Basic Embryology Exam Review Info

Question 1

What are the 3 germ layers?

Answer 1

Ectoderm, Mesoderm, and Endoderm

Question 2

what does the ectoderm form?

Answer 2

forms the:
- nervous system (brain and SC)
- epidermis
- hair
- nails
- glands

Question 3

what does the mesoderm develop into?

Answer 3

• muscle (skeletal, cardiac, and smooth)
• bone
• circulatory system
• connective tissue (dermis of the skin)
• Reproductive system

Question 4

what does the endoderm form?

Answer 4

• digestive tract
• respiratory system
• parts of the endocrine system
• liver

Question 5

what happens to the egg in ovulation?

Answer 5

egg is released into peritoneal cavity and enters the fallopian tube

Question 6

what is and where does fertilization occur?

Answer 6

• occurs in the fallopin tube
• it is when the maternal and paternal genetic material combine and form a zygote

Question 7

what is a morula?

Answer 7

a cluster of cells that is formed when the zygote divides as it travels through the fallopin tube

Question 8

how many blastomeres make up a morula?

Answer 8

12-16 at about 72 hours

Question 9

when does a morula become a blastocyst?

Answer 9

around day 4

Question 10

when does a blastocyst implant in the uterus?

Answer 10

around day 7

Question 11

blastocyst stage facts…

Answer 11

• hanging out in the uterus for about 3 days
• two cell types (inner cell mass and trophoblast)
• implantation on about day 7

Question 12

what are the two cell types in a blastocyst?

Answer 12

• inner cell mass: forms the embryo
• trophoblast: forms the placenta (surrounds the cavity)

Question 13

trophoblast _____ uterine wall?

Answer 13

erodes

Question 14

how do monozygotic (identical) twins occur?

Answer 14

inner cell mass of a single blastocyst splits into two

Question 15

Week 2: what is in each, explain?
- bilaminar embryonic disc
- 2 fluid filled sacs

Answer 15

• bilaminar embryonic disc
  epiblast - extend around amniotic cavity
  hypoblast - extend into blastocyst
• 2 fluid filled sacs
  epiblast -> amniotic sac -> protection
  hypoblast -> yolk sac -> mnutrients and blood flow, will serve as blood cells and germ cells -> until week 4

Question 16

week 3:
what happens with the layers?

Answer 16

• bilaminar to trilaminar disc
• three primary germ layers develop all the body tissues
• formation of the 3 germ layers

Question 17

what takes place in the formation of the 3 germ layers?

Answer 17

• primitive streak on dorsal surface or epiblast
• gastrulation

Question 18

gastrulation?

Answer 18

invagination of epiblast cells

Question 19

week 3: days 14-15

Answer 19

endoderm replace hypoblast
ectoderm - epiblast cells remaining on surface

Question 20

week 3: day 16

Answer 20

mesoderm (a new third layer) form between

Question 21

Notochord?

Answer 21

• days 16-18
• primitive node epiblast cells invaginate and migrate anteriorly
• rod defining the body axis is formed
• future site of the vertebral column

Question 22

divisions of the mesodermal lateral plate

Answer 22

• forms serous cavities of the ventral body
• somatic (parietal) mesoderm cells -> connected to ectoderm
• splanchinic (visceral) mesoderm cells -> connected to endoderm

Question 23

different somatic (parietal) mesoderm cells?

Answer 23

peritoneal
pericardial
pleural

Question 24

what does the serous membrane cells surround?

Answer 24

each organ

Question 25

closure of neural tube is when?

Answer 25

end of week 4

Question 26

mesoderm begins to differentiate when?

Answer 26

week 3

Question 27

when does the heart start pumping?

Answer 27

day 29
4 weeks
one month

Question 28

by 8 weeks:

Answer 28

all major organs are placed in at least a rudimentary form; this is why drugs early in pregnancy are so important to avoid - many cause birth defects

embryo is a little over 1 inch long

Question 29

embryonic period

Answer 29

first 8 weeks

all major organs are formed during this time
crucial because exposure to teratogens can result in significant birth defects

Question 30

fetal period

Answer 30

weeks 9-38

organs grow and become more complex
body develops into more recognizable human form

Question 31

neurlation

Answer 31

neural tube begins to form around day 16-18 and closes by the end of week 4
vital for central nervous system development

Question 32

importance of folic acid

Answer 32

essential during early pregnancy to prevent neural tube defects (spina bifida) during the first 4 weeks