21. formed from both endoderm and ectoderm: a. pharathryoid glands

b. pharyngeal groove

c. pharyngeal pouch

d. thymus

e. tympanic membrane

22. nephron development begins with migration of cells from around uretric bud tip to region of the uretric stalk. these cells differentiate to form the

a. renal cortex

b. renal vesicle

c. renal pyramid

d. penal papilla

e. renal pelvis