The human anus from Latin anus meaning "ring", "circle"   is the external opening of the rectum. Two sphincters control the exit of feces from the body during an act of defecation , which is the primary function of the anus. These are the internal anal sphincter and the external anal sphincter , which are circular muscles that normally maintain constriction of the orifice and which relaxes as required by normal physiological functioning. The inner sphincter is involuntary and the outer is voluntary. It is located behind the perineum which is located behind the vagina or scrotum. With anal sex , the anus can play a role in sexuality.
The human body is made up of 11 organ systems that work with one another interdependantly. These systems include the integumentary system, skeletal system, muscular system, lymphatic system, respiratory system, digestive system, nervous system, endocrine system, cardiovascular system, urinary system, and reproductive systems. We will briefly discuss the major functions of each organ system below. Integumentary system — skin, hair, nails Forms the external body covering and protects deeper tissues from injury. Houses cutaneous receptors, sweat glands, oil glands, and synthesizes vitamin D. Provides a framework muscles use movement.
This article contains a list of organs of the human body. It is widely believed that there are 79 organs; however, there is no universally standard definition of what constitutes an organ, and some tissue groups' status as one is debated. For example, this list contains much more than 79 different organs.