This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fertilization and Development of Embryo, Subject name: Anatomy
Number of somites developed in human fetus - 
Select and explain. 
A. 10 pairs, B. 21 pairs, C. 32 pairs, D. 42 pairs
D: 42 pairs
Answer: D: 42 pairs 
Explanation: Ans. is 'd' i.e.,42 pairs o Paraxial mesoderm differentiates into somites.o By the end of 20th day, the first pair of somites have formed in neck region.o After this, about 3 pairs of somites are formed per day and by the end of 5th week about 42-44 somite pairs are formed (4-occipital, 8-cervical, 12-thoracic, 5-lumbar, 5-sacral and 8-10 cooccygeal).o Somites are further differentiated intoi) Dermatomyotome :- Give rise to skeletal muscles and dermis.ii) Sclerotomes Give rise to vertebral column and ribs.