Describe the life cycle of the porcine ovary (steps)
- primordial follicle
- primary follicle
- secondary follicle
- early antral follicle
- atretic follicle
- graafian follicle
- ovulation
- early corpus luteum
- mature corpus luteum
- corpus albicans
Describe the primordial follicle, stage of oocyte and influence
it has a central located oocyte and single layer of granulosa cells
- basement lamina
- dictyate oocyte
- granulosa cells
oocyte is in arrested meiotic prophase
Growth independent on gonadotropin
Describe the primary follicle, stage of oocyte and influence
follicle growth, proliferation of granulsa cells, zona pellusicda formation, theca cell differentiation
fully grown oocyte
growth is gonadotropin independent
Describe the secondary follicle, stage of oocyte and hormonal influence
follicle growt, increased number of granulosa cell layers
fully grow oocyte
dependent upon gonadotropins to grow
Describe early tertiary (antral) follicle
state of oocyte
Hormone relations
formation of the antrum, increased number of granulosa cells
fully grown oocyte
gonadotropin dependent growth, secretion of steroids by granulosa and theca cells
Which follicles have a Gonadotropin dependent growth?
Secondary follicle, early tertiary follicle
Secretions by theca and granulosa cells
Theca cells: androstendion
Granulosa cells: estradiol
Describe the structures present in a pre-ovulatory follicle
stage of the oocyte
Blood vessles inbetween the theca cells
basement membrane, granulosa cells
‘antrum with follicular fluid and
oocyte at metaphase II stage
What is the cause for the increasing progesterone level judt before the ovulation?
Just before the ovulation, the wall of the follicle has an increasing number of lutein cells growing - glutein patches
they produce progesterone
What is special about the pre-ovulatroy follicle? structurally
It has an antrum with follicular fluid
What hormones are found in the follicular fluid
estradiol in the follicular phase
progesterone at ovulation
Describe the Peri-ovulatory/luteinizing follicle
theca-luteal cells
increase vascularization
granulosa-luteal cells
disruption og basement membrane –> oocyte ovulating
What causes the oocyte to leave the follicle?
The increaseing pressure inside the follicle due to the increasing FF, the basement membrane ruptures and the oocyte is pushed out
Define follicle rupture
“flow out”
of a mature follicle and discharge of an oocyte into the oviduct
Why is the ovulation a inflammation like process?
There is structural changes
- the follicular wall will change
- there will be a dissolutionof the CT of tunica albuginea and theca interna
Canges in vascularization
- marked hyperemia and edema
- increased ovarian and follicular blood flow
- increased vascular permeability
proteolytic enzymes
- plasmin activating system
- collagenase
influence of prostaglandin
What is the cumulus-oocyte complex
the ovulated oocyte protected by a cloud of granulosa cells
What are the main elements of corpus luteum development
- preovulatory
- periovulatory
- post-ovulatory
preovulatory
- vascular elements
- granulosa cells
- thea cells
periovulatory
- hyperaemia
- enlargement
- lutein patches producing progesteron
post ovulatory
- increasing vascularization
- break of the theca-granulosa barier
- invasion of vascular elements into the luteal parenchyma
- dispersion of theca cells throughout the corpus luteum
What celltypes are present in the corpus luteum?
immune system cells
fibrocytes
large and small luteal cells
vascular cells
Define luteolysis
the process whereby the corpus luteum degenerates near the end of the nonfertile estrous cycle
What are the mechanisms regulating the lifespan of CL?
reduction of LH pulse of CL
increased estrogen production
influence of PGF2a
Difference of the secretion of LH in the luteal and follicular phase
follicular: LH is secreted in smaller concentration but in higher amplitude
luteal phase: LH is secreted in higher concentration but at lower amplitude
Length of the pig cycle
21 days
Define recruitment
the process wherin the follicle departs from the resting pool to begin a pattern of grwoth and development
Define selection
final winnowing of maturing follicular cohort by atresia down to a size equal to the species characteristic ovulatory quota
How many days does it take for the follicule to get to the preantral phase?
