Infertility (Week 6--Pregler) Flashcards
Two functions of testes
1) Production of sperm
2) Secretion of testosterone
Male requirements for successful fertilization
Large enough amount of viable sperm
Sperm capable of fertilizing egg
Sperm contain appropriate genetic material to produce viable conceptus
Sperm delivered to vagina
What do testes contain?
80% seminiferous tubules (produce/develop sperm)
20% Leydig cells (synthesize testosterone from cholesterol)
What do seminiferous tubules contain and what stimulates them to produce sperm?
Spermatogonia = sperm precursor
Spermatocytes = developing sperm
Sertoli cells = provide nutrients; form tight junctions (blood/testes barrier); secrete aqueous fluid
FSH stimulates sperm production
Inhibin (produced by Sertoli cells of testes (and granulosa cells of ovaries in females)) inhibits sperm production by acting on anterior pituitary to inhibit FSH secretion
What causes secretion of testosterone by Leydig cells?
LH onto Leydig cells stimulates testosterone secretion
Testosterone negative feedback to hypothalamus and pituitary inhibits testosterone secretion
4 stages of sexual response
1) Excitement/arousal
2) Plateau/maintenance and intensification of arousal
3) Orgasm
4) Resolution
Is the sexual response parasympathetic or sympathetic?
Mainly parasympathetic
However, “point and shoot” (erection is parasympathetic and ejaculation is sympathetic)
What nerves are involved in the sexual response?
Parasympathetic: pelvic splanchnic; inferior hypogastric (pelvic plexus S2-4)–release ACh, NO
Sympathetic: sacral splanchnic; lower thoracic, upper lumbar
Motor/sensory: pudendal nerve (S2-4)
What is responsible for sexual desire?
In men we know it is related to testosterone levels, but in women it is less clear (only small effect of testosterone)
How do we prevent ejaculate from entering the bladder?
Sympathetic system closes/constricts external urethral sphincter
Note: in men, alpha agonists for prostate problems (BPH) can cause problems with this sympathetic response because they RELAX smooth muscle of prostate and bladder neck
What happens when you have an orgasm?
Female (whether you have an orgasm or not): facilitation of sperm transport (contraction of vagina, uterus, dilation of cervix)
Male: ejaculation (semen expelled from urethra, ischiocavernosis, bulbospongiosis, pelvic floor muscles contract)
Note: these responses are due to spinal cord reflex via pudendal nerve (somatic sensory/motor)
Note: also oxytocin released by both male and female
Where does fertilization occur?
Ampulla of fallopian tube
Egg goes from ovary into peritoneal cavity into ampulla of fallopian tube (fimbriae have chemotactic mechanism)
Sperm go into vagina through cervix, into uterus, into fallopian tube then into ampulla of fallopian tube
What does an IUD do?
IUD prevents fertilization
Usually fertilization doesn’t occur because sperm can’t get through uterus, which now has different milieu due to IUD
What is the first thing you do to evaluate male fertility?
Sperm count (easy, noninvasive)
If sperm count is normal and man is able to initiate/maintain sexual intercourse/ejaculate, should be fine
Female requirements for fertility
Produce viable egg
Egg must be able to be fertilized by sperm
Conceptus must travel down fallopian tube to uterus
Fertilized egg must contain appropriate genetic material to develop to viability
Uterus must be capable of supporting pregnancy to point of fetal viability
What hormones are required for ovaries to release an egg?
FSH and LH must be released in appropriate amount at appropriate time
What hormones do the ovaries secrete?
Progesterone and 17-beta-estradiol
Theca cells synthesize and secrete progesterone (LH stimulates cholesterol desmolase)
Granulosa cells convert testosterone from theca cells to estradiol (FSH stimulates aromatase to do this)–remember “GirlFriEnd”
What triggers ovulation?
Midcycle high level of estradiol triggers surge of LH, which triggers ovulation
(optimal time to have sex to make baby is a few days before or day of ovulation)
What can STDs do to a woman to make her infertile?
Can scar reproductive organs so egg cannot be fertilized by sperm and travel to uterus
How does the morning after pill work?
Prevents ovulation and fertilization but does NOT prevent implantation
Keeps egg from making itself available to sperm
However, if already had fertilization before taking pill, it probably won’t help
Gives 50% reduction in pregnancy
How does RU486 work?
Prevents implantation (can do this many days after intercourse)
Imbalances of which hormones can cause infertility?
TSH
Prolactin
