Embryology

Question 1

What is formed when the (pro)Nucleus of sperm enters and fuses with the (pro)nucleus of the ovum?

Answer 1

Diploid cell called zygote is produced

Question 2

Are mitochondrial diseases inherited from the mother or father?

Answer 2

The mother

Question 3

What is a morula?

Answer 3

Solid ball of cells formed from the cell division of zygote

Question 4

What cavity allows nutrition to reach the core of cells?

Answer 4

Blastocystic cavity

Question 5

What is the outer lining of cells called?

Answer 5

The trophoblast

Question 6

What does the morula convert into?

Answer 6

Blastocyst

Question 7

Where does the blastocyst travel to?

Answer 7

Moves through uterine tube, to reach uterine cavity

Question 8

Does the cell division from the zygote to blastocyst increase or decrease in speed?

Answer 8

Increase

Question 9

How does the zygote/morula/blastocyst move to reach the uterine cavity?

Answer 9

Ciliated epithelium

Question 10

What could occur if pregnancy is abnormal?

Answer 10

Ectopic pregnancy

Question 11

What process occurs at day 7 (or 6) of pregnancy?

Answer 11

Implantation - the blastocyst begins to burrow into the uterine wall (endometrium)

Question 12

What plays an important role in burrowing the blastocyst?

Answer 12

The chorion

Question 13

What are the finger-like processes on the chorion?

Answer 13

Chorionic villi

Question 14

What are the main processes of the chorion?

Answer 14

1. Implantation process
2. Forms part of the placenta
3. Secretes human Chorionic gonadotropin (HCG)

Question 15

What is human chorionic gonadotropin (HCG) used for?

Answer 15

Used to detect pregnancy

Also helps maintain the endometrium

Question 16

What is the Decidua basalis?

Answer 16

Part of the endometrium deep to the implanted conceptus.

Question 17

What do the cells of the inner cell mass form?

Answer 17

A 2-layered flat disc called the Bilaminar Disc.

Question 18

What 2 cavities begin to form after the formation of the bilaminar disc?

Answer 18

Amniotic cavity and Yolk sac

Question 19

What is the placenta?

Answer 19

A flattened circular organ in the uterus of pregnant eutherian mammals, nourishing and maintaining the fetus through the umbilical cord.

Question 20

What are the main functions of the placenta?

Answer 20

1. Foetal nutrition
2. Transport of waste and gases
3. Immune etc

Question 21

Features of foetal part and surface of placenta

Answer 21

Smooth with foetal blood vessels and end of umbilical cord.

Question 22

Maternal part of placenta

Answer 22

Decidua basalis of endometrium. Rough and has maternal blood vessels.

Question 23

Features of fraternal/dizygotic twins

Answer 23

• 2 ova released, 2 sperms = 2 separate zygotes

- Different genetic makeups, 2 placentae

Question 24

Features of identical/monozygotic twins

Answer 24

• 1 ovum, 1 sperm = 1 zygote which divides into 2

- Same genetic makeup, share one placenta.

Question 25

What is Gastrulation?

Answer 25

Formation of germ layers

Question 26

What is Neurulation?

Answer 26

Formation of neural tube

Question 27

What is the primitive streak?

Answer 27

Formed in the midline of the epiblast by the dipping in of cells (invagination)

Question 28

What are the 3 germ layers formed during gastrulation?

Answer 28

1. Ectoderm 2. Mesoderm 3. Endoderm =TRILAMAR DISC

Question 29

How is the the trilaminar disc formed?

Answer 29

Cells from primitive streak invaginate, displacing hypoblast.

Question 30

Solid tube of cells formed when cells from primitive streak sink down

Answer 30

Notochord

Question 31

What does the notochord induce?

Answer 31

Notochord induces ectodermal cells in the midline to form a neural tube.

Question 32

What does the neural tube do to the mesoderm?

Answer 32

Induces the mesoderm to thicken causing it to separate into three parts.

Question 33

What 3 parts does the mesoderm separate to?

Answer 33

- Paraxial mesoderm - Intermediate plate mesoderm - Lateral plate mesoderm Lateral plate mesoderm splits to form a somatic and splanchnic mesoderm.

Question 34

What do paraxial mesoderms form?

Answer 34

Somites

Question 35

What occurs 4th-8th weeks - embryonic/organogenetic period

Answer 35

- Folding into a tube (lateral folds) which started in 3rd week completes - Heart starts to beat on day 24 - 43 pairs of somites form in the paraxial mesoderm and differentiate further. Etc

Question 36

What does each somite (paraxial mesoderm) divide into?

Answer 36

1. Dermatome 2. Myotome 3. Sclerotome

Question 37

What are the dermatome, myotome and sclerotome responsible for?

Answer 37

``` Dermatome = dermis of skin Myotome = muscles Sclerotome = bones including vertebrae ```

Question 38

What is Teratology?

Answer 38

Study of when things go wrong during development.

Question 39

What are teratogens?

Answer 39

Environmental factors that cause abnormal development.

Question 40

During which weeks is there greatest sensitivity to teratogens?

Answer 40

Weeks 3-8