Embryology Flashcards
What impedes the movement of sperm?
Female antibodies
Cervix
Uterotubal junction
Where does fertilisation usually occur?
In the ampulla (wider middle) of the uterine tube
What is the maternal egg surrounded by?
Outer corona radiata
Tough covering zona pellucida
Oocyte cell membrane
What happens at the first cell division?
Male and female chromosomes condense and divide by mitosis.
It is still contained in the zone pellucida
What is the bundle of cells the stage after the zygote called?
Morula
What is the name of the inner cells of the morula?
Embryoblast - will become the embryo
What is the name of the outer cells of the morula?
Trophoblast - will become the placenta
What is a blastocyst?
When the inner cells of the morula move to one end and leave a fluid filled cavity
What happens during implantation?
Blastocyst attaches to the uterine wall.
If more than one they spread evenly along the horns
What are the two layers of the embryoblast?
Epiblast
Hypoblast
What does the epiblast form?
The amniotic cavity
What does the hypoblast form?
The yolk sac - the first bit of nutrition before the placenta forms
What is the trilaminar germ disc?
Ectoderm
Mesoderm
Endoderm
What is the slit at the caudal end of the disc called?
Primitive streak
What occurs at the primitive streak?
The epiblast cells migrate through the streak to form the trilaminar layers
What is the ectoderm?
The cells that remains in the epiblast on the outside
What is the mesoderm?
The cells that migrate through the primitive streak and lie in the middle
What is the endoderm?
The cells that migrate through the primitive streak and displace the hypoblasts
What does the ectoderm form in the body?
The CNS and the PNS
The epidermis of the skin
What does the mesoderm form in the body?
The connective tissues
most stuff
?What does the endoderm form?
The gastrointestinal tract - organs and epithelium
The respiratory tract epithelium
What are the 3 parts of the mesoderm?
Paraxial mesoderm
Intermediate mesoderm
Lateral plate mesoderm
What does the paraxial mesoderm form?
The somites
What does the intermediate mesoderm form?
The urogenital systems
What does the lateral plate mesoderm form?
Visceral - muscular gut wall
Parietal - body wall
What is it called when all the organs are the wrong way round?
Situs invertus
What is the notochord?
The midline, skeletal rod in embryos
What does the notochord induce?
Proliferation(growth) of the paraxial mesoderm
Development of the neural folds to form the neural groove
What does the neural tube form?
The CNS
hat do the neural crest cells form?
The PNS
What is head to tail folding called?
Cephalocaudal folding
What is folding round the body called?
Lateral folding
What are non identical twins called?
Dizygotic
What are identical twins called?
Monozygotic
