Embryology, Growth And Development Part 1

Front 1

What are the three stages of prenatal development?

Back 1

1. Germinal Period: first 2 weeks of development during formation of primitive germ layers
2. Embryonic Period: second to end of 8th week, organ systems develop (developing human is called an embryo)
3. Fetal Period: last 30 weeks, organ systems grow and mature (now referred to as a fetus)

Front 2

What is the total amount of time (post-ovulatory) from conception to birth?

Back 2

38 weeks

Front 3

What are the two ways in which developmental events are timed?

Back 3

1. Clinical/medical events: date since last menstrual period (clinical age of unborn child)
2. Embryologists: post-ovulatory age when oocytes is releases (approx. 14 days less than the clinical age)

Front 4

What two layers of the egg (in order) does the sperm have to penetrate (and digest)?

Back 4

Corona radiata and zona pellucida (made of glycoproteins)

Front 5

What is the purpose of the binding of sperm to the ZP3 receptor?

Back 5

The ZP3 recptor is species-specific, which only allows the sperm of the same species to bind and prevents cross-species fertilization

Front 6

What is the acrosomal reaction (during binding to ZP3)?

Back 6

The activation of digestive enzymes in the head of the sperm that will help it break down the membrane of zona pellucida

Front 7

What does the first sperm to penetrate the zona pellucida encounter?

Back 7

They meet the receptor, integrin alpha 6 beta 1 which causes depolarization of the oocyte (changing the electric potential across the plasma membrane which shocks any other sperm from attaching to the membrane) and results in either fast block or slow block to polyspermy

Front 8

What occurs during fast block to polyspermy?

Back 8

-Depolarization
-Keeps extra sperm from entering and dropping off genetic material

Front 9

What is polyspermy?

Back 9

Having multiple sperm fertilize one egg

Front 10

What occurs during slow block to polyspermy?

Back 10

-Ions from inside the cell are releases (Ca ions)
-Intracellular release of Ca2+ which results in exocytosis of water (pulling water out of cell)
-Oocyte shrinks because of loss of water and zona pellucida denatures (affects the proteins)
-ZP3 deactivates

Front 11

Second meiotic division of the nucleus occurs once sperm has entered, forming a _____________ ______________ ______________

Back 11

Secondary polar body

Front 12

Genetic material inside female nucleus is now the _____________ ______________

Back 12

Female pronucleus

Front 13

Sperm head has detached from tail and now becomes the __________ ________________

Back 13

Male pronucleus

Front 14

Fusion of male and female pronucleus produces a ___________ ending the fertilization stage.

Back 14

Zygote (contains a full compliment of genetic material from male and female)

Front 15

What occurs during the first day of cell division?

Back 15

-One cell into two cells
-Longest division during the process
-Cells divide and are propelled into the uterus by cilia present in the Fallopian tubes

Front 16

How many cells are present during the second day of cell division?

Back 16

4 cells

Front 17

Cells that are able to differentiate into any tissue in the body are referred to as _____________

Back 17

Totipotent

Front 18

What is the structure when 12 cells are formed?

Back 18

Morula

Front 19

When cells can be become many types of tissue but not necessarily every type of cell are referred to as ____________

Back 19

Pluripotent

Front 20

The fluid filled cavity growing inside the morula is referred to as a ______________

Back 20

Blastocele

Front 21

The new structure (after morula) that has a cavity (blastocele) growing on the inside is called the ___________

Back 21

Blastocyst

Front 22

The outside layer of cells of a blastocyst are called the ________________ cells

Back 22

Trophoblast (the feeding layer that surrounds most of the blastocele and becomes extra amniotic tissues such as the placenta)

Front 23

What is the inner cell mass?

Back 23

The area in which the blastocyst is thicker and becomes the embyro and develops various sorts of tissues within the body

Front 24

What is implantation?

Back 24

When the blastocyst attaches itself to the uterine wall with the inner mass cells directed towards the wall of the uterus and come into contact with the wall

Front 25

What are the two types of twins that can occur?

Back 25

1. Dizygotic: not identical (fraternal), when 2 oocytes are released and fertilized and then implanted into uterine wall
2. Monozygotic: identical, when zygotic cells are split during development creating two identical embyros

Front 26

When do conjoined twins occur?

Back 26

After day 8, if the zygotic cell splits, the blastocysts cannot separate properly while in the uterine wall

Front 27

What are characteristics during the implantation and formation of the placenta stage (8-12 days)

Back 27

-Uterine walls must be optimal for implantation and have become highly vascular
-Blastocyst now gets nutrients and gets rid of wast products through the uterine wall and allows exchanges with the mother through a connection to maternal blood supply

Front 28

Trophoblasts form the placenta... what are the two types?

Back 28

Syncytiotrophoblasts: invade the uterine wall (multi-nucleated)
Cytotrophoblasts: the second layer that remains close to the embryonic tissue

Front 29

What is a syncytiotrophoblast?

Back 29

A multinucleated cell that invades the endometrium

Front 30

What is a cytotrophoblast?

Back 30

A cell that remains close to the embryonic tissue

Front 31

What are the lacunae?

Back 31

Pools of blood that are formed when syncytiotrophoblasts surround maternal blood vessels and digest their walls forming pools of blood

Front 32

What is the placenta?

Back 32

The exchange of nutrients and waste between mother and embryo

Front 33

What happens at the 10-20 day mark?

Back 33

-Further invade in the wall until they reach maternal artery and then break down the vascular wall in order to receive blood supply
-Pools of blood form that are called lacunae
-Connecting stalk develops

Front 34

What happens at the 1 month mark?

Back 34

-Cytotrophoblast provides a protective barrier between maternal and embryonic blood and then forms cords, starting to get own blood cells
-Protective barrier prevents the body from attacking since it would be considered a foreign object
-Chorionic villi are formed (finger-like projections)

Front 35

What's a chorionic villi?

Back 35

Finger-like projections that are formed by the chorion and occur where the exchange between fetal and maternal blood happens

Front 36

What are characteristics of the mature placenta and fetus stage?

Back 36

-Chorionic villi present
-Fetal blood vessels have formed and are in contact with the chorionic villi (previously cytotrophoblast)
-Umbilical cord forms
-Blood, nutrients and waste products are exchanged with the mother
-Cytotrophoblast degrades

Front 37

The fetal arteriole carries ____________________ blood.

Back 37

Deoxygenated

Front 38

The fetal venule carries ______________________ blood.

Back 38

Oxygenated

Front 39

In the fetus, the vein carries ________________ blood and the artery carries _______________ blood.

Back 39

Oxygenated, deoxygenated