Embryology

Question 1

How many weeks does pregnancy last?

Answer 1

38-40 weeks

Question 2

What is the term for weeks 0-3?

Answer 2

Conceptus/ Embryo

Question 3

What is the term for weeks 3-8?

Answer 3

Embryonic period

Question 4

How much risk does the embryonic period carry?

Answer 4

Greatest risk for birth defects

Question 5

What is the term for weeks 9-40?

Answer 5

Foetal period

Question 6

What are the 6 phases of embryogenesis

Answer 6

Gametogenesis
Fertilisation
Cleavage
Gastrulation
Formation of body plan
Organogenesis

Question 7

How many days does it take for a spermatogonia to mature into a spermatozoa?

Answer 7

64 days

Question 8

When is the reproductive life span of a female determined?

Answer 8

In foetal life

Question 9

By which weeks are primary oocytes arrested in prophase 1? When does it resume again?

Answer 9

Week 28-30.

Resumes in puberty

Question 10

What is mosaicism?

Answer 10

Individuals with 2 or more cell lines with different karyotypes

Question 11

3 ways in which trisomy 21 can occur IN UTERO?

Answer 11

Meiotic nondisjunction
Mitotic disjunction
Translocation of 21p to 14p

Question 12

Which layer does the acrosin from the acrosomal sperm head help to penetrate to reach the oocyte?

Answer 12

Zona pellucida

Question 13

Which is released to prevent polyspermy after 1 sperm has successfully penetrated?

Answer 13

Lysosomal enzymes from cortical granules at plasma membrane

Question 14

What are the products of meiosis II in oogenesis? (4)

Answer 14

Definitive oocyte

3 Polar bodies

Question 15

What glycoprotein maintains sperm binding after it has penetrated the corona radiata?

Answer 15

ZP3 via human-specific interaction

Question 16

When is meiosis II of oocyte completed?

Answer 16

When the spermatozoon enters

Question 17

What size changes occur in cleavage?

Answer 17

No increase in size

*Confined/ compacted within zona pellucida

Question 18

What are the mitotic daughter cells produced during cleavage called?

Answer 18

Blastomeres

Question 19

How many blastomeres make up a morula?

Answer 19

12-16

Question 20

What is the structure with an inner cell mass (embryo) and outer cells (trophoblast) called?

Answer 20

Blastocyst

Question 21

What is the fluid in the cavity of the inner cell mass called?

Answer 21

Blastocele cavity

Question 22

When does the formation of the 3 germ layers from 2 occur?

Answer 22

Week 3

Question 23

At which phase are the body axes established by primitive streak?

Answer 23

Gastrulation

Question 24

What occurs during foetal period? (4)

Answer 24

1. Growth and weight gain (2nd trimester in length and 3rd in weight)
2. Tissue mature and becomes functional
3. Overt sexual differentiation
4. Bone laid down and connections made in CNS

Question 25

What is induction?

Answer 25

1 cell causing another to directly/ indirectly differentiate

Question 26

What are the 2 secondary processes?

Answer 26

1. Axis formation/ polarity | 2. Folding/ rotation - for complex 3D organ

Question 27

What can deletion in maternal chromosome 15q11-13 result in?

Answer 27

Angelman syndrome

Question 28

What can deletion in paternal chromosome 15q11-13 result in?

Answer 28

Prader-willis syndrome

Question 29

What is the outermost layer that penetrates into the endometrium? Where did it originate from?

Answer 29

Syncytiotrophoblast (multi-nucleated) | From trophoblasts

Question 30

Which cells produces hCG (pregnancy marker)? Where did it originate from?

Answer 30

Cytotrophoblast | From trophoblasts

Question 31

Why may some bleeding happen near 28th of menstrual cycle despite successful implantation?

Answer 31

Increased blood flow to lacunar spaces

Question 32

What does the embryoblast differentiate into?

Answer 32

Hypoblast (ventral) | Epiblast (dorsal)

Question 33

Where are amnioblasts from?

Answer 33

Epiblast, lines the amniotic cavity

Question 34

What becomes the umbilical cord?

Answer 34

Connecting stalk from the extraembryonic mesoderm

Question 35

When and where does the primitive streak appear?

Answer 35

Week 3 | Midline at caudal end of epiblast

Question 36

Where are the 3 locations where an ectopic pregnancy can occur

Answer 36

Uterine tube Peritoneum (Pouch of Douglas) Internal os

Question 37

What layer becomes of the cells that migrate through the primitive streak between the epiblast and definitive endoderm (hypoblast)?

Answer 37

Mesoderm

Question 38

What does the ectoderm contribute to?

Answer 38

Epidermis of skin | Nervous system

Question 39

What does the endoderm contribute to?

Answer 39

Lining of GIT, Respi tract, bladder and urethra

Question 40

What does the paraxial mesoderm contribute to?

Answer 40

Axial skeletion, voluntary sketal muscles, parts of demis (back)

Question 41

What does the intermediate mesoderm contribute to?

Answer 41

Urogenital systems

Question 42

What does the lateral somatic mesoderm contribute to?

Answer 42

Most of dermis, body wall lining, parts of limb

Question 43

What does the lateral visceral mesoderm contribute to?

Answer 43

CVS, Mesothelium of organs, smooth muscles

Question 44

What % of non-disjunction events occur during oogenesis?

Answer 44

75%

Question 45

When does cleavage occur?

Answer 45

Day 1-3

Question 46

Where does the embryo normally implant?

Answer 46

Endometrial lining of Anterior/ Posterior uterine wall