embryology

Question 1

what is embryology

Answer 1

• The study of:
• Molecular – sequencing the human genome and gene expression
• Cellular – creation of organs
• Structural
• It is the factors that make up an organism

Question 2

what is embryogenesis

Answer 2

Single cell to organ primordia (0-8weeks) is called embryogenesis

Question 3

what is the foetal period

Answer 3

From 9 weeks to birth is the foetal period

Question 4

what is teratology

Answer 4

The study of embryological origins and causes for birth defects

Question 5

what does the first trimester include?

Answer 5

• Pre-embryonic
• Embryonic
• Cleavage
• Implantation
• Placentation
• Embryogenesis

Question 6

what is fertilisation?

Answer 6

Fertilisation is the first step- This is when a sperm and an oocyte unite to create a diploid cell called a zygote (46 chromosomes)

Question 7

what are some features of fertilisation and where does it occur?

Answer 7

• Only 1 sperm can fertilise the oocyte due to changes in the cell membrane
• This occurs in the uterine tube
• Chromosomal sex of the embryo is determined at fertilisation
• Initiation of cleavage then commences

Question 8

what are the stages of the pre embryonic period?

Answer 8

1. fertilisation (0)
2. cleavage (1-3)
3. blastocyst formation (4-5)
4. implantation (6-10)
5. bilaminar disc formation (7-14)
   outcome

Question 9

briefly explain what is the cleavage stage

Answer 9

• Rapidmitotic divisionsoccur without cell growth, increasing the number of cells (blastomeres)
• Forms a solid ball of cells called themorula after 3 days (~16 cells).
  -day 5- morula reached uterine cavity and is now called a blastocyst.

Question 10

blastocyst formation say 4-5

Answer 10

• The morula develops into ablastocyst(hollow structure).
• Composed of:
  
  • Trophoblast(outer layer → placenta formation).
  • Inner Cell Mass (ICM)(future embryo).
  • Blastocoel(fluid-filled cavity).

Question 11

implantation day 6-10

Answer 11

• The blastocystattaches and embedsinto the uterine lining (endometrium).
• The trophoblast differentiates into:
  
  • Cytotrophoblast(inner layer, retains cell boundaries).
  • Syncytiotrophoblast(outer layer, invades endometrium and secretes hCG).

Question 12

bilaminar disc formation 7-14

Answer 12

• The inner cell mass forms two layers:
  
  • Epiblast(develops into the embryo).
  • Hypoblast(contributes to the yolk sac).
• Formation of:
  
  • Amniotic cavity(fluid-filled sac for protection).
  • Yolk sac(nutrient supply before placenta forms)