Week 6 Flashcards
What commonalities are found between both sexes?
- Formation of gametes
- Hypothalamic pituitary control of reproduction
Gametogenesis
Gametes with 23 chromosomes are produced from cells in gonads with 46 chromosomes.
What process does gametogenesis include?
Meoisis
Mitosis
DNA replicated once and cells undergo division once
Meiosis
DNA replicated once and cells undergo division twice
Where is GnRH secreted from?
Hypothalamus
How is GnRH secreted?
In pulses from neuroendocrine cells in hypothalamus. It is regulated by hormonal feedback and higher brain centers. The pulse frequency/amplitude changes during development.
Where do sperm further mature after production?
epididymis
In males, what is overlapping between the reproductive system and urinary system?
Urethra
Where are sperm produced?
Testis
Two types of cells in testis
Sertoli and Leydig cells
Sertoli cells
Also called sustentacular cells. They support sperm development.
Leydig cells
Also called interstitial cells. they secrete testosterone.
What cells create tight junctions?
Sertoli cells; they are responsible for blood-testis barrier.
Spermatogenesis
- Following mitosis, one spermatogonium stays to produce more.
- The other cell begins to undergo meiosis forming spermatocytes.
- Four speramtids produced from 1 starting cell.
- Spermatids mature into spermatozoa.
- Lose cytoplasm and gain a tail.
- 4 and 5 called spermiogenesis.
Where is the acrosome derived from?
Golgi apparatus
What does the acrosome contain?
Hyaluronidase and acrosin
What do hyaluronidase and acrosin do?
Breakdown the zona pellucida, a glycoprotein coat that covers the oocyte.
Parts of spermatozoa
Head (contains acrosome, nucleus and centrioles), Mid pice (Mitochondrial spiral), Tail - also called flagellum (Microtubules)
What are the secretions of accesory glands in sperm?
Water, Mucuos, buffer (to neutralize urine), Nutrients, Enzymes, Zinc, Prostoglandins(Smooth muscle contration)
What is in semen
Spermatozoa (1%) and secretions of accesory glands
What nutrients are present in semen?
Fructose, Citric acid, Vitamin C, Carnitine
Exocrine glands in male reproductive system
Seminal vesicles, Prostate gland and bulbourethral gland
Role of FSH in male reproductive system
- FSH stimulates sertoli cells
- LH stimulates Leydig cells
What happens after FSH stimulates Sertoli cells?
- Sepport sperm development
- Secrete inhibin (inhibits FSH release)
- Secrete androgen binding proteins (helps to concentrate androgens in testis)
What happens after LH stimulates leydig cells?
Secretes testosterone in reponse to LH
Testosterone secretion through life
fetal - moderate levels
between - 0
neo-natal- moderate levels
pre-pubertal-0
pubertal-rising
between pubertal and adult - high (peaks)
a=between adult and senescence - lowers
Sertoli cell levels - comparison between childhood and puberty
childhood - majority of testicular volume sertoli cells
puberty - majority germ cells
Hypogonadism
- decreased functional activity of testes
- decreased production of androgens, inhibin B, AMH and/or impaired sperm production
Primary hypogondism
high GnRH, High LH and FSH, problem with testis - low testosterone
Secondary hypogonadism
problem with hypothalamus - low GnRH, low LH and FSH, low testosterone
Testosterone function - sex specific tissues
- promtoes spermatogenesis
- Maintains and stiulates secretion from prostate and seminal vesicles
- Maintains reproductive tract
Testosterone function - other reproductive functions
- increase sex drive
- negative feedback effects on gnRH, LH (and FSH) secretion
Testosterone function - secondary sex charecteristics
- Male pattern of hair growth (including baldness)
- promotes muscle growth
- increases sebaceous gland secretion
Testosterone function - non reproductive effects
- protein synthesis
- increases agression
- stimulates erythripoiesis
What can be used to treat benign prostate enlargement and male pattern baldness?
inhibitors of 5 alpha-reductase (Finasteride)
How are oocytes produced?
Oogenesis
What happens before birth in oogenesis?
before birth, the oogonia will enter meiosis 1 - duplicate their DNA and STOP - at birth they have primary oocytes
What happens after puberty in oogenesis?
After puberty, one primary oocyte completes meiosis I and enters meiosis II to become a secondary oocyte every ~28 days.
