Embryology and human development Flashcards
Most development takes place in the first 45 days. True or false?
True
What are the six main stages of embryonic development?
Cleavage Blastula Gastrulation Neuralation Organogenesis Enlargement
What does the animal:vegetal pole determine?
the future anterior:posterior axis
The anterior:posterior axis is determined by the oocyte. True or false?
True
What is the dorso-ventral axis determined by?
The point of sperm entry
What causes the rotation of the cortical cytoplasm?
the entry of sperm
the proximal distal axis is important in limb formation. True or false?
True
What is removed from the woman’s ovaries in IVF?
ova
Which techniques are routinely used in IVF?
ovarian hyperstimulation to produce multiple eggs
ultrasound-guided transvaginal oocyte retrieval from ovaries
egg and sperm preparation
culture and selection of embryos before transfer into the uterus at approx 3-5 days after fertilisation
At what developmental stage is IVF carried out?
late cleavage to early blastocyst formation
The blastula is a hollow ball of cells. True or false?
True
How does the blastocoel develop?
develops at the 16 cell stage via the action of Na+ pumps and osmosis
What is a blastula?
A hollow ball of cells held together at the surface by tight junctions to form an epithelium
In the formation of the gastrula, the single layered blastula becomes a __________ gastrula
3 layered
What marks the point of invagination?
blastopore
What are the 3 layers of gastrula?
ectoderm
mesoderm
endoderm
How is the neural tube formed?
an infolding of the ectodermal layer along the dorsal surface of the developing embryo
What is spina bifida?
a developmental disorder caused by the incomplete closing of the neural tube
The incidence of spina bifida can be decreased by 70%. How can this be done?
The mother takes folic acid supplements prior to conception
What is the precursor for the backbone?
The notochord
What is the role of the ectoderm?
Gives rise to the skin, nervous system and sense organs
What is the role of the mesoderm?
Gives rise to the connective tissues e.g. heart, skeleton, urogenital system
What is the role of the endoderm?
Gives rise to the gut and associated organs e.g. lungs, liver, pancreas
Is the embryonic body plan initially male or female?
Female and if the genes on the Y chromosome are expressed, the foetus develops into a male
Which gene co-ordinates the changes between female to male?
SRY (Sex determining Region Y)
At around 5-6 weeks of development, the cells of the primordial gonads are in a bipotential state. What does this mean?
They can become either male or female cells. SRY initiates testis differentiation by activating male-specific transcription factors that allow the ovarian cells to differentiate into testes
What are corresponding parts in a male and female called?
homologous
At how many weeks is an organism referred to as a foetus?
14
