repro physiology Flashcards
levels of sexual dimorphism
genetic sex, gonadal sex, phenotypic sex
important genes in the Y chromosome
86 genes - impt is SRY (sex region Y) gene coding for TDF (testes determining factor) and also SOX9 (less important)
development of male genitalia
TDF activated at week 6 –> Sertoli cells produce Mullerian inhibiting substance –> Mullerian duct regression
TDF activated at week 6 –> Leydig cells produce testosterone –> Wolffian duct develops into male internal genitalia (vas deferens, seminal vesicles, epididymis, efferent ducts, ejaculatory ducts)
testosterone converted by 5α-reductase to DHT (dihydrotestosterone) –> development of male external genitalia (penis, scrotum, prostate gland, penile urethra, prostatic urethra)
important genes in female genital development
FOXL2, WNT4, FST (not that impt lah)
development of female genitalia
no Y chromosome –> no TDF –> no Leydig cells –> Wolffian duct regression
no Y chromosome –> no TDF –> no Sertoli cells –> no MIS –> Mullerian duct development –> female internal genitalia (uterus, fallopian tube, upper 2/3 of vagina)
ovary exists –> production of estradiol/estrogen –> female external genitalia (clitoris, labia minora, labia majora, lower 1/3 of vagina)
Turner syndrome cause and presentation
cause: X0 (only 1 X chromosome) - 1/2500 births
presentation:
• no gonadal development
• born phenotypically female
• underdeveloped gonadal structures –> little estrogen production –> poor breast development, no menstruation, infertile
• short stature, usually low IQ
Klinefelter’s syndrome cause and presentation
cause: XXY genotype - 1/700 births
presentation:
• normal testicular function + testosterone + MIS
• sexually underdeveloped due to extra chromosome
• infertile, small testes, decreased sperm production
• taller (insufficient testosterone –> late closure of growth plates)
• low IQ
Triple X syndrome cause and presentation
cause: XXX (non disjunction error)
presentation:
• normal physical development and no major medical problems
• decreased IQ
• risk of epileptic seizures
disorders causing true hermaphroditism
true hermaphroditism: gonadal tissue and germ cells of both sexes present
causes: XX (2/3 of patients), X0 / XY (1/3 of patients) due to mosaicism during gonadal development
disorders causing pseudohermaphroditism
pseudohermaphroditism: carries sex organs of one gender but looks like opposite gender
causes: androgen insensitivity syndrome, 5α-reductase deficiency
components of the female reproductive system
ovary, fallopian tube, vagina, uterus
describe the regulation of female sex hormones
GnRH (from hypothalamus) –> LH and FSH (from anterior pituitary)
LH –> testosterone (from theca cells) + estrogen and progesterone (from granulosa cells)
FSH –> estrogen and progesterone (from granulosa cells)
negative feedback inhibition of female sex hormones
estrogen inhibits anterior pituitary (FSH and LH) and inhibits hypothalamus (GnRH)
inhibin inhibits anterior pituitary (FSH and LH)
types of estrogen
E1: estrone
E2: estradiol (most reactive)
E3: estriol (supports pregnancy)
functions of estrogen
- development of ovaries, fallopian tubes, uterus, vagina, external genitalia
- secondary female sexual characteristics
- folliculogenesis
- lipid and protein metabolism (anabolic)
- libido
- stimulate bone growth
- inhibit lactation
- control menstrual cycle and maturation of sperm in men
- puberty
functions of progesterone
- promotes secretory changes in uterine endometrium
- reduce maternal immune response
- decrease contractility of uterine smooth muscle
- promotes development of lobules and alveoli of breasts
- inhibits lactation
- decreases libido
progress of folliculogenesis
primordial follicle - (enlarge) -> primary follicle - (zona pellucida, theca interna and externa) -> secondary follicle - (single fluid-filled antrum) -> Graafian follicle –> OVULATION: oocyte + corpus luteum -(degenerates)-> corpus albicaans
parts of the ovarian cycle
follicular phase, ovulation phase, luteal phase
parts of the uterine cycle
menstruation (7 days), proliferative phase (7 days), secretory phase (14 days)
hormone levels during the menstrual cycle
14: LH SURGE stimulating ovulation (FSH surge is smaller)
15-26: surge of estrogen first (inhibits FSH and LH with inhibin) by corpus luteum followed by progesterone surge, estrogen proliferates endometrium and progesterone maintains it, LH creates corpus luteum
27-28: decrease in estrogen and progesterone production by corpus luteum, endometrium starts to necrose
1-7: loss of negative feedback from estrogen causes increased FSH and LH, no progesterone = endometrium sheds
8-14: gradual increase in estrogen bc of FSH and LH causes endometrium proliferation, super high estrogen levels cause positive FSH and LH feedback and LH SURGE
changes during puberty in females
• at 9-12 yo
• thelarche, pubarche, menarche
• increased GnRH secretion by hypothalamus
changes during menopause in females
• 40-50yo
• ovulation fails to occur and menstrual cycle becomes irregular then ceases
• production of estrogen by ovaries decreases
• loss of estrogen: hot flushes, psychological and emotional changes, insomnia, breast/uterine/vaginal atrophy, increased risk of CVS disease and osteoporosis
