Week One: Embryology - Prenatal Development

Question 1

What is Embryology?

Answer 1

Embryology is the branch of biology that studies the prenatal development of gametes, fertilisation and development of embryos and fetuses.

Question 2

What is teratology?

Answer 2

The study of congenital disorders in embryology that occur before birth.

Question 3

What are the three key periods in human development?

Answer 3

1. Germinal Period 2. Embryonic Period 3. Fetal Period The total gestation period is approx 40-weeks

Question 4

What is the Germinal Period?

Answer 4

0-14 Days Rapid cell Division and Growth, Implantation and formation of embryonic (germinal) discs.

Question 5

What is the Embryonic Period?

Answer 5

3rd Week - 8th Week Visible advances in differentiation

Question 6

What is the Fetal Period?

Answer 6

9th-40th Weeks Differentiation and growth of tissues and organisation occur and the rate of body growth increases.

Question 7

When is a critical period?

Answer 7

Where development and differentiation are primarily taking place.

Question 8

What occurs during disruption?

Answer 8

A teratogen will occur (An Abnormality)

Question 9

Before any processes begin with the development what happens in regard to a male counterpart?

Answer 9

Spermatogenesis. This is a Meiotic Process

Question 10

Before any processes begin with the development what happens in regard to a female counterpart?

Answer 10

Oogenesis. has taken place (Meiotic Process) Ovulation has also occurred: There is a release of an egg (ovum) from the ovaries.

Question 11

What occurs during fertilisation?

Answer 11

1. Fusion of Haploid gametes (sex cells) 2. Forms a Diploid zygote 3. Nuclear membrane breaks down, DNA replication commences (mitosis)

Question 12

Where does fertilisation occur?

Answer 12

It occurs at the distal end of the fallopian tube (OVI Duct)

Question 13

Once fertilisation occurs where does the newly formed zygote travel?

Answer 13

The newly formed zygote travels via motions generated by microscopic cilia and contractions towards the uterus.

Question 14

What occurs on Day 0 of the Germinal Period?

Answer 14

Fertilisation. - Zygote Formation

Question 15

What occurs on Day 0-3 of the Germinal Period?

Answer 15

Cleavage - Rapid Cell Division without cell growth - total cytoplasm remains constant - Cell size rapidly decreases as number of cells increased.

Question 16

What occurs on Day 4 of the Germinal Period?

Answer 16

Morula - Now a ball of 16-20 cells flattened against the zona pellucida (The Morula is now located at the proximal end of the OVIduct)

Question 17

What occurs on Day 5 of the Germinal Period?

Answer 17

Blastocyst - A cavity forms within the morula, and the ball of cells is now termed the blastocyst.

Question 18

What occurs on Day 7 of the Germinal Period?

Answer 18

Implantation - Motility slows, Adhesion to uterine epithelium, as the cells of the blastocyst digest the uterine endometrium, permitting deeper penetration and attachment.

Question 19

What occurs on Day 8-9 of the Germinal Period?

Answer 19

Formation of a Bilaminar Embryo - Epiblast: Gives rise to future germ cell layers Hypoblast: Transient - Gives rise to some umbilical tissues.

Question 20

What are the four embryonic membranes that develop for the bilaminar embryo?

Answer 20

1. Amniotic Sac/Amnion 2. Yolk Sac (nourishment for disc) 3. Chorion (Eventually becomes the chorionic sac, which will, along with the uterine wall become the placenta) 4. Allantois (Connecting Stalk) - Contributes blood vessles from the embryo to the placenta; eventually becoming the umbilical cord.

Question 21

What occurs at week 2-3?

Answer 21

Gastrulation: This is the emergence of the primitive streak (caudal) and node formation There is induction and migration of cells into three layers to become the trilaminar (3 Layered embryonic disc)

Question 22

What is the Trilaminar Embryonic Disc?

Answer 22

It is made up of three layers. The Ectoderm, Mesoderm and Endoderm

Question 23

The Ectoderm later gives rise to…

Answer 23

CNS, PNS, parts of sensory system, epithelium of skin, Oral mucosa, mucosa of nasal and sinus cavities, teeth enamel.

Question 24

The Mesoderm later gives rise to..

Answer 24

Blood, bone, muscles, some organs, remainder of tooth structures.

Question 25

The Endoderm later gives rise to…

Answer 25

Epithelial lining of pharynx, stomach, intestines, lungs, bladder and organs of the urogenital tract.

Question 26

What is Neuralation?

Answer 26

The formation of primitive nervous system.

Question 27

What is somitogenesis?

Answer 27

Mesoderm differentiates into specific sections that will later give rise to particular body tissues. (e.g. splanchnic mesoderm - Heart & GI tract tissues)

Question 28

When does embryonic folding occur?

Answer 28

On the establishment of the trialaminar embryonic disc, the embryo then undergoes embryonic folding to establish the bodies axis.

Question 29

What does embryonic folding allow?

Answer 29

The formation of body cavities as a series of tubes.