Embryology

Question 1

What is embryology?

Answer 1

The study of progression from a single cell to a baby in 9 months

Question 2

What is special about zebra fish?

Answer 2

Translucent eggs that are outside the mother
Sequenced genome
Study birth defects

Question 3

Where does fertilisation take place?

Answer 3

Ampullary region of the fallopian tube

Question 4

How long is a sperm viable for?

Answer 4

5 days

Question 5

How long is a secondary oocyte viable for?

Answer 5

12-24 hours

Question 6

Why aren’t sperm rejected as they are foreign bodies?

Answer 6

Antibodies only form if the sperm gets in contact with the blood
Tight junctions stop sperm passing into blood

Question 7

When is the germinal stage?

Answer 7

Fertilisation to the end of the second week

Question 8

When is the embryonic period?

Answer 8

Beginning of third week till the end of the eighth week

Question 9

When is the Foetal period?

Answer 9

Beginning of ninth week to birth (38 weeks)

Question 10

What is the Zona Pellicuda?

Answer 10

Stops the blastocyte from adhering to oviduct

The loss of it is called hatching

Question 11

What does trophoblast mean?

Answer 11

Food bud- becomes the yolk sac and placenta

Question 12

What is Histiotrophic nutrition?

Answer 12

Nutrition provided to the embryo not from the maternal blood
Before week 12

Question 13

What is haemoptrophic nutrition?

Answer 13

Nutrition provided by the mothers blood

After week 12

Question 14

What is the implantation site?

Answer 14

Site of formation the placenta

Usually upper part of the body of the uterus in the posterior wall

Question 15

What is an ectopic pregnany?

Answer 15

Fetus develops outside the Uterus

Question 16

What is placenta previa?

Answer 16

Placenta blocks the neck of the uterus so interferes with delivery

Question 17

What is Syncytium?

Answer 17

Together cells

Question 18

What is syncytiotrophoblast?

Answer 18

Cells that merge together in the trophoblast

Question 19

What is Cytotrophoblast?

Answer 19

Cells in the trophoblast

Question 20

What happens in the second week of development?

Answer 20

Trophoblast differentiates into 2 layers
Embryoblast forms 2 layers- epiblast and hypoblast
Hypoblast forms the yolk sac and chorionic cavity

Question 21

What happens during the embryonic period?

Answer 21

All major systems and structures are formed

Question 22

When is the greatest risk of major congenital malformations?

Answer 22

Embryonic period

Question 23

What are the key events and processes in early development?

Answer 23

Fertilisation and implantation
Gastrulation
Neurulation
Segmentation
Folding

Question 24

Where do new features appear in the third week?

Answer 24

Dorsal surface of the epiblast

Question 25

What is an ectoderm?

Answer 25

Organs and structures that maintain contact with outside world

Question 26

What is a mesoderm?

Answer 26

Supporting tissues

Question 27

What is an endoderm?

Answer 27

Internal structures

Question 28

What is Situs inversus?

Answer 28

Complete mirror image viscera Commonly results from immotile cilia No associated morbidity Problem arise if normal and mirror image disposition

Question 29

What are the clear right and left body differences?

Answer 29

Liver on the right Stomach and spleen on the left Left lung has 2 lobes Right lung has 3 lobes

Question 30

When is Gastrulation?

Answer 30

Third week

Question 31

What is Gastrulation?

Answer 31

Bilaminar disks are converted into trilaminar disks | Three germ layers, ectoderm, mesoderm and endoderm

Question 32

How does Gastrulation occur?

Answer 32

Primitive streak forms in caudal epiblast, leading to migration and invagination of epiblast cells

Question 33

Why does Gastrulation occur?

Answer 33

To ensure the correct placement of precursor tissues to allow subsequent morphogenesis to take place

Question 34

What does the ultimate fate of invaginating epiblasts depend on?

Answer 34

Where in the streak or node they invaginate

Question 35

What is the notochord?

Answer 35

Solid rod of cells running in the midline with important signalling role Directs conversion of overlying ectoderm to neurectoderm

Question 36

What do norochord signals cause?

Answer 36

Ectoderm to thicken

Question 37

What is somites?

Answer 37

Organisation of paraxial mesoderm into segments

Question 38

When and where do the 1st pair of somites appear?

Answer 38

Day 20 in the occipital region

Question 39

How many somites will there be in total?

Answer 39

31

Question 40

What do somites appear as?

Answer 40

Regular block of mesoderm cells arranged around a small cavity

Question 41

What is organised degeneration of somites?

Answer 41

Ventral wall of somite breaks down, leading to formation of the sclerotome

Question 42

What forms the dermomyotome?

Answer 42

Organisation of the dorsal portions

Question 43

What is dermatome?

Answer 43

Skin section

Question 44

What is myotome?

Answer 44

Muscle section

Question 45

What is sclerotome?

Answer 45

Hard tissue section e.g. bone

Question 46

What does organisation of mesoderm into somites give rise to?

Answer 46

Repeating structures e.g. vertebrae, ribs, intercostal muscles, spinal cord segments

Question 47

How many pairs of spinal nerves are there?

Answer 47

31

Question 48

What does folding achieve?

Answer 48

Draws together the margins of the disk which creates a ventral body wall pulling amniotic membrane around the disc pulling connective stalk ventrally

Question 49

What happens by the end of the fourth week?

Answer 49

The nervous system has started to form segments have appeared, assigning specific tasks to specific cells, the embryo has folded, putting everything in the right place