Sigmoid Flexure Absent – Species

Sigmoid flexure is absent in:

Correct Answer: Both Stallion and Dog

The sigmoid (S-shaped) flexure is a curve in the non-erect penis that straightens during erection. It is absent in both the stallion and the dog — these species have musculocavernous (vascular) type penises that rely primarily on blood engorgement for erection.

Penis Types in Domestic Animals

• Fibroelastic type (with sigmoid flexure): Bull, Ram, Buck, Boar, Camel — the penis is rigid even when non-erect; erection mainly involves straightening of the sigmoid flexure.
• Musculocavernous (vascular) type (no sigmoid flexure): Stallion, Dog — penis enlarges greatly due to blood engorgement. ✔

Location of Sigmoid Flexure

• Pre-scrotal (in front of scrotum): Boar, Camel
• Post-scrotal (behind scrotum): Bull, Ram, Buck