What happens during the process of defecation?

During the process of defecation, the internal anal sphincter is indeed relaxed, which is crucial for allowing bowel contents to exit the body. The relaxation of this sphincter is a reflex action that occurs as part of the defecation reflex, which is triggered when the rectum fills with stool. As stool accumulates, stretch receptors in the rectal wall send signals to the central nervous system, prompting the internal anal sphincter to relax and allowing the fecal matter to move toward the anal canal.

In conjunction with the relaxation of the internal anal sphincter, the external anal sphincter, which is under voluntary control, may initially remain contracted to allow an individual to hold bowel contents until they are ready to defecate. Once the decision to defecate is made, the external anal sphincter will relax, allowing for the exit of stool. Additionally, rectal muscle contractions help propel the fecal matter through the anus.

Therefore, the relaxation of the internal anal sphincter is a key component of the defecation process, facilitating the necessary opening to allow for the expulsion of waste.