recto-, rect-

(Latin: straight [intestine], direct, right; that is, "the part of the large intestine that ends at the anus")

rectosigmoidectomy (s) (noun), rectosigmoidectomies (pl)
The surgical excision of the rectum and sigmoid; proctosigmoidectomy: Dr. Thompson explained to Jim that a rectosigmoidectomy was necessary in order to to remove the infected rectum and sigmoid colon.
rectotomy (s) (noun), rectotomies (pl)
In surgery, an incision into the rectum; proctotomy: In his medical class, Tom learned about a rectotomy as being an operation to divide a rectal structure.
rectum (s) (noun), rectums (pl)
The last part of the large intestine: Bill learned that feces passed through the rectum after leaving the colon, but before exiting the body through the excretory opening at the end of the alimentary canal.
rectus (s) (noun), recti (pl)
One of the straight muscles in a body: One rectus is located at the anterior abdominal wall, while other recti are found in the eye, neck, and thigh.