Inguinal Region Anatomy Notes

Inguinal Region

Overview

  • The inguinal region, commonly known as the "groin", is the area extending between the anterior superior iliac spine (ASIS) and the pubic tubercle.

  • It contains the myopectineal orifice.

Key Structures

1. Aponeurosis of External Oblique

  • Forms several important structures:

    • Inguinal Ligament (IL):

      • The inferior border of the aponeurosis of the external oblique.

      • Extends from the ASIS to the pubic tubercle.

    • Lacunar Ligament:

      • Deeper fibers of the IL pass posteriorly, attaching to the superior pubic ramus.

    • Superficial Inguinal Ring:

      • An opening in the aponeurosis of the external oblique.

      • Created by three points of attachment:

        • Lateral crus attaches to the pubic tubercle.

        • Medial crus attaches to the pubic crest.

        • Intercrural fibers connect the two.

2. Ligaments and Structures

  • Pectineal ligament.

  • Lacunar ligament.

  • Interpubic disc.

  • Cavity in the interpubic disc.

  • Obturator membrane.

  • Acetabular labrum.

  • Transverse acetabular ligament.

  • Obturator canal.

Inguinal Canal

  • Approximately 4 cm long.

  • An obliquely oriented, tubular passage.

  • Runs parallel to the inguinal ligament.

  • Entrance: Deep inguinal ring

    • An evagination in the transversalis fascia.

    • Located lateral to the inferior epigastric artery.

  • Exit: Superficial inguinal ring

    • Opens inferomedially in the lower part of the anterior abdominal wall, superolateral to the pubic tubercle.

  • Conjoint tendon is present.

Boundaries of the Inguinal Canal

  • Anterior wall:

    • Aponeurosis of the external oblique.

  • Posterior wall:

    • Transversalis fascia and conjoint tendon (inguinal falx).

  • Roof:

    • Arching fibers of the aponeurosis of the internal oblique and transversus abdominis; medially, the medial crus of the aponeurosis of the external oblique.

  • Floor:

    • Iliopubic tract, inguinal ligament, and lacunar ligament.

Layers and Structures in the Inguinal Region

  • Internal spermatic fascia.

  • Origin of cremasteric muscle.

  • Inguinal falx (conjoint tendon).

  • Femoral vessels.

  • Superficial inguinal ring.

  • External spermatic fascia.

  • Peritoneum.

  • Transversalis fascia.

  • Transversus abdominis muscle.

  • Internal oblique muscle.

  • External oblique muscle.

  • Testicular artery and veins.

  • External oblique aponeurosis.

  • Ductus deferens.

  • Ilio-inguinal nerve.

  • Inferior epigastric vessels.

  • Extraperitoneal fat in the retro-inguinal space (of Bogros).

  • Deep inguinal ring.

  • Intercrural fibers.

  • Skin.

  • Fatty layer.

  • Inguinal canal.

  • Spermatic cord.

  • Membranous layer of subcutaneous tissue.

  • Anterior wall of the inguinal canal (intercrural fibers).

  • Ductus deferens.

  • Fascia lata of the thigh.

  • Aponeuroses of external oblique, internal oblique, transversus abdominis.

  • Retro-inguinal space (of Bogros) - space occupied by extraperitoneal fat.

  • Aponeurosis of external oblique and rectus abdominis reinforces the pubic symphysis.

  • Reflected inguinal ligament.

  • Cremasteric muscle and fascia.

  • Spermatic cord.

  • Musculo-aponeurotic arcades of internal oblique & transversus abdominis.

  • Testis.

Layers of the Anterior Abdominal Wall

  • Skin

  • Subcutaneous tissue (fatty/membranous)

  • External oblique muscle and fascia

  • Internal oblique muscle

  • Fascia of both superficial and deep surfaces of the internal oblique muscle

  • Transversus abdominis muscle

  • Transversalis fascia

  • Peritoneum

Additional Structures

  • Obliterated umbilical artery

  • Urinary bladder

  • Inguinal falx (conjoint tendon)

  • Medial umbilical fold

  • Extraperitoneal fat

  • Inferior epigastric vessels

  • Testicular artery and vein and ductus deferens

  • Intercrural fibers

  • Superficial inguinal ring

  • Pampiniform plexus of veins

  • Testicular artery

  • Ductus deferens

  • Scrotum and coverings of testis

Coverings of Testis

  • Skin

  • Subcutaneous tissue (dartos fascia) and dartos muscle

  • External spermatic fascia

  • Cremaster muscle

  • Cremasteric fascia

  • Internal spermatic fascia

  • Tunica vaginalis

    • Visceral layer (covering testis and epididymis)

    • Parietal layer

Other Layers

  • Membranous layer (Scarpa)

  • Fatty layer (Camper)

  • Subcutaneous tissue

  • Deep inguinal ring formed by transversalis fascia

  • Cremasteric vessels

  • Dartos muscle/fascia (including scrotal septum)

  • Vestige of processus vaginalis

  • Coverings of the spermatic cord

Contents of the Inguinal Canal

  • Passageway for:

    • Ilioinguinal nerve

    • Spermatic cord (males)

    • Round ligament of the uterus (females)

    • Conjoint tendon

Development of the Inguinal Region

  • Testes and ovaries develop in the superior lumbar region of the posterior abdominal wall.

  • Gubernaculum: A fibrous CT cord.

    • Males: Connects testes to the anterolateral abdominal wall at the deep inguinal ring (scrotal ligament).

    • Females: Connects ovaries & uterus to the labia majora.

      • Ovarian ligament (ovary to uterus) & round ligament of the uterus (uterus to anterior abdominal wall).

