EMBRYOLOGY Flashcards
What is embryology
Is the process by which a multicellular organism arises from a single cell
List the types of basic cell movement
Invagination Involution Ingression Delamination Epibody Convergence Extension Cavitation
What is invagination
Including of a layer of cells
What is involution
Outer cellular layer growing on the inside of the layer
What is ingression
Invasion of cells into an embryo
What is delamination
One layer splitting into two layers
What is epibody
Second layer on outer surface
What is convergence
Cells converge towards central midline point
What is extension
Cells group together and form long cylindrical like structure
What is Cavitation
Where spaces are formed
What is an oocyte
Egg cell
What is a zygote
Egg and sperm nuclei have fused
What is a morula
Contains lots of early cells - can’t count how many
What is gastrulation
Process where the 3 primary germ layers (endoderm, mesoderm and ectoderm) are established in the embryo
The basic body plan is established
The primary body axes are established
What is the primitive streak
A depression in the surface of the epiblast
In what direction does the primitive steak form
Grows crainally
What starts the formation of amniotic fluid
Embryo implantation- causes cell death in epiblast
Describe the process of gastrulation
Some epiblast cells detach and move towards primitive steak and node. They slip beneath the epiblast , then some of the cells then displace the hypoblast
In gastrulation which cells form the endoderm
The cells that displace the hypoblast become the endoderm
In gastrulation which layer of cells become the mesoderm
The cells that lie between the epiblast and hypoblast become the mesoderm
In gastrulation which cells become the ectoderm
The cells remaining in the epiblast
What is neurulation
Formation of neural tube
What is the notochord
Extended columns of cells ventral to the central nervous system. Induces the formation of the neural tube
How is the notochord formed
- Cells that form mesoderm move in a cranial direction
- Cells in hypoblast intercalate to form notochordal plate
- Hypoblast cells replaced by endoderm. Cells of the plate proliferate and detach to become notochord
- Notochord produces growth factors which act on the ectoderm, starting the formation of the neural tube
In what direction does the notochord develop
Head to tail direction
What is the effect of the notochord on the ectoderm above
The growth factors produced by the notochord causes ectoderm to thicken and form neural plate
How does the neural tube develop
- Notochord induces formation of neural plate
- Lateral edges of neural plate elevate to form folds (and depressed mid region becomes neural groove )
- Folds fuse together- occurs in cervical region and precedes in both directions - forming neural tube
What are neural crest cells also known as
4th germ cell layer
How are neural crest cells formed
Get cut off after closure of the nurrral tube
What do neural crest cells form
Many rural and skeletal and other cell types
E.g form sympathetic and parasympathetic components of the PNS
