Ossification & Bone Disease Flashcards
What is osteoporosis?
Depletion of bone mass. Type 1 - post menopausal women have greater osteoclastic activity. Type 2 - senile osteoporosis, occurs after approx. 65 years. Risk factors - genetic, calcium intake, vitamin D, sunlight, immobility, cigarettes
What is osteogenesis imperfecta?
Autosomal dominant - mutation in collagen. It affects skeleton, joints, ears, ligaments, teeth, sclerae and skin.
What is achondroplasia?
Short limb dwarfism. Normal mentation and average lifespan. Autosomal mutation. Less endochondrial ossification, less cellular hypertrophy, less cartilage matrix production
What is rickets?
Occurs in children who have a deficiency in vitamin D or calcium. Bones don’t harden properly, resulting in soft bones. Skeletal deformity, muscle weakness, bone pain.
What is osteomalacia?
Occurs in adults with calcium deficiency or lack of vitamin D. Results in inadequate mineralisation of bone. Bone pain, muscle weakness and back pain.
What is paget’s disease?
Excessive breakdown and formation of bone, leading to disorganised bone remodelling. Bones are weakened typically leading to localised disease. Pain, misshapen bones, fractures, arthritis. Possible causes: viral, genetic
Describe endochondrial ossification
Cartilage model enlarges, collar of periosteal bone appears in shaft, central cartilage calcifies and nutrient artery penetrates - primary oc created, medulla becomes cancellous bone - cartilage forms epiphyseal growth plates, epiphyses develop secondary oc, epiphysis ossify and growth plates move apart - lengthening bone
Describe the zone of proliferation
Cells actively divide to form columns. Cells enlarge ans secrete matrix
Describe the zone of reserve cartilage
No cellular proliferation or active matrix production
Describe the zone of hypertrophy
Cells enlarge greatly. Matrix compressed into linear bands between cell columns
Describe the zone of calcified cartilage
Enlarged cells begin to degenerate and matrix calcifies
Describe the zone of resorption
Calcified matrix is in direct contact with the marrow cavity. Small blood vessels and connective tissue invade the region occupied by the dying chondrocytes, leaving the calcified cartilage as spicules between them. Bone is laid down on these cartilage spicules.
Describe intramembranous ossification
Primary oc, mesenchymal cells differentiate into osteoblasts, trabeculae form primitive osteons surrounding blood vessels (spongy bone), osteoblasts trapped in lacunae (osteocytes), peripheral regions (compact bone), connective tissue around bone oragnised into periosteum
What are the effects of growth hormone?
Excessive - gigantism (pre puberty) acromegaly (post puberty)
Deficiency - pituitary dwarfism
What are the effects of sex hormones?
Excessive - retards bone growth
Deficiency - tall stature due to epiphyseal plates persisting longer
