Fertilization/Placentation Flashcards
Primary germ cells originate near?
Yolk sac
After an oogonia enters prophase of the first meiosis division it is referred to as a _________ oocyte, which is contained in a __________ follicle
Primary
Primordial
What promotes meosis to continue after resting at prophase meosis I to be resumed?
Ovulatory surge of LH
Oocyte growth is complete at _________ follicle formation
Antral
Following telophase of meosis I the oocyte will make ?
Oocyte and a polar body
What is required for geminal vesicle breakdown?
LH peak
Following and LH peak and geminal vesicle breakdown, an oocyte goes through ?
Metaphase 1- assembly of chromosomes into metaphase plate
What is the ovulation stage for most mammals?
Second meiotic division
In dogs, at what stage do oocytes ovulate?
Metaphase 1
What occurs during ovulation
Oocyte and cumulus mass moved into infundibulum of uterine tube by fimbria
Fertilization occurs in ampulla of uterine tube
Meiosis is blocked at what phase unless fertilized?
Second meiotic metaphase
Where does the sperm gain ability to fertlize?
Epididymal transit
How is sperm moved from site of deposition to the uterine tube ?
Contractions of the female tract
What is the functional sperm reservoir?
Isthmus of uterine tube -near utertubual junction
Sperm adhere to tubal epithelium
What is capacitation and how does it occur?
Changes in sperm so it is capable of fertilization
- change membrane cholesterol, glycosaminoglycans
- tyrosine phosphorylation
- acrosome reaction
- hypermotility
- oocyte receptor expression
What initiates the acrosome reaction?
Contact of sperm with zona pellucida
What is the acrosome reaction?
Fusion of sperm plasma membrane with outer acrosomal membrane
Calcium dependent
Orderly release of acrosoamal enzymes
What is the process of the sperm penetrating the zona pellucida?
Sperm migrate between cumulus cells
Attach to and migrate through zona pellucida
Fusion of sperm and oocyte membrane
What is the binding site for sperm to the ZP?
ZP3
Binding mediated by oligosaccharides
The oocyte membrane is also called?
Vitelline membrane
Less species specific than zona pellucida
Fusion of sperm to the vitelline membrane requires?
Completion of acrosome reaction
Postcards all sperm membrane (equatorial region)
How is polyspermy blocked?
Oocyte granules are released ton perivitelline space (cortical reaction) ->enzymes released -> reorganization of ZP structure
What is the process of fertilization?
Haploid chromosomes of male and female enclosed in pronucleus.
Sperm nuclear envelope disintegrates
Male forms pronucleus
Male and female pronuclei migrate to cell center
Nuclear envelopes disperse
Intermixing of chromosomes ->prophase
Proximal centriole of sperm forms zygote centriole
What are the stages of development following fertilization ?
Zygote -> morula ->blastocyst ->hatched blastocysts
Undergoes cleavage/reduction division
How is the zygote supported metabolically?
Maternal secretions
Protein sysnthesis at 2-16cell stage
How does the bastocyts hatch from the zona pellucida?
Increase fluid in the blastocele
Proteolytic enzyme from trophoblast
Blastocysts contraction
What are the extraembryonic membranes?
Yolk sac
Amnion
Chorion
Allantois
What is the process by which the mother “recognizes” she is pregnant?
Corpus luteum - prolonged period of function
Transition to cyclic pregnant state
What are the two major stragaties to maintaining a pregnant state?
- Anti-luteolytic - diversion or inhibition of PGF
2. Luteotrophic - maintain CL
How is pregnancy maintained in the ruminants?
Blastocyst elongates to fill and contact most of uterine luminal epithelium
Trophoectoderm produces IFN tau (T)
- inhibit oxytocin receptor synthesis
- inhibit prostaglandin
- simulate endometrial glands
How is pregnancy maintained in swine?
Bastocyts produces estradiol
Changes direction of PGF secretion by the endometrium
PGF in uterine lumen is inactivated
How is pregnancy maintained in the Mare?
Suppression of PGF
- embryo motility (through uterine horns several times a day)
- movement mediated by uterus
A polysaccharide-rich membrane between the trophoectoderm and zona pellucida present only in equids
Embryo capsule
-round shape and rigidity necessary for uterine migration
How is pregnancy maintained in the llama ?
PGF synthesis or release is inhibited
What is eCG
Equine chorionic gonadotropin
Placental lactose not is also known as? And is present in what species?
