The area where the lower abdomen meets the thigh, commonly called the groin, is known anatomically as the inguinal region. Structures critical for sensation, movement, and blood circulation pass through this space, connecting the torso and the lower limb. Understanding the anatomy of this area is important because it is a frequent site for muscle injuries and certain medical conditions.
Defining the Inguinal Region
The inguinal region is located on the lower, anterior portion of the abdominal wall. The most significant anatomical landmark is the inguinal ligament, which creates the visible crease between the torso and the thigh. This ligament is the thickened, free inferior edge of the aponeurosis of the external oblique muscle, one of the major abdominal wall muscles. This band of connective tissue anchors the abdominal muscles to the pelvis and forms the superior boundary of the femoral triangle in the upper thigh.
The inguinal region also contains the inguinal canal, a short, obliquely running passage situated just above the inguinal ligament. This canal serves as a pathway for structures traveling between the abdomen and the external genitalia or thigh. In males, the spermatic cord passes through this canal, while in females, it transmits the round ligament of the uterus. The arrangement of the inguinal ligament and the inguinal canal makes this area a region of weakness in the abdominal wall.
Key Structures of the Femoral Triangle
Directly beneath the skin in the upper thigh, just below the inguinal ligament, lies the femoral triangle. This triangle is formed by the inguinal ligament superiorly, the sartorius muscle laterally, and the adductor longus muscle medially. It acts as a conduit for the major neurovascular structures supplying the lower limb.
The contents of the femoral triangle are often remembered using the acronym “NAVEL,” which lists the structures from lateral (outside) to medial (inside):
- N: The femoral nerve, responsible for motor function to the muscles on the front of the thigh and providing sensation to parts of the leg.
- A: The femoral artery, the main arterial supply to the leg. Its pulse can be easily palpated here, making it a common site for arterial access in medical procedures.
- V: The femoral vein, positioned next to the artery, which returns deoxygenated blood from the lower limb back toward the heart.
- E: The empty space, known as the femoral canal. This space allows the nearby vein to expand when there is an increase in blood flow volume.
- L: The deep inguinal lymph nodes and vessels, which filter fluid and fight infection from the lower limb and external genitalia.
Common Conditions Affecting the Area
The inguinal region’s complex anatomy and its role as a passageway make it susceptible to several medical issues. One of the most common is an inguinal or femoral hernia, where a part of an internal organ, often the intestine, protrudes through a weak spot in the surrounding muscle or fascia. A hernia appears as a bulge in the groin area that may become more prominent when a person coughs or strains.
A “pulled groin” is a common sports injury involving a muscle strain in the adductor muscle group of the thigh. These muscles are located on the medial side of the thigh and are responsible for drawing the legs inward. A strain results from overstretching or tearing of the muscle fibers, causing sharp pain and tenderness in the upper, inner thigh region.
Swollen lymph nodes, known as lymphadenopathy, are also common in this area. Because the deep inguinal lymph nodes filter fluid from the lower limbs, swelling often indicates an infection or inflammation in the foot, leg, or external genitalia. While hernias present as a soft lump that may disappear when lying down, swollen lymph nodes are firmer and can be tender to the touch.