Embryonic Development

Question 1

How many days can sperm survive in the uterus?

Answer 1

5

Question 2

What is auto-immune orchitis?

Answer 2

Where a man’s own body produces antigens against his own sperm - a cause of infertility.

Question 3

What marks the gestational age?

Answer 3

From last menstruation to fertilisation.

Question 4

What marks the embryonic period?

Answer 4

The end of the 2nd week to the end of the 8th week.

Question 5

What marks the foetal period?

Answer 5

The end of the 8th week to birth.

Question 6

What marks the embryonic age?

Answer 6

Fertilisation to birth.

Question 7

What day does implantation in the embryonic period occur?

Answer 7

Day 6

Question 8

Before implantation, what is the name of the layer a blastocyst must shed and what does it do?

Answer 8

Zona Pellucida - this layer prevents the blastocyst from sticking to the oviduct, however is no longer necessary for implantation.

Question 9

What the removal of the zona pellucida known as?

Answer 9

Hatching

Question 10

What the trophoblast become in later stages of pregnancy?

Answer 10

The yolk sac and placenta

Question 11

What is placenta previa?

Answer 11

When the placenta implants itself across the cervix. A C-section is needed to deliver the baby.

Question 12

What is an ectopic pregnancy?

Answer 12

What the blastocyst implants OUTSIDE the uterus…

Question 13

During implantation, what does the trophoblast differentiate into?

Answer 13

The cytrophoblast and syncytiotrophoblast

Question 14

What does the embryoblast differentiate into?

Answer 14

The epiblast and the hypoblast.

Question 15

During implantation, what two cavities does the hypblast differentiate into?

Answer 15

The yolk sac and the chorionic cavity.

Question 16

During gastrulation, what key feature appears at the end of the third week?

Answer 16

A primitive streak

Question 17

What is the name of the new layer created by the primitive streak? What are the names of the three layers that now make up the new trilaminar disk?

Answer 17

Mesoderm
Ectoderm (top), mesoderm (middle), endoderm (bottom).

Question 18

Describe the future functions of the a)ectoderm b)mesoderm and c)endoderm.

Answer 18

Ectoderm - structures that maintain contact with the outside world e.g. Skin
Mesoderm - supporting tissues e.g. Muscle, cartilage
Endoderm - internal structures e.g. Epithelial lining of GI tract

Question 19

During gastrulation after the development of the primitive layer, two small gaps occur in the mesoderm layer. What will these gaps become later on in fetal life?

Answer 19

The mouth and the anus.

Question 20

What is situs inversus?

Answer 20

When the heart is on the wrong side of the body - symmetrical.
Only an issue if there is normal and abnormal mirror image disposition.

Question 21

After the development of the primitive streak and creation of new mesoderm layer - what happens in neurulation?

Answer 21

A notochord appears from the primitive streak.
This sends signals to the ectoderm to change shape.
The edges of the ectoderm curl towards each other, lifting out to create a neural tube.
This feature makes up the basis of the foetal backbone.

Question 22

During neurulation the mesoderm layer changes considerably, what are the name of the some of the sections it creates?

Answer 22

Paraxial mesoderm
Somatic mesoderm
Intraembryonic coelem 
Splanchnic mesoderm
Intermediate mesoderm

Question 23

What are somites?

Answer 23

Groves on the neural tube that make up future spinal discs.

They are created thorough organisation of the paraxial mesoderm into segments.

Question 24

What three areas do somites differentiate into and what are their future functions?

Answer 24

Myotome - ‘muscle’ section
Dermatome - ‘skin’ section
Sclerotome - ‘hard tissue’ section

Question 25

What is the cardiogenic area on the neural tube?

Answer 25

A half ring area at the cranial end of the neural tube, soon to be the foetal heart.

Question 26

How many somites are there?

Answer 26

31

Question 27

How does the trilaminar disc look different after its folded?

Answer 27

Folds into itself - the embryo becomes suspended into amniotic fluid with a connective stalk connecting it to the outside.