Bone Histology and Development

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Bone Histology and Development
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Skeletal System

• 205 bones
• Associated CT
• Cartilage
• Tendons
• Ligaments
• discs

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Functions Bone

• Maintain body shape
• Protect internal organs, brain, spinal cord
• System of levers for the muscle system to act
  upon
• Mineral storage Ca2 and Phosphorus
• Blood formation hematopoiesis
• Surface features for muscle insertions and
  origins

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Cartilage

• Hyaline
• Fibrocartilage
• Elastic

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Functions cartilage

• Rigid, yet more flexible than bone more elastic
  than bone
• Support and protection
• Abundant in the fetus and embryo
• Site of skeletal growth
• Covers joints
• Supports nose, ears, trachea, ribs, etc

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Functions Ligaments, Tendons

• Strong bands of fibrous CT
• Muscle to bone
• Aponeuroses
• Bone to bone

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Shapes of Bones

• Long arms, legs, clavicle
• Short wrists, sternum
• Irregular vertebrae, facial, hyoid, tarsals
• Flat skull, ribs
• Sesamoidal imbedded in tendons patella
• Sutural small bones between sutures in skull

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Bone Matrix

• 35 collagen organic
• Some chondroitin sulfate, hyaluronic acid and
  polysaccharides
• 65 calcium phosphate minerals hydroxyapetite
• Combination provides strength and rigidity
• Laid down by osteoblasts

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Hormones and Bone Development

• Hormones affect Calcium Phosphate deposition and
  reabsorption
• From the parathyroid parathormone
• Increases Ca2 plasma
• From the thyroid calcitonin
• Ca2 is deposited into bone
• Growth Hormone
• Stimulates new cartilage development in long
  bones
• Too much ? giantism
• Too little ? dwarf
• Adults ? Acromegally where the bone thickens
• Estrogen and Testosterone ? stimulate bone growth
• Deficiency ? osteoporosis

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Periosteum where you find pain receptors and
more vessels
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Hematopoiesis
Trabeculae have lamellae and osteocytes like
osteons
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Terms
Red Marrow Yellow Marrow
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Bone Formation

• Intramembranous
• Within membranes, no cartilage precursor
• Forms flat bones

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Intramembranous bone formation

• Connective tissue develops embryonically and
  gives rise to bone
• Cells in connective tissue differentiate into
  osteoblasts
• Osteoblasts lay down collagen eventually starts
  to calcify and cells become osteocytes
• Cancellous bone eventually becomes compact bone

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Skull cavity increases without increasing bone
thickness Osteoblasts and Osteoclasts are at work
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Endochondral bone formationfrom hyaline
cartilage covered in perichondrium

• http//www.e-radiography.net/articles/ossification
  /ossification.htm

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Bone Repair