These are congregations of proteins and lipids (including sphingolipids and cholesterol) that float within the cell membrane, and play a role in the regulation of membrane function. Lipid rafts are more ordered or rigid than the membrane bilayer surrounding them. Their involvement in regulation stems mostly from their association with proteins; upon binding substrates, some proteins have a higher affinity for attaching to lipid rafts. This brings them in close proximity with other proteins, allowing them to affect signaling pathways. Cholesterol specifically acts as a spacer and a glue for lipid rafts; absence of cholesterol leads to the dissociation of proteins.Given its prevalence in cell membranes, cholesterol is highly involved in certain transport processes. It may influence the function of ion channels and other membrane transporters. For example, cholesterol is necessary for the ligand binding activity of the serotonin receptor. In addition, it appears to be very important in exocytosis. Cholesterol modulates the properties of the membrane (such as membrane curvature), and may regulate the fusion of vesicles with the cell membrane. It may also facilitate the recruitment of complexes necessary for exocytosis. Given that neurons rely heavily on exocytosis for the transmission of impulses, cholesterol is a very important part of the nervous system. One particularly relevant pathway in which cholesterol takes place is the Hedgehog signaling pathway. This pathway is very important during embryonic development, and involved in deciding the fate of cells (i.e., which tissue they need to migrate to).
An ingrown nail, also known as onychocryptosis from Greek: ὄνυξ (onyx) nail and κρυπτός (kryptos) hidden, is a common form of nail disease. It is an often painful condition in which the nail grows so that it cuts into one or both sides of the paronychium or nail bed. While ingrown nails can occur in the nails of both the hands and the feet, they occur most commonly with the toenails (as opposed to fingernails), and for the most part are only problematic and painful on the big toe. A common conception is that the nail enters into the paronychium, but an "ingrown toenail" can simply be overgrown toe skin. The condition starts first from a microbial inflammation of the paronychium, and then a granuloma, which results in a nail buried inside of the granuloma. A true ingrown toenail is caused by actual penetration of flesh by a sliver of toenail. Signs and symptoms
Symptoms of an ingrown nail include pain along the margins of the nail (caused by hypergranulation that occurs around the aforementioned margins), worsening of pain when wearing tight footwear, and sensitivity to pressure of any kind, even the weight of bedsheets. Bumping of an affected toe can produce sharp and even excruciating pain as the tissue is punctured further by the nail. By the very nature of the condition, ingrown nails become easily infected unless special care is taken early to treat the condition by keeping the area clean.