Humans possess anatomical structures analogous to the anal glands found in dogs and cats, but their function is radically different. In canines and felines, these paired sacs are used for territorial marking and communication, releasing a distinct, pungent secretion. Human anatomy includes small glands within the wall of the anal canal, which are considered largely vestigial, meaning they have lost their original function over evolutionary time. These structures are not involved in scent-marking or social signaling.
The Human Anal Gland System
The structures referred to as “anal glands” in humans are a system of small, tubular glands embedded deep within the anal canal wall. These glands are situated in the intersphincteric space, the area between the internal and external anal sphincter muscles. They are also sometimes called proctodeal glands. The glands extend from the anal canal lumen, where their ducts empty into tiny pouches called the anal crypts, or sinuses of Morgagni. The openings of these crypts are found along the dentate line. The number of these glands varies, but an average of six to ten glands are present around the circumference of the canal.
Distinct Function and Evolutionary Role
The function of the human anal gland system is the production of a lubricating fluid or mucus. This secretion helps to moisten the anal canal, assisting in the smooth passage of stool. This lubricating role contrasts sharply with the purpose of anal glands in many other species. In species like dogs, skunks, and various mustelids, the secretions are used for identification, territorial marking, and defense. The human glands play no known part in modern social communication. Anatomists view them as reduced or non-functional remnants of structures that were more developed in distant ancestors.
Common Issues Stemming from These Glands
Despite their reduced function, these structures are susceptible to infection and disease. Problems begin when one of the narrow ducts leading from the gland to the anal crypt becomes blocked. This blockage can trap bacteria and fecal matter within the gland, leading to an acute infection.
The resulting accumulation of pus creates an anal abscess, a painful, swollen collection of infected material near the anus or rectum. An anal abscess is the most common affliction related to the human anal gland system. Roughly 50% of people who experience an anal abscess will subsequently develop an anal fistula.
An anal fistula is a small, abnormal tunnel that forms beneath the skin, connecting the infected anal gland to an opening on the skin near the anus. This tract develops as the body attempts to drain the persistent infection. Fistulas often require surgical intervention because they rarely heal on their own and can cause ongoing discharge of pus, blood, or fluid.