Bone Tissue

1
Bone Tissue

• Chapter 7

2
Objectives

• Know the functions of the skeletal system
• Understand how bones are classified
• Identify the macroscopic and microscopic features
  of bone
• Understand how bone is developed and
  physiologically controlled
• Know what a fracture is and how it is repaired
• Know some bone disorders

3
Skeletal System

• Composed of bones, cartilages, and ligaments
  joined tightly together to form a strong,
  flexible framework for the body
• Skeleton functions
• Support
• Protection
• Movement
• Electrolyte balance
• Acid-base balance
• Blood formation
• Osseous tissue
• Connective tissue with a hardened matrix
• Deposition of calcium phosphate and other
  minerals
• Part of the composition of a bone

http//www.amersol.edu.pe/class09/_09pdelaf/7th/sc
ience/webpages/skeleton.html
4
Classification of Bones

• Classified based on shape and corresponding
  function
• Four categories
• Long bones
• Short bones
• Irregular bones
• Flat bones

massasoit-bio.net
5
General Features of Bones

• Epiphysis
• Ends of the bone
• Composed of cancellous (spongy) bone
• Diaphysis
• Shaft of the bone
• Composed of compact bone
• Medullary cavity
• Contains yellow bone marrow
• Epiphyiseal plate

http//pathologyoutlines.com/bone.html
6
Structure of Bone
Figure 5.1
7
Histology

• Four main types of bone cells
• Osteogenic (osteoprogenitor) cells
• give rise to osteoblasts , osteocytes
• Osteoblasts
• Bone-forming cells
• Found along endosteum and periosteum
• Secrete osteocalcin
• Osteocytes
• Former osteoblasts that have been trapped in
  their lacunae
• Maintain bony matrix
• Strain sensors
• Octeoclasts
• Bone-dissolving cells

• Matrix
• composed of inorganic and organic components
• Inorganic component
• Hydroxyapaptite
• Composed mainly of CaPO4 salt
• Organic components
• Protein and carbohydrate
• Collagen
• Bone is a composite

8
Compact Bone

• Osteon (haversian system)
• Basic structural unit of compact bone
• Central (haversian) canal surrounded by
  concentric lamellae (matrix)
• Perforating canals
• Transverse or diagonal passages into the central
  canal
• Originate at nutrient foramen

ask.com
9
Spongy Bone

• Composed by a network of spicules and trabeculae
• Spaces filled with red marrow
• Beams arranged to sustain stress

commons.wikimedia.org
10
Bone Development

• Ossification or osteogenesis
• Formation of bone
• Two methods
• Intramembranous ossification
• Endochondral ossification

11
Intramembranous Ossification

• Produces flat bones of skull and clavicles
• Starts with
• osteoid
• End with
• diploe

massasoit-bio.net
12
Endochondral Ossification

• Bone develops from a hyaline model

trjohn.blogspot.com
13
Bone Growth and Remodeling

• Bone Elongation
• Involves epiphyseal plates
• Hyaline cartilage between to transitional zones
  (metaphysis)
• Zones of mataphysis
• Reserve cartilage
• Cell proliferation
• Cell hypertrophy
• Calcification
• Bone deposition
• Spongy bone

nzdl.org
14
Bone Growth and Remodeling

• Interstitial growth
• Result from growth of cartilage within the
  metaphysis
• Finite process
• Epiphyseal line
• Appositional growth
• Growth in diameter and thickness
• Circumferential lamellae
• Remodeling
• Wolffs law of bone
• The architecture of bone is determined by the
  mechanical stresses placed up it.
• Bone adapts to withstand stress

15
Physiology of Osseous Tissue

• Mineral deposition
• Calcium and phosphate are allowed to reach their
  solubility product
• Precipitate in the matrix
• Ectopic ossification
• Abnormal calcification of soft tissue
• Calculus
• Mineral resorption
• HCl secreted by osteoclasts
• Acid phosphatase
• Absorbs collagen

16
Calcium Homeostasis

• Hypocalcemia
• Leads to excitability of nervous system
• Hypercalcimia
• Leads to depression of nervous system

17
Calcium Homeostasis

• Regulated by three hormones
• Calcitonin
• Secreted by parafollicular cells in thyroid
• Promote deposition of calcium in the bone
• Decreases calcium level in blood
• Inhibit osteoclasts, promote osteoblast activity
• Parathyroid hormone
• Secreted by parathyroid glands
• Promotes bone resorption
• Increases calcium level in blood
• Raise osteoclast population
• Promotes calcium reabsorption in kidneys
• Promotes calcitriol synthesis
• Inhibits collagen deposition
• Calcitriol
• Increases calcium level in blood
• Promotes more calcium absorption by intestine
• Promotes reapsorption from skeleton

18
Fractures and Repair

• Fracture
• Break in the bone
• Two types
• Stress
• Pathological
• Table 7-2 for classifications
• Granulation tisssue
• Fibrous mass of capillaries and cells within
  hematoma

medical-definitions.com
19
Bone Disorders

• Osteoporosis
• Sever loss of bone density
• Osteoclast more active than osteoblasts
• Osteosarcoma
• Most common and deadly form of bone cancer
• Metastasizes quickly
• Osteogenesis imperfecta
• Brittle bones
• Defect in collagen deposition