Groin

In human anatomy, the groin (the adjective is inguinal, as in inguinal canal) is the junctional area (also known as the inguinal region) between the abdomen and the thighon either side of the pubic bone. This is also known as the medial compartment of the thigh that consists of the adductor muscles of the hip or the groin muscles. A pulled groin muscle usually refers to a painful injury sustained by straining the hip adductor muscles. These hip adductor muscles that make up the groin consist of the adductor brevis, adductor longus, adductor magnus, gracilis, and pectineus. These groin muscles adduct the thigh (bring the femur and knee closer to the midline). The groin is innervated by the obturator nerve, with two exceptions: the pectineus muscle is innervated by the femoral nerve, and the hamstring portion of adductor magnus is innervated by the tibial nerve.

In the groin, underneath the skin, there are three to five deep inguinal lymph nodes that play a role in the immune system. These can be swollen due to certain diseases, the most common one being a simple infection, and, less likely, from cancer. A chain of superficial inguinal lymph nodes drain to the deep nodes.

Groyne

A groyne (groin in the United States) is a rigid hydraulic structure built from an ocean shore (in coastal engineering) or from a bank (in rivers) that interrupts water flow and limits the movement of sediment. It is usually made out of wood or concrete. In the ocean, groynes create beaches or prevent them being washed away by longshore drift. In a river, groynes prevent erosion and ice-jamming, which in turn aids navigation. Ocean groynes run generally perpendicular to the shore, extending from the upper foreshore or beach into the water. All of a groyne may be under water, in which case it is a submerged groyne. The areas between groups of groynes are groyne fields. Groynes are generally made of wood, concrete or rock piles, and placed in groups. They are often used in tandem with seawalls. Groynes, however, may cause a shoreline to be perceived as unnatural.

In coastal engineering

A groyne's length and elevation, and the spacing between groynes is determined according to local wave energy and beach slope. Groynes that are too long or too high tend to accelerate downdrift erosion, and are ineffective because they trap too much sediment. Groynes that are too short, too low, or too permeable are ineffective because they trap too little sediment. If a groyne does not extend far enough landward, water (for example at a high tide combined with a storm surge) may flow past the landward end and erode a channel bypassing the groyne, a process known as flanking.

Groin (disambiguation)

For Groin see: