Alimentary Canal Secretion: Mucus and Hydrochloric Acid

The question asks which part of the alimentary canal produces both mucus and hydrochloric acid ($\text{HCl}$).

Stomach Functions

• The stomach contains specialized glands in its lining that secrete gastric juice.
• This gastric juice includes hydrochloric acid ($\text{HCl}$), which creates a highly acidic environment (pH 1.5-3.5) necessary for activating pepsinogen into pepsin (an enzyme for protein digestion) and killing ingested pathogens.
• The stomach lining also secretes mucus. This mucus layer is crucial as it protects the stomach wall from being digested by the strong acid and enzymes.

Other Organs

• The small intestine primarily absorbs nutrients and secretes digestive enzymes and bicarbonate, but not significant amounts of $\text{HCl}$.
• The liver produces bile, which aids in fat digestion, but it does not secrete $\text{HCl}$ or mucus directly into the alimentary canal.
• The large intestine absorbs water and electrolytes and secretes mucus to lubricate the passage of waste, but it does not secrete $\text{HCl}$.

Therefore, the stomach is the correct answer as it is responsible for secreting both mucus and hydrochloric acid.