27. Reproductive Physiology Review Flashcards
Function of leydig cells in males
Synthesize and secrete testosterone via actions of LH
Functions of sertoli cells in males
Spermatogenesis via actions of FSH and testosterone
Secrete inhibin —> negative feedback on pituitary
Spermatogenesis begins at ______ with spermatogonia; full development takes ~2 months. Spermatogenesis takes place in the ______
Puberty; seminiferous tubules
Spermatogenesis produces ______ that undergo spermiogenesis, which produces mature _______
Spermatids; spermatozoan
3 phases of spermatogenesis
- 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
- 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
- Spermiogenesis (maturation) — nuclear and cytoplasmic changes produce mature spermatozoa
Actions of LH and FSH in males
LH acts on leydig cells to promote testosterone synthesis
FSH acts on sertoli cells to maintain spermatogenesis
Functions of testosterone in males
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
Actions of dihydrotestosterone in males
Differentiation of penis, scrotum, and prostate
Male hair pattern
Male pattern baldness
Sebaceous gland activity
Growth of prostate
Action of inhibin in males
Inhibits secretion of FSH from anterior pituitary
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
Kallman’s syndrome (hypogonadotropic hypogonadism)
Clinical manifestations of Kallman’s syndrome
Infertility (low sperm count in males; amenorrhea in females)
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
Klinefelter’s syndrome
Clinical manifestations of Klinefelters syndrome
Testicular atrophy, eunichoid body shape, tall, long extremities, gynecomastia, female hair distribution
Phases of ovarian cycle and associated hormone changes
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
Phases of endometrial cycle and their corresponding phases in ovarian cycle
Menstrual phase
Proliferative phase — corresponds to follicular phase in ovary
Secretory phase — corresponds to luteal phase in ovary
Function of activins in females
Stimulatory effect on FSH release independent of GnRH action
Intraovarian action of stimulating the synthesis of estrogens
Hormonal changes associated with menopause
Reduction in estrogen, low levels of inhibin
High levels of LH and FSH d/t lack of feedback inhibition
Hormonal changes and their pathophysiological effects in the development of PCOS
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)
Function of acrosomal reaction in fertilization process
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
Function of cortical reaction in fertilization process
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
Explain how implantation occurs
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)
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
Progesterone
During pregnancy, hCG is produced by ________. hCG stimulates ____ receptors of the corpus luteum
Syncytiotrophoblasts; LH
______ is similar to GH and prolactin and is also produced by syncytiotrophoblasts, contributing to diabetogenicity of pregnancy
HPL [HPL is also lactogenic]
The uterus is quiet throughout pregnancy due to the hormones ____ and _____-
Progesterone; relaxin
During parturition, estrogen increases the degree of uterine contractility and stimulates the synthesis of ____
Oxytocin
________ are believed to initiate labor, while ____ plays a role in uterine contraction following fetal expulsion to limit blood loss
Prostaglandins; oxytocin
______ softens and dilates the cervix during labor
Relaxin
Describe the hormones and stimuli involved in initiation of lactation after birth
Increased prolactin
Decreased estrogen and progesterone
Suckling (inhibits hypothalamic dopaminergic neurons)
Oxytocin enhances milk ejection by stimulating contraction of myoepithelial cells
