Pregnancy, parturition and late foetal development Flashcards
(98 cards)
early embryo nutrition?
Histiotrophic
Derivation of nutrients from the breakdown of surrounding tissues
Breakdown of maternal capillaries
Glands within the endometrium provide uterine milk
What happens between first and second trimester?
Rapid increase in rate of growth
what happens in first trimester
limited growth due to histiotrophic nutrition
what is the nutrition in second trimester
haemotrophic
how is histitrophic nutrition supported in the early implantation of the embryo
Syncytiotrophoblast breaks down maternal cells and uses their products to support embryo development
breakdown of maternal capillaries + uterine gland secretions exposes syncytiotrophoblast to maternal blood to derive nutrients from
what is the amnion
Derivative of epiblast - extraembryonic structure
First foetal membrane
Forms the amniotic cavity that goes on to become the amniotic sac
two key foetal membranes
amnion
chorion
what is the chorion
outer membrane surrounding whole conceptus unit
what is the connecting stalk
extra embryonic tissues which grows from the embryo and connects the conceptus with the chorion
What are the trophoblastic lacunae?
Large spaces filled with maternal blood formed by breakdown of maternal capillaries and uterine glands
Become intervillous spaces aka maternal blood spaces
How are trophoblastic lacunae formed?
Breakdown of maternal capillaries and glands
Lumens of the glands and capillaries start to fuse
Create a continuous space where maternal blood can flow
what are the foetal membranes and their function
extraembryonic tissues that form a tough but flexible sac which encapsulates the fetus and forms the basis of the maternal-fetal interface
what happens in the 5th week to amniotic fluid
Amnion begins to secrete amniotic fluid from 5th week – forms a fluid filled sac that encapsulates and protects the fetus
chorion main features
Formed from yolk sac derivatives and the trophoblast
highly vascularized
forms chorionic villi
what are chorionic villi (cell and function)
cytotrophoblast outgrowths from the chorion that form the basis of the fetal side of the placenta
how is the amniotic sac expanded?
fluid accumulation forces the amnion into contact with the chorion, which fuse, forming the amniotic sac
layers of amniotic sac
amnion on the inside
chorion on the outside
what is the allantois
yolk sac outgrowth
grows along connecting stalk embryo-chorion
becomes coated in mesoderm and vascularises
FORMS UMBILICAL CORD
what forms the umbilical cord
connecting stalk
allantois
plus mesoderm cells
what are cytotrophoblast cells
Important in the development of the placenta
form finger-like projections through syncitiotrophoblast layer Into maternal endometrium (primary chorionic villi)
fingerlike projections of cytotrophoblast into endometrium
primary chorionic villi
role of chorionic villi
Provide substantial surface area for exchange (gases and nutrients)
phases of chorionic villi development
primary secondary tertiary
primary phase of chorionic villi development
outgrowth of the cytotrophoblast and branching of these extensions