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

the glands which are associated with each description is given below:

pancreas - is an endocrine and exocrine gland that secretes juices with enzymes for digestion. salivary glands- with protection and digestion in the mouth. liver- secretes bile for digestion.   lachrymal glands - secrete tears to moisten eyes and protect them from particles and infection.   sweat gland -regulates water, salt, and temperature. oil glands - to form a protective barrier on the skin.   goblet cells - secrete mucus for protection.

Sorry its not enough info

It depends on the surface of the levels. the rougher the surface, the greater is the frictional force. for rougher surfaces, you would need to exert greater force to move the object. the concept is that, you must overcome the frictional force in order to bring the object into motion. this is the reason why we add lubricants to the joints so they could easily move. this answer was on