Embryology

Question 1

What is the path of the sperm cell?

Answer 1

-corona radiata

-zona pellucida

-plasma membrane of secondary oocyte

-cytoplasm of secondary oocyte

Question 2

Explain the stages of formation of the morula and blastocyst

Answer 2

Day 1- cleavage of zygote, two cell stage

Day 2- cleavage of zygote, four cell stage

Day 4- morula

Day 5- blastocyst

Question 3

What events take place within the first week of development

Answer 3

1. fertilisation= occurs within uterine tube after ovulation
2. cleavage= first completed 30 hours after fertilisation
3. morula= 3-4 days after fertilisation
4. blastocyst= 4.5-5 days after fertilisation
5. Implantation= 6 days after fertilisation

Question 4

What are the two layers that make up the uterus?

Answer 4

endometrium and myometrium

Question 5

What is neuralation

Answer 5

Neural plate starts to develop at days 18-23

Question 6

What is angiogenesis 1?

Answer 6

-individual blood cells appear, join together to form tubes
-heart starts to develop
-heart starts beating around day 23

Day 22

Question 7

What is angiogenesis 2?

Answer 7

-rudimentary blood system
-folded heart single chamber

Day 26

Question 8

What is identifiable of an embryo at week 8?

Answer 8

-foetus recognisable as an infant
-internal organs developed as structures
-limbs developed
-genitalia starting to develop

Question 9

What does the foetal phase consist of?

Answer 9

-from 9 weeks to full term
-characterised by growth, development of structures and development of functionality

Question 10

What is the main difference between the 2nd and third trimester in terms of development?

Answer 10

2nd trimester mainly grow in length
3rd trimester mainly grow in weight

Question 11

What is the difference between identical and non identical twins?

Answer 11

identical twins:
-share genes
-same gender
-monozygotic
-1 placenta

nonidentical twins:
-50% of genes are the same
-dizygotic
-2 placentas

Question 12

What happens during fertilisation to produce a single diploid nucleus?

Answer 12

the genetic material from a haploid sperm cell and a haploid secondary oocyte merges to form the single diploid nucleus

Question 13

How is a zygote produced?

Answer 13

penetration of the zona pellucid is facilitated by enzymes in the sperms acrosome, forming a zygote

Question 14

What is a blastocyst?

Answer 14

-the morula (solid sphere of cells) develops into a blastocyst which is a hollow ball of cells differentiated into a trophoblast and an inner cell mass

Question 15

What is implantation?

Answer 15

the attachment of a blastocyst to the endometrium

Question 16

What does the hypoblast form and do?

Answer 16

-forms the yolk sac
-this transfers nutrients to the embryo, forms blood cells, produces primordial germ cells and forms part of the gut

Question 17

What are the 3 primary germ layers and what do they do?

Answer 17

-ectoderm, mesoderm, endoderm
-these from all tissue and organs of the developing organism

Question 18

What is the role of the chorionic villi?

Answer 18

-projections of the chorion
-connect to the embryonic heart so that maternal and fatal blood vessels are brought into close proximity so nutrients and wastes are exchanged between maternal and fetal blood

Question 19

What is the placenta and what are its functions?

Answer 19

-site of exchange of nutrients and wastes between the mother and foetus
-protective barrier, stores nutrients and produces several hormones to maintain pregnancy

Question 20

How is the umbilical cord different from the placenta?

Answer 20

it is the actual connection between the placenta and embryo