Describe the external structure of the small intestine and large intestine.

(N/A) Small Intestine: It is a tube approximately $6.25 \,m$ long, beginning at the pyloric sphincter of the stomach. It is divided into three parts:
$(i)$ Duodenum: The initial $'U'$-shaped part, approximately $25 \,cm$ long.
$(ii)$ Jejunum: The long, coiled middle portion, approximately $1 \,m$ long.
$(iii)$ Ileum: The final, highly coiled part of the small intestine.
Function: Primary site for digestion of food and absorption of nutrients.
$(b)$ Large Intestine: It is approximately $1.5 \,m$ long and consists of the caecum, colon, and rectum.
$(i)$ Caecum: $A$ small blind sac that hosts symbiotic microorganisms. $A$ narrow, finger-like tubular projection, the vermiform appendix (a vestigial organ), arises from it.
$(ii)$ Colon: Divided into three parts: Ascending, Transverse, and Descending colon.
$(iii)$ Rectum: The descending colon opens into the rectum, which stores feces until it is eliminated through the anus.
Function: Absorption of water, minerals, and certain drugs.