90 days
how many days does it take for the early antral phase to get to the antral phase?
14 days
Does pigs have 1 or 2 waves of LH?
1
During which phase does the recruitment occur?
during the luteal phase
During which phase does the selection occur?
Follicular phase
What is the dual function of the follicle?
steroidgenesis
gametogenesis
What is the FF?
serum transudate modified by follicular metabolic activities
Functions of the FF
- regulation of granulosa cell function, initiation of folliuclar growth and steroidgenesis
- oocyte maturation and ovulation
- preparation of the follicle for the formation of subsequent corpus luteum
- regulation of the follicular cycle (inhibitory and stimulatory factors
Meiotic maturation
the progression from the dictyate stage to metaphase II of meiosis
Characterization of meiotic mautration
dissolution of oocyte’s nuclear membrane
condensation of chromatin
separation of homologous chromosomes
emission of the first polar body
arrest of meiosis with chromosome aligned ont he metaphase II spindle
describe the progression from primoridal germ cells to oocte at ovulation
In the fetus
- initiation of meiosis
- meiotic arrest
in the post partum adult
- growt of the follicle
- respumption of meiosis at full growth
- metaphase II
- meitoc arrest
How long will all the recruited cells keep growing?
the primoridal follicles that are recruited from the resting pool willgrow for 3 months until it reaches the preantral stage, and then during the estrous cycle they will grom from small antral to preovulatory follicles
What is the boar:sow ratio?
1:25
minimum age of breeding, boar
7.5 months
Gloved hand collection
easy, observation of penis and seminal fuid
first ejaculation should be discarded
filter out the seminal plasma gel
Functions of the oviduct
Pick up of oocyte
transport of both sperm and oocytes
sperm reservoir
sperma and oocyte development: capacitation
fertilization
early embryonic development
Histiroarchitecture of the oviduct
infundibulum
ampulla
isthmus
Uterotubal junction
Where the sperm cells are stored
ampuleric istmic junction
the exact site of fertilization
The oviduct changes its milieu during the different part of th cycle, which are the factors being altered?
pH
osmotic pressure
nutrients
specific secretory products
signal molecules
Describe the sperm transport
- rapid passage through the uterus
- clonization of a sperm reservoir in the caudal isthmus - UTJ
- slow release toward the site of fertilization - AIJ
what is the ration of sperm to oocyte in the ampullary part of the oviduct?
relatively equal porpotion to prevent polyspermy
What are the mechanism of regulation to prevent the polyspermy?
sperm gradient
ovarian control of sperm release from the functional sperm reservoir to ensure a relevant sperm/oocyte ratio
What is the sperm gradient in the uterus as opposed to the AIJ?
billions to couple 100
How are sperm cells kept at the reservoir?
