27. Reproductive Physiology Review

Question 1

Function of leydig cells in males

Answer 1

Synthesize and secrete testosterone via actions of LH

Question 2

Functions of sertoli cells in males

Answer 2

Spermatogenesis via actions of FSH and testosterone

Secrete inhibin —> negative feedback on pituitary

Question 3

Spermatogenesis begins at ______ with spermatogonia; full development takes ~2 months. Spermatogenesis takes place in the ______

Answer 3

Puberty; seminiferous tubules

Question 4

Spermatogenesis produces ______ that undergo spermiogenesis, which produces mature _______

Answer 4

Spermatids; spermatozoan

Question 5

3 phases of spermatogenesis

Answer 5

1. Mitotic divisions (spermatocytogenesis) — proliferative phase at puberty; mitotic cycles increase and spermatogonia divide to produce daughter spermatogonia. After last division, resulting cells are called primary spermatocytes
2. Meiotic divisions (production of haploid gametes) — primary spermatocytes undergo 2 meiotic divisions, in the end producing 2 spermatids, each with haploid number of unduplicated chromosomes
3. Spermiogenesis (maturation) — nuclear and cytoplasmic changes produce mature spermatozoa

Question 6

Actions of LH and FSH in males

Answer 6

LH acts on leydig cells to promote testosterone synthesis

FSH acts on sertoli cells to maintain spermatogenesis

Question 7

Functions of testosterone in males

Answer 7

Differentiation of epididymis
Pubertal growth spurt
Cessation of pubertal growth spurt
Libido
Spermatogenesis in sertoli cells
Deepening of voice
Increased muscle mass
Growth of penis and seminal vesicles
Negative feedback on anterior pituitary

Question 8

Actions of dihydrotestosterone in males

Answer 8

Differentiation of penis, scrotum, and prostate

Male hair pattern

Male pattern baldness

Sebaceous gland activity

Growth of prostate

Question 9

Action of inhibin in males

Answer 9

Inhibits secretion of FSH from anterior pituitary

Question 10

Condition characterized by failure to complete puberty d/t defective migration of GnRH cells and formation of olfactory bulb —> decreased synthesis of GnRH in the hypothalamus, anosmia, and decreased levels of GnRH, FSH, LB, and testosterone

Answer 10

Kallman’s syndrome (hypogonadotropic hypogonadism)

Question 11

Clinical manifestations of Kallman’s syndrome

Answer 11

Infertility (low sperm count in males; amenorrhea in females)

Question 12

Condition characterized by dysgenesis of seminiferous tubules resulting in decreased inhibin and increased FSH, as well as abnormal leydig cell function —> decreased testosterone —> increased LH —> increased estrogen

Answer 12

Klinefelter’s syndrome

Question 13

Clinical manifestations of Klinefelters syndrome

Answer 13

Testicular atrophy, eunichoid body shape, tall, long extremities, gynecomastia, female hair distribution

Question 14

Phases of ovarian cycle and associated hormone changes

Answer 14

Follicular phase (days 0-14) — increased etradiol, low progesterone, low FSH and LH

Ovulation (day 14) — burst of estradiol synthesis has positive feedback effect on secretion of FSH and LH. Ovulation occurs d/t estrogen-induced LH surge

Luteal phase (days 14-28) — corpus luteum produces estrogen and progesterone, decrease in LH and FSH, if fertilization does not occur, there is abrupt decrease in estrogen and progesterone resulting in menses

Question 15

Phases of endometrial cycle and their corresponding phases in ovarian cycle

Answer 15

Menstrual phase

Proliferative phase — corresponds to follicular phase in ovary

Secretory phase — corresponds to luteal phase in ovary

Question 16

Function of activins in females

Answer 16

Stimulatory effect on FSH release independent of GnRH action

Intraovarian action of stimulating the synthesis of estrogens

Question 17

Hormonal changes associated with menopause

Answer 17

Reduction in estrogen, low levels of inhibin

High levels of LH and FSH d/t lack of feedback inhibition

Question 18

Hormonal changes and their pathophysiological effects in the development of PCOS

Answer 18

Elevated LH, low FSH, elevated testosterone

High androgens promote atresia in developing follicles and disrupt feedback relationships

Enlarged polycystic ovaries are known to be associated with increased androgen levels (DHEA)

Question 19

Function of acrosomal reaction in fertilization process

Answer 19

Increase in Ca in sperm cell triggers fusion of outer acrosomal membrane with sperm cell’s plasma membrane and results in exocytosis of most of the acrosomal contents; allows spermatozoon to penetrate zona pellucida

Question 20

Function of cortical reaction in fertilization process

Answer 20

Cortical reaction initiated by increase in Ca inside oocyte —> massive exocytosis of cortical granules, releasing enzymes that act on glycoproteins in the ZP and cause them to harden

Purpose is to prevent polyspermy

Question 21

Explain how implantation occurs

Answer 21

Trophoblasts secrete proteases that digest outer lying zona pellucida = hatching of blastocyst

Blastocyst is able to adhere and implant into uterine endometrium

Eventually the trophoblasts differentiate into cytotrophoblasts (inner cell layer) and syncytiotrophoblasts (outer cell layer)

Question 22

Decidualization is the response of maternal cells (stromal cells) to ________, which causes endometrial stroma to transform into enlarged and glycogen filled decidual cells to prepare for implantation

Answer 22

Progesterone

Question 23

During pregnancy, hCG is produced by ________. hCG stimulates ____ receptors of the corpus luteum

Answer 23

Syncytiotrophoblasts; LH

Question 24

______ is similar to GH and prolactin and is also produced by syncytiotrophoblasts, contributing to diabetogenicity of pregnancy

Answer 24

HPL [HPL is also lactogenic]

Question 25

The uterus is quiet throughout pregnancy due to the hormones ____ and _____-

Answer 25

Progesterone; relaxin

Question 26

During parturition, estrogen increases the degree of uterine contractility and stimulates the synthesis of ____

Answer 26

Oxytocin

Question 27

________ are believed to initiate labor, while ____ plays a role in uterine contraction following fetal expulsion to limit blood loss

Answer 27

Prostaglandins; oxytocin

Question 28

______ softens and dilates the cervix during labor

Answer 28

Relaxin

Question 29

Describe the hormones and stimuli involved in initiation of lactation after birth

Answer 29

Increased prolactin

Decreased estrogen and progesterone

Suckling (inhibits hypothalamic dopaminergic neurons)

Oxytocin enhances milk ejection by stimulating contraction of myoepithelial cells