Embryology, Growth and Development

Question 1

label the parts of the female reproductive system

Answer 1

• drawn out

Question 2

what are sex cells called

Answer 2

gametes

Question 3

how many ovaries do females have

Answer 3

2

Question 4

after how many days after menstruation does an ovary mature a females’ gamete and prepare its release

Answer 4

14

Question 5

difference between the secondary and primary oocyte

Answer 5

secondary = have only done 1st meiotic division,

primary = gives rise to the secondary oocyte and polar bodies

Question 6

what is ovulation

Answer 6

when the secondary oocyte (mature egg) is released from ovary

Question 7

explain how oocyte and sperm reach each other to fertilize

Answer 7

the oocyte leaves the ovary
finger like projections push it into the uterine
then it enters the ampulla (where fertilization occurs)
the muscular contractions in the uterus and uterine tube help push sperm to the oocyte

Question 8

what are the muscular contractions in the uterine tube and uterus caused by

Answer 8

hormones like oxytocin released during sex

Question 9

what is semen

Answer 9

prostaglandins from liquid secretions that support sperm

Question 10

what is the fertilization window

Answer 10

6 days before ovulation and 1 day after
- b/c sperm can live up to 6 days and can only be fertilized for 24 hours after

Question 11

what are the three prenatal development periods

Answer 11

germinal, embryonic and fetal

Question 12

what is the germinal period

Answer 12

• first 2 weeks of development
• when cells multiply and primitive germ layers form (which become body tissues)

Question 13

what is the embryonic period

Answer 13

• 3 to end of week 8
• embryo forms - organ systems develop

Question 14

what is the fetal period

Answer 14

• 9th week till birth
• so organ systems can grow and mature

Question 15

what are the 2 terms used for timing of developmental events

Answer 15

clinical/medical events = date since last period (clinical age of unborn kid)

embyrologists = post-ovulatory age - 14 days less than clinical age (POINT OF FERTILIZATION) = we use this

Question 16

describe the 6 steps of fertilization

Answer 16

1. sperm penetrate the corona radiata of secondary oocyte
2. the zona pellucida have ZP3 receptors that allow species-specific binding
3. after several sperms bind to the zp3 receptors it starts an acrosomal reaction
4. the acrosomal reaction breaks up the zona pellucida because it releases digestive enzymes
5. one sperm then makes it through to the plasma membrane and binds to the integrin 6ab1 and causes depolarization
6. this sperm enters the oocyte and its tail disintegrates so only head is left
7. female nucleus undergo second meiotic division –> forms ovum and 2nd polar body
8. female pronucleus and male pronucleus form
   - sperm head
   - ovum + second polar body
9. fusion of haploid pronuclei = single nucleus –> zygote (diploid)

Question 17

how can you stop multiple sperm from fertilizing the oocyte?

Answer 17

fast block to polyspermy:
- depolarization
- through the integrin receptor the sperm binds to the receptor and the fast electrical charge on plasma shocks the other sperm from entering

slow block to polyspermy:
- when calcium moves out of the cell which causes the oocyte to shrink an the zona pellucida to denature –> this means he ZP3 also denatures and sperms can bind to it anymore

Question 18

explain day 1 to 6 when the egg is fertilized

Answer 18

day 1:
first cleavage = 2 cells

day 2:
2nd cleavge = 4 cells

day 5:
morula - when there are 12 or more cells

day 6:
blastocyte - Fluids will be secreted and push the cells to the side creating a fluid-filled cavity with all the cells pushed into a single layer around the outside

Question 19

What happens during hatching and when?

Answer 19

when - from day 5 to 6

what - the zona pellucida will break free at the point of hatching

Question 20

describe and label the parts of the blastocyte

Answer 20

Trophoblast layer = Thin layer of cells that forms structures like placenta and extra embryotic membranes

inner cell mass (aka embryo proper) = becomes a developing embryo

blastocele - fluid-filled cavity

Question 21

where does the blastocyst move after the cleavages and formations have occurs

Answer 21

uterine cavity and implants itself to the uterine wall

Question 22

how does the blastocyst get its energy after being implanted?

Answer 22

before implantation:
cells were living off of og cell cytosol nutrients and secretions by the uterus wall called uterus milk (glycogen rich)

now:
As it gets bigger diffusion can not be relied on and it needs to make a connection with moms circulatory system for nutrients

Question 23

define totipotent

Answer 23

One single cell can divide and differentiate into every single cell type in the body

ex.
Single cell, zygote, morula

Question 24

define pluripotent

Answer 24

They’ve started to differentiate so they cant form all different cell types anymore
- Already in a specific cell line
- Morula stage

Question 25

what happens between day 8-12 (implantation and formation of placenta)

Answer 25

- As the blastocyst enters the cavity it orients itself with the inner cell, ass towards the wall of the endometrium and implants itself to the endometrial wall - The inner cell mass starts to differentiate into 2 diff cell types = syncytiotrophoblasts and cytotrophoblast

Question 26

what is the endometrium?

Answer 26

- Inside the uterine cavity the wall closest to the cavity - this layer of uterus changes in thickness with each menstrual cycle - When blastocyst reaches uterine cavity endometrium is hella thick and vascular so it has a lot of blood supply

Question 27

what do the synctiotrophoblast and cytotrophoblast do?

Answer 27

syncytiotrophoblasts: - job is to invade uterine wall and digest some blood vessels found in the uterine endometrium cytotrophoblast: - They provide layer of seperation between embryo proper and maternal blood supply

Question 28

differentiated cell synctiotrophoblast release hormone called

Answer 28

"human chronic gonadotropin" into maternal blood supply - Use this in pregnancy tests - Helps maintain thickened and vascular wall of endometrium of uterus

Question 29

what happens during day 14-20 (implantation and formation of placenta)

Answer 29

- Synctiotrophoblasts continue to invade uterine wall - Changes in placenta and embryo proper - Blastocyst is in uterine wall and covered by uterine wall cells - Syncytiotrophoblasts and cytotrophoblasts are changing to make placenta - Starting to make a connecting stalk - which later becomes the umbilical cord

Question 30

define implantation

Answer 30

burrowing the blastocyte into uterine wall

Question 31

define placenta

Answer 31

exchange of nutrients and waste between the mother and embryo

Question 32

define Syncytiotrophoblasts

Answer 32

multinucleated cell invades endometrium

Question 33

define cytotrophoblasts

Answer 33

remains close to the embryonic tissue

Question 34

define lacunae

Answer 34

syncytiotrophoblast surrounds maternal blood vessels and inject their walls which makes pools of blood

Question 35

what happens at 1 month

Answer 35

cytotrophoblasts provides a protective barrier between maternal and embryonic blood - they dont mix - embryo makes its own blood now + circulatory system - Cytotrophoblast's finger like projections form cytotrophoblast chords that surround syncytiotroblasts and lacuna - connecting stock has formed

Question 36

what happens when the placenta matures

Answer 36

- Finger like projections are now chorionic villi and are gonna fill the blood vessels from the fetus - New blood comes in from maternal arterioles and leaves through maternal venules - Hella gas exchange occurs - Chorion is the chorionic barrier - the final division between maternal and embryonic blood - cytotrophoblast cells have disintegrated by now only syncytiotrophoblast left

Question 37

at 1 month describe the Umbilical cord - 2 types of blood vessels

Answer 37

- Umbilical arteries (blood away from the heart) and veins (Carrying blood to heart) - Maternal blood supplies their oxygenated blood to baby via umbilical cord - With deoxygenated blood umbilical veins go up into chronic villi, pick up oxygen in capillary beds from lacunal blood and come back in the form of umbilical veins