Infertility (Week 6--Pregler)

Question 1

Two functions of testes

Answer 1

1) Production of sperm
2) Secretion of testosterone

Question 2

Male requirements for successful fertilization

Answer 2

Large enough amount of viable sperm

Sperm capable of fertilizing egg

Sperm contain appropriate genetic material to produce viable conceptus

Sperm delivered to vagina

Question 3

What do testes contain?

Answer 3

80% seminiferous tubules (produce/develop sperm)

20% Leydig cells (synthesize testosterone from cholesterol)

Question 4

What do seminiferous tubules contain and what stimulates them to produce sperm?

Answer 4

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

Question 5

What causes secretion of testosterone by Leydig cells?

Answer 5

LH onto Leydig cells stimulates testosterone secretion

Testosterone negative feedback to hypothalamus and pituitary inhibits testosterone secretion

Question 6

4 stages of sexual response

Answer 6

1) Excitement/arousal
2) Plateau/maintenance and intensification of arousal
3) Orgasm
4) Resolution

Question 7

Is the sexual response parasympathetic or sympathetic?

Answer 7

Mainly parasympathetic

However, “point and shoot” (erection is parasympathetic and ejaculation is sympathetic)

Question 8

What nerves are involved in the sexual response?

Answer 8

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)

Question 9

What is responsible for sexual desire?

Answer 9

In men we know it is related to testosterone levels, but in women it is less clear (only small effect of testosterone)

Question 10

How do we prevent ejaculate from entering the bladder?

Answer 10

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

Question 11

What happens when you have an orgasm?

Answer 11

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

Question 12

Where does fertilization occur?

Answer 12

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

Question 13

What does an IUD do?

Answer 13

IUD prevents fertilization

Usually fertilization doesn’t occur because sperm can’t get through uterus, which now has different milieu due to IUD

Question 14

What is the first thing you do to evaluate male fertility?

Answer 14

Sperm count (easy, noninvasive)

If sperm count is normal and man is able to initiate/maintain sexual intercourse/ejaculate, should be fine

Question 15

Female requirements for fertility

Answer 15

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

Question 16

What hormones are required for ovaries to release an egg?

Answer 16

FSH and LH must be released in appropriate amount at appropriate time

Question 17

What hormones do the ovaries secrete?

Answer 17

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”

Question 18

What triggers ovulation?

Answer 18

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)

Question 19

What can STDs do to a woman to make her infertile?

Answer 19

Can scar reproductive organs so egg cannot be fertilized by sperm and travel to uterus

Question 20

How does the morning after pill work?

Answer 20

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

Question 21

How does RU486 work?

Answer 21

Prevents implantation (can do this many days after intercourse)

Question 22

Imbalances of which hormones can cause infertility?

Answer 22

TSH

Prolactin