EMBRYOLOGY OF RESPIRATORY SYSTEM
WEEK 1
Fertilsation occurs in oviduct.
Embryo divides to form a morula (ball of undifferentiated cells).
Then get 1st differentiation which is the orange inner cell mass.
Rest of cells is known as the trophoblast (extra embryonic tissue). End of 1st week, embryo is
called a blastocyst.
WEEK 2
Blastocyst implants into uterine lining of mother which is driven by trophoblast.
Trophoblast develops into different types and it’s the cystrophoblast which helps embed the
blastocyst into the uterine wall.
Primitive circulation gets set up and nutrients/blood can be fed from the mother. (Day 9)
Amniotic cavity = eventually surrounds foetus. (Storage of waste products/protection)
Mesoderm = surrounds the whole thing.
Yolk sac = gut tube.
Connecting stalk = placenta.
WEEK 3
Gastrulation – transform from bilaminar disc into a three layered creature. (3 germ layers –
from which all your tissue are derived).
Eppiblast cells migrate through the primitive streak to form three distinctive layers:
Endoderm – gut
Mesoderm – musculature and paraxial skeleton.
Ectoderm – Skin and CNS.
MESODERM
3 different types:
Paraxial mesoderm – closest to midline, and gives rise to somites and MS system.
Intermediate mesoderm – urogenital system.
Lateral plate mesoderm – forms muscular wall of gut.
Neural Tube
Development of nervous system is inducted by the notochord.
Notochord sends signals out so you get proliferation of paraxial mesoderm and
development of neural folds.
EMBRYONIC FOLDING
Embryonic disc flexes around the yolk sac giving it a curvature shape.
The cephalic folding is what brings structures to the anterior of the body such as
mouth and cardiac region (so it brings mouth to face etc).
WEEK 1
Fertilsation occurs in oviduct.
Embryo divides to form a morula (ball of undifferentiated cells).
Then get 1st differentiation which is the orange inner cell mass.
Rest of cells is known as the trophoblast (extra embryonic tissue). End of 1st week, embryo is
called a blastocyst.
WEEK 2
Blastocyst implants into uterine lining of mother which is driven by trophoblast.
Trophoblast develops into different types and it’s the cystrophoblast which helps embed the
blastocyst into the uterine wall.
Primitive circulation gets set up and nutrients/blood can be fed from the mother. (Day 9)
Amniotic cavity = eventually surrounds foetus. (Storage of waste products/protection)
Mesoderm = surrounds the whole thing.
Yolk sac = gut tube.
Connecting stalk = placenta.
WEEK 3
Gastrulation – transform from bilaminar disc into a three layered creature. (3 germ layers –
from which all your tissue are derived).
Eppiblast cells migrate through the primitive streak to form three distinctive layers:
Endoderm – gut
Mesoderm – musculature and paraxial skeleton.
Ectoderm – Skin and CNS.
MESODERM
3 different types:
Paraxial mesoderm – closest to midline, and gives rise to somites and MS system.
Intermediate mesoderm – urogenital system.
Lateral plate mesoderm – forms muscular wall of gut.
Neural Tube
Development of nervous system is inducted by the notochord.
Notochord sends signals out so you get proliferation of paraxial mesoderm and
development of neural folds.
EMBRYONIC FOLDING
Embryonic disc flexes around the yolk sac giving it a curvature shape.
The cephalic folding is what brings structures to the anterior of the body such as
mouth and cardiac region (so it brings mouth to face etc).
