The rectum is a hollow muscular tube that connects the sigmoid colon to the anus at the terminal segment of the digestive system. It acts as a temporary storage site for fecal matter until the body gets ready to eliminate the waste through the process of defecation. The rectum is about 6 inches in length and divided into three or four chambers from the internal cavity. Each chamber keeps apart from the others by permanent transverse folds called valves of Houston which play a vital role in supporting the rectal contents. The pelvic diaphragm and longitudinal muscle surrounding outside wall of rectum perfect the systolic function of the rectum. The rectum is classified into four layers: the mucosa, submucosa, muscularis, and serosa. Rectal disorders like hemorrhoids, abscesses, incontinence, and cancer are quite common in clinic. A rectal exam or rectal endoscopy may be conducted to diagnose certain diseases. In addition, a variety of target molecules on the rectum tissue could be used to detect related disorders.