HIstology of Female Reproductive Tract Flashcards
2 main roles of the ovary?
produce gametes (oogenesis) produce steroids (oestrogens and prgesterone, mainly progesterone)
general structure of ovary?
inner medulla (core) containing loose connective tissue, contorted arteries, veins and lymphatics and is continuous with the hilum of the organ
outer cortex containing scattered follicles in a highly cellular connective tissue stroma
outer shell of cortex is a dense connective tissue layer called the tunica albuginea which is covered by single layer of cuboidal cells called germinal epithelium
blood supply to ovary?
group of helicine arteries enter the hilum from the broad ligament and supply blood to the organ
outermost layer of ovary?
superficial fibrous cortex (tunica albuginea) covered by germinal epithelium
where do germ cells originate?
invade ovaries from the yolk sac around week 6 and proliferate by mitosis to form oogonia
these cells will undergo development and division via meiosis to from mature oocytes which are termed ova
what is oogenesis?
development of oocytes from oogonia
what is folliculogenesis?
growth of the follicle which consists of oocyte and any associated support cells
describe the number of germ cell present at each stage of life
6 week embryo = 1700 (germ cells) 7 month foetus = 5,000,000 (oogonia) birth = 1,000,000 (primary oocyte) puberty = 500,000 (all types of follicles) menopause = few left
what is the process of loosing oocytes and oogonia called?
atresia (apoptosis based)
not all follicles progress to full development, true to false?
before birth, meiosis begins in oocytes but halts at prophase 1
if the oocyte undergoes further development, meiosis with restart but many will remain in this state for several decades
how does the number of follicles which restart development each day change with age?
in a 20 year old = around 15 follicles restart development every day
drops to around 1 per day in a 40 y/o
describe histology in primordial follicle
primary oocyte surrounded by follicle cells (pregranulosa cells)
stroma cells fill space in between oocytes/follicle cells
describe primary follicle?
cuboidal granulosa cells surround the follicle (zona granulosa)
the oocyte has enlarged inside the follicle and a layer of special extracellular matrix (zona pellucida) is beginning to form between the oocyte and granulosa cells
how does the primary follicle change with development?
granulosa cell layer proliferates
inner layers of the adjacent stromal cells (theca folliculi) transform to form a layer called the theca interna which will go on to secrete oestrogen precursors which will be converted to oestrogen by granulosa cells
outer layer remain fibroblast-like and form the theca externa
describe the secondary follicle?
follicle enlarges further and a follicular fluid filled space called the antrum forms and enlarges in the granulosa cell layer forming a secondary follicle
overall the follicle enlarges as the antrum enlarges and the granulosa and thecal layers (interna and externa) continue to proliferate
how is the dominant follicle chosen and what happens?
one day before ovulation, the oocyte in the largest graafian follicle (largest antral follicles) will be selected
this will complete meiosis 1 and produce one secondary oocyte (similar size to primary oocyte) and one tiny polar body (carries 2nd nucleus away to degenerate)
secondary oocyte begins 2nd phase of meiosis but stops at metaphase 2
only complete meiosis to become fully mature oocyte after it has been released (ovulation) and fertilized by a sperm (producing a 2nd polar bodY)
