Developmental and Reproductive Biology Week 1

does the uterine system have direct contact with ovaries

no

what does the female duct/tube system include

1 vagina

1 uterus

2 uterine tubes (fallopian tubes)

where are the follicles located

cortex of ovaries

what is an oocyte

immature egg cell

how many oocytes in each follicle

1

What surrounds the oocyte in a primordial follicle

A single layer of flat follicle cells

what surrounds more mature follicles

multiple layers of granulosa cells

what structure forms in mature follicles

antrum

what happens to the oocyte in ovulation

it is expelled from the ovary

what happens to the follicle after ovulation

it becomes a corpus luteum

what is the HPG axis

a hormonal feedback loop that regulates reproduction and cycles

what organs are involved in the HPG axis

hypothalamus

pituitary gland

gonads

what are the 3 key events in the female reproductive tract

ovarian cycle (in ovaries)

menstrual cycle (in uterus)

changes in cervical mucus composition

what is the ovarian cycle

Monthly series of events associated with maturation of the ovum

what are the phases of the ovarian cycle

follicular phase

ovulaton

luteal phase

what is the follicular phase

period of vesicular follicle growth

when does the follicular phase occur

days 1-14

what is the luteal phase

period of corupus luteum activity

when does the luteal phase occur

days 14-28

what do ovarian follicles do

house and nurture developing oocytes

what causes the ovary wall to rupture in ovulation

rising levels of LH

what do granulosa cells respond to

FSH

what do granulosa cells secrete in response to FSH

estradiol and inhibin

what do theca cells respond to

LH

what do theca cells release in response to LH

androgens and progesterone

what does the corpus luteum secrete

progesterone + estradiol + inhibin

what is the corpus hemorrhagicum

a temporary structure filled with clotted blood

when does the corupus hemorrhagicum form

immediately after ovulation and before the corpus luteum develops

what happens to the corpus luteum if no pregancy occurs after 10-12 days

it regresses and becomes corpus albicans (scar tissue)

what happens to the corpus luteum if pregancy occurs

it is supported by HCG (human chorionic gonadotrophin)

what happens to gonadotrophins LH and FSH during the ovarian cycle

they both spike right before ovulation (LH spikes much more) and come back down

what happens to estrogen during the ovarian cycle

gradually rises and sharp peak right before ovulation, then another moderate rise due to corpus luteum

what happens to progesterone during the ovarian cycle

dramatic rise after ovulation and falls sharply if no pregnancy

what happens to inhibin during the ovarian cycle

small rise before ovulation and a larger rise due to corpus luteum

what is oogenesis

production of female gametes (oocytes/ova) in the ovaries

when does oogenesis begin

begins during fetal development

how many new ova are formed after birth

none

how many primordial follicules does the ovary contain at birth

around 2 million

how many of these follicules actually mature

only about 400-500 oocytes

when does female meiosis begin and end

begins at fetal stage

ends at time of fertilisation

what are primordial germ cells

diploid stem cell precursors of oocytes

what is an oogonium

when the primordial germ cell arrives in the ovary, it is called an oogonium

how many oocytes does each oogonium form via mitosis

2

what happens to primary oocytes in meiosis

they start meiosis and arrest in prophase 1 of meiosis 1

what happens to primordial follicules each month after puberty

5-20 primordial follicules grow into primary follicules

what is the difference between these primordial and primary folllicles

primary follicles have an extra layer of granulosa cells

extra outer layer of theca cells

what happens when primary follicles become secondary follicles

granulosa cells multiply and produce fluid, which creates the antrum

what is the zona pellucida

surrounds the primary oocyte

what is the corona radiata

the innermost layer of granulosa cells

what does the secondary follicle mature into

graafian follicle

what happens to the graafian follicle if fertilisation occurs

it becomes a mature ovum and degnerates its 2nd polar body

what does estrogen do

builds up endometrial lining

makes mucus fluid so sperm can pass to reach oocyte

what does progesterone do

maintains endometrial lining

what is menses/menustration due to

progesterone withdrawal due to corpus luteum dying

what are the phases of the menstrual cycle

menstrual phase (days 1-4)

proliferative phase (days 5-14)

secretory phase (days 15-26)

premenstrual phase (days 27-28)

what triggers the start of menstrual phase

lack of progesterone

what is the loss of blood due to

breakdown of superficial layers of uterine endometrium

how much blood is lost during menstruation

30-50ml of mainly arterial blood

how long does menstruation occur

3-6 days and often heavier on the 2nd day

what happens in the proliferative phase

FSH grows follicles and oocytes which produce estrogen

how does estrogen thicken the endometrium

it travels through blood to get to the uterus

what is the size of the uterine glands during the proliferative phase

small and round

what triggers corpus luteum formation

LH

what does the corpus luteum do in the secretory phase

produces progesterone and estrogen

what does progesterone and estrogen do in the secretory phase

maintains endometrial lining and enlarges glands

what do uterine glands do

secrete uterine milk

what is the size of the uterine glands in the secretory phase

elongated and coiled

what happens in the premenstrual phase

breakdown of glands

blood vessels leak

tissue death

what causes these outcomes of the premenstrual phase

lack of progesterone

what type of tissue is present on the luminal surface of the cervix

mucus secreting simple columnar epithelium

what type of tissue is present on the external surface of the cervix

moist non-keratinized stratified squamous epithelium

what is the transformation/transitional zone

area between columnar and squamous cells

how big is a cervix during ovulation

22m in length

6mm in diameter

where is cervical mucus released from

the cervix

why does cervical mucus change composition

in response to hormonal changes

what are the 2 major fractions of cervical mucus

insoluble gel/mucin

aqueous phase containing the soluble components

what are the soluble components

lipids, fatty acids, prostaglandins, proteins, enzyme inhibitors, and immunoglobulins

what type of barrier is cervical mucus

physical or immune barrier to pathogens

what is the cervical mucus composition during early follicular phase

mucus is thick and sticky

what is the cervical mucus composition during late follicular phase

copious, watery, thin & alkaline

has a fern-like pattern when dried on a slide

sperm can penetrate mucus

what is the dominant influence on cervical mucus composition during late follicular phase

estrogens

what is the cervical mucus composition during ovulatory period

mucus is thinnest and wet and clear at time of ovulation

has a arborizing fernlike pattern when dried on a slide

sperm can easily penetrate mucus

what is the cervical mucus composition during luteal phase

mucus is thick, viscous and cellular

mucus is scanty

no ferning pattern when dried

what is the dominant influence on cervical mucus composition during luteal phase

progesterone

where are the testes located

in the scrotum

what do septa (septum plural) do

divide testis into around 250 lobules

what does each lobule contain

1-4 seminiferous tubules

where do male gametes develop

in the seminiferous tubules

what does spermatogonia mature into

spermatozoa

how is sperm delivered to exterior

through a system of ducts

what is the path of sperm

Seminiferous tubules

Straight tubules

Rete testis

Efferent ductules

Epididymis

Vas deferens

ejaculatory duct

urethra

how long is the duct of the epididymis

around 6m in length

what happens in the seminiferous tubules

sperm production

what tissue lines the seminiferous tubules

complex stratified epithelium