Embryology Flashcards
What term is given to the developing baby from when fertilisation occurs to the end of week 2?
Conceptus
What term is given to the developing baby from week 3 to the end of week 8?
Embryo
What term is given to the developing baby from week 9 to birth?
Foetus
What are the 6 phases of embryonic development?
Gametogenesis Fertilisation Cleavage Gastrulation Morphogenesis Organogenesis
What occurs in gametogenesis?
Formation of haploid germ cells (sperm, ovum) as a result of meiosis
What occurs in fertilisation?
Formation of zygote via the fusion of the sperm and oocyte
What happens in cleavage?
Rapid mitotic cell division with no increase in size
Termed a Morula at 16+ cells and then a blastocyst
What happens in gastrulation?
Formation of germ layers (ectoderm, mesoderm, endoderm)
What happens in morphogenesis?
Folding of embryo forms 3D human-like shape
What will the ectoderm go on to produce?
Epidermis
Nervous system
What will the mesoderm go on to produce?
Organs, bones and dermis
What will the endoderm go on to produce?
Lining of gut
Lung bud
Bladder lining
Urethra lining
What is the zona pellucida?
Tough protein coat surrounding oocyte to give it protection
In cleavage, zygote divides into morula and then further into blastomeres. At which stage are blastomeres still totipotent (can give rise to any cell/structure)?
Up until the 8-cell stage, blastomeres are totipotent
What are the 4 components of Tetralogy of Fallot?
Pulmonary stenosis
Right ventricular hypertrophy
Overriding aorta
Ventricular septal defect
When do primary oocytes begin meiosis?
Week 28-30 but arrest in prophase until puberty
What is the most common site of fertilisation?
Ampulla
How does ferilisation occur?
Sperm binds zona pellucida glycoprotein (ZP3), acrosomal enzymes are released allowing fusion. Sperm content then enter the oocyte triggering completion of meiosis 2. Oocyte in response releases cortical granules that prevent multiple fertilisation.
How is the trophoblast layer formed?
Outer cells in the merula which are in contact with ZP form extensive gap junctions. Forming the trophoblast in the blastocyst
When does blastocyst hatching occur?
Day 5/6
When does implantation occur?
Day 6
What layers does the trophoblast split into?
Cytotrophoblast - made of individual cells
Syncytiotrophoblast - a large multinucleated cell
Which early embryonic structure produces hCG?
Syncytiotrophoblast
Describe the bilaminar embryonic disc structure
Epiblast (dorsal) - encloses the amniotic cavity
Hypoblast (ventral) - encloses the primitive yolk sac
