Human Embryology and Developmental Biology – Lecture 2
09-02-2018
Blastulation:
More cells, due to cleavages.
Blastocoel:
1. Prevents the animal cells from premature induction by underlying vegetal cells
into mesoderm.
2. Permits cell migration during gastrulation.
Gastrulation: stage where the three germ layers (ectoderm, mesoderm, endoderm)
are formed.
Gastrulation in Xenopus:
Holoblastic cleavage
Combination of involution and epiboly;
The endoderm moves inward, creating the mesoderm layer.
*Specialization of mesoderm: Notochord important for formation of our body axis
because of the availability of the Notochord, we are classified as Chordates.
Ventral side = sperm-entry point
Dorsal side = opposite site. side where blastopore forms.
Sperm-entry leads to the dorsal-ventral axis of an embryo.
The Notochord is created, during gastrulation.
After gastrulation follows neurulation.
*Summary of steps: Cleavage blastulation gastrulation organogenesis
(neurulation).
, High amounts of yolk meroblastic (incomplete cleavage).
Low amounts of yolk holoblastic (complete cleavage).
Neural crest cells: form at fusion point, migrate to different places, differentiating
into all sorts of different things. Differentiation is locally influenced by paracrine
factors.
09-02-2018
Blastulation:
More cells, due to cleavages.
Blastocoel:
1. Prevents the animal cells from premature induction by underlying vegetal cells
into mesoderm.
2. Permits cell migration during gastrulation.
Gastrulation: stage where the three germ layers (ectoderm, mesoderm, endoderm)
are formed.
Gastrulation in Xenopus:
Holoblastic cleavage
Combination of involution and epiboly;
The endoderm moves inward, creating the mesoderm layer.
*Specialization of mesoderm: Notochord important for formation of our body axis
because of the availability of the Notochord, we are classified as Chordates.
Ventral side = sperm-entry point
Dorsal side = opposite site. side where blastopore forms.
Sperm-entry leads to the dorsal-ventral axis of an embryo.
The Notochord is created, during gastrulation.
After gastrulation follows neurulation.
*Summary of steps: Cleavage blastulation gastrulation organogenesis
(neurulation).
, High amounts of yolk meroblastic (incomplete cleavage).
Low amounts of yolk holoblastic (complete cleavage).
Neural crest cells: form at fusion point, migrate to different places, differentiating
into all sorts of different things. Differentiation is locally influenced by paracrine
factors.
