Text of Bone Growth & Development BPK 375. Bone Growth & Development When do the first bones ossify?...
Bone Growth & Development BPK 375
Bone Growth & Development When do the first bones ossify? Which is the first bone to ossify? Does exercise affect bone growth & development?
10 weeks gestation
16 weeks gestation
Osteocyte Mature bone cell that turns over bone mineral and assists in repairs Osteoblast Immature bone cell that secretes organic components of matrix Osteoprogenitor Cell Stem cells whose divisions produce osteoblasts Osteoclast Multinucleated cell that secretes acids and enzymes to dissolve bone matrix
Intramembranous Ossification Ossification of Mesenchymal Connective Tissue Osteoblast Osteoclast Osteocyte
Growth of Skull Fontanelles Suture Joints Proportions
Growth of Vault of Skull
Acromegaly Oversecretion of growth hormone Prior to growth plate fusion, causes increased height with normal proportions After fusion, causes bone thickening and connective tissue overgrowth
Endochondral Bone Growth Short bones e.g. carpals
Articular Cartilage Periosteum Haversian System Compact Bone Yellow Bone Marrow Spongy (Cancellous) Bone Compact Bone
Chondrocytes at the center of the cartilage model begin to hypertrophy and disintegrate as the matrix calcifies Endochondral Ossification
Blood vessels grow around the edges of the cartilage, and the perichondrial cells convert to osteoblasts. The shaft of the cartilage then becomes ensheathed in a layer of bone Endochondral Ossification
Blood vessels penetrate the cartilage and invade the central region, growing toward the epiphyses at either end. Fibroblasts migrating with the vessels differentiate into osteoblasts and begin producing spongy bone Endochondral Ossification
Remodelling occurs as growth continues, creating a marrow cavity. The bone of the shaft becomes thicker, and the cartilage near each epiphysis is replaced by shafts of bone.
Cartilaginous Growth Plate
HAND Primary Centres FOOT Secondary CentresFOOT Primary Centres HAND Secondary Centres Fuse f.m. = fetal month, m = postnatal month, y = year Time of Appearance of Primary & Secondary Ossification Centres
Hand most commonly used in studies of child development Fairly representative of the total maturational status of the skeleton Greater number of ossification centres than any other area in the arms and legs Hand is an easy area to X-ray
Skeletal Age Greulich and Pyle radiographic Atlas of Skeletal Development of the hand and wrist American children Reliability: 95% 0.8 1.0 yrs on repeat ratings Tanner & Whitehouse Bone Specific Ratings English children Reliability: 95% 0.6 yrs on repeat ratings American boys matured about 6 months earlier than English children
Longitudinal series of X-rays on a girl X-ray shows bone not cartilage
TW2 Tanner- Whitehouse Bone specific ratings Fulfill written criteria Assign score for chosen stage
Bone Maturity Charts Growth Hormone and Gonadotrophin Deficiency
Turner Syndrome Bone Maturity Charts
Hippocrates That which is used develops and that which is not used wastes away
Lines of Stress in a metal form loaded at its head Lines of spicules of bone seen in head of the femur Bone Development in response to Mechanical Forces
Exercise & Bone Growth HOWELL(1917) Dogs Retardation in diameter growth in later life Length & Basic Configuration genetically determined Width influenced by exercise Some evidence for Longer more Slender bones in sedentary animals (Steinhaus;1933)
Exercise & Bone Growth KATO & ISHIKO (1966) Children Femur and epihyseal plates showed early closure by several years in heavy workers. Poor environment
Exercise and Bone Size BUSKIRK (1956) Nationally ranked tennis players. Dominant hands & forearms had longer bones. IVANITSKY - Soccer players Femur larger in diameter than nonathlete Marrow cavity of tibia in runners active over five years is often enlarged
Demineralization Bed rest causes a loss in bone mass. Astronauts had decreased bone mineralization after Gemini V and VI flights. Exercises were arranged on Gemini VII and deminerallization was reduced.
Bone Density DONALDSON (1970) 30 week bed rest Increased Calcium & Nitrogen in urine Decrease 4.2% in total body calcium Decreased bone mineralization 2hr/day quiet standing prevented the loss
Bone Density ISSEKUTZ (1966) 3 hr quiet standing reduced calcium loss 4 hr supine exercise did not WYSE & PATTEE (1954) Human paraplegics did not benefit from weight bearing using a tilt table EXERCISE causes increased bone density
Dynamic Changes Woman with no teeth How do braces work? Why do teeth tend to return to their original position after braces are removed?
Genetic or Environmental Boy born without a tibia Fibula surgically moved over One year later fibula had taken on the appearance of a tibia
Genetic or Environmental 3 year old impaled by nail, causing paralysis of one leg At time of injury normal hip development One year later drastic changes