Embryology

Question 1

What time period is covered by the term conceptus?

Answer 1

Fertilisation to end of week 3

Question 2

What time period is covered by the term embryo?

Answer 2

Week 4-week 8

Question 3

What is happening with regards to organs in an embryo?

Answer 3

They are all present but not yet matured

Question 4

What time period is covered by the term foetus?

Answer 4

Week 9- birth

Question 5

What does gametogenesis phase comprise?

Answer 5

Germ cell formation (formation of egg and sperm)

Question 6

What does the fertilisation phase comprise?

Answer 6

Formation of sperm and oocyte to form the zygote

Question 7

What is a zygote?

Answer 7

Single cell embryo

Question 8

What is the period of cell division with no size increase as a protein coat is forming known as?

Answer 8

Cleavage

Question 9

What is a blastocyte?

Answer 9

First point where differentiation can be seen in cells

Question 10

Which cells in the cluster of a blastocyte will form embryo structures?

Answer 10

Cells in the centre of the cluster

Question 11

What happens in gastrulation?

Answer 11

Germ layers and formed and body axis determined

Question 12

What are the 3 germ layers?

Answer 12

Ectoderm- outer
Mesoderm- middle
Endoderm- inner

Question 13

What happens in organogenesis?

Answer 13

Formation of organs and organ systems

Question 14

The basis of organs and organ systems will all be in place by ? and will continue developing through ?

Answer 14

Embryonic period/foetal period

Question 15

What are 5 things which happen in the foetal period?

Answer 15

• Growth and weight gain
• Tissues mature and become functional
• Sexual differentiation
• Bone laid down
• Connections made in CNS

Question 16

When are you able to tell the sex of a foetus?

Answer 16

12 weeks

Question 17

What is the ability of one cell type to cause another one to differentiate known as?

Answer 17

Induction

Question 18

What 3 factors control development?

Answer 18

Genetic, epigenetic and environmental

Question 19

What is the difference between genetic and epigenetic control?

Answer 19

Genetic- expression of genes

Epigenetic- preferential expression of maternal or paternal genes

Question 20

What is Angelman syndrome?

Answer 20

Deletion of maternal chromosome 15 which leads to mental retardation and poor motor development

Question 21

What is Prader-Willi syndrome?

Answer 21

Deletion of paternal chromosome 15 which leads to mental retardation, obesity and hypogonadism

Question 22

Where does fertilisation take place?

Answer 22

Ampulla of the fallopian tube

Question 23

What does the sperm first bind with?

Answer 23

Glycoproteins of the zona pellucida

Question 24

What happens before the sperm nucleus enters the egg?

Answer 24

Sperm and zona pellucida membranes fuse

Question 25

What does sperm entry trigger?

Answer 25

Completion of meiosis 2 and release of cortical granules to prevent fertilization from a second sperm

Question 26

After fertilisation, the zygote undergoes mitotic divisions to produce daughter cells known as what?

Answer 26

Blastomeres

Question 27

What is the point where are cells are confined within the zona pellucida known as?

Answer 27

Compaction

Question 28

What will the outer cells closer to the zona pellucida form?

Answer 28

Extensive gap junctions

Question 29

Is the zona pellucida impermeable?

Answer 29

No

Question 30

As early events of week 1 take place, where is the embryo moving towards?

Answer 30

Uterine cavity

Question 31

How long does it take the embryo to reach the uterine cavity and what forms when it does?

Answer 31

About 4-5 days, forms the blastocyte

Question 32

What is the function of the zona pellucida?

Answer 32

Protection

Question 33

When is the zona pellucida lost?

Answer 33

When the embryo reaches the uterine cavity and it blocks entry to here

Question 34

Where are the normal sites of implantation?

Answer 34

Middle/upper dorsal uterine wall

Question 35

Where are abnormal sites of implantation?

Answer 35

Ovary, ampulla, uterine tube, lower uterus, cervix, peritoneum

Question 36

What does implantation in abnormal sites lead to?

Answer 36

Ectopic pregnancy

Question 37

Implantation is an active process driven by what?

Answer 37

Trophoblast

Question 38

At around 7.5 days, the embryo divides into 2 cell layers, what are these?

Answer 38

Epiblast- dorsal surface of an embryo | Hypoblast- ventral surface of an embryo

Question 39

What else begins to form during implantation, and when does implantation finish?

Answer 39

Amniotic cavity | Finishes around day 9

Question 40

What do the epiblast and hypoblast become during gastrulation?

Answer 40

Hypoblast- endoderm | Epiblast- ectoderm

Question 41

What does the endoderm become?

Answer 41

Lining of GI tract, respiratory tract, bladder and urethra

Question 42

What does the ectoderm become?

Answer 42

Epidermis of skin, hair, nails, associated glands, nervous system

Question 43

Somatic and visceral coverings of organs are derived from what?

Answer 43

Mesoderm

Question 44

What does lateral folding create?

Answer 44

Thoracic and abdominal cavities

Question 45

What does lateral folding close?

Answer 45

Foregut and hindgut

Question 46

Which gut is the last to close?

Answer 46

Midgut

Question 47

What happens during cranial folding?

Answer 47

Formation of the foregut and defines the thoracic cavity, developing heart tube is displaced into the thoracic cavity

Question 48

What is formed during caudal folding?

Answer 48

Hindgut, anus and umbilical cord

Question 49

When does the heart begin to develop?

Answer 49

Week 4

Question 50

What is the normal development of the atrial septum?

Answer 50

Grows as 2 septa (primum/secundum),

Question 51

When does communication between the 2 atrial septa continue until and what does this communication occur through?

Answer 51

Continues until birth through the foramen ovale

Question 52

What are the relative pressures of the atria before and after birth?

Answer 52

Before: right higher, left lower After: right lower, left higher

Question 53

What are three causes of an atrial septal defect?

Answer 53

Excessive resorption of septum primum Absent septum secundum Patent foramen ovale

Question 54

What are the 2 different types of ventricular septal defect?

Answer 54

Muscular defect- most common and least severe | Membranous defect- less common and most severe

Question 55

What happens in transposition of the great vessels?

Answer 55

Aorta exits right ventricle and pulmonary trunk exits left ventricle causing deoxygenated blood to be carried around the body

Question 56

What are the 4 factors in Tetralogy of Fallot?

Answer 56

Pulmonary stenosis, hypertrophy of right ventricle, VSD, overriding aorta