primary vs secondary amenorrhea
primary: failure of onset of menstrual cycle by age 16
secondary: absence of menstrual cycle for 6 months
causes of female infertility
Turner’s syndrome, hypogonadotropism, hyperprolactinemia
fertilisation definition
fusion of 2 haploid gametes to produce a diploid zygote
adaptations to encourage fertilisation
mobility of sperm tails, contraction of uterus and oviducts, chemical attraction of sperm to ovum
sperm pH changes after leaving testes
- maturation after leaving testes (pH 7.4)
- stored in epididymis (pH 6.5)
- ejaculation in seminal plasma (pH 6.9)
- capacitation to enter oviduct (pH 7.4)
acrosome reaction trigger and result
sperm dissolutes granulosa cells layers and penetrates zona pellucida by releasing acrosomal enzymes –> redistribution of membrane constituents, increased membrane fluidity and permeability of sperm acrosome head to penetrate zona pellucida
steps in the fertilisation process
- sperm cell approaches egg
- contact between sperm and zona pellucida
- sperm enters zona pellucida and contacts oolemma
- second meiotic division of oocyte
- completion of oocyte meiosis
- formation of male and female pronuclei
- migration and union of male and female pronuclei
- zygote then begins first meiotic division
process of fertilized ovum implantation
day 3-5: ovum goes through fallopian tube into uterus, becoming blastocyst in the process
day 5-7: blastocyst implants in endometrium and syncytiotrophoblast secretes hormones
day 14: development of zygote starts
functions of the placenta
- nutritional: diffusion of nutrients from/to maternal and fetal blood
- endocrine: produce hormones estrogen, progesterone, relaxin, hCG, hPL to support pregnancy
- respiratory: oxygen from mom to fetus, carbon dioxide from fetus to mother (fetal HbF)
- immune: transports maternal antibodies (IgG) to fetal blood for passive immunity
- excretory: transports excretory products from fetus to mother for excretion
substances crossing the placenta
from mom to fetus: oxygen, water and electrolytes, carbs, lipids, amino acids, vitamins, hormones, antibodies, (some) drugs and viruses
from fetus to mom: carbon dioxide, water and urea, waste products, hormones
function of human chorionic gonadotropin (hCG) in pregnancy
produced by syncytiotrophoblasts in placenta, max amount at 10-12 weeks then decreases
1. binds to LH receptors on corpus luteum to prevent involution of corpus luteum
2. promotes progesterone production by placenta
3. promotes testosterone production by fetus (for sex differentiation)
detectable in urine and used for urinary pregnancy test (30 days after last menstrual period)
function of estrogen and progesterone in pregnancy
both produced by corpus luteum from weeks 1-8, then produced by syncytiotrophoblasts in placenta
estrogen (estriol):
1. enlargement of mother’s uterus and breasts
2. enhances progesterone and oxytocin functions
3. encourages fetal development
progesterone:
1. support pregnancy
2. decidual cell development in uterine endometrium
3. decreases contractility of pregnant uterus
4. suppresses maternal immunologic responses
function of human chorionic somatomammotropin (hCS)/human placental lactogen (hPL) in pregnancy
produced by syncytiotrophoblasts in direct proportion to weight of placenta
- promotes breast growth to prepare for lactation
- weak actions on GH to form protein tissue
- supports fetal nutrition (decreased insulin sensitivity in mother and increased release of fatty acids in mother)
function of prolactin in pregnancy
promotes development of breasts and regulates milk production
function of relaxin in pregnancy
softens cervix of pregnant woman during delivery, loosens connective tissues of pelvis
maternal adaptations during pregnancy
- CVS: increased blood volume, RBCs and cardiac output, increased coag factors and active bone marrow
- respi: increased ventilation with decreased arterial pCO2, uterus compressed diaphragm to decrease total diaphragm excursion
- renal: increased GFR + increased reabsorptive capacity of electrolytes and water
- GIT: smooth muscle relaxation and decreased motility
- enlargement of sexual organs
- weight gain
- metabolism
- endocrine system
hormonal control of parturition
prostaglandins: activated by phospholipase A2 to stimulate uterine contractions, cervical dilation
progesterone: PREVENTS release of phospholipase A2 to suppress uterine contractions but is opposed by estrogen
oxytocin: causes uterine contractions, lactation, social behaviour, inflammation and wound healing
relaxin: encourages cervical ripening and softens pubic symphysis
what are Braxton Hicks contractions?
periodic episodes of weak and slow rhythmical contractions
describe the positive feedback loop of hormones during partuition
estradiol from placenta readies the uterus to respond to oxytocin + fetus head pushes against cervix to send stimulatory signals to hypothalamus –> hypothalamus stimulates oxytocin secretion from posterior pituitary –> oxytocin stimulates stronger uterine contractions + prostaglandins from uterus also enhance contractions
what are the 3 stages of labour?
