Embryology 1

Question 1

When does meiosis 1 and 2 occur in female germ cells?

Answer 1

1 is the foetus while were in the womb
2 is during adolescence

Question 2

How many sperm do you need to fertilise 1 ovum?

Answer 2

1000’s. only 1 inserts its DNA but this needs many others too

Question 3

Where is the zygote formed and how does it travel to the uterus?

Answer 3

Formed at distal end of Fallopian tube. Travels along ciliated simple columnar epithelium

Question 4

What happens when the zygote divides?

Answer 4

It forms a morula, and then a blastocyst

Question 5

Why is a blastocyst formed? What’s its structure?

Answer 5

Morula struggles to receive nutrients as it divides.

Has a cavity inside, inner cell mass and outer cell mass called trophoblast

Question 6

What helps implantation on the uterine cavity?

Answer 6

Chorionic villi, formed from trophoblast. Finger like processes

Question 7

What hormones help with endometrium production?

Answer 7

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

Question 8

Why do females get morning sickness?

Answer 8

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

Question 9

What happens to the inner cell mass of the blastocyt?

Answer 9

It flattens and forms 2 layers - epiblast on top and hypoblast below

Question 10

Which cavities are formed due to the flattening of the inner cell mass?

Answer 10

Amniotic sac is formed above epiblast, and yolk sack is formed below hypoblast

Question 11

What is the chorion?

Answer 11

The outer sack of the entire embryo, and forms villi and placenta which holds the foetus to the uterine wall

Question 12

Where does the waste from the yolk sac end up?

Answer 12

Allantoic cavity

Question 13

What are the main functions of the placenta? (3)

Answer 13

Foetal nutrition, gas and waste transport and immunity

Question 14

What is the primitive streak?

Answer 14

The line which the epiblast and hypoblast lay perpendicular to. Allows mitosis where it crosses

Question 15

How are 3 layers of gastrulation initially formed?

Answer 15

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

Question 16

How is the notochord formed?

Answer 16

Ectoderm continues multiplying, forming rod structure down past mesoderm. This eventually breaks off and nerves a notochord below mesoderm. Primative streak disappears.

Question 17

How is the neural plate formed?

Answer 17

Notochord released chemical signals to ectoderm, which bends to form the neural plate

Question 18

How is the neural tube formed? What is it?

Answer 18

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

Question 19

How are 3 sections of the mesoderm formed and what are they called?

Answer 19

Cells continue being added to mesoderm, causing it to thicken.

Layers formed are paraxial mesoderm, intermediate plate mesoderm and lateral plate mesoderm

Question 20

What does the intermediate plate mesoderm go on to form?

Answer 20

Urogenital system

Question 21

What does the lateral plate mesoderm go on to form?

Answer 21

Lateral place splits in half, forming a somatic and a splanchnic mesoderm

Body cavities and coverings, including pleural and peritoneal cavities

Question 22

How are somites formed and what do they look like?

Answer 22

Form in pairs on either side of your paraxial mesoderm. There’s 43 pairs and they each divide into 3 structures.

Question 23

What do somites divide into? (3)

Answer 23

Dermatome, myotome and sclerotome

Question 24

What is teratology?

Answer 24

Study of abnormal development of embryo

Question 25

When is a foetus most and least susceptible to effects from teratogens?

Answer 25

1-2 week embryo wont survive. 3-8 weeks exposure can cause maximal effect. 9+ weeks, sensitivity decreases