embryo and human health

Question 1

What is fertilization

Answer 1

The process by which two haploid sex cells fuse to form a diploid cell (now called a zygote)

Question 2

T/F: fertilization is series of events (a process), rather than a single event

Answer 2

True

Question 3

Requirements for succesful fertilization:

Answer 3

1. Mature, fully motile sperm
2. Unobstructed female reproductive tract
   3.Both sperm and secondary oocyte are still viable
3. capacitation: final stage of maturation that happens in the isthmus of the uterine tube
4. acrosome reactin

Question 4

Where and when do sperm undergo capacitation

Answer 4

Inside the uterine tube, spermatazoa bind to the epithelium of the isthmus for 24 hours

Question 5

What prohibits premature capacitation

Answer 5

cholesterol. Cholesterol is removed from the surface of the sperm head AFTER it undergoes capacitation .

Question 6

What has to happen in order to initate the acrosome reaction

Answer 6

glycoproteins deposited on the sperm head in the epidymis are removed

Question 7

What factors help move the sperm to the ampullae

Answer 7

muscular contractions, chemo attractants, and thermal gradient

Question 8

What exactly allows the egg to move down the tube and the sperm to move up?

Answer 8

compartmentalized contractions, one area moving in isolation

Question 9

T/F only capacitate sperm seem to be able to respond to chemical and thermal stimuli

Answer 9

true.
also, sperm are usually viable in female reproductive tract for 80 hrs.

Question 10

What allows the sperm to penetrate the corona radiate and reach the zona pellucida.

Answer 10

The ICM has lots of hyaluronic acid, the sperm head contains hyaluranidase which breaks down the hyaluronic acid.

Question 11

When does sperm undergo the acrosome reaction

Answer 11

after penetrating the corona radiata, the spermatozoa binds to the zona pellucida.

Question 12

What prevents other sperm from binding to the egg after one has already fused

Answer 12

the change in membrane potential

Question 13

What is the zona reaction

Answer 13

secretory products of cortical granules hydrolyze sperm receptor molecules in the zona. the zona reaction eliminates the ability of other sperm to adhere to the zona

Question 14

At the 8 cell stage, the zygote undergoes a process called _______

Answer 14

compaction: cells in outer areas adhere to each other tightly through gap and tight junctions.
E-cadherin plays a big role in this
The result of compaction is that these cells become organized into an epithelium.

Question 15

16 cell stage is called the

Answer 15

morula

Question 16

what is the blastocyst

Answer 16

a fluid filled cavity that separates the inner cells from the outer epithelium

Question 17

morula forms _____ days after fertilization
blastocyst forms ______ days after fertilization

Answer 17

Morula: 3-4 days
blastocyst: 5-6 days

Question 18

Explain these three terms together

embryoblast, trophoblast, blastocyst

Answer 18

The inner cell mass of a blastocyst is called the embryoblast and the outer layer is called the trophoblast.

Question 19

The embryoblast forms what structures

Answer 19

embryonic and extraembryonic

Question 20

The trophoblast form ______ structures

Answer 20

ONLY EXTRAembryonic structures (placenta)

Question 21

What is the blastocyst cavity

Answer 21

fluid filled space in between the trophoblast and embryoblast

Question 22

In one sentence, what happens during week 1

Answer 22

blastocyst implants into functional layer of the endometrium.

adhesion molecules, especially INTEGRINS, faciliate implantation into the uterine lining

Question 23

During week 2, the outer trophoblast differentiates into ____ parts

Answer 23

2 parts (think week 2)
the outer cellular layer= trophoblast
cells surrounding the inner cell mass fuse= syncytium

Question 24

How do nutrients from maternal blood cross over into the developing embryo?

Answer 24

Via the syncytiotrophoblast.
-these cells penetrate into the uterine lining, the projections will contact maternal vessels and create blood filled lacunae (little lakes)
trophoblast projections will enter the lakes and form junctions with blood vessel epithelial cells and this is how nutrients from mom cross over into embro**

Question 25

What produces hCG

Answer 25

synccytitrophblast

Question 26

In week ____, the bilaminar germ disc form

Answer 26

Week 2 Cells of the inner cell mass become epithelialized and separate into two layers upper layer= epiblast lower layer= hypoblast

Question 27

the bilaminar germ disc is surrounded by the

Answer 27

trophoblast

Question 28

Epiblast cells form the ______

Answer 28

amniotic membrane and cavitation results in amniotic cavity

Question 29

Hypoblast is also called the _________

Answer 29

primitive endoderm.

