Inguinal Canal, Vas Deferens and Ampulla

The inguinal canal allows passage of the vas deferens, which carries sperm to the ampulla, where it is stored and mixed with seminal fluid before ejaculation.

The inguinal canal is a short passage in the lower abdominal wall that allows the spermatic cord to pass from the abdomen to the scrotum. The vas deferens is a muscular tube within the spermatic cord that carries sperm from the epididymis to the urethra. Near its end, it enlarges to form the ampulla, which serves as a temporary sperm reservoir and contributes to seminal fluid, especially in species like bulls, rams, and stallions.

Inguinal Canal

The inguinal canal is a slit-like space between the internal and external inguinal rings. The internal inguinal ring is formed by the internal oblique abdominal muscle, while the external inguinal ring is formed by the tendons of the external oblique abdominal muscle.

In dogs, bulls, and boars, the internal inguinal ring is larger, but the inguinal canal is short.

In stallions, the inguinal canal is longer, but the internal inguinal ring is smaller.

Vas Deferens or Ductus Deferens

The vas deferens extends from the tail of the epididymis to the colliculus seminalis of the pelvic urethra. It is a siphon-shaped structure that facilitates the exit of spermatozoa.

The vas deferens runs parallel to the testis, enters the spermatic cord, passes through the inguinal canal, and continues dorsomedially to the neck of the urinary bladder. It maintains a uniform thickness up to the urinary bladder—approximately 3 mm in bulls and 6 mm in stallions.

• Blood supply: Internal pudic artery and spermatic artery
• Nerve supply: Pelvic plexus

Ampulla

The terminal, fusiform, enlarged glandular portion of the vas deferens is called the ampulla of the vas deferens.

• Bull: Length 10–15 cm, Diameter 1–1.5 cm
• Stallion: Length 15–20 cm, Diameter 2–2.5 cm
• Dog and cat: Ampulla is absent
• Boar: Ampulla is small

The ampulla lies dorsal to the urinary bladder, passes beneath the body of the prostate, and opens into the pelvic urethra at a rounded prominence known as the colliculus seminalis.