- cervical dilation: 3cm-10cm cervix, lasts for 8-10h in first pregnancy
- fetal expulsion: fully dilated cervix to baby birth
- placental expulsion: fetal expulsion to delivery of placenta, lasts for 10-15min
hormonal control of lactation
estrogen: stimulates growth of mammary glands, inhibits milk secretion (sudden reduction after birth triggers milk production)
progesterone: converts terminal alveolar cells into secretory cells to make milk, inhibits milk production (sudden reduction after birth triggers milk production)
prolactin: stimulates alveolar cells to produce milk, inhibits GnRH (thus inhibiting menstruation and ovulation)
oxytocin: stimulates myoepithelial cell contraction to eject milk, triggered by suckling on nipple of breast
breastfeeding benefits
to baby: contains substances with antimicrobial/immunological properties, contains many nutrients, suckling and swallowing motions may reduce the risk of otitis media
to mother: reduce risk of cancer, type 2 DM, stress level etc, increase bonding with child and intervals between pregnancies
what are the three steps of spermatogenesis?
- proliferation (3-4 weeks): diploid spermatogonia divide by mitosis into primary spermatocytes
- growth (4 weeks): primary spermatocytes divide by meiosis 1 to become secondary spermatocytes, secondary spermatocytes divide by meiosis 2 to become spermatids
- maturation/differentiation (3 weeks): spermatids differentiate and elongate into spermatozoa in epididymis
parts of spermatozoa
head (contains acrosome and nucleus), midpiece (contains mitochondria), tail/flagella (provides motility for sperm)
describe the regulation of male sex hormones
GnRH secreted by hypothalamus –> stimulates release of LH and FSH from anterior pituitary gland
LH stimulates Leydig cells to release testosterone –> testosterone + FSH stimulate Sertoli cells to release estradiol, inhibin, activin, follistatin for spermatogenesis
testosterone inhibits secretion of GnRH (hypothalamus), LH and FSH (anterior pituitary)
inhibin and follistatin inhibit secretion of FSH (anterior pituitary) while activin stimulates secretion of FSH
functions of testosterone (8)
- development of internal and external genitalia before birth
- support spermatogenesis
- develop and maintain secondary sexual characteristics
- increases basal metabolism rate
- regulate libido
- negative feedback on hypothalamus and anterior pituitary
- promotes protein synthesis and muscle growth
- erythropoiesis and bone health
functions of dihydrotestosterone (DHT)
converted from testosterone by 5α-reductase enzyme
1. produces male external genitalia and prostate
2. produces male body/pubic hair
functions of luteinizing hormone (LH)
secreted by anterior pituitary gland to stimulate Leydig/Theca cells to secrete testosterone
functions of follicle-stimulating hormone (FSH)
secreted by anterior pituitary gland to stimulate Sertoli/Granulosa cells to produce hormones (estrogen+follistatin+activin+inhibin / estrogen+progesterone) for spermatogenesis/oogenesis
hormonal changes during puberty in male
usually occurs at 10-14yo
increased secretion of GnRH by hypothalamus –> increased secretion of FSH and LH by anterior pituitary –> LH causes testosterone secretion by Leydig cells + FSH causes spermatogenesis by Sertoli cells + FSH and LH cause increased GH secretion –> increased secretion of testosterone causes development of secondary sexual characteristics
causes of male infertility
Kallmann syndrome, Androgen Insensitivity Syndrome, 5α-reductase deficiency among others
Kallmann syndrome cause and presentation
cause: genetic mutations causing failure in function of GnRH –> insufficient production of LH/FSH/T/E
presentation: hypogonadotropic hypogonadism, absent puberty, infertile
Androgen Insensitivity Syndrome cause and presentation
cause: body cells insensitive to testosterone
presentation: genetically XY with testes present, female external genitalia with blind-ended vagina and lack of internal genitalia, infertile, primary amenorrhea, female secondary sexual characteristics
5α-reductase Deficiency cause and presentation
cause: mutation of 5α-reductase gene rendering it non-functional –> testosterone is not converted to DHT
presentation: genetically XY with testes present, range of (somewhat female) external genitalia, male internal genitalia, infertility, primary amenorrhea, male secondary sexual characteristics