Pregnancy-associated glycoproteins
Ruminants
What is the temporary organ providing support and protection for a developing embryo
Placenta
The outermost layer of the placenta is?
Chorion
The cavity that immediately surrounds the embryo/fetus?
Amnion
What cavity originates as an outpouching of the hindgut??
Allantois
How is placentation classified?
Shape
Degree of invasiveness
Intimacy of attachement
Nature of fetal placental vasculature
What type of placental interacts over the entire surface of the endometrium?
Diffuse
Diffuse embryos are found in what species?
Horse, pig, camelid
What type of placenta has attachments at caruncles? What species has this?
Cotyleonary
Ruminants
What time of placenta is seen in dogs and cats as a band?
Zonary
Humans and mice have what kind of placenta?
Discoid
What are the degrees of invasiveness of a placenta?
Epitheliochoridal
Syndesmochorial
Endotheliochorial
Hemochorial
What is an epitheliochorial placenta and what species is it present in?
Has both endometrium and chorionic epithelial cells, CT and endothelial cells
Horse and pig
Syndesmochroial placenta? In what species?
Some degree of fusion between the epithelial cells of the endometrium and the chorion
Sheep and cow
Endotheliochorial placenta? In what species?
Maternal epithelial cells gone, but chorionic epithelial cells present
Dog and cat
Hemochorial placenta? In what species?
Fetus invades maternal blood vessels, completely bathed in blood
Human, mouse, guinea pig
What is an adeciduate placenta? What species has this?
None of the maternal tissue is shed after birth
Horse and pig
A semideciduate placenta is? What species has this?
Caruncles shed a couple days after birth
Ruminants
What is a deciduate placenta??
Endometrium is passed out with placenta
Dog, human, cat
What species have villous placental vasculature?
Pig, horse, ruminant, human
What species have a labyrinthine placental vasculature?
Dog and cat
What species has cotyledonary, chorioallantoic, epitheliochorial, and syndesmochorial, villous, adequate placenta?
Bovine
What species has a diffuse, chorioallantic, epitheliochorial, villous (miccrocotyledonary), adeciduate placenta?
Horse
What species has a zonary, chorioallantoic, endotheliochorlal, labyrinthine, deciduate?
Canine/cat
What is the fetal period?
Fetus has organs, placenta, limb buds
What are endometrial cups, and what is their function?
Cells of chorionic girdle that has migrate to the endometrium
Clumps of these cells become hormonally active to produce eCG
What is an allantoic pouch?
Where the endometrial cup has been attached by the immune system and expressed from the endometrium
What is the function of eCG?
Acts like LH
Recruits follicles -> lutenize -> progesterone production
Pregnancy is maintained in the horse by what hormone?
5-alpha-pregnanes
Interacts with progesterone receptors and acts like progesterone
What is the function of fetal fluids?
Protection
Nutrient reservoir
Water reservoir
How does progesterone maintain pregnancy?
Placental development and function
Myometrial quiescence
Cervical closure
Immune mediation
What physiolocal changes occurs in the mother during pregnancy?
Increased circulating volume- lower hematocrit
Increased insulin resistance
Decreased residual volume- sensitive to anthetesia
Kidney, GI, immune tolerance
What is the trigger for parturition?
Fetal hypothalamic-pituitary maturation
Production of CRH–>cortisol
What effect does an elevated fetal cortisol have?
Progesterone production changed to androgen production
Androgen converted to estradiol
Increased prostaglandin production
Prostaglandin effect on parturition?
Fetal secretion of CRH
Myotonic
Estrogen is synergistic with ____________, causing softening of ligaments and cervical ripening
Relaxin
What effect do cytokines have on parturition
Similar effect to an immune inflammatory response
Leukocytes to placental, endometrium cervix
Enzymes cause cervical ripening, placental detachment, and uterine remodeling
What is Fergusson’s Relflex
Pressure on cervix, vagina
Increase secretion of oxytocin
Urge to push
What must the neonate do to adjust to postnatal life?
Respiration
Circulatory changes
Thermoregulation
What stimulates the first breath in the neonate?
Fluid compressed from lung during vaginal deliver
Cold, tough, sound
Central chemoreceptors increase respiratory derive
The respiratory rhythm is generated in the ______________ medulla and is modulated by?
Ventrolateral medulla
Chemoreceptors CO2, pH, and O2
How does the fetal circulation change post parturition?
Change in pressures due to perfusion of lungs Closure of -foreamen ovale -ductus arteriosus -ductus venous