Fhd Zygote To Embryonic Disk

Front 1

The zona pellucida is a viscous gel surrounding the oocyte, what is the name for the cells that surround it?

Back 1

Cumulus cells (need to be broken through by the spermatozoon)

Front 2

What is 'cleavage'? Where does it go on?

Back 2

Partitioning of the single large zygote into a ball of smaller cells. Goes on along the uterine tube, towards the uterine cavity

Front 3

Each of the cells that results from cleavage is known as a __________

Back 3

Blastomere

Front 4

What is a 'morula'? When is it present?

Back 4

Cleaving division converts the single large egg into a solid mass of smaller cells known as a morula.

~12-16 cells, day 3

Front 5

During the 8-16 cell stage, outer cells of the morula flatten against each other in a change called _____________

Back 5

compactation (increases cell-to-cell contact)

Front 6

During compactation, , outer cells make watertight 'tight junctions' to form an epithelium. They pump fluid into the interior of the morula, creating a cavity known as the...

Back 6

Blastocoele

Front 7

When the blastocoele is formed, the morula changes name to become known as a:

Back 7

Blastocyst

Front 8

What is the name for the cells on the outer epithelium of the blastocyst?

Back 8

Trophoblast cells

Front 9

What is the name for the cell clump inside the blastocyst?

Back 9

Inner cell mass (embryoblast)

Front 10

What is 'ectopic implantation'?

Back 10

Implantation in an abnormal place

Front 11

How many days after fertilisation does implantation take place?

Back 11

6-7 days

Front 12

What is the 'syncytiotrophoblast'? What cells does it consist of?

Back 12

A specialsed tissue, formed by the fusing of trophoblast cells and uterine epithelial cells (it is a very early stage of implantation)

It consists of giant cells which make 'proteolytic' enzymes which break down surrounding maternal tissue - ensuring proper implantation within 2-4 days of attachment

Front 13

Once the blastocyst attaches to the uterine wall, how long does it take to become full yimplanted?

Back 13

2-4

Front 14

When the blastocyst burrows into the uterine wall, maternal tissue is damaged. What does it then do?

Back 14

Forms a fibrin plug, sealing it in place in the uterine wall

Front 15

Where does implantation normally take place?

Back 15

Middle or upper part of the uterine cavity - hight on the dorsal wall between openings of the uterine (fallopian) tubes

Front 16

What is 'placenta praevia'?

Back 16

A condition where, due to ectopic implantation, the placenta grows over the cervix - leading to haemorrhaging in late pregnancy

Front 17

What is the effect of the antiprogesterone drug 'RU-486' (mifepristone)?

Back 17

It dislodges an already implanted embryo by triging menstruation artificially (it s a safe abortifacient up to the sixth week of development)

Front 18

What is 'luteinisation'?

Back 18

When the ovarian follicle becomes filled with secretory cells forming a yellowish swelling called the luteal body (corpus luteum)

Front 19

Which hormone does the corpus luteum secrete? What effect does it have?

Back 19

Progesterone. It prepares the endometrium for implantation.

If, after 10-14 days, it does not occur - levels fall and trigger menstruation

Front 20

After 10-14 days, ordinarily the corpus luteum will normally stop secreting progesterone - causing mensturation. If there is an implantation - what is done to stop it?

Back 20

The trophoblast cells secrete 'human chronic gonadotrophin' (hCG)

This causes the CL to keep secreting progesterone until the placenta itself can make it

Front 21

What are common causes of infertility?

Back 21

Fairly of oocyte maturation
Failure to make enough motile sperm
Ejaculation of semen into the bladder
Female production of antibodies against sperm!
Maternal ageing - chromosomal abnormalities

Front 22

What are the two types of trophoblast cells present during implantation ~day 8

Back 22

Syncytiotrophoblast - Giant, invasive cells
Cytotrophoblast

Front 23

What is 'gastrulation'?

Back 23

When the morphology of the embryo is reorganized to form the three germ layers: ectoderm, mesoderm, and endoderm

Front 24

Back 24

Front 25

What forms the amniotic cavity?

Back 25

The fluid pumping action of the epithelial cells of the epiblast

Front 26

Day 9: What is the name for epiblast cells that lie in close contact with the cytotrophoblast? What is the name for the membrane formed later on?

