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Flashcards in Embryology Deck (39):
1

Define Embryology

Study of the origin and development of an organism

2

How long is the "fetal" age?

38 weeks

3

How long is the "gestational" age?

40 weeks

4

How long and what defines the "embryonic" period?

First 8 weeks
All major organs formed

5

How long and what defines the "fetal" period?

Remaining 30 weeks
Organs grow larger and increase in complexity

6

Define Ovulation

Egg released into the peritoneal cavity

7

Define Fertilization

Occurs as egg travels down the fallopian tube

8

Define Zygote

The cell that forms when the ova and sperm fuse

9

Define Cell Division

Begins immediately as the zygote travels down the fallopian tube and into the uterus

10

What occurs during the first week after conception?

Zygote divides repeatedly
Daughter cells = blastomeres
Morula
Blastocyst

11

Define Morula

Solid cluster of 12-16 blastomeres at about 72 hours

12

When occurs on day 4 post conception?

Morula enters uterus and takes up fluid becoming a blastocyst

13

Types of Cells in the Blastocyst Stage

Inner cell mass
Trophoblast

14

Define Inner Cell Mass

Forms the embryo

15

Define Trophoblast

Layers of cells surrounding the cavity which helps form the placenta

16

What occurs on day 6 post conception?

Implantation of the zygote

17

What occurs during implantation?

Tropholast erodes uterine wall

18

Three Primary Germ Layers

Ectoderm
Endoderm
Mesoderm

19

The ectoderm and endoderm form what?

Sheets of epithelial tissue

20

The mesoderm forms what?

Mesenchyme tissue

21

Define Gastrulation

Invagination of epiblast cells

22

When does the endoderm form?

Days 14-15

23

When does the mesoderm form?

Day 16

24

What occurs during days 16-18?

Epiblast cells invaginate
Migrate anteriorly with endoderm cells
Rod defining body axis formed
Notochord is future site of vertebral column

25

Define Neurulation

Formation begins of spinal cord and brain

26

What occurs during neurulation

Neural plate to neural groove to neural tube

27

What are the three regions of the mesoderm?

Somites: beginning of vertebral bones
Intermediate mesoderm
Lateral plate: forms cavity

28

When does the neural tube close?

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

29

What is the somatic mesoderm opposed to?

Ectoderm

30

What is the splanchnic mesoderm opposed to?

Endoderm

31

What is between the somatic mesoderm and splanchnic mesoderm?

Coelom

32

What serous cavities form from the coelom?

Peritoneal
Pericardial
Pleural

33

Major Derivatives of the Ectoderm

Epidermis, hair, nails, glands of skin
Brain & spinal cord
Neural crest: sensory nerve cells, nervous structures, pigment cells, portions of skeleton, blood vessels in H&N

34

Major Derivatives of the Endoderm

Epithelial lining and glands of digestive and respiratory tracts

35

Major Derivatives of the Mesoderm

Nucleus pulposus
Vertebrae & ribs
Dermatomes
Trunk & limb musculature
Kidneys
Gonads
Parietal serosa
Ventral body dermis
CT of limbs
Wall of digestive & respiratory tracts
Visceral serosa
Heart
Blood vessels

36

When does the heart start pumping?

4 weeks to 1 month

37

When Does Organogenesis Occur?

Weeks 3-8

38

What occurs during organogenesis?

Stem cell populations established for each organ
MOST gross structural birth defects are induced

39

What is the significance of organogenesis?

Mother MUST avoid environmental, dietary, and drug exposure during this period