Sexual Response Cycle and Female Sexual Physiology
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Direct answer
The female sexual response cycle describes the physiological phases of arousal, identified by Masters and Johnson as excitement, plateau, orgasm and resolution, driven by parasympathetic vasocongestion through the pelvic nerves. The Kaplan model adds desire as the first phase, and these models underpin the classification of female sexual dysfunction. Most lubrication comes from transudation through the vaginal wall rather than from glands.
What you must remember
- Excitement phase: vasocongestion of the clitoris, labia and vaginal walls produces lubrication through transudation across the vaginal epithelium.
- Plateau phase: the outer third of the vagina swells into the orgasmic platform, the uterus elevates and the clitoris retracts.
- Orgasm: rhythmic contractions of the pelvic floor, perineal muscles and uterus, mediated by a spinal reflex through the pudendal nerve.
- Resolution: congested tissue drains and returns to baseline, and many women can repeat the orgasm phase, unlike the typical male refractory period.
- Kaplan model: adds desire before excitement and orgasm, treating sexual response as a sequence that begins with motivation.
- Neural control: parasympathetic S2 to S4 fibres in the pelvic nerves drive vasocongestion, and nitric oxide mediates relaxation of the erectile tissue.
- Dysfunction classes: DSM-5 groups female sexual dysfunction into interest or arousal disorder, orgasmic disorder and genito-pelvic pain or penetration disorder, including dyspareunia and vaginismus.
Mapping each phase to its physiology
A woman who reports low libido or pain on intercourse needs the failing phase identified before treatment is chosen. The table sets out what each phase involves and what drives it, and examiners often ask for the basis column directly.
| Phase | Physiological change | Basis |
|---|---|---|
| Desire (Kaplan) | Sexual interest and motivation | Hormonal and psychological, including androgens |
| Excitement | Vasocongestion, lubrication, clitoral engorgement | Parasympathetic, nitric oxide |
| Plateau | Outer vaginal swelling, uterine elevation, clitoral retraction | Sustained vasocongestion |
| Orgasm | Rhythmic pelvic and uterine contractions | Spinal reflex via pudendal nerve |
| Resolution | Return to baseline, drainage of congested tissue | Vascular recovery |
Excitement problems point to vascular or neural causes, orgasmic problems to reflex or psychological causes, and pain disorders to vaginal or pelvic floor causes such as vaginismus. Matching the complaint to the phase is the first step in classifying the dysfunction. Pain disorders also need a pelvic examination to look for vaginal atrophy or pelvic floor spasm before any treatment is started.
Where the exam tries to catch you
Sexual physiology questions usually test a term that has been mixed up with another.
- Trap: Crediting Bartholin glands with most vaginal lubrication. Correct: Most lubrication is transudate through the vaginal epithelium, and Bartholin glands add only a little mucus at the vestibule.
- Trap: Treating the Kaplan model as a replacement for Masters and Johnson. Correct: Both are taught; Masters and Johnson describe the physiological phases, and Kaplan adds desire as the first phase.
- Trap: Classifying vaginismus as an orgasmic disorder. Correct: Vaginismus is a genito-pelvic pain or penetration disorder driven by involuntary pelvic floor spasm, not an orgasm problem.
Frequently asked questions
What are the four phases of the female sexual response cycle?
The four phases are excitement, plateau, orgasm and resolution, as described by Masters and Johnson. Each phase reflects a predictable change in the genital and pelvic tissues.
How does the Kaplan model differ from the Masters and Johnson model?
The Kaplan model adds desire as the first phase, before excitement and orgasm. It is used clinically because low desire, a common complaint, sits outside the original four-phase sequence.
Where does vaginal lubrication come from?
Vaginal lubrication comes mainly from transudation of plasma through the vaginal epithelium during excitement, not from glands. Bartholin glands add only a small amount of mucus at the vestibule.
Which nerves control physiological arousal in women?
Parasympathetic fibres from S2 to S4 travelling in the pelvic nerves drive vasocongestion and lubrication during arousal. The pudendal nerve drives the rhythmic pelvic floor contractions of orgasm.