When is the secondary oocyte released?
Ovulation
Difference between oogenesis and spermatogenesis
- Assymetric cell division - only one secondary oocyte produced from each oogonium
- Limited duration (no oocyte production after menopause)
- Limited number of primary oocytes
What does maturation cycle do with follicles?
Maturation cycle recruit 5-10 follicles in eahc ovary, only one will fully mature. remaining oocytes undergo atresia
When does secondary oocyte complete meiosis II?
Completes meiosis II only if it is fertilized (stops in metaphase II)
atresia
hormonally regulated cell death
What happens to polar bodies
they disintegrate; they do not have enough cytoplasm
What surrounds oocyte in stasis until puberty
primary follicles
Main types of cells in the follicle
Granulosa and theca cells
What are granulosa cells’ roles?
Support oocyte development
Follicular phase of ovarian cycle
- Small number of primordial follicles develop.
- They become a primary follicle with theca and granulosa cells. Thecal cells synthesize androgens which are converted to estrogens in granulosa cells.
- Some follicles develop into secondary follicles.
- An antrum filled fluid cavity forms. Fluid contains hormones and enzymes. Structure now called a tertiary follicle.
- Dominant (graafian) follicle develops.
- graafian follicle ruptures, oocyte released into fimbria, and ovulation occurs.
What are theca cells’ roles?
Secrete steroid hormone precursors
What are the two main components of the menstrual cycle?
Ovariana and uterine cycles
What do androgens released by thecal cells convert to? Where do they convert?
Androgens released by thecal cells are converted to estrogens in granulosa cells.
What do follicular cells release during an LH surge?
Collagenase (connective tissue digested)
Progesterone (smooth muscle contraction)
What is taken up by fingers of fimbria?
Oocyte and surrounding cumulus cells expelled into abdomen
Luteal phase of ovarian cycle
- Follicular cells left behind become corpus luteum.
- Corpus luteum releases estrogen and progesterone.
- if fertilization doe snot occur, corpus luteum degernates, the scar tissue remaining is called corpus albicans.
- If fertilization occurs, the corpus luteum continues to make progesterone and estrogen until the end of the first trimester.
Corpus luteum
Follicular cells left behing in ovary become crps luteum
What does corpus luteum release
Estrogen and progesterone
Corpus albicans
After corpus luteum degenerates, the scar tissue remaining is called corpus albicans. it is fibroblast connective tissue.
3 parts of uterine cycle
menses, proliferative phase,, secretory phase
Menses
Blood vessels supplying the endometrium undergo constriction causes shedding of the endometrial lining because of declining levels of progesterone and estrogen.
Proliferative phase
Endometrium develops in response to estrogen, the endometrial lining thickens as the blood supply to the tissue is re-established and cells proliferate.
Secretory phase
Glands in endometrium secrete more viscous fluid. Endometrial cells deposit lipid and glycogen in the cytoplasm under the influence of progesterone and estrogen.
What phase occurs because of corpus luteum?
Luteal phase
Ovarian cycle and uterine cycle overlap
Follicular phase - menstrual and proliferative phase
luteal phase - secretory phase
Early to mid follicular phase
- LH stimulates the release of androgens from theca cells.
- FSH stimulates conversion to estrogen by granulosa cells.
3 Granulosa cells also secrete AMH which prevents recruitment of additional follicles. - Estrogens exert positive feedback on granulosa cells, increasing proliferation, increasing estrogen.
- Estrogens exert negative feedback at pituitary and hypothalamus.
- Shuts down FSH and Lh
Late follicular phase and ovulation
- tertiary follicle present,
- Follicular cells secrete inhibin, progesterone and estrogen (inhibin inhibits FSH)
- Progesterone increases pituartary sensitivity to GnRH
- High estrogens increase frequency of GnRH pulses to one every 65 mins (+ve feedback)
- Causes Lh surge - trigger completion of meoisis 1 and ovulation
Early to mid luteal phase
- Corpus luteum under the influence of LH and FSH releases progesterone, inhibin and estrogen
- these hormones exert negative feedback at hypothalamus and pituitary
- progesterone and estrogen inhibit GnRH pulses
Late luteal phase
- intrinsic life span of corpus luteum is 12 days
- if fertilizaton does not take okace, corpus luteum undergoes apoptosis
- progesterone and estrogen levels fall
- reduced negative feedback at hypothalamus and pituitary returns GnRH pulss to one every 1.5 hour.
