Part (i): Hydrochloric Acid:
Hydrochloric acid (HCl) in the stomach establishes an acidic environment vital for food digestion. It converts pepsinogen to pepsin, which facilitates protein breakdown. HCl also eliminates ingested harmful bacteria.
Part (ii): Villi:
Villi are small, finger-like projections lining the small intestine. They significantly increase the surface area for absorbing digested nutrients, such as amino acids, fatty acids, and glucose, into the bloodstream.
Part (iii): Anal Sphincter:
The anal sphincter is a muscular ring located at the terminal end of the rectum. It is instrumental in regulating the expulsion of feces. Relaxation permits defecation, while contraction retains stool until the appropriate time.
Part (iv): Lipase:
Lipase is an enzyme produced by the pancreas that aids in fat digestion within the small intestine. It breaks down fats into absorbable fatty acids and glycerol.