Download BONE TISSUE

BONE TISSUE
DEVELOPMENT
and GROWTH
FUNCTIONS
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Support/Movement
Protection
Mineral reservoir
Site of blood cell
production
• Storage of fat
Skeletal Cartilage
• Consists primarily of water
• Contains no nerves or blood
vessels
• Surrounded by perichondrium
– Dense irregular connective tissue
– Maintains shape
Skeletal Cartilage
• Basic components
– Chondrocytes in lacunae
– Extracellular matrix with jellylike
ground substance
• 3 Types
– Hyaline
– Elastic
– Fibrocartilage
Hyaline Cartilage
• Most abundant
• Fiber not detectable
• Locations
• Articular cartilage
• Costal cartilage
• Respiratory cartilage
• Nasal cartilage
Elastic Cartilage
• Contains more elastic fibers; more flexible
• Found in ear and epiglottis
Fibrocartilage
• Highly compressible
• Great strength
• Locations
– Knee
– Vertebral disks
Cartilage Growth
• Two methods
– Appositional – adds to outside
– Interstitial – growth from inside
• Growth stops during adolescence
Bone Histology - Cell Types
• Osteocytes – mature bone cells
– Osteoblasts – bone forming cells
– Osteoclasts – bone destroyers
BONE OSSIFICATION
Process by which tissue becomes
bone
Also called osteogenesis
Bone Formation
• Bone formation begins approx. 8 weeks
into fetal development from a skeleton that
is mostly fibrous membranes and cartilage
• Intramembranous ossification – bone forms
from the fibrous membranes
• Endochondral ossification – bone forms
from hyaline cartilage
Intramembranous Ossification
• Osteoprogenitor (mesenchymal) cells in fibrous
C.T. develop into osteoblasts
• Osteoblasts secrete collagen matrix
• Calcification occurs in ossification centers;
forming a network of bone rather than layers
• Bony plates form which are later converted into
compact bone
• Flat bones only; skull & clavicles
• Fontanelles are areas not ossified at birth
ENDOCHONDRAL
OSSIFICATION
• Forms most bones
• Hyaline cartilage model in shape of the bone
initially; a pH change causes cartilage to calcify
and the cells to die
• Primary ossification center forms as blood vessels
from periosteum and osteoblasts invade calcified
cartilage
• Matrix formed (osteoid= unmineralized bone
matrix)
• Ossification occurs = calcium salts deposited
• Primary centers form before birth; Secondary
centers form 8th month dev.
Epiphyseal Plate
• Cartilage region between primary and
secondary ossification centers
• Responsible for postnatal bone growth
• Zone of resting cartilage
• Growth Zone – mitosis occurs
• Transformation Zone – cartilage matrix
deteriorates
• Osteogenic Zone - bone salts deposited
Calcium regulation
• Calcium is most abundant mineral in
the body; 99% located in the bone
• Regulated by two hormones: PTH
(parathyroid hormone) and calcitonin
• PTH - raises blood calcium levels
• Calcitonin - lowers blood calcium
levels
Hormones and Vitamin Effect on
Bone Growth
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Testosterone
Estrogen
Growth Hormone
Throxine Vitamin D – calcium absorption
Bone Types
• Compact Bone
– also called dense
bone
– hard, strong and
solid bone that
forms the outer
layer of all bone
– provides support,
protection and
resists stress
• Contains osteons
• Cancellous
– also called spongy
bone
– found more toward
the inner portion of
bone
– open lattice-work
of struts and plates
that serves to store
bone marrow
• Trabeculae
Osteons = Haversian System
• Haversian canal
• Volkmann’s
canals
• Lamellae
• Lacunae
• Canaliculi
Bone Types
• Long – arms and legs
• Short – wrist and ankle
– Sesamoid – forms within a tendon
(patella)
• Flat – sternum, scapula, ribs, skull
• Irregular – vertebrae & coxal bones
Structure of a Long Bone
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Diaphysis
Epiphysis
Articular cartilage
Periosteum – connective tissue covering
bone
• Medullary cavity
• Endosteum – connective tissue; lines inside
Bone Fractures
• Open ( Compound) – penetrates
skin
• Closed (Simple)
• Partial/Complete - Greenstick
• Comminuted – broken into 3 or
more pieces
Bone Repair
• Formation of clot ( hematoma)
• Callus ( soft followed by hard)
• Mineralization of callus by calcium &
phosphorus
• Remodeling