Principles of embryology

Question 1

What are weeks 0-3 classified as

Answer 1

Conceptus

Question 2

What are weeks 3-8 classified as

Answer 2

Embryonic period

Question 3

What are weeks 9-40 classified as

Answer 3

Foetal period

Question 4

How many stages of embryogenesis are there

Answer 4

6

Question 5

What are the six stages of embryogenesis

Answer 5

1. Gametogenesis
2. Fertilisation
3. Cleavage
4. Gastrulation
5. Formation of body plan
6. Organogenesis

Question 6

what happens in Gametogenesis

Answer 6

Formation of a gamete - 23 chromosomes = haploid

Question 7

How do gametes arise

Answer 7

Mitosis and meiosis which causes genetic variation

Question 8

What is formation of female gametes called

Answer 8

oogenesis

Question 9

What is formation of male gametes called

Answer 9

spermatogenesis

Question 10

When does oogenesis occur in females

Answer 10

Starts in development and ends at menopause

By week 28-30 Primary oocytes begin myosis but arrest in prophase until puberty
Reproductive lifespan determined in fetal life

Question 11

When does spermatogenesis occur in males

Answer 11

Occurs at puberty and continues throughout life: outcome is 22+ X or 22+ Y

Question 12

What is trisomy 21

Answer 12

Down syndrome- happens when there is an additional copy of chromosome 21 cause by nondisjunction
75% nondisjunction occurs in oocyte formation

Question 13

What is non-disjunction

Answer 13

Failure of chromosomes to separate

Question 14

What happens in Fertilisation

Answer 14

Union of gametes forming a zygote
-fusion of sperm and egg

Question 15

What happens in Cleavage

Answer 15

Period of rapid mitotic cell division
Forms morula then blastocyst (days 1-4) (NO INCREASE IN SIZE)

Question 16

What happens in Gastrulation

Answer 16

Formation of germ layers (week 3)

Question 17

What are the germ layers that form in gastrulation

Answer 17

Ectoderm, mesoderm and endoderm (by mitosis in yolk sac)

Question 18

What happens in formation of body plane

Answer 18

Embryonic folding (Tube within a tube)
Specifically gut tube in body wall

Question 19

What happens in organogenesis

Answer 19

Formation of organs and organ systems
All in place by end of embryonic period

Question 20

What is the foetal period

Answer 20

Growth and weight gain

-tissues mature and become functional
-Apparent sexual differentiation
-Bone laid down, connections made in CNS

Question 21

What anatomical terminology is used for embryos

Answer 21

Superior= Cranial
Inferior= Caudal
Anterior= Ventral
Posterior= Dorsal

Question 22

What are the primary processes turning a zygote into a human

Answer 22

Cell division
Differentiation
Cell attachment
Apoptosis
Induction (1 cell causes other to differentiate)
Cell migration

Question 23

What are the secondary processes when turning a zygote into a human

Answer 23

Axis formation
(cells knowing position in relation to all other cells and embryo)

Folding/Rotation
(Gives 3D form to embryo and structures within e.g. heart)

Question 24

What controls are there of development

Answer 24

Genetic- gene expression is tightly regulated in time and space

Epigenic- Preferential expression of either maternal or paternal gene copy