1,473
edits
Changes
Jump to navigation
Jump to search
Implantation - Anatomy & Physiology (view source)
Revision as of 17:32, 30 December 2010
, 17:32, 30 December 2010→Pre-attachment period
==Pre-attachment period==
==Pre-attachment period==
For most domestic mammalian embryos, the pre-attachment period within the uterus is long (several weeks). During this time, extraembryonic membranes form by a folding process that generates:
1. Amnion
2. Chorion
3. Allantochorion
In primates, the blastocyst implants very soon after it enters the uterus and extraembryonic membranes form after implantation.
For further information on extraembryonic membranes, attachment, placentation and maternal recognition of pregnancy follow [[:Category:Pregnancy and Parturition|this link to Pregnancy and Parturition]].
Implantation is critical to the survival of the embryo; the embryo must adhere and embed itself in the endometrium in order to exchange waste and nutrients. For this reason, the first differentiation of cells is into trophoblasts and syncytiotrophoblasts and the inner cell mass (ICM). Trophoblastic cells posses adhesion molecules to adhere to the endometrium, whilst ICM cells form the organism. The extent of cellular growth and division, and the time taken for [[Implantation - Anatomy & Physiology|implantation]] differs between species. Shortly after implantation, cells of the ICM differentiate into different layers:
1.'''Epiblast''' - facing towards the uterine lumen, adjacent to syncytiotrophoblasts.
2.'''Hypoblast''' - facing towards the endometrium, adjacent to the blastocyst cavity.
3.'''Amnioblasts''' - cells of the epiblast that migrate up and around to allow the amniotic cavity to form.
After [[Gastrulation - Anatomy & Physiology|gastrulation]], the '''epiblast''' gives rise to the three germ layers:
1. Ectoderm
2. Mesoderm
3. Endoderm
The hypoblast gives rise to no persisting structure in the adult.
[[Category:Developmental Biology]]
[[Category:Developmental Biology]]
[[Category:Pregnancy and Parturition]]
[[Category:Pregnancy and Parturition]]
[[Category:To Do - A&P]]
[[Category:To Do - AimeeHicks]]