Embryology

Question 1

What are the main stages of embryo development?

Answer 1

• gametogenesis
• fertilisation
• cleavage
• gastrulation
• formation/folding
• organogenesis

Question 2

What is involved in gametogenesis?

Answer 2

germ cell formation of oocyte and spermatozoa

Question 3

What is involved in fertilisation?

Answer 3

fusion of sperm and oocyte to make zygote which lasts for 12-24 hours

Question 4

What is cleavage?

Answer 4

the zygote undergoes rapid cell division to form blastomeres

Question 5

What is gastrulation?

Answer 5

formation of germ cell layers so ectoderm, mesoderm and endoderm and the body establishes axes

Question 6

What is organogenesis?

Answer 6

organs and organ systems develop

Question 7

What happened in the foetal period?

Answer 7

growth, tissue maturation, sex differentiation, bone, CNS connections

Question 8

What are the primary processes?

Answer 8

cell division
differentiation
cell attachment
apoptosis
induction 
cell migration

Question 9

What are secondary processes?

Answer 9

axis formation

folding/rotation

Question 10

What is control of development governed by?

Answer 10

genetics and epigenetics

Question 11

What is the site of fertilisation?

Answer 11

ampulla

Question 12

What are the steps of fertilisation?

Answer 12

• sperm binds to zona pellucida glycoprotein
• acrosomal enzymes digest into egg
• egg and sperm membranes fuse and sperm contents enter egg
• egg completes meiosis 2 and there is release of cortical granules by oocyte

Question 13

What is compaction?

Answer 13

cells coming close together with cell junctions, gap junctions form for outer cells

Question 14

What does the trophoblast become?

Answer 14

embryonic part of placenta

Question 15

What does the inner cell mass of the embryo become?

Answer 15

embryo, amnion and yolk sac

Question 16

What happens in implantation?

Answer 16

• 6 days: active process by trophoblast and it divides into cut-trophoblast and synctiotrophoblast
• 7.5 days: embryo is epiblast at dorsal and hypoblast at ventral and the amniotic cavity begins to form

Question 17

Where does the embryo implant?

Answer 17

upper or middle dorsal surface of the uterus

Question 18

What is involved in gastrulation?

Answer 18

formation of the germ layers so epiblast cells move through the primitive streak to form he mesoderm

Question 19

What does the ectoderm become?

Answer 19

epidermis (hair, nails, glands) and nervous system

Question 20

What does the mesoderm become?

Answer 20

• paraxial: skeleton, voluntary muscles, dermis
• intermediate: urogenital system
• lateral somatic: lining of body walls, dermis, limb parts
• lateral visceral: cardiovascular, mesothelial covering organs, smooth muscle

Question 21

What does the endoderm become?

Answer 21

lining of the gut tube, respiratory tract, bladder and urethra

Question 22

What does cranial folding form?

Answer 22

foregut