W9- Lecture 48- Basic Embryology Flashcards
name the stages from fertilisation onwards in embryonic development
Fertilisation
Zygote
Cleavage
Morula
Blastocyst
Gastrulation
(Ectoderm, Mesoderm ,Endoderm)
Organogenesis
describe the cleavage stage of embryonic development
Cleavage- cells half the size of progenitor cell
alternate type of mitosis
After cleavage only one of the daughter cells contains lepton however the other doesn’t
Leptin stimulates production of gene transcription
what is a zona pellucida ?
+ function
the thickmembrane surrounding an ovum before implantation.
barrier for cell division takes place in
And restricts size of replication
Will Strech and expand a certain size but restricts
what is a morula ?
early-stage embryo consisting of 16 cells (called blastomeres) in a solid ball contained within the zona pellucida.
eventually secrete fluid
Differnce between blastocyst and morula ?
Morula ball of cells smaller
Blastocyst contains fluid filled sac called blastocoel and also more cell no
when does hatching from the zona pellucida take place ?( +what process causes)
where ?
Hatching takes the same amount of time that is does for the fertilised ball of cells takes to move from the ampulla to the uterus
Hatching occurs when the blastocyst stage pumps too much liquid and the zona pellucida breaks open
hatching will occur in the uterus
when does gastrulation takes place ?
what is it
gastrulation takes place
Formation of there germ layers
Commitment into different developmental paths
what is Organogenesis?
how does this aid Foetal development
organs are formed so when foetal
development happens the organs only have to increase in size and complexity
describe the distribution of some cellular products e.g., leptin.
unequal due to cleavage producing blastomeres(2 cells )
what is rotational cleavage/ what does it produce ?
each successive replication happens in a diff place
produces cell at 8-cell stage
what is compaction ?
what does it form ?
Flattening of blastomeres(outside cells of embryo ) maximising cell-cell contacts.
Formation of tight junctions.
+ 16-cell morula
what day do we expect the embryo enters the uterine cavity ?
approx day 6
what is the trophoblast ?
– inner cell membrane
inside zona pellucida
what do the external polarised cells cells develop into ?
Trophectoderm;
what do the Internal non-polar cells develop into ?
Inner cell mass (ICM
formation of which structure leads to hatching ?
Formation of blastocoel (fluid filled cavity )
Trophectoderm develops into
syncytiotrophoblast(forms gap junctions) - spreads around blastocyst
the Inner cell mass (ICM) develops into
Epiblast & Hypoblast
what does the epiblast form ?
Embryonic epiblast then the
embryo
Amniocytes. Secrete fluid which form the amnion
what does the hypoblast form ?
lines blastocoel form the yolk sac
name all the structures the three germ layers form
Ectoderm
Mesoderm
Endoderm
Ectoderm
Epidermis
Nervous system
Pigment cells
Mesoderm Kidneys Gonads Bones Muscle Heart Blood cells (Part of most internal organs)
Endoderm
Lining of gut
Respiratory system
what is pattern formation ?
+ examples
what does this involve ?
is the process by which a spatial and temporal pattern of cell activities is organized within the embryo” (Wolpert, 2002).
E.g.: Axis specification, formation of germ layers.
Involves the co-ordination of a variety of mechanisms of cellular communication
what is induction of cells
Cell types specified under influence of other cell types.
Production of signals that bring about response in target cells.
what is Morphogenesis?
e.g
what influences this
The achievement of developmental diversity by formation of different structures from the same initial structure.
E.g.: Gastrulation, neurulation, limb formation etc.
by signalling
