMNS OF ARE NOT AS PRONOUNCED

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HOW BONES INCREASE IN DIAMETER

• APPOSITIONAL GROWTH

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FACTORS THAT AFFECT BONE GROWTH

• NUTRITION
• HORMONES

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NUTRITION

• VITAMIN D
• VITAMIN C

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VITAMIN D

• NECESSARY FOR ABSORPTION OF CALCIUM
• SYNTHESIZED BY BODY OR INGESTED
• LACK CAN CAUSE RICKETS OR OSTEOMALACIA

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VITAMIN C

• NEEDED FOR COLLAGEN SYNTHESIS

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HORMONES

• GROWTH HORMONE
• THYROID HORMONE
• ESTROGENS
• ANDROGENS

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GROWTH HORMONE

• INCREASE TISSUE GROWTH
• INCREASE BONE GROWTH
• STIMULATES INTERSTITIAL CARTILAGE GROWTH
• STIMULATES BONE GROWTH

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THYROID HORMONE

• STIMULATES NORMAL CARTILAGE GROWTH

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ESTROGENS

• STIMULATE GROWTH
• CAUSES RAPID GROWTH AT EPIPHYSEAL PLATE
• CAUSE QUICKER CLOSURE OF EPIPHYSEAL PLATE
• THIS IS WHY FEMALES ARE GENERALLY SMALLER THAN
  MALES

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TESTOSTERONE

• STIMULATES BONE GROWTH
• SLOWER TO CLOSE EPIPHYSEAL PLATE
• THAT IS WHY MALES ARE GENERALLY TALLER

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BONE REMODELING

• REMOVAL OF OLD BONE BY OSTEOCLASTS
• DEPOSITION OF NEW BONE BY OSTEOBLASTS

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FUNCTIONS OF REMODELING

• CONVERTS WOVEN BONE INTO LAMELLAR BONE
• BONE GROWTH
• CHANGES IN BONE SHAPE
• ADJUSTMENTS TO STRESS
• BONE REPAIR
• CALCIUM ION REGULATION

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CALCIUM HOMEOSTASIS

• PARATHYROID HORMONE
• CALCITONIN

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PARATHYROID HORMONE

• MAJOR REGULATOR OF BLOOD CALCIUM LEVELS
• DIRECT EFFECT ON OSTEOBLASTS
• INDIRECT EFFECT ON OSTEOCLASTS
• INCREASES UPTAKE OF CALCIUM BY GI TRACT
• PROMOTES FORMATION OF VITAMIN D BY KIDNEYS
• INCREASES REABSORPTION OF CALCIUM BY KIDNEYS

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CALCITONIN

• DECREASES OSTEOCLAST ACTIVITY
• INCREASES CALCIUM STORAGE

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CLINICAL CONDITIONS

• FRACTURES
• RICKETS AND OSTEOMALACIA
• METATASTIC CALCIFICATION
• OSTEOPOROSIS
• OSTEOMYELITIS
• TUBERCULOSIS OF THE BONE
• TYPHOID OF THE BONE
• TUMORS OF THE BONE

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BONE FRACTURES AND REPAIR
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TYPES OF FRACTURES
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SIMPLE
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SIMPLE
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COMPOUND
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COMMINUTED
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DEPRESSED FRACTURE
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IMPACTED
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SPIRAL
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GREENSTICK
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COLLES FRACTURE
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Repair of a Fracture (1)

• Formation of fracture hematoma
• damaged blood vesses produce clot in 6-8 hours,
  bone cells die
• inflammation brings in phagocytic cells for
  clean-up duty
• new capillaries grow into damaged area
• Formation of fibrocartilagenous callus formation
• fibroblasts invade the procallus lay down
  collagen fibers
• chondroblasts produce fibrocartilage to span the
  broken ends of the bone

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Repair of a Fracture (2)

• Formation of bony callus
• osteoblasts secrete spongy bone that joins 2
  broken ends of bone
• lasts 3-4 months
• Bone remodeling
• compact bone replaces the spongy in the bony
  callus
• surface is remodeled back to normal shape

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BONE REPAIR

• HEMATOMA FORMATION
• INTERNAL CALLUS FORMATION
• EXTERNAL CALLUS FORMATION
• CARTILAGE OSSIFICATION
• BONE REMODELING

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HEMATOMA
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CALLOUS FORMATION
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CARTILAGINOUS CALLUS
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CONVERSION TO BONY CALLUS
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BONE REMODELING
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IMPORTANCE OF STRESS IN BONE REPAIR
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OSTEOCLAST
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CLINICAL CONDITIONS

• PITUITARY DWARFISM
• PITUITARY GIGANTISM
• ACHONDROPLASTIC DWARFISM
• ACROMEGALY

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EFFECTS OF AGING ON THE SKELETAL SYSTEM

• LOSS OF CALCIUM FROM BONE
• MORE SEVERE IN WOMEN THAN MEN
• PROTEIN SYNTHESIS MAY SLOW LEADING TO BRITTLE
  BONES

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FINI