7) Conception & Contraception Flashcards
What are the 4 main places semen is produced?
Testes
Seminal vesicles
Prostate gland
Bulbourethral glands (Cowper’s glands)
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
What is the normal volume of ejaculate?
2-4ml
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)
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
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)
How does the process of emission occur?
Peristalsis of vas deferens
Secretions from seminal vesicles
Move ejaculate into prostatic urethra before ejaculation
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
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)
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
What happens to the arteries in the corpus spongiosum during erection?
Arteries dilate
Not very much - avoid compression & closing off of urethra
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
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)
What drug can be used to treat erectile dysfunction?
Viagra
Inhibits breakdown of cGMP
Maintains erection
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
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)
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)
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
