7) Conception & Contraception Flashcards by Lauren Croft

What are the 4 main places semen is produced?

Testes
Seminal vesicles
Prostate gland
Bulbourethral glands (Cowper’s glands)

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What is the semen from the testes made up of?

20-200x10^6 sperm per ejaculate
>60% sperm swimming forward vigorously
<30% sperm have abnormal morphology

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What is the normal volume of ejaculate?

2-4ml

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What is the semen from the seminal vesicles made up of?

60% of volume
Alkaline fluid (neutralises acid in male urethra & female repro tract)
Fructose
Prostaglandins
Clotting factors (fibrinogen, holds sperm in place after ejaculation, before liquefaction)

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What is the semen from the prostate gland made up of?

25% of volume
Milky, slightly acidic fluid
Proteolytic enzymes (break down clotting factors, re-liquefying sperm in 10-20mins)
Citric acid
Phosphotase

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What is the semen from the Bulbourethral (Cowper’s) glands made up of?

Very small volume
Alkaline fluid
Mucous (lubrication of end of penis & urethral lining)

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How does the process of emission occur?

Peristalsis of vas deferens
Secretions from seminal vesicles
Move ejaculate into prostatic urethra before ejaculation

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Describe the physiological processes involved in erection of the penis

Stimulants - psychogenic, tactile (sensory afferents)
Efferents - Somatic & autonomic, pelvic nerve (PNS), pudendal nerve (somatic)
lead to Haemodynamic changes

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Describe the haemodynamic changes in erection

Inhibition of sympathetic arterial vasoconstrictor nerves
Activation of parasympathetic nervous system (pelvic nerve, formation of nitric oxide, NO)
Activation of non-adrenergic, non-cholinergic nerves to arteries releasing NO
NO diffuses into & causes relaxation of vascular smooth muscle (vasodilation)

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What happens to the arteries in the corpa cavernosa during erection?

Central helicine arteries straighten
Enlarge lumen
Blood flows into & dilates cavernous spaces in corpora of penis

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What happens to the arteries in the corpus spongiosum during erection?

Arteries dilate

Not very much - avoid compression & closing off of urethra

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What is the role of the bulbospongiosus & ischiocavernosus muscles during erection?

Compress veins egressing from corpora cavernosa
Impede venous return
Corpora cavernosa engorged with blood (arterial dilation + venous constriction)
Erectile bodies become turgid (enlarged & rigid)
Erection

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Name some causes of erectile dysfunction

Vascular problems (most common)
Psychological (inhibition of spinal reflexes)
Tears in fibrous tissue of corpa cavernosa
Factors blocking NO (alcohol, anti-hypertensives, diabetes)

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What drug can be used to treat erectile dysfunction?

Viagra
Inhibits breakdown of cGMP
Maintains erection

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What physiological changes take place in a female to facilitate coitus?

Vaginal lubrication
Swelling & engorgement of external genitalia
Internal enlargement of vagina
Cervical mucus
- Oestrogen - abundent, clear, non-viscous mucous
- Progesterone + Oestrogen - Thick, sticky mucous plug

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Describe the mechanism of ejaculation

Spinal reflex
SNS control:
1. Contraction of glands & ducts (smooth muscle)
2. Bladder internal sphincter contracts (prevents entry of semen into bladder)
3. Rhythmic striatal muscle contractions (pelvic floor, ischiocavernosus & bulbospongiosus - pudendal S2-4, hip & anal muscles)

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Describe sperm transport through the cervix & uterus

Immediately after ejaculation semen coagulates (clotting factors, prevents sperm being lost from vagina)
10-20mins later semen re-liquefies (enzymes
Vast majority of sperm don’t enter cervix
Sperm in uterus travel 15-20cm to uterine tube (hours)

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How is the transport of sperm facilitated?

Own propulsive capacity

Fluid currents caused by action of ciliated cells in uterine tract

What changes do sperm undergo during their passage through the uterus to the uterine tube?

Maturational changes:
Capacitation
Acrosomal reaction
Both induced by influx of Ca & rise in cAMP in spermatozoa

What is capacitation?

Further maturation of sperm in female repro tract (6-8hrs)
Removal of sperm glycoprotein coat to allow fusion with oocyte cell surface
Tail movement changes, Beat > Whip-like action
Sperm become responsive to signals from oocyte

What is the acrosomal reaction?

