1. Embryology

Question 1

How long is the “fetal/conceptional” age?

Answer 1

38 weeks (Gestation age: from LMP, 40w)

Question 2

How long is the “gestational” age?

Answer 2

40 weeks

Question 3

How long and what defines the “embryonic” period?

Answer 3

First 8 weeks

All major organs formed

Question 4

How long and what defines the “fetal” period?

Answer 4

Remaining 30 weeks

Organs grow larger and increase in complexity

Question 5

Define Zygote

Answer 5

The cell that forms when the ova and sperm fuse

Question 6

What occurs during the first week after conception? (4)

Answer 6

1. Zygote divides repeatedly
2. Blastomeres = Daughter cells
3. Morula (day 3)
   - - - Entering uterus
4. Blastocyst (day 4)
   - Inner cell mass
   - Trophoblast

Question 7

Define Morula

Answer 7

Solid cluster of 12-16 blastomeres at about 72 hours

Question 8

When occurs on day 4 post conception?

Answer 8

Morula enters uterus and takes up fluid becoming a blastocyst

Question 9

Types of Cells in the Blastocyst Stage (2)

Answer 9

Inner cell mass

Trophoblast

Question 10

Define Inner Cell Mass

Answer 10

Forms the embryo

Question 11

Define Trophoblast

Answer 11

Form the placenta

Question 12

What occurs on day 8-9 post conception?

Answer 12

Implantation of the zygote

Question 13

Three Primary Germ Layers (3)

Answer 13

Ectoderm

Endoderm

Mesoderm

Question 14

The ectoderm and endoderm form what?

Answer 14

Sheets of epithelial tissue

Question 15

The mesoderm forms what?

Answer 15

Mesenchyme tissue

Question 16

Define Gastrulation

Answer 16

Invagination of epiblast cells

Question 17

When does the endoderm form?

Answer 17

Days 14-15

(Mesoderm Day 16)

Question 18

When does the mesoderm form?

Answer 18

Day 16

Question 19

What occurs during days 16-18? (4)

Answer 19

1. Epiblast cells invaginate (Gastrulation)
2. Migrate anteriorly with endoderm cells
3. Rod defining body axis formed
4. Notochord is future site of vertebral column

Question 20

What occurs during neurulation

Answer 20

Neural plate to neural groove to neural tube

Question 21

What are the three regions of the mesoderm?

Answer 21

Somites: beginning of vertebral bones

Intermediate mesoderm

Lateral plate: forms cavity

Question 22

When does the neural tube close?

Answer 22

Starts at the end of week 3 and completes at end of week form

Question 23

What is the somatic mesoderm opposed to?

Answer 23

Ectoderm

Question 24

What is the splanchnic mesoderm opposed to?

Answer 24

Endoderm

Question 25

What is between the somatic mesoderm and splanchnic mesoderm?

Answer 25

Coelom

Question 26

What serous cavities form from the coelom? (3)

Answer 26

Peritoneal

Pericardial

Pleural

Question 27

Major Derivatives of the Ectoderm (3)

Answer 27

Epidermis, hair, nails, glands of skin

Brain & spinal cord

Neural crest: sensory nerve cells, nervous structures,

portions of skeleton,

pigment cells,

blood vessels in H&N

Question 28

Major Derivatives of the Endoderm (1)

Answer 28

Epithelial lining and glands of digestive and respiratory tracts

Question 29

Major Derivatives of the Mesoderm (13)

Answer 29

1. Vertebrae & ribs, 2. Nucleus pulposus
2. Trunk & limb musculature, 4. Connective tissues of limbs,
3. Dermatomes, 6. Ventral body dermis
4. Kidneys, 8. Gonads
5. Parietal serosa, 10. Visceral serosa, 11. Wall of digestive & respiratory tracts
6. Heart, 13. Blood vessels

Question 30

When does the heart start pumping?

Answer 30

4 weeks

Question 31

When Does Organogenesis Occur?

Answer 31

Weeks 3-8

Question 32

What occurs during organogenesis (week 3-8)?

Answer 32

Stem cell populations established for each organ

Most gross structural birth defects are induced