embryology

Question 1

what is a zygote?

Answer 1

a fertilised ovum

Question 2

what is a morula?

Answer 2

a solid mass of cells at 4-6 days

Question 3

what is a blastocyst?

Answer 3

a hollow ball of cells- inner cell mass and outer(trophoblast) at 6-10 days

Question 4

what is the embryo’s life support/nutrient supply?

Answer 4

the placenta

Question 5

how is the baby’s blood replenished from the mothers?

Answer 5

the circulations don’t mix as they are separated by a thin barrier, it is permeable to most molecules but not cells

Question 6

what is the bilaminar embryo?

Answer 6

at 10-12 days the implanted trophoblast contains an embryo with 2 cell layers

Question 7

what is the epiblast?

Answer 7

the layer in the bilaminar embryo which gives rise to embryonic ectoderm, mesoderm and endoderm

Question 8

what is the hypoblast

Answer 8

the layer in the bilaminar embryo which participates in formation of endoderm and extraembryonic mesoderm

Question 9

what does the embryo develop during gastrulation?

Answer 9

an axis (bilateral symmetry), the 3 embryonic cell layers and a groove- the primitive streak

Question 10

how is the mesoderm formed?

Answer 10

some ectodermal cells are introduced to and migrate thru the primitive streak towards the hypoblast

Question 11

how is the endoderm formed?

Answer 11

an interaction between the mesoderm and hypoblast.

Question 12

what is the trilaminar embryo?

Answer 12

the mesodermal cells push thru the primitive streak and spread out to form a 3rd layer

Question 13

what is organogenesis?

Answer 13

during weeks 3-8 the major organs develop from the 3 basic germ layers

Question 14

when is the neural groove evident?

Answer 14

20 days

Question 15

what is the neural tube the forerunner of?

Answer 15

CNS

Question 16

what defect can occur where the neural groove persists?

Answer 16

spina bifida

Question 17

what is weird about the neural crest?

Answer 17

it is derived from ectoderm but has the characteristics of mesenchyme

Question 18

how does the trilaminar embryo begin to take shape?

Answer 18

the front and back ends begin to fold under the middle, the embryo folds around the yolk sac, and important organs appear

Question 19

at which week does and embryo become a fetus?

Answer 19

week 9

Question 20

what are stem cells?

Answer 20

unspecialised cells that can develop into more specialised cells

Question 21

describe adult stem cells

Answer 21

committed to cell lines

Question 22

what embryonic stem cells are totipotent?

Answer 22

inner cell mass

Question 23

what embryonic stem cells are pluripotent?

Answer 23

cells in the 3 germ layers

Question 24

what does the ectoderm consist of?

Answer 24

outer- skin, mucous membranes, brain, spinal cord, tooth enamel

Question 25

what does the mesoderm consist of?

Answer 25

middle- CT, muscle, b.v, kidneys, urinary system, reproductive system, serous membranes

Question 26

what does the endoderm consist of?

Answer 26

inner- alimentary canal, respiratory system, parts of urogenital system

Question 27

what is ectomesenchyme?

Answer 27

a 4th layer which gives rise to: PNS, melanocytes, adrenal medulla, mesenchyme in head, dentine, ementum, pulp, PDL, jaw bones

Question 28

when do most developmental defects occur?

Answer 28

weeks 3-12