Embryology - Fertlisation to Trilaminar

Question 1

What happens when a single sperm enters the oocyte?

Answer 1

Cortical granules are released which react which react with the zona pellucida causing it to harden to prevent other sperm from entering. Slide 3

Question 2

What are blastomeres?

Answer 2

Smaller daughter cells from the subdivided fertilised egg. Slide 4

Question 3

What happens during compaction?

Answer 3

It maximises available space by coming into closer contact with each other and form cell junctions. Slide 5

Question 4

What happens between the outer cells and the zona pelllucida?

Answer 4

There are formations of extensive gap junctions. Slide 5

Question 5

what is in a blastocyst?

Answer 5

A cell lining on the zona pellucida called trophoblast, the inner cell mass, blastocyst cavity and the zona pellucida. Slide 6

Question 6

What is blastocyst hatching?

Answer 6

When the blastocyst is at the uterine cavity and it leaves the zona pellucida. Slide 8

Question 7

How does the blastocyst hatch?

Answer 7

The zona pellucida breaks down and the blastocyst moves out of it. Slide 8

Question 8

Why does the blastocyst need to ‘hatch’?

Answer 8

So the embryo can interact directly with the endometrial lining of the uterus. Slide 8

Question 9

Where are the normal implantation sites?

Answer 9

Middle or upper dorsal uterine wall. Slide 10

Question 10

Where are the abnormal implantation sites?

Answer 10

Ovary, ampulla, uterine tube, lower part of uterus, cervix or peritoneum. Slide 10

Question 11

What drives the active implantation process?

Answer 11

Trophoblast cells. Slide 11

Question 12

The trophoblast cells divide into two types, what are they?

Answer 12

CYTOtrophoblast and SYNCYTIOtrophoblast. Slide 11

Question 13

What are cytotrophoblasts?

Answer 13

Original layer of individual cells. Slide 11

Question 14

What are syncytiotrophoblasts?

Answer 14

They are cytotrophoblasts which lose their membranes and combine together so it is one single multinucleated cell. Slide 11

Question 15

The embryo organises into 2 cell layers, what are they?

Answer 15

The epiblast which is the dorsal surface of the embryo and hypoblast which is the ventral surface. Slide 11

Question 16

How is the amniotic cavity formed?

Answer 16

When the epiblast divide and new cells form a new layer and secrete fluid between them. Slide 11

Question 17

How is the primary yolk sac made?

Answer 17

When the hypoblast cells migrate out along the inner surface of the trophoblast. Slide 12

Question 18

What is the extra embryonic mesoderm?

Answer 18

The new layer and it separates the lining of the yolk sac and the cytotrophoblast and continues to moves it will separate the amnion as well. Slide 13

Question 19

When does the chorionic cavity and the secondary yolk sac begin to form?

Answer 19

In days 12-13. Slide 14

Question 20

How does the placenta form?

Answer 20

The syncytiotrophoblast extends and contacts maternal blood supply. Slide 16

Question 21

Where is the amniotic cavity and the definitive yolk sac situated?

Answer 21

Amniotic cavity I present above the bilaminar embryonic disc and the definitive yolk sac is below. Slide 16

Question 22

What does the epiblast and hypoblast form?

Answer 22

Bilaminar embryo. Slide 17

Question 23

What is the dorsal side of the embryo?

Answer 23

The epiblast. Slide 18

Question 24

What is the ventral side of the embryo?

Answer 24

Hypoblast. Slide 18

Question 25

What is the primitive streak?

Answer 25

It allows gastrulation and looks like a scratch on the surface of the embryo. Slide 18

Question 26

Where is the primitive streak situated?

Answer 26

Midline at caudal end of epiblast and the cranial end of the primitive streak is the primitive pit and node. Slide 18

Question 27

What happens during the formation of the germ layers?

Answer 27

The 2 layers become 3 layers; Ectoderm, mesoderm and endoderm. The cells migrate through the primitive streak to form the mesoderm. Slide 19

Question 28

What happens during gastrulation in the embryo?

Answer 28

Movement of epiblast cells through the primitive streak to form the three primary germ layers: Hypoblast is replaces to form the definitive endoderm, the intraembryonic mesoderm layer is formed between and the epiblast becomes the ectoderm. Slide 20

Question 29

What is the fate of the ectoderm?

Answer 29

It becomes the epidermis of the skin and the nervous system. Slide 22

Question 30

What is the fate of the mesoderm?

Answer 30

Divides into 3 regions either side of the notochord. The three regions are paraxial, intermediate and lateral plate (somatic and visceral). Slide 23

Question 31

Where is the paraxial part of the mesoderm?

Answer 31

paraxial means along side the axis. Slide 23`

Question 32

Where is the intermediate part of the mesoderm?

Answer 32

Only found within the trunk. Slide 23

Question 33

Where are the lateral parts of the mesoderm?

Answer 33

It is flattened sheets looped round with a gap at the loop, the somatic part is the top. The gap allows body cavities between the somatic and visceral parts. Slide 23

Question 34

What is the fate of the paraxial mesoderm?

Answer 34

Axial skeleton, voluntary muscle and parts of the dermis. Slide 24

Question 35

What is the fate of the intermediate mesoderm?

Answer 35

Urogential systems e.g. kidney, ureter, gonads. Slide 25

Question 36

What is the fate of the lateral plate mesoderm (somatic)?

Answer 36

Lining of the body wall, most dermis an parts of limbs. Slide 26

Question 37

What is the fate of the lateral plate mesoderm (visceral)?

Answer 37

Cardiovascular system, mesothelial covering of organs and smooth muscle. Slide 27

Question 38

What is the fate of the endoderm?

Answer 38

Lining of the gut tube, lining of the respiratory tract and lining of the bladder and urethra. Slide 28

Question 39

How is the bladder formed by the endoderm?

Answer 39

Expansion of the endoderm at the cloaca, splits into two parts and the anterior part forms the bladder. Slide 28