Embryology 1 and 2

Question 1

What are the three periods of human development in the womb?

Answer 1

• Pre-embryonic (weeks 0-3)
• Embryonic (weeks 4-8)
• Foetal (weeks 9-40)

Question 2

What cells does gametes arise from?

Answer 2

Spermatogonium and oogonium

Question 3

Describe the genetics of gametes?

Answer 3

Genetically distinct

Question 4

Describe the process of fertilisation?

Answer 4

Pronuclei of gametes form one diploid cells called a zygote

Question 5

What happens to the zygote after its formed?

Answer 5

Divides to form zygote, moves through uterine tube to uterine cavity

Question 6

What does the zygote develop into?

Answer 6

A solid ball of cells (morula) then into a blastocyst

Question 7

Which parent passes on mitochondrial disease?

Answer 7

Mother

Question 8

What does Leber’s Hereditary Optic Neuropathy cause?

Answer 8

Blindness

Question 9

Why does the morula develop into a blastocyst?

Answer 9

As the morula gets larger, distribution of nutrients gets harder - - therefore the blastocystic cavity develops

Question 10

Describe the structure of the blastocyst?

Answer 10

• Cells accumulated at one end - called an inner mass

- The outer lining of cells is called the trophoblast

Question 11

Where is the pre-embryonic material at the stage of being a zygote, morula and blastocysts respectively?

Answer 11

Zygote - Fallopian tube

Morula and blastocyst - Uterine cavity

Question 12

What structures are required to transport the morula through thebFallopian tube? How can malfunction of this structure lead to pathology?

Answer 12

Healthy ciliated epithelium - malfunction can cause ectopic pregnancy

Question 13

What are the key features of the second week of pregnancy?

Answer 13

• Implantation of morula in the endometrial wall
• Cells from the embryo form bilaminar disc
• Sacs, membranes and cord to nourish the human conceptus develop

Question 14

Approx. at what day of pregnancy does implantation occur?

Answer 14

7

Question 15

What layer of the uterus does the blastocyst implant into?

Answer 15

Endometrium

Question 16

What structure plays a key role in implantation?

Answer 16

Chorion - the outermost membrane surrounding the blastocyst

Question 17

How does the formation of the chorion arise?

Answer 17

The trophoblast of the blastocysts divides several times to form the chorion

Question 18

What does the chorion do?

Answer 18

• Implantation
• Forms part of the placenta
• Secretes HCG

Question 19

What layer of the uterus is deep to the endometrium?

Answer 19

Myometrium

Question 20

What is the purpose of HCG?

Answer 20

Maintains the endometrium

Question 21

The inner cell mass of the blastocyst splits into two layers; what is this called? What is its function?

Answer 21

Bilaminar disc - Epiblast and Hypoblast

Separate amniotic and yolk sac

Question 22

What are the three functions of the placenta?

Answer 22

• Foetal nutrition
• Transport of waste and gas
• Immune etc

Question 23

How long does it take for the placenta to mature:

Answer 23

18-20 weeks

Question 24

What are the different kind of twins that occur? What are the developmental differences?

Answer 24

Fraternal (dizygotic) and Identical (monoygotic)

Question 25

What four things occur during the third week of pregnancy?

Answer 25

Gastrulation, neurulation, development of somites and early development of cardiovascular system

Question 26

What feature of the epiblast determines the axis of the embryo?

Answer 26

The primitive streak (invagination of the epiblastic layer of cells)

Question 27

Describe the formation of the three germ layers?

Answer 27

Epiblastic cells migrate ito space between hypoblast and epiblast - formation of trilaminar disc

Question 28

From what germ layer does the notochord arise?

Answer 28

Ectoderm (primitive notch of of epiblast)

Question 29

What induces the ectoderm to form a neural tube?

Answer 29

Notochord - neural plate arises from ectoderm and sinks down to form the neural tube

Question 30

What does the neural tube induce?

Answer 30

Thickening and segmentation of the mesoderm

Question 31

What three parts does the mesoderm split into?

Answer 31

Paraxial, Intermediate plate and lateral plate

Question 32

How does the lateral plate mesoderm further divide?

Answer 32

Into the somatic and splanchnic mesoderm

Question 33

What is the space between the splanchnic and somatic mesoderm called?

Answer 33

Intra-Embryonic coelom

Question 34

What do each parts of the mesoderm develop into?

Answer 34

Paraxial mesoderm - somites
Intermediate - urogenital system
- Lateral plate - body coverings and cavities q

Question 35

After the process of gastrulation, what happens?

Answer 35

Folding of embryo (lateral)

Question 36

How does the paraxial mesoderm differentiate?

Answer 36

Into dermatomes, myotomes and sclerotomes

Question 37

What is teratology?

Answer 37

The study of when things go wrong during development

Question 38

What is the cause of 60% of all developmental abnormalities?

Answer 38

Unknown causes

Question 39

What environmental factors can effect development?

Answer 39

Drugs - prescription/other
Alcohol/ tobacco
Infectious agents
Others e.g. radiation

Question 40

What infectious agents can transfer through the placenta?

Answer 40

ToRCH

Toxoplasma, Rubella, Cytomegalovirus, Herpes

Question 41

What genetic factors can cause developmental issues?

Answer 41

Too many/few chromosomes

Structural changes

Question 42

How is the diagnosis of malformations aided?

Answer 42

Prenatal and postnatal test

• Blood -AFP
• Ultrasound (12 week anomaly)
• Invasive tests e.g. chroionic vilus sampling and amniocentesis
• Hip stability
• Testes (descent)
• Fingers and toes
• Hearing