- Causes LH and FSH release.
Action of estrogens - sex specific tissues
- promotes follicular development and ovulation
- Stimulates growth of endometrium
- Maintains reproductive tract
Actions of estrogen - other reproductive effects
Negative feedbakc on GnRH, LH (and FSH) secretion
Actions of estrogen - secondary sex characteristics
- stimulates development and growth of breast tissue
- increases sebaceous gland secretion
Action of estrogen - non reproductive effecst
promotes fat deposition around hips and thighs
function of adrenal androgens in adult femailes
increses sex drive and pubic and axillary hair growth
What is the average age-related fertility decline at age 33?
About 25% less chance of successful pregnancy per cycle.
What decreases with age regarding oocytes and follicles?
viability and genetic quality of oocytes.Number of follicles
Menopause
end of the female reproductive cyle
What happens in menopause
- ovaries lose their ability to respond to FSH and LH
- Estradiol and progesterone levels fall
- Lack of negative feedback causes FSh and LH to rise.
What do sperm undergo in order to become hyperactive
capacitation
what binds to sperm
albumin, enzymes and lipoprotein
what happens when albumin, enzymes and lipoprotein bind to sperm
- glycoprotein coat removed
- intracellular changes
- develop strong whip like motion
how do sperm reach oocyte
chemotaxis (progesterone from cumulus cells)
What contraction aid sperm transport
uterine and oviduct contractions
Fertilization
- Sperm docks with sperm binding proteins on oocyte membrane.
2, trigger depolarization of oocyte. - fusion of cortical granules 9oocyte intracellular vesicles) with router membrane
- coat fertilized oocyte and prevent penetration by additional sperm ( prevents polyspermy)
How do sperm tunnel through barriers a
acrosomal enzymes
Hormone secreted from trophoblast
Homun Chorionic gonadotropin
What happens after fertilization
- Cell division takes place
- blastocyst (contains trophoblast) reaches uterus and implants
What does human chorionic gonadotropin do
takes over from pituitary to maintain corpus luteum and prevent next menstrual cycle. similar in structure to Lh and basis of pregnancy tests.
Placenta
performs role of digestive, repiratory and renal systems for the fetus
what keeps endometrium intact
progesterone
what mainatins copus luteum
human chorionic gonadotropic hormone
what does placenta aid in exchange of
nutrients/was6e, oxygen/carbon dioxide, proteins, chemicals, etc
How do fetal corionic villi transfer gases and solute between mother and fetus
maternal vasculature not physically linked to fetal vasculature
Maternal blood forms a lacunae
temporary endocrine gland
palcenta
human placental lactogen
human chorionic somatomammotropin
trend similar to estrogena nd progesterone in preganancy
Secretion of progesterone. by placenta
Cholestrol from mother’s blood gets converted to progesterone in placenta and released from there
secretion of estrogen by placenta
cholestrol from mother’s blood travels trhough placenta then fetal blood then fetal adrenal cortex, gets converted to DHEA there, reaches placenta, gets converted to estrogen and it is released.
function of human placental lactogen
- structually related to growth hormone and prolactin
- high in mother, low in fetis
- decreases maternal cellular uptake of glucose. ehances maternal lipolysis
Maternal adaptations to pregnancy
- renal: increased vasopressin levels increase blood volume; increased activity RAS sodium and fluid retention
- cardiovascular: increased output
- immune system: partially suppressed
4: calcium homeostasis: preganacy associated with hyperparathyroidism, calcium transfer ti fetus, increases calcitonin to limit mobilization of maternal bone
labour trigger s
↑ Estrogen & oxytocin receptors in
uterus increase
↑ Fetal cortisol
↑ Placental corticotropin-releasing
hormone (CRH)
↑ Prostaglandins
How is labour triggered?
Before parturition, relaxin released from ovary and placenta
loosens the ligaments in the pelvic bone and cause the cervix to
soften
Hormones necessary for breast milk - before parturation
Estrogens and
progesterone needed for
the development of
mammary glands but
inhibit milk production
Hormones necessary for breast milk - after parturation
prolatin - epithelial milk prodcuing cells
oxytocin- myoepthelial cells
