Physiology of Human S exual Response and contraception

1. Physiology of Human Sexual Response and contraception DR. ZAHOOR ALI DR. AMEL EASSAWI

2. SEXUAL ACT • Union of sperm and ovum requires sexual act between male and female to deliver semen containing sperms, in female vagina ( coitus, copulation ).

3. Erection of Penis • Accompanied by engorgement of erectile tissue with blood. • Erectile tissue (cords of spong like vascular spaces) : • Corpora cavernosa: two paired on dorsal side • Corpus spongiosum: one on ventral side • During sexual arousal, these arterioles reflexly dilate and erectile tissue fills with blood- penis to enlarge both in length and width and to become more rigid. • Veins that drain the erectile tissue are mechanically compressed –reducing venous outflow and thereby contributing even further to vasocongestion. • Erection can occur in 5-1o seconds

4. Erectile tissue in Males

5. Erection

6. Erection reflex

7. Role of Nitric Oxide in Penile Erection Parasympathetic stimulation NO release from vascular endothelium Acivates Guanylate cyclase breaks down Phosphodiesterase 5 Activates cGMP Relaxation of arteriolar smooth muscles Vasodilatation and vascular engorgement

8. MALE SEXUAL PERFORMANCE

9. SEMEN • Average volume 3 ml (2-6 ml) • Sperm count 180 - 400 million (66 million/ ml) • Both quality and quantity of sperm is important • Quality means motility and structure of sperm, if abnormal motility or distorted tails of sperm there will be less chances of fertilization. • Applied – Man is considered clinically infertileif his sperm count falls below 20 million/ml

10. Composition of human semen

11. Erectile Tissue in Female • Clitoris is like male homolog the penis and is composed of erectile tissue. • Clitoris is much larger than it is visible externally • Function of clitoris-- Increased pleasure signaling, support vaginal wall.

12. Erectile tissue in females

13. HUMAN SEXUAL RESPONSE • Physiological responses which occur during sexual act are similar in male and female. There are four stages 1) Excitement phase 2) Plateau phase 3) Orgasmic phase 4) Resolution phase

14. HUMAN SEXUAL RESPONSE CYCLE PHASES The resolution time for men is longer resulting in an increased refractory period to further stimulation

15. Sexual Response Cycle in males • Excitement Phase(Arousal): • Initiated by either physical or psychological stimuli • Heightened sexual awareness. • Vasocongestion (engorgement of sexual organs)-includes erection • Plateau Phase: • Includes intensification of earlier responses • Characterized by steadily increasing heart rate, blood pressure, respiratory rate, and increase muscle tone.

16. Orgasmic phase • Includes ejaculation, Rhythmic throbbing of pelvic muscles.All generalized body responses reaches to peak: • Heavy breathing • Heart rate up to 180 beats/min • Marked generalized skeletal muscle contraction • Heightened emotions • These responses that are collectively experienced as intense physical pleasure( feeling of release) • an experience known as orgasm.

17. Resolution Phase: • - Return of genitalia and body systems to pre-arousal state • Erection subside(decrease blood flow to penis) • Deep relaxation ( may feel fatigue) • Muscle tone returns to normal • Cardiovascular and respiratory activity returns to pre-arousal state. • Following orgasm men enters refractory period of variable duration before sexual erection can produce another excitation.

18. Sexual Response Cycle in Females • Female sexual cycle is similar to male cycle • Also experience same four phases of the sexual cycle 1. Excitement Phase: • Initiated by either physical or psychological stimuli • Parasympathetically induced vasodilation of arterioles in vagina & external genitelia( specially clitoris), that results in • Swelling of labia and erection of clitoris (bulbs engorge with blood) • Secretion of fluid in vagina (act as a lubricant) • Erection of nipples & enlargement of breast as a result of vasocongetion. • Flushing ( increased blood flow through skin)

19. Plateau Phase: • - Changes initiated during excitement phase intensify • - Systemic responses similar to those in male occur • Increase heart rate • Increase respiratory rate • Increase muscle tension • Vasocongetion of lower third of vagina reduces its inner capacity.Uterus raises upwards-enlarging upper two third of vagina (creates space for ejaculate deposition).

