Choose the function of the pancreatic juice from the following:

Give reasons for the following:
$(a)$ Rings of cartilage are present in the trachea.
$(b)$ Mucus is secreted along with $HCl$ in the stomach.

If salivary amylase is lacking in the saliva,which of the following events in the mouth cavity will be affected?

State two functions of stomata.

$(a)$ How does the exchange of respiratory gases,oxygen and carbon dioxide,take place between tissues and blood in human beings?
$(b)$ Name the respiratory pigment in humans. Where is it found?

$(a)$ Name the organs which secrete the following enzymes in the human digestive system:
$(i)$ Pepsin
$(ii)$ Salivary amylase
$(iii)$ Trypsin
$(iv)$ Lipase
$(b)$ Name the organs which perform the following functions in the human alimentary canal:
$(i)$ Absorption of digested food
$(ii)$ Absorption of water