31. Through what structure do epiblast cells migrate to form the mesoderm? 
A. lacunae
B. chorionic villi
C. hypoblast
D. primitive streak
E. blastocele

32.  Which of the following is derived from ectoderm?  
A.  lens of the eye
B.  thymus gland
C.  tonsils
D.  urinary bladder
E.  dermis of skin

33.  Which of the following is derived from endoderm?  
A.  brain
B.  muscle
C.  epidermis of the skin
D.  lining of the digestive tract
E.  cardiovascular system

34.  Which of the following is formed from mesoderm?  
A.  autonomic neurons
B.  dermis of the skin
C.  adrenal medulla
D.  teeth
E.  tonsils

35.  Damage to the mesoderm during embryological development would affect the formation of the  
A.  thyroid.
B.  brain.
C.  heart.
D.  teeth.
E.  urinary bladder.

36.  Which of the following organ systems is derived from all three germ layers?  
A.  nervous
B.  cardiovascular
C.  endocrine
D.  integumentary
E.  skeletal

37.  Which germ layer is most muscle derived from?  
A.  ectoderm
B.  mesoderm
C.  endoderm

38.  Which germ layer is the thymus derived from?  
A.  ectoderm
B.  mesoderm
C.  endoderm

39.  Which germ layer is the thyroid derived from?  
A.  ectoderm
B.  mesoderm
C.  endoderm

40.  Which germ layer is the epidermis derived from?  
A.  ectoderm
B.  mesoderm
C.  endoderm