Embryology

Question 1

what is a fertilised egg called?

Answer 1

zygote

Question 2

what is a morula and when does it appear?

Answer 2

solid mass of cells from 4-6 days

Question 3

what is a blastocyst and when does it appear?

Answer 3

a hollow ball of cells from 6-10 days

Question 4

what are the two parts of a blastocyst?

Answer 4

inner cell mass and trophoblast

Question 5

what is the baby’s blood replenished by?

Answer 5

the mothers blood

Question 6

what are the mothers and baby’s circulations mixed by?

Answer 6

a thin barrier

Question 7

what happens at 10-12 days?

Answer 7

the implanted trophoblast contains an embryo which has 2 cell layers

Question 8

what are the two layers of the bilaminar embyro?

Answer 8

epiblast and hypoblast

Question 9

what does the epiblast give rise to?

Answer 9

the embryonic ectoderm, mesoderm and endoderm

Question 10

what does the hypoblast give rise to?

Answer 10

endoderm and extraembryonic mesoderm

Question 11

what does the embryo develop during gastrulation?

Answer 11

an axis (to become bilaterally symmetrical) and the third embrionic cell layer

Question 12

where does the mesoderm come from?

Answer 12

ectodermal cells which migrate through the primitive streak towards the hypoblast

Question 13

what forms the endoderm?

Answer 13

an interaction between the mesoderm and the hypoblast

Question 14

what forms the third layer of the embryo?

Answer 14

the mesodermal cells pushing through the primitive streak

Question 15

what is organogenesis and when does it happen?

Answer 15

the major organs developing from basic germ cell layers and it happens at week 3-8

Question 16

what is the neural tube?

Answer 16

the forerunner of the central nervous system

Question 17

where does the neural crest come from?

Answer 17

the ectoderm but has characteristics of the mesenchyme

Question 18

what is the neural crest also called?

Answer 18

the ectomesenchyme

Question 19

what organs appear when the embryo folds around the yolk sac?

Answer 19

the heart liver and lungs

Question 20

what are stem cells?

Answer 20

unspecialised cells that can develop into more specialised cells

Question 21

what are totipotent cells?

Answer 21

inner cell mass

Question 22

what are pluripotent cells?

Answer 22

cells in the 3 germ layers that are more restricted in potential

Question 23

what does stem cell development involve?

Answer 23

genes and various signalling molecules

Question 24

what are the 3 primary embryonic layers?

Answer 24

ectoderm, mesoderm and endoderm

Question 25

what is the ectoderm?

Answer 25

the outer covering

Question 26

what is the mesoderm?

Answer 26

the middle

Question 27

what is the endoderm?

Answer 27

the inner lining

Question 28

what does the ectoderm form?

Answer 28

the skin, mucous membranes of mouth, anus, brain, spinal cord and tooth enamel

Question 29

what does the mesoderm form?

Answer 29

most connective tissues, muscle, blood vessels, kidney, urinary system, reproductive system and serous membranes

Question 30

what does the endoderm form?

Answer 30

alimentary canal, respiratory system, parts of urogenital system

Question 31

what is the ectomesenchyme?

Answer 31

a fourth layer

Question 32

what does the ectomesenchyme give rise to?

Answer 32

most of the peripheral nervous system: sensory and autonomic nerves, melanocytes in skin, adrenal medulla, most of the mesenchyme in the head, dentine, cementum, pulp, periodontal ligament, jaw bones

Question 33

if a developmental abnormality occurs during the first 2 weeks what happens?

Answer 33

spontaneous abortion

Question 34

what is the period of greatest sensitivity?

Answer 34

first trimester

Question 35

what is the period of functional maturity?

Answer 35

weeks 13-39