Fertilisation to trilaminar

Question 1

What does the sperm bind with on the surface of the egg?

Answer 1

The zona pellucida glycoprotein (ZP3)

Question 2

How does the sperm enter the egg?

Answer 2

It releases acrosomal enzymes from the acrosome of the sperm head

Question 3

How does the egg cell prevent polyspermy?

Answer 3

Sperm penetration causes cortical granules in the cytoplasm to release their contents which hardens the zone pellucida

Question 4

What does sperm entry trigger in the egg cell?

Answer 4

Completion of meiosis 2
Release of cortical granules by oocyte

Question 5

What occurs when the sperm and egg bind?

Answer 5

The sperm contents enter the egg

Question 6

Where does fertilisation occur within the uterine tube?

Answer 6

Ampulla

Question 7

What is the name given to the smaller daughter cells of the fertilised egg?

Answer 7

Blastomeres

Question 8

What happens to the overall size of the ovum during mitosis?

Answer 8

It stays the same

Question 9

What is the definition of totipotent?

Answer 9

Can differentiate to form any type of adult cell, as well as embryonic and placental cell. Blastomeres up to the 8 cell stage are thought to be totipotent

Question 10

What is mosaicism?

Answer 10

When non-disjunction occurs during the first cell division, not during gametogenesis, so only some cells contain the increased number of cells. In trisomy 21, this leads to less prominent features

Question 11

What is meant by a morula?

Answer 11

When the ovum contains 16 or more blastomeres

Question 12

What occurs during compaction of the morula?

Answer 12

Blastomeres come into closer contact and form cell junctions, outer cells that are in contact with the zone pellucida form extensive gap junctions

Question 13

How many cells are in a blastocyst?

Answer 13

70-100

Question 14

What are the 4 regions of a blastocyst?

Answer 14

Trophoblast layer
Inner cell mass
Blastocyst cavity
Zona pellucida

Question 15

What does the trophoblast layer form?

Answer 15

The placenta

Question 16

What does the inner cell mass form?

Answer 16

Embryo

Question 17

What occurs during hatching?

Answer 17

Trophoblasts release enzymes that begin to break down the zone pellucida. Embryonic contractions allow for hatching as the zone pellucida is released

Question 18

In what does the ovum mature?

Answer 18

A preovulatory follicle

Question 19

What happens to the preovulatory follicle after ovulation?

Answer 19

It forms a corpus luteum, a temporary gland that secretes progesterone, maintaining the thick endometrial lining for implantation

Question 20

What are the 2 layers formed from the trophoblast layer?

Answer 20

Cytotrophoblast
Syncytiotrophoblast

Question 21

What forms the syncytiotrophoblast?

Answer 21

A single, multinucleate cell

Question 22

What hormone does the syncytiotrophoblast form?

Answer 22

Human chorionic gonadotrophin

Question 23

What is the function of Human chorionic gonadotrophin?

Answer 23

Stimulates the corpus luteum to thicken the endometrial lining and is the basis of pregnancy tests

Question 24

What 2 layers does the embryo split into?

Answer 24

Epiblast
Hypoblast

Question 25

What surface of the embryo is the epiblast?

Answer 25

Dorsal surface

Question 26

What surface of the embryo is the hypoblast?

Answer 26

Ventral surface

Question 27

On what day does the bilaminar embryo form?

Answer 27

Day 7.5

Question 28

What 2 cavities form on day 9?

Answer 28

Amniotic cavity from the epiblast Primitive yolk sac (Exocoelomic cavity) from the hypoblast

Question 29

What occurs in the syncytiotrophoblast on day 9?

Answer 29

Vacuoles appear and unite to form lacunae

Question 30

What closes the site of embryonic implantation of the endometrium?

Answer 30

A fibrin coagulum

Question 31

What is the name of the hypoblast membrane that surrounds the yolk sac?

Answer 31

Exocoelomic (Heuser) membrane

Question 32

What fills the trophoblastic lacunae on day 12?

Answer 32

Maternal sinusoids formed from nearby capillaries pass blood into the trophoblastic lacunae, establishing a uteroplacental circulation

Question 33

What layer forms around the exocoelomic membrane?

Answer 33

Extraembryonic mesoderm

Question 34

What are the 3 components of the extra embryonic mesoderm?

Answer 34

Extraembryonic somatic mesoderm (Outer) Extraembryonic splanchnic mesoderm (Inner) Extraembryonic cavities

Question 35

What happens to the embryonic mesoderm on day 13?

Answer 35

The extraembryonic splanchnic mesoderm degenerates to form the chorionic cavity

Question 36

What structure forms to connect the embryo and trophoblast layer?

Answer 36

Connecting stalk

Question 37

What is the exocoelomic cyst?

Answer 37

The remnants of the primary yolk sac, found in the chorionic membrane. A secondary yolk sac forms within the embryo

Question 38

During what week does the primitive streak form?

Answer 38

Week 3

Question 39

What are the 3 parts of the primitive streak?

Answer 39

Primitive pit at the cranial end Primitive node at the cranial end Primitive groove at the caudal end

Question 40

What is established by the formation of the primitive streak?

Answer 40

The body axes

Question 41

What occurs during the first stage of gastrulation?

Answer 41

Epiblast cells move through the primitive streak and replace the hypoblast layer with a definitive endoderm layer

Question 42

What occurs during the second layer of gastrulation?

Answer 42

More epiblast cells move in through the primitive streak and move in-between the epiblast layer and definitive endoderm to form three layers

Question 43

What are the 3 layers of the trimlaminar embryo?

Answer 43

Ectoderm Mesoderm Endoderm

Question 44

What 2 membranes form on the trilaminar embryo?

Answer 44

Oropharyngeal membrane (Cranial end) Cloacal membrane (Caudal end)

Question 45

What structures form from the ectoderm?

Answer 45

Epidermis of the skin, hair, nails and associated glands Nervous system; brain, spinal chord and peripheral nerves

Question 46

what are the 3 regions of the mesoderm?

Answer 46

Paraxial mesoderm Intermediate mesoderm Lateral plate mesoderm

Question 47

What are the 2 layers of the lateral plate mesoderm?

Answer 47

Somatic layer Visceral layer

Question 48

What is the notochord?

Answer 48

A flexible, rod-like structure that forms from mesodermal cells that forms the spinal chord in vertebrates

Question 49

What structures form from the paraxial mesoderm?

Answer 49

Axial skeleton, skeletal muscle and parts of the dermis of the back

Question 50

What structures form from the intermediate mesoderm?

Answer 50

Urogenital systems; kidney, ureter, gonads and associated structures

Question 51

What structures form from the somatic layer of the lateral plate mesoderm?

Answer 51

Most of the dermis, lining of body wall and parts of limbs

Question 52

What structures form from the visceral layer of the lateral plate mesoderm?

Answer 52

Cardiovascular system, mesothelial covering of organs and smooth muscle

Question 53

What structures form from the endoderm?

Answer 53

Lining of the gut tube Lining of the respiratory tract Lining of the bladder and urethra