Reproduction Flashcards
How many oocytes are formed in embryonic development?
How many remain by birth?
How many are released into the fallopian tubes?
5 million form in embryonic development
0.5 million by birth
500 released into fallopian tubes
Primordial oocyte features
Quiescent
Incomplete meiotic division
lined by squamous follicle cells on basal lamina
Primary oocyte
Enlarged cuboidal follicle cells - form granulosa cells
Active and dividing
Striatum granulosum makes oestrogen
External stromal cells form thecal cells - Theca internal and theca externa
Theca interna makes androgens
Surrounded by zona pellucida
Secondary follicle
Stratum granulosa thickens; forms corona radiata
Antrum appears
Cumulus oophorus - stalk suspends oocyte in antrum
Thecal cells - outermost
Ovulation
Graafian follicle - mature follicle
Released due to LH surge –> follicle ruptures, SM contracts to squeeze egg out
Survives for 24hrs unfertilised
Uterus histology
Perimetrium
Myometrium - 3 SM layers
Endometrium - ciliated and secretory simple columnar cells
Cervix histology
Endocervix - Simple columnar epithelium, glandular
Ectocervix - Stratified squamous epithelium
Cervical transformation zone histology
Simple squamous epithelium and cervical glandular epithelium
Reproductive years - junction at external os
Oestrogens - expansion of cervical stroma - eversion of columnar epithelium near external os and exposure to hostile vaginal environment - metaplasia into durable stratified squamous epithelium
Location of boundary changes over menstrual cycle
Increased risk of tumerous change
Terminal duct lobular unit
Acini and intralobular collecting duct. Form functional metabolic unit
Leydig cells
Produce testosterone. Between seminiferous tubules
Sertoli cells
Support cells, in seminiferous tubulous. Fluid –> fluid flux
Origin of epididymis and vas deferens
Wolffian (mesonephric) duct
Clitoris histology
2 extra masses of cavernous tissue not present in males - bulbs of clitoris. Function unknown.
Fibrocystic change
Benign
Common - almost considered physiological
Mid-late reproductive years
Variable dilation of ducts - cysts may form
Fibrosis, adenosis (acini proliferation), apocrine metaplasia (epithelial cells become pink and granular)
Lumps may result from fibrosis/cysts
High pathogenic HPV types
16 and 18
HPV oncogenic potential
E6/E7
Role of E2 in HPV
E2 encodes transcription factor which suppresses E6/E7
If there is a break in HPV DNA as it integrates into the host genome - dysregulation of E6/7
E6 binds p53 - deactivation
E7 binds Rb
Results in uncontrolled proliferation of squamous epithelial cells
Spermatogenesis
Spermatogonia (present in foetal life)
Mitosis - 2 daughter cells; 1 remains on outer edge, replacing germinal stem cells. Other moves towards lumen.
Daughter spermagonium divides by mitosis to again - 2 spermagonia
Spermagonia divide by mitosis - primary spermatocytes
First meitotic division - secondary spermatocytes
Secondary meitotic division - spermatids
Maturation - spermatozoa
Production of sex hormones
Testes - testosterone, DHT (dihydrotestosterone)
Ovary - oestrogen, progesterone
Adrenal gland - Small amounts of sex steroids
Regulation of sex hormones - male
Hypothalamus - GnRH
Anterior pituitary - FSH and LH
FSH acts on Sertoli cells - Inhibin (Keep FSH/testosterone levels in check via negative feedback to anterior pituitary), Spermatogenesis, androgen-binding protein (required to bind testosterone)
LH acts on leydig cells - Testosterone
Nutrients in semen and source
Seminal vesicles - fructose and vitamin C
Prostate - citric acid
Epididymis - Carnitine
Testosterone
Before birth - sexual differentiation; promotes testicular descent
Continuous secretion from puberty - sex drive, control of gonadotropin secretion, secondary sexual characteristics, protein anabolic effects, bone growth and closure of epiphysis, sebaceous gland secretion
Oestrogen
Breast developmetn and body fat distribution
Adrenal androgens
Hair growth and libido
Oogenesis
Oogonium divide - primary oocytes
Primary oocytes - arrest in first meiotic division
After puberty - 1 primary oocyte reaches maturity and ovulated 1ce a month
Primary oocyte complets first meiotic division prior to ovulation - secondary oocyte
Secondary oocyte completes second meiotic division after fertilization - mature ovum
Menstrual cycle - phases
Follicular/proliferation phase
Ovulation
Luteal/secretory phase
Early-mid follicular phase
Hypothalamus secretes GnRH - FSH and LH from anterior pituitary
LH - thecal cells to produce androgens
FSH - granulosa cells to convert androgens in estrogen
Oestrogen - negative feedback to hypothalamus and AP; positive feedback to granulosa cells
Late follicular phase and ovulation
High oestrogen levels - negative feedback switches to positive feedback at the hypothalamus
Granulosa cells produce inhibin - negative feedback on FSH
Granulosa cells also produce small amount of progesterone (positive feedback on GnRH and LH)
Early to mid luteal phase
Corpus luteum - high oestrogen, progesterone and inhibin
Negative feedback at hypothalamus and pituitary
Endometrium maintained
Cervical mucus thick, sticky and viscous
Increased basal body temperature
Late luteal phase
Corpus luteum dies - decreased estrogen and progesterone
Blood vessels constrict - decrease trophic support of endometrium - dies and sloughs off - menses
Loss of negative feedback - Increased FSH and LH
Cycle begins again
Fertilisation
Ovulation Day 1 - fertilisation (sperm capacitation in vagina, swims upstream, reaches oocyte in fallopian tube, acrosomal reaction - digests zona pellucida and cell junctions, membranes fuse, sperm nucleus enters, cortical reaction blocks polyspermy, nuclear fusion - zygote produced, 2nd meiotic division completed producing polar body) Day 2-4 - Cell division Day 4-5 blastocyst reaches uterus Day 5-9 Blastocyst implants
Critical weeks
Early pregnacy (weeks 1-2) - not susceptible to teratogens, susceptible to chromosomal abnormalities Embryonic period (weeks 3-8) - major organs develop. Susceptible to teratogens. Foetal period (week 9-40) - affected by genetic and environmental factors (multiple, pregnancy, maternal under nutrition, oxygenation, placental function, smoking, alcohol etc)
