Embryology

Question 0

What is the embryonic period?

Answer 0

First 8 weeks

Question 1

During the 8 weeks what can be said about the organs?

Answer 1

They are all formed, but not developed

Question 2

How long does it take the single fertilised egg to become a new human baby?

Answer 2

Normally 9 months

Question 3

What is the conceptus stage?

Answer 3

Fertilisation to the end of week 3

Question 4

What is the embryo stage?

Answer 4

Week 4 to week 8

Question 5

What is the foetus stage?

Answer 5

Week 9 to birth

Question 6

What is gametogenesis?

Answer 6

Germ cell formation

Question 7

What two process take place during gametogenesis?

Answer 7

Oogenesis to oocyte (egg)

Spermatogenesis to spermatoza (sperm)

Question 8

What is fertilisation?

Answer 8

The formation of the zygote

Question 9

What is cleavage?

Answer 9

The period of rapid cell division

Question 10

What forms after the Morula in cleavage?

Answer 10

Blastocyst

Question 11

What is gastrulation?

Answer 11

The formation of the germ layers

Question 12

What are the 3 germ layers?

Answer 12

Ectoderm, mesoderm, endoderm

Question 13

At what stage are the body axes (head end and tail end) established?

Answer 13

Gastrulation

Question 14

What is morphogenesis?

Answer 14

Formation of the body plan (embryonic folding (tube within a tube)

Question 15

What is organogenesis and what weeks does it occur?

Answer 15

Primordia of all organ systems (weeks 4 - 8)

Question 16

During what period does growth and weight gain occur?

Answer 16

Foetal period

Question 17

During what period do tissues mature and become functional?

Answer 17

Foetal period

Question 18

What period does overt sexual differentiation occur in?

Answer 18

Foetal period

Question 19

What period is bone laid down and connections made in the CNS?

Answer 19

Foetal period

Question 20

Processes underlying development: What are the 6 primary processes?

Answer 20

Cell division - increase in number of cells
Apoptosis - programmed cell death
Differentiation - change in appearance; adoption of new functions
Cell attachment - physical linkages between cells creating tissues
Induction - ability of one cell type to cause another to differentiate
Cell migration - movement from one location to another

Question 21

Processes underlying development: What are the 3 secondary processes?

Answer 21

Axis formation/polarity
Folding/rotation - entire embryo or structures within
Increases/decreases in mass/dimension

Question 22

What are the two sub processes of the secondary process increaseing/decreasing mass and dimension?

Answer 22

1. Expansion - hypertrophy and hyperplasia

2. Compaction - decrease in cell mass with decrease in dimension, increase in cell number with no increase in dimension.

Question 23

What is hypertrophy?

Answer 23

Increase in dimension with no increase in cell number

Question 24

What is hyperplasia?

Answer 24

Increase in cell number with an increase in dimension

Question 25

What 3 factors control development?

Answer 25

Genetic Epigenetic Environment

Question 26

Where is the site of fertilisation?

Answer 26

Ampulla

Question 27

What are the 4 stages of fertilisation?

Answer 27

1. Sperm binds in a human specific interaction with the zona pellucida glycoprotein 2. Acrosomal enzymes released from sperm head; the sperm digests its way into egg 3. Egg and sperm plasma membrane fuse and sperm contents enter the cell 4. Sperm entry triggers cortical granule release in egg cortex triggering formation of fertilisation membrane, which is impenetrable to sperm

Question 28

What does sperm penetration of the egg also trigger?

Answer 28

Completion of the second meiotic division that leads to the formation of the haploid gamete.

Question 29

What does fusion of the male and female pronuclei restore?

Answer 29

The diploid number of chromosomes = zygote (day 0)

Question 30

Once the zygote is formed what does it then undergo?

Answer 30

A series of mitotic divisions which subdivide the fertilised egg into many smaller daughter cells called blastomeres.

Question 31

Up to what stage blastomeres are thought to be totipotent?

Answer 31

Up to the 8 cell stage

Question 32

What process forms blastocysts?

Answer 32

Compaction

Question 33

What is the outer layer of a blastocyst?