they get into a temporary arrest becuase of
- narrowed lumen,, increased oedema of the mucosa and a viscous mucus
- lower temperature
- local enzymatic and ionic milieu
- selective binding of spermatoxoa to the epithelium
- dramatically reduced sperm motility
- delayed capacitation
What causes the sperm cells to move out from the reservir (peri-ovulatory progression of spermatozoa from the functional reservoir)
- ovarian signals (progesterone)
- opening of the lumen, decreased oedema
- capacitation, acrosomal reaction
- dissolution of the hyaluronicacid rich mucus
- hyperactive sperm motility - only in isthmic section
- directed oviductal contraction - peristalsis
Describe the oocyte pick-up and transport
the oocytes are ovulated at the metaphase stage II
oocytes are picked up by the cilia-covered fimbria and guided through the indundibulum intot he ampulla
oocytes in their cumulus aggregate within a so-called egg or cumulus plug - the cumulus fights off the ciliary cells protecting the oocyte allowing it to move forward untouched
oviductal contractions will also move it toward the ampulla
ovum transport and fertilization
rapid transport - 30 min . thorugh the infundibulum and to the ampulla to the AIJ
cumulus expansion - dissolution of the remaining cumulus investment
at the same time the sperm are let out of the reservoir and transported/swims to AIJ
Fertilization - Explain in general steps
Oocyte MII + spacitated spermatozoa attaches
(ZP-binding, acrosome reaction, oocyte activation MII–>AII)
penetration
zona hardening and pronucleus formation
fusion of x and c pronucleus
zygote
early embryonic development within the oviduct
- development form zygote to IV cell embryo
- zygote after 8h
- cleavage starts one day later
- IV after 26-32h
- IV-cell embryo enters the uterus after 50-56h
at this time the concentration of progesterone ahs gone up and the lumen os the isthmic section is increasing so that the embry is able to enter the uterus
Factors influencing the fertilization within the oviduct
sperm aging - premature inseminaiton
oocyte aging - belated insemination
infulence of endogenous hormone dysregulation and of exogenous hormones - superovulation
sperm - steps during fertilization
- the sperm penetrates the cumulus
- acrosomal sperm activation
- contact with ZP (hardening) - loosing the tail
- penetration into the perivitelline space
- completion of the second meitoic division
- polar body is extruded
- decondensation of sperm head
- pronucleus formation
- extrusion of 2nd polar body
- pronuclus migrate to oocyte center
- dispersion of nuclear enveloped
- prophase of 1st mitosis division
Describe the zygote stages in the
- oviduct
- uterus
Oviduct: zygot –> IV-cell
uterus: VIII-cell –> blastocyst (32)
Blastocyst formation
development of tight intracelluar junctions of the morula during compaction is folloed by th accumulation of fluid with the central cavity froming a blastocoele
or explained differently
after the morula stage there will be growing and dividing blastocysts that are slowly differing from eachoter - differ into two types of cells in the expanded blastocyst whilst a cavity is formed along side filled with fluid
How is the position of the cells in the growing blastocyst relevant?
with the expansion of the blastocoele (fluidcavity) it will position cells on the inside or outside of the vesicle where they differentiate into trophoblasts (outside) or embryobladt (inside)
Zonal hatching
The growing blastocyst is getting too big for the ZP - it takes 6 days for the blastocyst to outgrow the ZP
it is a combination of physical and enzymatic process
Why is it important to know when the zonal hatching occurs?
In embro collection. it is impossible to find the embryo after it has hatched
Intrauterine migration
after th hatching, and the loss of XP the emrby can now attch to the maternal uterine epithelium
Intrauterine spacing
it is important with equidistant spacing to ensure embryonic survival. the embryos must be spread out to as cover most of the tissue of the uterus so that less estrogen can be produced
For how many days does the embry migrate and space?
until day 12
Explain the most important steps of early pregnancy
Fertilization
- sperm attachment
- sperm penetration
- pronucleus formaiton
cleavage
- 2- cell embry to morula
ealry embryonic development
- blastocyst formation
- zona hatching
- intrauterine migration and spacing
implantation
- conceptur expansion
- implantation
Time events in early embryonic development
blastocyst formation
blastocyst elongation
initial placentation
birth
Blastocyst formation
- blastocyst: 5-6
- hatching: >6
blastocyst elongation
- 11-15days
initial placentation
- 13d
birth
- 112-115 d
At the late blastocystic stage the blastocyst will divide into ICM and trophectoderm cells - what will these further develop into?
Trophectoderm cells: placenta
inncer cell mass: fetus
Gastrulation
establishing the further development
3 cell layers of ICM
3 cell layers of ICM
Ectoderma, mesoderma, endoderma
further differentiation of ectoderm
skin, hair, mammary gland, nerovous system
further differentiation of mesoderm
heart, blood vessel, kidneys, bones, musces, reproductiveorgans, CT, adipose tissue
further differentiation of endoderm
liver, pancreas, epithel layer of GI organs, resp orgnas