Embryology 1 Flashcards
When does meiosis 1 and 2 occur in female germ cells?
1 is the foetus while were in the womb
2 is during adolescence
How many sperm do you need to fertilise 1 ovum?
1000’s. only 1 inserts its DNA but this needs many others too
Where is the zygote formed and how does it travel to the uterus?
Formed at distal end of Fallopian tube. Travels along ciliated simple columnar epithelium
What happens when the zygote divides?
It forms a morula, and then a blastocyst
Why is a blastocyst formed? What’s its structure?
Morula struggles to receive nutrients as it divides.
Has a cavity inside, inner cell mass and outer cell mass called trophoblast
What helps implantation on the uterine cavity?
Chorionic villi, formed from trophoblast. Finger like processes
What hormones help with endometrium production?
Oestrogen and progesterone. They maintain the endometrium for 2 weeks until the foetus has set in
Then chorion produces HCG which secretes perfect amount of oestrogen and progesterone
Why do females get morning sickness?
HCG released by chorion is a hormone and travels all through blood causing nausea and unwell feeling. This can be detected in urine - pregnancy test
What happens to the inner cell mass of the blastocyt?
It flattens and forms 2 layers - epiblast on top and hypoblast below
Which cavities are formed due to the flattening of the inner cell mass?
Amniotic sac is formed above epiblast, and yolk sack is formed below hypoblast
What is the chorion?
The outer sack of the entire embryo, and forms villi and placenta which holds the foetus to the uterine wall
Where does the waste from the yolk sac end up?
Allantoic cavity
What are the main functions of the placenta? (3)
Foetal nutrition, gas and waste transport and immunity
What is the primitive streak?
The line which the epiblast and hypoblast lay perpendicular to. Allows mitosis where it crosses
How are 3 layers of gastrulation initially formed?
Epiblast mitosis and cells migrate to hypoblast and space between the 2 layers. Epiblast cells replace hypoblast and forms endoderm. Middle layer of cells forms mesoderm
How is the notochord formed?
Ectoderm continues multiplying, forming rod structure down past mesoderm. This eventually breaks off and nerves a notochord below mesoderm. Primative streak disappears.
How is the neural plate formed?
Notochord released chemical signals to ectoderm, which bends to form the neural plate
How is the neural tube formed? What is it?
The neural plate continues growing until a small tube is formed which sinks down and sits between ectoderm and mesoderm. This is the neural tube, which goes to form spinal cord and brain
How are 3 sections of the mesoderm formed and what are they called?
Cells continue being added to mesoderm, causing it to thicken.
Layers formed are paraxial mesoderm, intermediate plate mesoderm and lateral plate mesoderm
What does the intermediate plate mesoderm go on to form?
Urogenital system
What does the lateral plate mesoderm go on to form?
Lateral place splits in half, forming a somatic and a splanchnic mesoderm
Body cavities and coverings, including pleural and peritoneal cavities
How are somites formed and what do they look like?
Form in pairs on either side of your paraxial mesoderm. There’s 43 pairs and they each divide into 3 structures.
What do somites divide into? (3)
Dermatome, myotome and sclerotome
What is teratology?
Study of abnormal development of embryo
When is a foetus most and least susceptible to effects from teratogens?
1-2 week embryo wont survive. 3-8 weeks exposure can cause maximal effect. 9+ weeks, sensitivity decreases