Answer 33

Zona pellucida

Question 34

At what day will the zygote attach to the uterus wall?

Answer 34

5.5 to 6 days

Question 35

Name the 3 layers of the uterus from external to internal?

Answer 35

Myometrium Perimetrium Endometrium

Question 36

What part of the blastocyst gives rise to the embryo?

Answer 36

Inner cell mass

Question 37

What do the remaining cells in the inner cell mass of a blastocyst form once some have given rise to the embryo?

Answer 37

The trophoblast

Question 38

What contributes to the placenta?

Answer 38

The trophoblast

Question 39

Where are embryonic stem cells derived from?

Answer 39

The inner cell mass of blastocyst

Question 40

Where does the embryo hatch from?

Answer 40

The zona pellucida

Question 41

Once hatched, where does the embryo interact directly with?

Answer 41

Endometrial lining of uterus

Question 42

Where are the normal implantation sites?

Answer 42

Middle or upper dorsal uterine wall

Question 43

Name 6 abnormal sites for implantation

Answer 43

``` Ovary Ampulla Uterine tube Lower part of uterus Cervix Periotneum ```

Question 44

What is another term for the outer cell mass of a embryo?

Answer 44

Trophoblast

Question 45

Where do trophoblast cells of the embryo begin to invade?

Answer 45

The uterine epithelium

Question 46

What has occured after 9 - 12 days?

Answer 46

The implanted embryo

Question 47

By 9 - 12 days what has the syncytiotrophoblast done to the implanted embryo?

Answer 47

Extended and by erosion contacts maternal blood supply

Question 48

Where is the amniotic cavity present in an implanted embryo?

Answer 48

Present above the bilayered embryonic disc and the definitive yolk sak below

Question 49

What cavity other than the amniotic cavity has developed at 9 - 12 days (implanted embryo)?

Answer 49

Chorionic cavity

Question 50

What does the chorionic cavity encircle?

Answer 50

The entire embryo

Question 51

What streak has formed at the end of Week 2?

Answer 51

Primitive streak

Question 52

At what end of the embryo is the primitive streak at?

Answer 52

Caudal

Question 53

At what end of the embryo is the buccopharyngeal membrane at?

Answer 53

Cranial

Question 54

During the formation of the germ layers, where do cells migrate through?

Answer 54

The primitive streak

Question 55

What process is the movement of epiblast cells through the primitive streak to form the three primary germ layers?

Answer 55

Gastrulation

Question 56

In gastrulation - what is the hypoblast replaced by?

Answer 56

Definitive endoderm

Question 57

During gastrulation - where is the intraembryonic mesoderm formed between?

Answer 57

The endoderm and epiblast

Question 58

During gastrulation what does the epiblast become?

Answer 58

Ectoderm

Question 59

After 16 days what germ layer has formed?

Answer 59

Mesoderm

Question 60

What is the fate of the ectoderm?

Answer 60

Epidermis of skin | Nervous system

Question 61

What is the fate of the mesoderm?

Answer 61

Becomes subdivided

Question 62

What is the fate of the endoderm?

Answer 62

Lining of the gut tube | Lining of respiratory tract

Question 63

During the development of the mesoderm, it becomes three regions either side of what structure?

Answer 63

Notochord

Question 64

What three regions does the mesoderm divide into?

Answer 64

Paraxial Intermediate Lateral plate (somatic mesoderm and visceral mesoderm)

Question 65

What is the fate of the paraxial mesoderm?

Answer 65

Axial skeleton, parts of dermis, voluntary muscle

Question 66

What is the fate of the intermediate mesoderm?

Answer 66

Urogenital symptoms

Question 67

What is the fate of the lateral plate mesoderm?

Answer 67

Somatic part: lining of body wall, most of dermis, parts of limbs Visceral part: Mesothelial covering of organs, cardiovascular system

Question 68

What type of folding: converts the open coelom into a closed cavity, creating thoracic and abdominal cavities and closing fore and hind gut...mid gut is last to close?

Answer 68

Lateral folding

Question 69

What type of folding: Forms the foregut and defines the thoracic cavity; developing heart tube displaced into thoracic cavity?

Answer 69

Cranial folding

Question 70

What type of folding: Cloacal membrane and connecting stalk are displaced ventrally alongside the neck of the yolk sac, forming the hindgut, anus and umbilical cord?

Answer 70

Caudal folding

Question 71

What four developments have occured in the 3rd month of foetal development?

Answer 71

Face more human looking (position of eyes and ears) Limbs lengthen First degree ossification centres in long bones and skull Sex can be determined by external genitalia

Question 72

What development occurs in months 4 and 5 of foetal development?

Answer 72

Rapid increase in length

Question 73

What occurs in the 6th month to birth stage of foetal development?

Answer 73

Rapid increase in weight

Question 74

At what stage is the critical neural development period?

Answer 74

weeks 3 - 16

Question 75

At what stage is the critical period for heart development?

Answer 75

3.5 - 9 weeks

Question 76

At what stage is the critical development period for upper limbs?

Answer 76

4 - 9 weeks

Question 77

At what stage is the critical development period for lower limbs?

Answer 77

4.5 - 9 weeks

Question 78

At what stage is the critical period of development for ears?

Answer 78

4.5 - end of 16 weeks

Question 79

At what stage is the critical development period for eyes?

Answer 79

4.75 - end of 38 weeks

Question 80

What is the critical development period for the palate?

Answer 80

6.5 - end of 9 weeks

Question 81

What is the critical development period for teeth?

Answer 81

6.5 - End of 38 weeks

Question 82

What is the critical development period for external genitalia?

Answer 82

7.5 - end of 38

Question 83

What occurs in remodelling of the heart?

Answer 83

Going from a single tube to a four chambered structure

Question 84

What 2 septa are grown during normal atrial septation?

Answer 84