20. Orgasmic Phase: • Sympathetic stimulation triggers rhythmic contraction of pelvic muscle. More intense contraction of lower two third of vagina. Systemic responses similar to that of male orgasm.Experience in females is similar to that in males except: • - There is no ejaculation in female • - Female do not become refractory following an orgasm • (multiple orgasm possible). • Resolution Phase: • Pelvic vasocongestion and systemic manifestations gradually subside.Time of great physical relaxation

21. Erectile dysfunction or Impotence • Failure to achieve or maintain an erection suitable for sexual intercourse. Affect 50% of men between 40 and 70 years old. May be due to: • 1. Psychological factors: Stress, anxiety, , depression, fear of sexual failure • 2. Physical factors: • A. Nerve damage as a result of disease e.g. Diabetes, kidney disease, chronic alcoholism, multiple sclerosis. • B. Medication that interfere with autonomic function antihypertensive, antidepressants • C. Problem with blood flow to the penis. • Sildenafil (Vigra): prescribed to treat erectile dysfunction. It does not produce an erection but it amplifies and prolongs an erectile response triggered by usual means of stimulation.

22. Effect of sildenafil (Viagra)on Penile Erection Parasympathetic stimulation NO release from vascular endothelium sildenafil Acivates Guanylate cyclase X breaks down Phosphodiesterase 5 Activates cGMP Relaxation of arteriolar smooth muscles Vasodilatation and vascular engorgement

23. Contraception Prevention of pregnancy before the implantation has taken place . Methods of Contraception: • Blockage of sperm transport to ovum • Prevention of ovulation • Blockage of implantation

24. Methods of Contraception 1. Blockage of Sperm Transport to Ovum: A. Natural Methods: 1. Rhythmic Abstinence: • Periodic or rhythmic abstinence i.e. avoidance of sexual intercourse during woman’s fertile period. The Following methods are used: A. Calendar method: • The women predicts when ovulation to occur based on keeping careful records of previous cycles B. Basal body temperature method: • Body temperature rises slightly a day after the ovulation • safe period is considered to begin after the basal body temperature remains elevated for 3 days 2. Coitus Interrupts: • Withdrawal before ejaculation

25. B. Barrier Methods: • Prevents entry of sperm into vagina or uterus • For males (condom) • For females ( diaphragm or cervical cap ) • Contraceptive Sponge (combined both barrier and spermicidal) • C. Spermicidal Chemical: • Suppositories • Gel • Foam tablets • Creams

26. D. Sterilization: • Permanent Methods: • Female sterilization ( tubal ligation or Tubectomy) • Male sterilization (vasectomy):

27. Methods of Contraception 2. Prevention of Ovulation • Oral contraceptive (OCP) • Combined pills • Progesterone only pill • Once a month pill • Contains synthetic estrogen and progesterone like steroids (ethinyl estradiol and norgesterel/norethesterone) Mechanism of Action: • They act by inhibiting the release of FSH & LH by anterior pituitary by negative feedback mechanism, preventing the development of graffian follicle ,ovulation & formation of corpus luteum is prevented • Increases viscosity of cervical mucus ,preventing the sperm penetration • Endometrial maturation is also altered preventing blastocyst implantation

28. B. Injectable: • long acting pre-gestational preparation which can be given once in a three months. • Sub dermal implants of progesterone have also been tried • Dermal patch

29. Methods of Contraception 3. Blockage of Implantation: A. Intra Uterine Contraceptive Device (IUCD): • Are devices which are introduced & left inside the uterus for longer period of time . Mechanism of action : • They produce local nonspecific inflammatory reaction in the endometrium & prevent implantation of blastocyst . • Side effects : • Bleeding • Abdominal pain / backache • Displacement • Perforation

30. Average failure rates of common contraceptive techniques

31. Termination of unwanted pregnancies • When contraceptive practice fail or are not used and unwanted pregnancy occurs, women often turn to abortion, to terminate pregnancy • In USA each year number of pregnancy 6.4 million • Half of this are unintended (3.2 million) • Abortion is done 1.6 million • Surgical removal of embryo/fetus is legal in USA but there is emotional, ethical and political controversy.

32. References • Human Physiology, Lauralee Sherwood, seventh edition. • Text book Physiology by Guyton &Hall,11th edition. • Text book of Physiology by Linda s. Contanzo, third edition. • Physiology by Berne and Levy, sixth edition.