Sphincter Pupil

Sphincter of the Pupil: Basic functions and role in the body

The sphincter pupillae, also known as the sphincter pupillae (anatomical designation), is the muscle responsible for controlling the size of the pupil of the eye. It is located in a radial direction around the pupil and has the ability to contract or relax, which allows you to change the diameter of the pupil and therefore regulate the amount of light entering the retina.

The function of the pupillary sphincter is important for maintaining optimal visual perception. When light conditions change, the pupillary sphincter automatically responds by constricting or dilating the pupil to control the amount of light passing through. For example, in bright light, the pupillary sphincter contracts, narrowing the pupil and limiting the amount of light to prevent oversaturation of the retina and reduce the possibility of blinding. In darkness or when there is a lack of light, the pupillary sphincter relaxes, allowing the pupil to dilate and let in more light to maximize the perception of the environment.

Physiological control of the pupillary sphincter is carried out by the nervous system. Sympathetic innervation, carried out by the sympathetic nerves, induces dilation of the pupil (mydriasis), while parasympathetic innervation, carried out by the vagus nerve (nerve of the facial terminal branch), causes constriction of the pupil (miosis). These two systems work together to provide dynamic adjustment of pupil size based on environmental conditions.

It is important to note that changes in pupil size can also be caused by emotional or physiological factors. For example, fear, anxiety, or physical stress can cause the pupil to dilate, which is often seen in response to threat or stressful situations. This is due to the activation of the sympathetic nervous system and an increase in the release of adrenaline in the body.

The sphincter of the pupil is also an object of study in medical practice. One of the disorders associated with the pupillary sphincter is called adium pubilla. With this disease, there is symptomatic dilatation of one or both pupils in low light and insufficient constriction of the pupil in bright light. Pupilla adia usually results from damage or degeneration of the parasympathetic nerves innervating the pupillary sphincter.

In conclusion, the pupillary sphincter plays an important role in regulating the size of the pupil and controlling the light that reaches the retina. This muscle, controlled by the nervous system, allows you to adapt to different light conditions and ensures optimal visual perception. The study of the pupillary sphincter and related disorders is important for understanding the functioning of the eye and ensuring the health of the ocular apparatus.