Coitus, Fertilisation and Contraception

Question 1

What is coitus?

Answer 1

Coitus is when the erect penis is introduced into the vagina (intromission) during sexual intercourse/copulation. When ejaculation occurs semen is released into upper part of vagina (insemination) so that sperm can travel to appropriate site for fertilisation (ampulla of uterine tube)

Question 2

What is the fascia of the penis?

Answer 2

The erectile tissues are surrounded by different layers of fascia. Venous plexus forms a network of veins over surface of columns of tissues. Lacunae are the spaces in between columns of erectile tissue, supported by smooth muscle which blood fills into during erection

Question 3

What happens to the fascia during erection?

Answer 3

During erection they press against layers of fascia (tissues fill up with blood) which pushes against venous plexus minimising blood flow back out of penis. Tunica albuginea around corpus cavernosum and another one around corpus spongiosum. Spongiosum is not as erectile as cavernosum hence tunica albugenia is not as dense nor fibrous around spongiosum as it is around cavernosum

Question 4

Comparative structures of clitoris and penis

Answer 4

Structure of the clitoris and penis share developmental origins, tissues of clitoris are erectile as in the penis

Question 5

Why is the gonad artery high up?

Answer 5

Gonadal artery (female = ovaries, male = testes) is high up on branch as, as migration (growing) takes place and gonads moves down so does the vascular supply

Question 6

What is the internal pudendal artery?

Answer 6

Internal pudendal artery feeds perineum and external genitalia including penis, branches to the penis include: artery to bulb, urethral artery, dorsal artery and deep (cavernosal) artery

Question 7

What is the nerve supply is the penis?

Answer 7

Penis richly innervated by sensory and motor neurons. Includes sensory fibres responsive to touch, pressure, temperature. Pudendal nerve supplies sensory and somatic motor innervation to perineum and external genitalia including penis (dorsal nerve). Autonomic innervation to penis derived from pelvic plexus

Question 8

Nerves involved in erection?

Answer 8

Parasympathetic nervous system stimulates production of nitric oxide (vasodilator - relaxes and widens vessels) by deep arteries of the penis. Deep arteries dilate and fill lacunae in corpora cavernosa

Question 9

Nerves involved in ejaculation?

Answer 9

Sympathetic nervous system stimulates contraction of smooth muscle (ductus deferens and urethra), reproductive ducts and accessory glands (seminal vesicle and prostate)
Somatic motor system stimulates contraction of skeletal muscles and bulb of penis

Question 10

What is the process of erection?

Answer 10

Erection of the penis is controlled by the parasympathetic nervous system (can be psychogenic or physical stimulation), arteries in erectile tissue dilate, erectile tissue becomes engorged with blood. Bulbourethral gland secretes bulbourethral fluid to help lubricate urethra and remove any urine that is present. Erect penis can be inserted into vagina

Question 11

What is the process of emission?

Answer 11

Emission is a sympathetic response, smooth muscle of ductus deferents contracts to move sperm into ampulla (peristaltic contractions), smooth muscle of ampulla, seminal vesicles and prostate gland contract moving sperm and seminal fluid into urethra. Release of secretions from seminal vesicles and prostate gland

Question 12

What is the process of expulsion?

Answer 12

Semen in urethra activates somatic and sympathetic reflexes, contractions of urethral smooth muscles, pelvic floor muscles contract and semen is ejected. Additional secretions from accessory glands, closure of internal urethral sphincter

Question 13

What is the process of resolution?

Answer 13

Blood flow to penis is reduced, penis becomes flaccid. Trabecular contract and remove blood from erectile tissue. Refractory period where males cannot have another erectile period

Question 14

What happens in the female sexual response?

Answer 14

Engorgement (increased blood flow) of clitoris, labia and vagina in response to autonomic stimulation (can be psychogenic or direct). Lubricating fluid secreted through vaginal wall; secretion of mucus into vestibule. Increased width and length of vagina, uterus elevates upwards. Rhythmic contraction of vaginal, uterine and perineal (pelvic floor) muscles

Question 15

What happens after insemination?

Answer 15

Semen released into upper part of vagina, sperm travel to uterine tube for fertilisation, sperm fuse with secondary oocytes oocyte completes meiosis II. Fertilised oocyte now a zygote, zygote initiates cleavage (~7days) and travels towards the uterus for implantation

Question 16

What is contraception?

Answer 16

Contraception is any method used to prevent pregnancy, regulates when and how many pregnancies. There are natural and artificial methods

Question 17

What are natural methods of contraception?

Answer 17

Natural methods rely on timing of coitus or behaviour during coitus, they have a high failure rate. Rhythm method (periodic abstinence - abstain from sexual intercourse around time of ovulation) and withdraw method (coitus interruptus - withdrawal of penis from vagina before ejaculation). Lactational infertility - when breastfeeding often not ovulating (dependent of release of GnRH)

Question 18

What are barrier methods of contraception?

Answer 18

Caps are imperfect barriers so should be used in conjunction with spermicidal foams/jellies/creams/sponges. Needs to remain at least 6 hours after intercourse. Not commonly used anymore as more effective and convenient methods
Condoms more commonly used as cheap, readily available, easy to use and reduce the risk of STIs

Question 19

What are IUD methods of contraception?

Answer 19

Copper IUD inserted into lumen of uterus, causes low grade inflammation, reduces sperm transport, toxic to oocyte and zygote and impairs implantation
Hormonal IUD contains progestins, affects cervical mucus reducing sperm transport, local affects on endometrium and may prevent ovulation

Question 20

What are steroidal contraceptives for females?

Answer 20

Variable depending on type, concentration and mode of delivery of hormones. Deliver a progestin with/without estrogen. Suppresses ovulation (affects feedback loops to hypothalamus and pituitary), affects mucus produced by cervix (prevents sperm penetration)

Question 21

What are combined oral contraceptive pills?

Answer 21

Contain estrogen and progestin. Suppress ovulation (affects feedback loops to hypothalamus and pituitary) and affects mucus produced by cervix (prevent sperm penetration)

Question 22

What are progestin-only methods of contraception?

Answer 22

Progesterone only pill has low does of progestin and effects only cervical mucus.
Subdermal impact/injectable progestins: Implant is long acting and acts primary by disrupting follicular growth and ovulation

Question 23

Types of sterilisation

Answer 23

Tubal ligation - cut uterine tubes ‘tubes tied’
Vasectomy - cut ductus deferens