Back 26

Amnioblasts
Amnion layer

Front 27

What is the name for the disk formed between epiblast cells in close contact with the hypoblasts?

Back 27

Bilaminar germ disk

Front 28

Day 9: What is the name for the epiblast cells that are very near to the cytotrophoblast? What membrane do the form?

Back 28

Amnioblast cells. They form the 'amnion' membrane.

Front 29

Day 9: Hypoblast cells spread out and line the blastocoele - this lined cavity is now known as the...

Back 29

...primary yolk sac.

Front 30

What is the name for the tissue that divides the cytotrophoblast from the primary yolk sac?

Back 30

The extraembryonic reticulum

Front 31

Day 12-13: The extraembryonic reticulum grows and develops microcavities that fuse to form a single, continuous cavity. What is the name for this?

This cavity is also connected at a certain point - what is this point called?

Back 31

The extraembryonic coelom.

The connecting stalk. (This later forms the umbilical chord)

Front 32

How, and when, is the secondary yolk sac formed?

Back 32

~Day 13. Hypoblast cells migrated around the wall of the primary yolk sac to form the secondary one.

The old sac is pinched off and degenerates

Front 33

What is the 'chorin'?

Back 33

A tough membrane formed by the fused outer layer of the extraembryonic reticulum (containing mesoderm) and the cytotrophoblast.

Front 34

What is the origin of mesoderm cells? (I.e. when and where)

Back 34

They are found in the extraembryonic reticulum around day 14

Front 35

Once the chorion has formed, the extraembryonic coelom is now called the...

Back 35

Chorionic cavity

Front 36

What is 'gastrulation'? When does it start.

Back 36

Starts: day 14. It is the conversion of the bilaminar germ disk into a three layered disk - the trilaminar germ disk (from which all the tissues of the embryo are derived).

Front 37

Day 14: What is the 'embryonic mesoderm' layer?

Back 37

A middle layer between formed when cells migrate between the epiblast and hypoblast layer

Front 38

Day 15: How is endoderm formed?

Back 38

Cells from the epiblast layer migrates into the hypoblast layer (not well understood)

Front 39

Day 15: After gastrulation, what is the name given to the remaining epiblast cells?

Back 39

Ectoderm

Front 40

What is the first visible sign of the head-to-tail axis of the embryo?

Back 40

The primitive streak

Front 41

What is the lump at the end of the primitive streak known as?

Back 41

The primitive node

Front 42

The primitive streak marks a V-shaped crease that cells burrow into, breaking away from the epiblast layer at its base

Back 42

.

Front 43

The head of the embryonic acis is called the _________ _____. This plate later becomes the _______________ ________ and has a role in the formation of the _____

Back 43

Prochordal plate, buccopharyngeal membrane, mouth

Front 44

Where is the heart formed from?

Back 44

The cardiogenic region - at the head of the body axis

Front 45

What is the 'cloacal membrane'?

Back 45

At the tail end of the embryonic axis - forms anal (teehee) canal and urogenital system

Front 46

What is the notochord?

Back 46

The part that establishes the main body axis.

It is important in sending signals to the ectoderm to set up the NS (this process is called neural induction')

Front 47

What does node-derived mesoderm/prechordal mesoderm develop into (near notochord)?

Back 47

Head formation.

Front 48

What is the name for the specialised region of ectoderm that results from neural induction? What does it ultimately form?

Back 48

The neural plate (ultimately forms brain and spinal chord)

Front 49

Why is the vascular system developed so early on? When does it begin to appear?

Back 49

Diffusion is ineffective over large distances and would limit growth. Middle of the third week

Front 50

What is the 'cardiogenic region'

Back 50

Clusters of angiogenic cells around the cranial edge of the embryonic disk involved in forming vascular tubes. Including 'primitive heart tubes' that fuse to form the basis of the heart.

Front 51

Fusion of the sperm to the egg membrane triggers a release of calcium. What are the two effects of this?

Back 51

Zona reaction - ZP2 cleaved to harden - this excludes sperm

Meiosis II is completed with extrusion of the second polar body

Front 52

Cleavage is/isn't synchronised in humans.

Back 52

Is not (i.e. cells do not neatly got 1-2, 2-4, 4-8, some will divide at other times)

Front 53

What are the four roles of the ZP?

Back 53

Preventing polyspermy
Stabilising the zygote
Preventing ectopic pregnancy
Protection from immune system