folliculogenesis

Question 1

what are the 2 parts of the ovary?

Answer 1

cortex and medulla

Question 2

what are the functions of the 2 sections of the ovaries?

Answer 2

cortex = gametogenic
medulla = supportive

Question 3

what differences are there between species and the arrangement of the 2 regions of the ovaries

Answer 3

bovine, ovine and porcine have the medulla on the inside.

equines have the cortex on the inside.

Question 4

what is folliculogenesis?

Answer 4

the development of ovarian follicles eligible for ovulation.

Question 5

what is oogenesis?

Answer 5

development of primary egg cells into a mature ovum which Is competent for fertilisation.

Question 6

what are the 2 stages of oogenesis?

Answer 6

prenatal.
after puberty ( during each cycle)

oogenesis occurs simultaneously with folliculogenesis.

Question 7

what is the aim of prenatal oogenesis?

Answer 7

to maximise the gametes, meaning to get a large pool of primary oocytes when born

Question 8

what are the stages of prenatal oogenesis?

Answer 8

Primordial germ cells (2N) (2N = diploid)
undergo mitosis
Oogonia (2N)
undergo mitosis again
Primary oocyte (2N)
undergo meiosis, prophase 1 begins
Primary oocyte (2N)
nothing more can happen until puberty
meiotic inhibitors cause nuclear arrest, prevent any more meiosis

Question 9

what occurs during post-puberty oogenesis ( each cycle)

Answer 9

cytoplasmic growth from the oocyte formation of Zona pellucida removes the meiosis inhibitors so meiosis can occur again
causing a secondary oocyte (1N) = Haploid.

Question 10

what occurs during post-puberty oogenesis ( each cycle)

Answer 10

cytoplasmic growth from the oocyte formation of Zona pellucida removes the meiosis inhibitors so meiosis can occur again ( LH surges)
causing a secondary oocyte (1N) = Haploid.

Question 11

what are the processes in the post-puberty oogenesis cycle?

Answer 11

a primary oocyte (2N) turns into a secondary oocyte (1N) via meiosis.
a polar body is added
the secondary oocyte ( after fertilisation) becomes a mature ovum via meiosis 2
second polar body is added

Question 12

what are the 4 stages of oocyte maturation

Answer 12

prenatal mitotic divisions
nuclear arrest
cytoplasmic growth
resumption of meiosis

folliculogenesis is essential to support these processes

Question 13

what are the first stages of folliculogenesis?

Answer 13

An oogonia has no follicle.

The primary oocyte will have granulosa cells around it and a primordial follicle

A primordial follicle is immature and flattened granulosa cells

Question 14

what happens next in folliculogenesis, after the primordial follicle?

Answer 14

Still on the primary oocyte, a primary follicle develps

the primary follicle consists of cuboidal granulosa cells

Question 15

what occurs after the primary follicle is formed?

Answer 15

Still on the primary oocyte, the number of granulosa cells increases
theca cells develop
and a secondary follicle is developed.

The secondary follicle:
2 or more layers of granulosa cells
a small number of theca cells
Zona pellucida has an initial formation

Question 16

what occurs after a secondary follicle has developed?

Answer 16

on the primary oocyte, theca interna and theca externa have developed
there are lots of granulosa cells
there is now an antrum
this is what the tertiary follicle

Question 17

what occurs after the tertiary follicle is produced?

Answer 17

the oocyte has developed into a secondary oocyte.

the antrum is a lot bigger
developing into a preovulatory follicle
Graafian follicle
Mature

Question 18

when does each process take place?

Answer 18

prenatal pool
oogonia
primordial follicle

pre and post-puberty: not gonadotropic hormone dependent:
primary follicle
secondary follicle

post-puberty: gonadotropic hormone-dependent, throughout the oestrous cycle:
tertiary follicle
preovulatory follicle

Question 19

what are the antral follicle dynamics?

Answer 19

recruitement
selection
dominance
atresia (over 90% of follicles)

Question 20

what does growing follicles secrete?

Answer 20

secrete oestradiol
which increases as the follicle grows

Question 21

what are the 3 hormones responsible for folliculogenesis?

Answer 21

follicle-stimulating hormone (FSH)
luteinising hormone (LH)
oestradiol from follicle helps to control

Question 22

hormone levels during folliculogenesis?

Answer 22

recruitment = ++ FSH and +LH

selection = ++ LH and + FSH

dominance = +++LH and + FSH

Question 23

what is the role of granulosa cells?

Answer 23

FSH receptors
use androstenedione to produce oestradiol
(oestrogen)

Question 24

what is the role of theca cells?

Answer 24

LH receptors
Use cholesterol to produce androstenedione

Question 25

where does ovulation occur in the mare?

Answer 25

in the ovulation fossa

Question 26

where does ovulation occur in other animals?

Answer 26

in the ovarian surface

Question 27

how does ovulation occur?

Answer 27

triggered by the preovulatory surge of LH

LH causes:
increase bloodflow
ovarian contractions
connective tissue destruction

this increases follicular pressure and weakened and thinned follicle walls

leading to ovulaiton

Question 28

what is ovulation?

Answer 28

ovulation is the release of the ovum

for the ovum to undergo fertilisation and meiosis 2
and follicular fluid

Question 29

what occurs after ovulation?

Answer 29

corpus luteum forms post ovulaiton

first, corpus Haemorrhagicum forms
follicle walls collapse
theca, granulosa and connective tissue cells mix
blood vessels rupture
small blood clot in the cavity

Question 30

what happens next after the initial Corpus Haemorrhagicum forms?

Answer 30

corpus luteum will increase in size

Luteinisation of theca interna and granulosa cells

More structure to the luteal tissue than in early Corpus Haemorrhagicum

Active corpus luteum = red/ orange / yellow
produces progesterone
cholesterol = precursor

Question 31

what happens next after the initial Corpus Haemorrhagicum forms?

Answer 31

corpus luteum will increase in size

Luteinisation of theca interna and granulosa cells

More structure to the luteal tissue than in early Corpus Haemorrhagicum

Active corpus luteum = red/orange/yellow
produces progesterone
cholesterol = precursor

Question 32

what is the final stage of corpus luteum formation?

Answer 32

luteolysis breaks down the corpus luteum

corpus albicans are formed

no glandular tissue
scar tissue
light yellow / white