  • Processus vaginalis:

    • Passes through the inguinal canal and carries muscular and fascial layers with it into the primordial scrotum in males & labia majora in females.

Development in Males

  • Week 7: Testes attached to the posterior abdominal wall.

  • Week 12: Testes have moved into the pelvis.

  • Week 28: Testes are close to the deep inguinal ring.

  • Takes 3 days to traverse the inguinal canal, moving posterior to processus vaginalis.

  • Week 32: Testes enter the scrotum.

  • Processus vaginalis is obliterated, forming the tunica vaginalis.

  • Cryptorchid: undescended testis.

Development in Females

  • Week 8: Ovaries attached to posterior abdominal wall.

  • Week 15: Ovaries relocate to the lateral wall of the greater pelvis.

  • Processus vaginalis passes through the abdominal wall, forming the inguinal canal.

  • Processus vaginalis degenerates.

  • Gubernaculum becomes:

    • Ovarian ligament (ovaries to uterus).

    • Round ligament of the uterus (uterus to the labia majora).

Round Ligament of the Uterus

  • Suspensory ligament of the ovary.

  • Mesovarium.

  • Deep inguinal ring.

  • Round ligament of the uterus.

  • Inguinal canal.

  • Superficial inguinal ring.

  • Ovarian vessels.

  • Labium majorus.

  • Ligament of the ovary.

Inguinal Hernias

1. Direct Inguinal Hernia

  • Acquired inguinal hernia.

  • Protrusion of parietal peritoneum and possibly abdominal contents through the anterior abdominal wall in the inguinal area.

  • Medial to the inferior epigastric vessels.

  • Medial inguinal fossae are potential sites for this type of hernia.

  • Caused by weakening of the muscular wall.

2. Indirect Inguinal Hernia

  • Congenital inguinal hernia.

  • Protrusion of parietal peritoneum and sometimes abdominal contents through the deep inguinal ring, into the inguinal canal and possibly the scrotum.

  • Lateral to the inferior epigastric vessels.

  • Most common type (2/3 to 3/4 of inguinal hernias).

  • Lateral inguinal fossae and deep inguinal ring are potential sites.

Spermatic Cord

  • Extends from the deep inguinal ring to the posterior border of the testis in the scrotum.

  • Contents:

    • Ductus (vas) deferens

    • Artery of the ductus deferens

    • Testicular artery

    • Cremasteric artery

    • Pampiniform plexus of veins (converge as testicular veins)

    • Sympathetic nerve fibers

    • Lymphatic vessels

    • Genital branch of the genitofemoral nerve (supplies cremaster muscle)

    • Coverings derived from anterior abdominal wall tissues

Coverings of the Spermatic Cord

  • Derived from anterior abdominal wall tissues:

    • Dartos fascia & muscle

      • Continuous with Scarpa’s fascia (scrotum)

      • Smooth muscle fibers

    • External spermatic fascia

      • External oblique

    • Cremasteric fascia & cremaster muscle

      • Internal oblique

      • Innervated by the genital branch of the genitofemoral nerve (L1, L2)

      • Striated muscle

    • Internal spermatic fascia

      • Transversalis fascia

Scrotum

  • Develops from lumbosacral swellings.

  • Two compartments (right & left).

  • Divided internally by a septum.

  • Externally visible division is called the scrotal raphe.

  • Heavily pigmented skin.

  • Dartos fascia

    • Continuous with Scarpa’s fascia.

  • Dartos muscle

    • Smooth muscle attached to the overlying skin.

  • Thermoregulation.

  • Scrotal ligament.

Testes

  • Singular - testis; plural - testes

  • Male gonads

  • Tunica vaginalis

    • Visceral layer covers the testis

      • Closed peritoneal sac

    • Parietal layer

      • Adjacent to the internal spermatic fascia lining the scrotum

  • Tough outer surface is the tunica albuginea (deep to the visceral tunica vaginalis)

  • Forms a thickened ridge posteriorly = mediastinum of the testis

Testes Function

  • Function:

    • Spermatozoa

    • Testosterone

  • Mediastinum of the testis

    • Rete testis

    • Seminiferous tubules

    • Septa

Innervation and Vasculature of Testes

  • Innervation

    • Autonomic nerves arise from the testicular plexus of nerves

    • Vagal parasympathetic fibers, visceral afferent fibers & sympathetic fibers from spinal level T7

  • Testicular artery

    • Branch of the abdominal aorta

    • Retroperitoneal; passes through the inguinal canal to the spermatic cord

  • Pampiniform plexus of veins

    • Involved in thermoregulation

    • Branches converge, forming:

      • Right testicular vein – drains into the IVC

      • Left testicular vein – drains into the left renal vein

  • Lymphatic drainage

    • Follows testicular vessels to lumbar and preaortic lymph nodes

    • Lymph from the scrotum drains into the superficial inguinal nodes

Epididymis

  • Located along the posterior border of the testes

  • Head of the epididymis

    • Superior expanded part

  • Body of the epididymis

  • Tail of the epididymis

    • Continues to the ductus (vas) deferens

Case Study

A 60-year-old male presents with a swelling in the right inguinal region. The swollen area is oval in shape, located above and lateral to the pubic tubercle and was first noticed by the patient 4 months ago. The area is reducible, non-tender, with an impulse on coughing. The patient's vital signs were normal. On abdominal examination, there was no tenderness or guarding. There was no sign or symptom of obstruction or peritonitis. Other systemic examinations were normal. Ultrasonography, X-ray of the abdomen, and blood work were normal on admission. The patient had a few bouts of coughing and developed a bigger bulge in the inguinal region into his right scrotum that was irreducible.

Based on the anatomy of the inguinal region, the “bulge” is likely caused by an inguinal hernia.