Extra Embryonic Membranes of Mammals and Avians Flashcards
Soon after successful fertilization, the zygote undergoes cleavage or segmentation division (type of cleavage depends on the amount of yolk material) and moves along the uterine tube and enters the uterus. Movement or transport of the embryo towards the uterus is a combination of ciliary (swaying movement of the epithelial cilia of the of the endometrium) and muscular contraction of the myometrium.
Implantation/Nidation
Implantation/Nidation occurs in three stages in domestic animals: (3)
- Apposition of the blastocyst or foetal membranes to the uterine epithelium
- Adhesion
- Firm attachment or invasion of the endometrium
*Forms of Implantation
Blastocyst implants itself interstitially by passing through the uterine epithelium and becoming completely cut off from the uterine lumen. This is true in primates, guinea pigs and human.
Interstitial/Invasive Implantation
*Forms of Implantation
-blastocyst remains small and becomes lodged in the fold of the uterine lumen, where it implants itself. Example of this form of implantation are rodents.
Eccentric Implantation
*Forms of Implantation
Blastocyst elongates and enlarges until it fills a good part of the uterine cavity. This form of placentation occurs in ungulates, carnivores, swine,sheep, cattle and horse.
Centric/Superficial Implantation
*Forms of Implantation
-Blastocyst implants in the endometrium on the same side as the attachment of the mesometrium.
MesometriaL Implantation
*Forms of Implantation
-implantation occurs at a site opposite to the attachment of the mesometrium.
Anti-mesometrial Implantation
OTHER Forms of Implantation (3)
Seasonal or Obligative
Facultative or lactational
Ectopic pregnancy
Sites of abnormal implantation (3)
- Ovary
- Uterine tube
- Peritoneal cavity
*OTHER Forms of Implantation
-Implantation occurs when the probability that offsprings are born at a time of year favorable for survival .
-Mink, ferrets, roe deer, bears, badgers and seals
Seasonal or Obligative
*OTHER Forms of Implantation
-The dam ensures that it does not have to support two litters contemporaneously
-Rodents and insectivores
Facultative or lactational
*OTHER Forms of Implantation
Implantation and subsequent embryonic development in an extra-uterine location
Ectopic pregnancy
*Anong animal yarn?
When single oocyte is fertilized, the blastocyst attaches to the middle or upper third of the uterine horn adjacent to the ovulating ovary.
Cattle
*Anong animal yarn?
Whe two blastocysts are derived from one ovary, one blastocyst usually migrates to the contralateral (opposite) horn where it becomes implanted.
Sheep
*Anong animal yarn?
Blastocyst implants in either the left or right horn close to the body of the uterus.
Horse
*Anong animal yarn?
Blastocysts are evenly spaced within the uterine horns.
Polytocous (litter bearing) animals
Mechanism underlying the equal spacing of embryo is unclear although ________ produced by the developing blastocyst is considered to have an important role in embryo spacing.
estrogen
After nidation/ implantation of the embryo to the endometrium, ___ start to form.
extra embryonic membranes
tissues derived from the developing embryo that enclose and contribute to the support of the developing embryo.
Extra embryonic membranes
four EEM;
yolk sac, allantois, amnion, and chorion.
The amnion and chorion are derived from the
________ (fused mesoderm and ectoderm).
somatopleure
The allantois and yolk sac are from the
__________ (fused mesoderm and endoderm).
splanchnopleure
is small, membranous structure in egg with scant yolk material like mammals but prominent in avian species with huge amount of yolk material.
Yolk sac
Primitive hematopoiesis takes place in the ____ before the ____ and ____ eventually take over.
Yolk sac
liver
bone marrow
