Sep 12 - Embryology

Question 1

Anatomically, where does fertilization occur?

Answer 1

Ampula of the fallopian tubes

Question 2

How long does fertilization take?

Answer 2

About a day

Question 3

Define fertilization

Answer 3

Begins when sperm fuses with oocyte. Ends when paternal and maternal nuclei fuse together.

Question 4

What happens the day after fertilization?

Answer 4

Cleavage of zygote.

Question 5

When and where does the first cleavage of the zygote occur?

Answer 5

Uterine tube on Day 2 (post-fertilization)

Question 6

Define cleavage of a zygote after fertilization

Answer 6

Cell division without growth

Question 7

What is the zygote called on day 3 post-fertilization?

Answer 7

Morula

Question 8

What is a morula?

Answer 8

12-16 (very) loosely attached cells formed after cleavage

Question 9

What is they zygote called on day 5 post-fertlization?

Answer 9

Blastocyte

Question 10

Define a blastocyte

Answer 10

A hollow ball filled with about 100 cells that are condensed to one side of the hollow ball.

Question 11

The ~100 condensed cells on the side of a blastocyst is called a _____ (3 options)

Answer 11

embryoblast OR inner cell mast OR embryonic stem cells

Question 12

The cells forming the wall of the blastocyst is called what?

Answer 12

Trophoblast

Question 13

What does the trophoblast develop into? (2 answers)

Answer 13

The fetal membranes and the placenta.

Question 14

When does implantation of the blastocyst occur?

Answer 14

Day 6 post-fertilization

Question 15

Define implantation of the blastocyst

Answer 15

The trophoblast cells of the blastocyst invades the epithelial wall of the uterus to anchor the blastocyst

Question 16

What happens in week 2 post-fertilization?

Answer 16

Formation of the bilaminar germ disc

Question 17

What are the first 3 steps in the formation of the bilaminar germ disc?

Answer 17

1. Formation of the amniotic cavity within the embryoblast.
2. Formation of lacunae in the syncytiotrophoblast.
3. Maternal blood vessels enlarge into sinusoids.

Question 18

What are the second set of 3 steps that finalize the formation of the bilaminar germ disc?

Answer 18

1. The sinusoids and lacunae fuse (forms uteroplacental circulation)
2. Extraembryonic mesoderm forms.
3. The chorionic cavity forms and the primary yolk sac disappears.

Question 19

What is the chorionic cavity?

Answer 19

A large cavity that forms inside the extraembryonic mesoderm

Question 20

What happens at the end of week 2 post-fertlization in the formation of the bilaminar germ disc?

Answer 20

The embryonic disc now has two layers, the epiblast and hypoblast.

Question 21

What is they zygote called between weeks 3 and 8 post-fertilization?

Answer 21

An embryo

Question 22

What happens in week 3 post-fertilization?

Answer 22

Formation of the trilaminar germ disc.

Question 23

What are the two steps in formation of the trilaminar germ disc?

Answer 23

1. Gastrulation

2. Neurulation

Question 24

Define gastrulation

Answer 24

The process in which all three germ layers are formed.

Question 25

What structure do the three germ layers develop from?

Answer 25

The epiblast.

Question 26

What are the three germ layers?

Answer 26

1. Ectoderm 2. Endoderm 3. Mesoderm

Question 27

What is the primitive streak?

Answer 27

An elongated depression located on the caudal (tail) end of the embryo.

Question 28

What happens in gastrulation?

Answer 28

The epiblast cells migrate through the primitive streak.

Question 29

The migrating cells in gastrulation develop into which two germ layers, which are located beneath which third germ layer?

Answer 29

The migrating cells develop into the mesoderm and the endoderm, both of which are situated beneath the ectoderm.

Question 30

Where is the notochordal process located?

Answer 30

Midline of the mesoderm in the cranial part of the embryo.

Question 31

What is the notochordal process?

Answer 31

Mesodermal cells that form the notochord

Question 32

Epithelium, hair, and nails come from which germ layer?

Answer 32

Surface Ectoderm (Ectoderm)

Question 33

Cutaneous and mammary glands come from which germ layer?

Answer 33

Surface Ectoderm (Ectoderm)

Question 34

The neural tube forms what?

Answer 34

Central Nervous System (CNS)

Question 35

The neural crest forms what?

Answer 35

Dorsal root ganglia, nerves, and pigment cells (Peripheral Nervous System PNS)

Question 36

The neural tube comes from which germ layer?

Answer 36

Neuroectoderm

Question 37

The neural crest comes from which germ layer?

Answer 37

Neuroectoderm

Question 38

The paraxial mesoderm forms into what?

Answer 38

1. Muscles of the trunk and limbs 2. Axial skeleton (except head) 3. Connective tissue

Question 39

The lateral plate mesoderm forms into what?

Answer 39

1. Appendicular skeleton (limbs) | 2. Connective tissue of muscles and viscera

Question 40

What are the 3 steps of neurulation?

Answer 40

1. Thickens into the neural plate 2. Forms a groove 3. Forms into the neural tube

Question 41

The mesoderm on each side of the notochord differentiates into what 3 sub-germ layers?

Answer 41

1. Paraxial mesoderm 2. Intermediate mesoderm 3. Lateral plate mesoderm

Question 42

How does the neural crest form?

Answer 42

Cells from the lateral side of the neural plate will migrate and form bars of tissue in the mesenchyme.

Question 43

What happens (what process) at the end of week 3?

Answer 43

Somite formation

Question 44

Which germ layer forms the somites by segmentation?

Answer 44

Paraxial mesoderm

Question 45

In which direction does somite formation occur?

Answer 45

Starts cranially and continues caudally (towards the tail)

Question 46

What happens (what process) in week 4?

Answer 46

Formation of the head and tail folds

Question 47

What is the mushroom stage and when does it occur?

Answer 47

Formation of the head and tail folds in week 4

Question 48

How many days is the human gestation period?

Answer 48

38 weeks (~266 days on average)

Question 49

When is the last normal menstrual period?

Answer 49

2 weeks before fertilization

Question 50

Are all three trimesters of the gestational period equal in length?

Answer 50

Yes

Question 51

Describe the status of the fetus after the first trimester?

Answer 51

All major organs present; fetus size = width of palm of hand

Question 52

Describe the status of the fetus after the second trimester?

Answer 52

Low chance of survival if born in this period (50% survival probability). Fetus size = as long as a hand

Question 53

Describe the status of the fetus after the third trimester?

Answer 53

Strong chance of living if born in this period. However, if born in the first month of the 3rd trimester, the child usually retains health problems throughout life.