What Is the Inguinal Region?
Clinical anatomy defines the inguinal region of the abdominal wall as the area between the anterior superior iliac spine and the pubic tubercle (in other words, the groin or lower lateral parts of the abdomen). This region is particularly important for examination of males because the spermatic cord, the testes, and the scrotum are included in this area.
The inguinal region is a site for herniations, especially in males where the spermatic cord runs through the inguinal canal.
The inguinal ligament and the iliopubic tract
The inguinal ligament is formed at the inferior end of the external oblique’s aponeurosis. Most of the inguinal ligament fibers insert into the pubic tubercle directly, but some of them form the lacunar and pectineal ligaments that attach to the superior pubic ramus.
The iliopubic tract is a fibrous band that runs just under the inguinal ligament. It reinforces the posterior wall and the floor of the inguinal canal.
The inguinal canal
Both males and females possess inguinal canals, but the contents vary considerably. For men, the inguinal canal gives passage to the spermatic cord, whereas in women, the inguinal canal houses the round ligament of the uterus. In both men and women, it also contains blood vessels, lymphatics, and the ilioinguinal nerve.
The inguinal canal is about four centimeters long in adults. The canal has a wall, a floor, and a roof that are formed from fascia and the aponeuroses of the abdominal muscles. It also has a ring at each end:
The deep ring is the internal entrance to the canal. It’s located above the inguinal ligament and lateral to the inferior epigastric vessels.
The superficial ring is where the inguinal canal exits between the fibers of the aponeurosis of the external oblique near the pubic tubercle. The edges of the superficial ring are called the lateral and medial crura, with intercrural fibers keeping the crura in place so they don’t spread apart.
The spermatic cord
The spermatic cord contains the structures that go to the testes and back and helps hold the testis in the scrotum. The cord starts at the deep inguinal ring and ends at the posterior part of the testes. It has three layers of fascia: the internal spermatic fascia, the cremasteric fascia, and the external spermatic fascia.
The cremasteric muscle works in conjunction with the dartos muscle, the subcutaneous smooth muscle of the scrotum to help maintain the testicles at the appropriate temperature for sperm development.
Two oval organs called the testes produce spermatozoa and a male hormone called testosterone. Spermatozoa are formed in the seminferous tubules. They open into a network of channels called the rete testis. The rete testis is connected to the epididymis (described later in this section) by efferent ductules. Each testis is enclosed by a fibrous capsule called the tunica albuginea and covered by the tunica vaginalis, which is a double layer of peritoneum that surrounds the testes inside the scrotal sac.
The testes are served by the testicular arteries that come from the abdominal aorta and pass through the spermatic cord (see the preceding section). Venous drainage is provided by the pampiniform venous plexus that surrounds the testicular artery and empties into the left and right testicular veins. The left testicular vein drains into the left renal vein, and the right testicular vein drains into the inferior vena cava.
Lymphatic vessels drain the testes and pass through the spermatic cord to empty into the lumbar and preaortic lymph nodes.
The coiled and compacted duct of the epididymis forms the epididymis. Sperm cells are transported from the rete testis to the epididymis through efferent ductules. The epididymis has a head at the superior part, a body in the middle, and a tail that becomes the ductus (vas) deferens, which is the tube that delivers spermatozoa to the ejaculatory ducts. The ductus deferens receives blood flow from the artery of the ductus (vas) deferens.
The testes are found within the scrotum, a sac that’s covered with a layer of skin over a layer of fascia called the dartos fascia, which contains the dartos muscle. Unlike the rest of the abdomen, the scrotum does not have a layer of fat. The scrotum is a sensitive area. Following are the several nerves that service the scrotum:
Genital branch of the genitofemoral nerve: Originates from the 1st and 2nd lumbar spinal nerves and supplies the anterolateral part
Anterior scrotal nerves from the ilioinguinal nerve: Originate at the 1st lumbar spinal nerves and supply the anterior part
Posterior scrotal nerves from the pudendal nerve: Originate from the 2nd through 4th sacral spinal nerves and supply the posterior part
Perineal branches of the posterior cutaneous nerve of the thigh: Originate at the 2nd and 3rd sacral spinal nerves and supply the inferior part
Blood is supplied to the scrotum by the following arteries (and returned by similarly named veins):
Posterior scrotal branches of the perineal artery: Branches of the internal pudendal artery
Anterior scrotal branches of the deep external pudendal artery: Stem from the femoral artery
Cremasteric artery: Branches off the inferior epigastric artery