Hint: At the time of sexual excitation, nerve muscles starts to stimulate the penis resulting in increased blood flow due to dilatation of penile arteries causing enlargement and hardening of the penis.
Complete Answer: Option A- Penis is an erectile copulatory intromittent organ. It is composed of three longitudinal cylindrical masses of erectile tissue. These masses are right and left corpora cavernosa and a median corpus spongiosum. It contains several blood vessels. Roots of penis containing muscles is called cura.
- During sexual excitation, parasympathetic part of the autonomic nervous system gets activated. It leads to the release of neurotransmitters which results in relaxation of smooth muscles. - After this, the corpora cavernosa become engorged with venous blood contrast to a normal state when these muscles are contracted allowing limited blood supply. Increased blood flow results in dilatation of penile arteries and arterioles causing tissue expansion. - Due to enlarged erectile tissue, extra pressure caused veins to squeeze against surrounding tissue leading to reduce blood flow. This more and more blood enters the penis than can leave. This causes enlargement and hardening of the penis. During this time the muscles of cura are relaxed.
Option B- the muscle of the penis is not contracted during sexual stimulation.
Option C- This option is incorrect, the collapse of penile muscles doesn’t happen during sexual stimulation
Hence the Correct answer is option is A.
Note: Corpus spongiosum located beneath corpora cavernosa contains urethra through which urine and semen pass. There is continuous blood supply in them due to the peripherally located vein. This prevents the urethra from being collapsed which in turn prevents the release of semen.