``` Septum primum (flexible) Septum secundum (more rigid) ```

Question 85

What does the communication between right and left atria occur through?

Answer 85

Foramen ovale

Question 86

When does atrial septation one occur?

Answer 86

30 days

Question 87

When does atrial septation 2 occur?

Answer 87

33 days

Question 88

When does atrial septation 3 occur?

Answer 88

37 days

Question 89

What valve is the septum primum?

Answer 89

Valve of foramen ovale

Question 90

Function of foramen ovale: before birth - describe the pressures of the right and left atrium

Answer 90

Right atrium has higher pressure | Left atrium has lower pressure

Question 91

Function of foramen ovale: describe the pressures of the right and left atrium after birth

Answer 91

Right atrium is lower pressure | Left atrium is higher pressure

Question 92

After birth, in relation to the function of the foramen ovale, what closes off the shunt?

Answer 92

The septum primum (valve of foramen ovale) closes over the foramen ovale

Question 93

Describe the growth of the muscular portion of normal ventricial septation?

Answer 93

Grows upwards from wall of expanding ventricle

Question 94

Describe the growth of the membranous portion of normal ventricular septation?

Answer 94

Growth of tissue from endocardial cushions

Question 95

What is ventricular septation closely related to?

Answer 95

Septation of the outflow tract

Question 96

Name 4 types of congenital heart defects?

Answer 96

Atrial septal defect Vebtricular defect Outflow tract defects e.g. transposition of the great vessels Combination of defects

Question 97

What occurs as a result of excessive resorption of septum primum?

Answer 97

Atrial septal defects

Question 98

What occurs as a result of absent septum secundum?

Answer 98

Atrial septal defects

Question 99

What occurs when the septum primum and septum secundum fail to fuse and the mixing of blood is prevented due to pressure difference?

Answer 99

Prove patent foramen ovale

Question 100

What 3 things occur in transposition of the great vessels?

Answer 100

Aorta exits right ventricle Pulmonary trunk exits left ventricle Deoxygenated blood pumped around the body

Question 101

What is the patent ductus arteriosus?

Answer 101

Connection between pulmonary trunk and aorta

Question 102

What are the 4 components of tetralogy of Fallot?

Answer 102

1. Pulmonary stenosis 2. Right ventricular hypertrophy 3. Ventricular septal defect 4. Over-riding aorta