Smaklök

Smaklök, the singular form of smaklökar, is the basic sensory unit responsible for the sense of taste in humans and many other mammals. A smaklök is a small cluster of specialized gustatory receptor cells embedded in the epithelium of the tongue and other parts of the oral cavity. Each taste bud contains about 50–150 receptor cells, supported by other cells, and opens to the oral cavity via a taste pore.

Taste buds are concentrated in certain structures called taste papillae. The main types are fungiform papillae on the anterior part of the tongue, circumvallate papillae at the back, and foliate papillae along the sides. Taste buds are also found in the soft palate, the epiglottis, and other mucosal areas. The receptor cells within a smaklök interact with tastants and transduce chemical signals into neural signals that are conveyed to the brain.

Five basic tastes are commonly recognized: sweet, sour, salty, bitter, and umami. Different receptor mechanisms underlie each quality: sweet and umami primarily involve G-protein–coupled receptors (such as T1R), bitter involves T2R receptors, and salty and sour stimuli act through ion channels and proton-sensitive mechanisms. Afferent taste signals travel mainly via the chorda tympani (cranial nerve VII) for the anterior two-thirds of the tongue, the glossopharyngeal nerve (cranial nerve IX) for the posterior third, and the superior laryngeal branch of the vagus nerve (cranial nerve X) for other areas.

Taste buds regenerate and turn over relatively quickly, typically renewing every 10–14 days. An average adult has roughly 2,000–8,000 smaklökar, enabling the perception of taste across the tongue and related oral surfaces.