Ovigenesis and fertilization Flashcards
Define oogenesis
formation and maturation of female gametes
Name the 4 phases of oogenesis
1) mitotic division of primordial germ cells
2) Nuclear arrest
3) cytoplasmic growth
4) resumption of meiosis
What is a dormant oocyte called?
dictyate oocyte
How many oocytes mature in a sow
10-25
When does the arrest of the primary oocyte occur?
In prophase 1
When does arrest of the secondary oocyte occur?
In metaphase 2
What kind of ovulators are production animals?
Spontaneous ovulators
How does stimulation take place in induced ovulators?
Copulation stimulates neurons in the vagina and/or cervix with direct neurons to the hypothalamus
What happens after neural stimulation?
1) neural stimulation results in the increase of GnRH and LH
2) LH initiates a sequence of events which leads to ovulation
3) The increase in LH causes an increase in P4 in the follicular fluid, Followed by PGF2alpha and PGE2.
What can possibly hinder ovulation?
Inhibition of ovarian steroid or PGF2alpha secretion.
What is the function of PGF2alpha
It ruptures lysosome like vesicles containing proteolytic enzymes, between the surface epithelium and surface albuginea.
What is the function of proteolytic enzymes?
It degenerates tunica albuginea, theca externa and theca interna.
What happens after the degeneration by the proteolytic enzymes?
1) plasmin acts as basement membrane
2) Wall of the follicle becomes thin and weak
3) Buldge (stigma) at the apex of the follicle is where the follicle will rupture.
4) When the follicle ruptures, follicular fluid, secondary oocyte and loosened granulosa cells will be extruded in the peritoneal cavity near the infundibulum.
Where is the ovulation site in mares
Ovulation fossa
Where is the ovulation site of all species except mares?
Anywhere on the ovarian surface
What is the cumulus mass?
Loose matrix of cumulus cells around the tightly packed corona radiate cells which surrounds the oocyte. The oocyte is embedded in the cumulus mass.
Granulosa cells is the sum of ….
cumulus + corona radiate
Define gamete transport
Movement of viable gametes to the site of fertilization
Where and how is the oocyte picked up?
In the infundibulum via ciliated cells, the cillia then moves the oocyte to the ampullary-isthmic junction.
The cillia also creates a directional flow of oviductal fluids which aids in transport.
What is the most important mechanism for normal transport of an oocyte?
segmented, peristaltic contractions of the ampulla.
What is the diffirent transport times of oocytes in the oviducts of the following animals? cattle, sheep, horse, swine.
Cattle= 90hrs sheep= 72hrs horse= 98hrs swine= 50hrs
What is the cause of the rapid phase transport of sperm?
Copulation-induced contractions, involving the smooth muscle in the cervix, uterus and oviduct.
What stimulates these copulation induced contractions?
oxytocin and prostaglandins
What follows the rapid transport phase of sperm?
Slower transport phase, which is the sustained transport of sperm to the oviduct.
What is the greatest barrier to sperm transport?
Cervix
What are the 2 types of cervical mucus in bovine?
1) sialomucins, low viscosity produced by cells in the basal portions of cervical folds.
2) Salfomucins, high viscosity produced by apical portions of the cervical folds.
What causes sperm to be washed away from the cervix towards the vestibule?
Highly viscous sulfomucins
What facilitates sperm transport through the cervix?
Low viscosity sialomucins
name 2 functions of the cervical mucus
1) Increases sperm motility
2) filters out dead and abnormal sperm
Retrograde loss of spermatozoa is _____ % of the deposited sperm.
18-30
What serves as a barrier and filter for sperm?
uterotubal junction
Name the first and second reservoir for sperm pooling.
1) cervix
2) isthmus
When does sperm retain viability for longer?
When it is in contact with oviductal epithelium.
What regulates the release of sperm?
Isthmic epithelium
Name the site of fertilization.
Ampullary-isthmic junction
Give the 5 major sequences of events when the sperm has been deposited into the female tract.
1) Immediate transport: includes retrograde loss, phagocytosis, entrance into the cervix/uterus
2) Cervix, removes abnormalities and nonmotile sperm
3) Uterus, capacitation initiated and phagocytosis
4) Oviduct, capacitation completed and sperm have a hyperactive motility
5) Fertilization, acrosome reaction, spermatozoon penetrates oocyte, male and female pronuclei form.
Define polyspermy
Fertilization by more than one sperm
The zygote has a polyploidy nucleus
Give the postcapacitation sequence of events that leads to fertilization
Hyperactive motility Binding to zona pellucida Acrosomal reaction Penetration of the ZP Sperm-oocyte membrane fusion Sperm engulfed Decondensation of sperm nucleus Formation of male pronucleus
What does PGF2 alpha cause in the ovary and follicle
Contractions to expel the oocyte towards the infundibulum.