Question

Which of the following is not a component of intra-abdominal tunics surrounding the testicles, in animals?

• A. Internal spermatic fascia
• B. External spermatic fascia
• C. Visceral lamina of vaginal tunic
• D. Parietal lamina of vaginal tunic

Hint:

A useful way to remember this is that the deep abdominal layers (peritoneum and transversalis fascia) form the deep, "internal" coverings: the vaginal tunics and the internal spermatic fascia.
The superficial external abdominal oblique muscle aponeurosis remains external, forming the external spermatic fascia.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
During embryonic development, the testes descend from their intra-abdominal position into the scrotum through the inguinal canal.
As they descend, they carry along layers of the abdominal wall, which form the protective tunics surrounding the testes and the spermatic cord.

Step 2: Detailed Explanation:
The layers surrounding the descended testicle are derived from specific layers of the abdominal wall:
1. Visceral and Parietal laminae of the vaginal tunic: These are direct continuations of the visceral and parietal peritoneum, respectively. The vaginal cavity is continuous with the peritoneal cavity.
2. Internal spermatic fascia: This is derived from the transversalis fascia, which is the deep, intra-abdominal fascia lining the abdominal cavity.
3. External spermatic fascia: This is derived from the aponeurosis of the external abdominal oblique muscle, which is a superficial layer of the abdominal wall. It lies outside the abdominal cavity proper.
Because the external spermatic fascia is formed from the superficial musculature/aponeurosis rather than the deep, internal lining (transversalis fascia and peritoneum), it is not classified as an intra-abdominal tunic.

Step 3: Final Answer:
Therefore, the external spermatic fascia is not a component of the intra-abdominal tunics surrounding the testicles.