Q. 31 - Biology

Question

Thalidomide was a morning sickness drug given to women that caused babies to be born without arm bones. If recent studies have shown that thalidomide prevents the formation of new blood vessels, describe the type of bone development inhibited by the drug and what stage of ossification was affected. 

Step-by-Step Solution

Answer

• Thalidomide interfered with the endochondral ossification of the long bones in the arms. 
• However, the bones could have evolved into a template made of the calcified cartilage matrix instead of new blood vessels.  
• The template is not transformed into trabecular bone because no vessels enter it.

Step 1 : Introduction

The blood vessels involved in this process are still immature at this stage of pregnancy, when they rapidly change and expand to accommodate the outgrowing limb". Babies born with stunted or malformed limbs were the most common birth defects caused by thalidomide. 

Step : 2 Endochondral Ossification

• In this procedure, hyaline cartilage is switched out for bone. Beginning with the differentiation of mesenchymal cells coming from the mesoderm into chondrocytes. 
• Chromophores multiply quickly and release an extracellular matrix to create the cartilage that serves as the model for bone.  
• The cartilage model consists of perichondrium-encircling membrane and hyaline cartilage that mimics the shape of the upcoming bone. 

Step : 3 Thalidomide

• By limiting angiogenic expansion during early limb formation - PMC, thalidomide causes limb abnormalities. 
• By blocking brain angiogenesis, thalidomide may have an impact on growing neuronal networks.