Capacitated sperm come into contact with oocyte zona pellucida
Membranes fuse
Acrosome swells, liberates contents by exocytosis
Proteolytic enzymes & further binding facilitate penetration of zona pellucida by sperm (15mins)

Describe what happens during ovulation

Ovum (primary oocyte) in ovulatory follicle has completed 1st meiotic division
- Secondary oocyte & 1st polar body
Secondary oocyte surrounded by follicular cells in gelatinous matrix released from ovulatory follicle
Picked up by fimbria of uterine tube to ampulla for fertilisation

What happens to the zygote once it has formed?

Cleavage - mitotic divisions (few hours)
Forms morula (ball of cells)
Forms blastocyst (hollow structure)
Gradually transported along uterine tube to uterus
Blastocyte enters uterine cavity 4-5 days later
Implantation

What is an ectopic pregnancy?

Failure of transport of egg
Embeds in uterine tube, ovary or abdomen
Embryo dies
Severe risk of maternal haemorrhage

What is 'natural' conception? (contraception)

Abstinence Coitus interruptus - sperm in pre-ejaculate (not effective) Rhythm method

What are the main contraceptive methods used?

``` Barrier methods e.g. condoms Hormonal contraception e.g. OCP, COCP, POP Vasectomy/Sterilisation Natural conception Post-coital contraception ```

What is a vasectomy and how does it work?

Division of vas deferens bilaterally | Prevent sperm from entering ejaculate

What are the main barrier methods of contraception?

Condoms (+ STI protection) Diaphragm (holds sperm in acidic vagina, reduces survival time) Cap (across cervix) Prevent sperm from reaching cervix

What is the role of progesterone in hormonal contraception?

``` Thick, 'hostile' cervical mucus plug Prevents sperm entering uterus -ve feedback to hypothalamus/pituitary: Decreases frequency of GnRH pulses Inhibits follicular development ```

What is the role of oestrogen in hormonal contraception?

-ve feedback on anterior pituitary Loss of +ve feedback mid-cycle No LH surge

What are the main types of hormonal contraceptives?

Combined Oral Contraceptive Pill (COCP) Progesterone Only Pill (POP) Depot Progesterone (3 monthly injections) Progesterone Implants

What contraceptive methods can be used to inhibit implantation?

Hormonal contraceptives (COCP, OCP, POP) Post-coital contraceptives (Morning-after pill) Intra-uterine contraceptive device (Copper coil)

How do intra-uterine contraceptive devices (e.g. coil) work?

Inert copper Interferes with endometrial enzymes & implantation May interefere with sperm transport into fallopian tube Progesterone impregnated

How does post-coital contraception (morning-after pill) work?

``` Combined oestrogen/progesterone or POP High Dose Up to 72hrs after intercourse May disrupt ovulation Blocks implantation May impair luteal function ```

What is the difference between primary and secondary infertility?

Primary - No previous pregnancy | Secondary - Previous pregnancy, successful or not

What can be the causes of male infertility?

20-25% cases Abnormal sperm production e.g. testicular disease Obstruction of ducts e.g. infection, vasectomy Hypothalmic/Pituitary dysfunction

Describe a normal semen analysis for a male

Volume >2ml Sperm count >20 million per ml Motility >50% Morphology >50%

What can be the causes of female infertility?

45-60% cases Anovulation - usually very irregular periods - Hypothalmic e.g. hyperprolactinaemia, weight loss, exercise, stress - Pituitary e.g. tumours, necrosis - Ovarian e.g. ovarian failure, radiotherapy, chemotherapy

How would you differentiate the causes of female infertility?

Look at hormone levels Menopause - High FSH & LH, Low oestrogen Ovarian failure - High FSH & LH, Low oestrogen Hypo/Pituitary - Low FSH, LH & oestrogen PCOS - Increased ratio FSH:LH, Normal oestrogen

How can ovulation be induced?

``` Anti-oestrogen therapy - reduce -ve feedback to hypothalamus/pituitary - Increase GnRH & FSH Gonadotrophins - FSH administration GnRH Agonists - Pulsatile to mimic secretion ```

What are the causes, diagnosis & treatment of tubal occlusion?

Causes - sterilisation, PID Diagosis - Laparoscopy, Hysterosalpingogram Treatment - Tubal surgery, Assisted conception

What is polycystic ovarian syndrome? (PCOS)

Increased androgen secretion Raised LH:FSH ratio Insulin resistance Multiple small ovarian cysts Coital problems, unexplained 20-30% cases

What questions would you ask when trying to manage infertility in a patient?

Regular, unprotected intercourse? Ovulating? Regular menstrual cycle? Day 21 progesterone? Patent tubes - infection/sterilisation? Adequate sperm count?

How can you treat infertility?

``` Induce ovulation Overcome tubal occlusion by surgery or IVF If inadequate sperm : - artificial insemination by donor - Intra-cytoplasmic sperm injection ```