Rickets and Osteomalacia Flashcards
What is ossification?
Bone formation
What is intramembranous bone formation?
When mesodermal cells are transformed into osteoblasts which secrete osteoid which becomes calcified.
What is endochondral bone formation?
Mesodermal cells differentiate into cartilage cells; the bones are initially formed from this.
What is the growth plate?
Ossification begins in the shaft of diaphysis and continues to the epiphysis. There is actively growing cartilage between the shaft of a long bone & the epiphysis this is called the epiphyseal plate (Growth plate)
When do bones keep growing until?
Bones continue to grow in length and thickness into adolescence.
What is bone remodelling?
Bones are constantly repairing themselves
Under normal daily stresses bones develop micro fractures and are repaired without the person being aware of it.
Vitamin D, Calcium, Phosphate, parathyroid hormone and other steroid hormones are required for this to continue.
How does rickets occur?
Vitamin D is produced naturally in UV light if above UV index 4.
Vit D promotes absorption of calcium from the intestinal tract.
If blood calcium falls the parathyroid glands
increase the secretion of parathyroid hormone which increase calcium levels in the blood but lower the level of
phosphate in the blood
This results in weak bones that become. bowed when weight bearing.
What is rickets?
Impaired calcification of bone in a growing child as a result of vit D deficiency. Leads to bowing of the leg bones when weight bearing is
attempted.
How does rickets occur in adults?
It is usually the result of the small intestine or liver and is called osteomalacia.
Treatment is with vitamin D supplements over time.
What is the Hx and epidemiology of rickets?
Affected 25% of children a century ago in the UK.
Absence of sunlight and poor nutrition highlights as a cause in 1861.