Question 30

The yolk sac forms in ______

Answer 30

week 2

Question 31

The primary yolk sac is formed by _______

Answer 31

hypoblast cells lining the blastocyst cavity

Question 32

The new cavity outside the yolk sac, chorionic cavity, is created by the _______

Answer 32

extraembryonic mesoderm

Question 33

the secondary yolk sac (aka definitive yolk sac) is formed by

Answer 33

a second wave of hypoblast cells that migrate -the membrane closes off an pinchess of the primary yolk sac

Question 34

Give a summary of the second week

Answer 34

1. Trophoblast differentiates into two layers (cytotrophoblast and syncytiotrophoblast) 2. Embryoblast differentiates into two germinal layers (epiblast and hypoblast) *Epiblast= becomes entire embryo hypoblast= forms extraembryonic mesoderm and yolk sac* 3. Two cavities form on either side of the bilaminar germinal disc (amniotic cavity and yolk sac)

Question 35

define totipotent, pluripotent, multipotent, oligpotent

Answer 35

totipotent: All powerful, cells that have potential to become anything pluripotent: Can become any of the 3 germ layers (cant become trophoblast or structures outside the epiblast) multipotent: can develop into more than one cell type (adult stem cells) oligopotent: Differentiate into a limited subset of cells

Question 36

In what week does the primitive streak appear

Answer 36

week 3

Question 37

What is the primitive streak

Answer 37

a condensation of cells migrating to the midline in the posterior area of embryo. *Begins: tail end of disc progresses about halfway up towards cranial end*

Question 38

Why is the primitive streak important

Answer 38

can define cranial and caudal ends, right and left, top and bottom aspect to the disc for the very first time

Question 39

Describe epiblast cell migration and gastrulation

Answer 39

*these cells form characteristics of mesenchymal cells which is what allows them to migrate* -some cells migrate to the primitive streak (nothing speical) -Some cells detach, invaginate, and replace the hypoblast=FORMING THE ENDODERM -Some cells migrate further and differentiate to become the mesoderm.

Question 40

Once the 3 germ layers are established (endoderm, mesoderm, and ectoderm) these cells are no longer ________

Answer 40

no longer pluripotent *now you have 3 layers of multipotent cells forming our trilaminar germ disc

Question 41

Endoderm cells give rise to

Answer 41

-liver -gall bladder -thymus -thyroid -parathyroid glands -tonsils -epithelial lining of respiratory -GI and urinary -auditory tube -tympanic cavity *Think everything INSIDE= ENDO*

Question 42

Mesoderm gives rise to

Answer 42

*Think: the one trying to get a date* -muscle -ct -dermic -adrenal cortex -heart -kidneys -spleen -internal repro organs

Question 43

Ectoderm gives rise to

Answer 43

Epidermis and its derivates nervous system enamel adrenal medulla pit. gland lens of eye

Question 44

Ectoderm gives rise to

Answer 44

Epidermis and its derivates nervous system enamel adrenal medulla pit. gland lens of eye

Question 45

Which germ layer contributes to the formation of the notochord

Answer 45

the mesoderm

Question 46

What induces the development of the neural plate?

Answer 46

the notochord

Question 47

The notochord also stimulates the differentiation of other types of mesoderm. The paraxial mesoderm, will further differntiate into structures called _______

Answer 47

somites

Question 48

Paraxial mesoderm will

Answer 48

-form a series of structures called somites -eventually form most of the axial skeleton

Question 49

Somites are formed from the ______ mesoderm

Answer 49

paraxial.

Question 50

Somites will subdivide into 3 parts. What are they

Answer 50

1. mytomes = develop into muscle 2. dermotomes= develop into dermis 3. sclerotomes= develop into skeletal elements

Question 51

Break down myotomes even farther. What will you find?

Answer 51

Two components 1. Dorsal epimere = gives rise to deep back muscles 2. ventral hypomere = muscles that move the upper limb and ribs

Question 52

______ join with _______ mesoderm to produce dermis

Answer 52

dermatome wil merge with the somatopleure which completes the epidermis and dermis`

Question 53

Intermediate mesoderm will form most of the

Answer 53

urinary and reproductive tracts

Question 54

lateral plate mesoderm near the ectoderm= combined layer of the somatic mesoderm and the ectoderm= lateral plate mesoderm near the endoderm=

Answer 54

near ectoderm= somatic mesoderm combined middle layer= somatopleure (soma means body) near endoderm: splanchnic mesoderm

Question 55

Folding of the embryonic disc happens during week ___

Answer 55

Week 4. 1. Cranial-caudal folding= head and tail closer together ventrally 2. lateral folding = two edges of the disc together

Question 56

Where is the notochord located on the embryo?

Answer 56

dorsal aspect of the embryo

Question 57

What is the vitelline duct

Answer 57

it is the connection as a result of laterally folding bringing the two edges of the disc together. The yolk sac pinches off and you are left with a narrow connection between the developing gut tube and yolk sac.

Question 58

Intraembryonic coelom forms _____

Answer 58

future body cavities

Question 59

body wall is formed from _______ and ______

Answer 59

somatic mesoderm and ectoderm

Question 60

gut tube formed from ______ and _______

Answer 60

splanchnic mesoderm and endoderm

Question 61

The primitive streak disappears by the end of the _____ week

Answer 61

end of the 4th week

Question 62

Overall summary of embryo week 2: week 3: week 3-4: Week 4:

Answer 62

Week 2: bilaminar embryonic disc forms "week of twos" Week 3: primitive streak, gastrulation (3 germ layers), trilaminar embryonic disc Week 3-4 notochord development, neurulation (development of the nervous system) week 4: craniocaudal and lateral folding of embryo, regression of primitive streak.