9-1: 10/24: Embryonal And Placental Development

Front 1

Sperm passes the ________ to penetrate the _________ of an oocyte.

Back 1

Passes corona radiata to penetrate zona pellucida (to form zygote)

Front 2

Fertilization occurs in the ______ of the fallopian tube.

Back 2

Ampulla

Front 3

Fractionation of Blastomeres

Back 3

Daughter cells of a zygote, constrained by zona pellucida when dividing, so have to dive into smaller cells (known as fractionation)

Front 4

Compacttion of Blastomeres

Back 4

Flattening and polarization of cells to form compact multicellular organism

Mediated by cell-surface adhesion glycoproteins (E-cadherin) to facilitate cell-cell interactions

Front 5

Morula

Back 5

12-32 cells in zygote (after blastula); begins to develop inner cell layer

Front 6

Blastocyst

Back 6

After morula enters uterus; formation of fluid-filled space (blastocele) inside morula

Outer cell layer = trophoblast (forms embryonic part of placenta)

Inner cell mass (embryoblast): becomes epiblast, endoderm

Front 7

Blastocyst hatching

Back 7

shedding of zona pellucida (hatching) of free-floating blastocyst; allows rapid increase in growth and endometrial nourishment

Front 8

Cyntotrophoblast vs Syncytiotrophoblast

Back 8

When trophoblast contacts endometrium, immediately differentiates into cytotrophoblast (INNER) and syncytiotrophoblast (multinuc'd without cell boundaries; OUTER)

Cytotrophoblasts are MITOTICALLY active; generate cells that migrate into syncytiotrophoblast (where they lose cell membranes)

Syncytiotrophoblasts makes contact with endometrium!

Front 9

Hypoblast

Back 9

After superficial implantation of blastocyst in endometrium, get formation of hypoblast (primitive endoderm) on surface of embryoblast facing blastocystic cavity

Front 10

Summarize week 1 of embryonal development.

Back 10

Zygote
Two-cell-->four-cell-->8-cell
Morula (mullberry)
Blastocysts
Attachment!

Front 11

Implantation is completed by _____.

Back 11

End of second week (usually on superior body of uterus)

Front 12

hCG is produced by ______.

What is the function of hCG?

Back 12

hCG produced by syncytriotrophoblast

Fn:
Antigonadotropin (inhibits LH, FSH to prevent ovulation)

Steroidogenic: stimulates PG production by corpus luteum

Front 13

Exocoelomic cavity

Back 13

During implantation of blastocyst

Space in embryoblast forms priomordium of amniotic cavity

Amnion-forming cells enclose amniotic cavity

Blastocyst now called exocoelomic cavity

Front 14

Embryonic Disc
Epiblast vs Hypoblast

Back 14

Transformatino of embryoblast results in flat plate of cells: embryonic disc

Epiblast: Dorsal, floor of amniotic cavity

Hypoblast (primitive endoderm): ventral; roof of exocoelomic cavity

Front 15

Fate of epiblast.

Back 15

Becomes fetus proper

Front 16

Fate of primitive endoderm.

Back 16

Primitive endoderm = hypoblast

Will become yolk sac, fetal membranes

Front 17

Fate of trophectoderm.

Back 17

Most of fetal contribution to placenta

Front 18

Lacunae are present in ________.

Role?

Back 18

Lacunae are present in syncytiotrophoblast and establish primordial uteroplacental circulation

Front 19

Extraembryonic mesoderm surrounds the ______________.

Back 19

Amnion and exocoelomic cavity

Front 20

This structure serves as the primary umbilical vessel (yolk sac).

Back 20

Exocoelomic cavity

Front 21

Extraembryonic coelomic spaces

Back 21

Form within extraembryonic mesoderm and fuse to form extraembryonic coelom

This coelom expands and splits into 2 layers:

Inner extraembryonic splanchnic mesoderm (surrounds umbilical vesicle)

Outer extraembryonic somatic mesoderm: lines trophoblast and covers amnion

The coleom is now the CHORIONIC SAC (lined by chorion:

Front 22

What structures become primary chorionic villi?

Back 22

Extensions of cytotrophoblast grow into syncytiotrophoblast (induced by mesoderm) to become primary chorionic villi

Front 23

Summarize the events of week 2 of embryogenesis.

Back 23

Completion of implantation

Formation of bilaminar embryonic disc (composed of epiblast and hypoblast; source of germ layers that form all tissues/organs)

Formation of extraembryonic structures: amniotic cavity, amnion, umbilical vesicle (yolk sac), connecting stalk, chorionic sac

Front 24

What is the decidual reaction?

Back 24

Transformation of endometrial CT in response to implantation; results in accumulation of glycogen and lipid (fn = nutrition, immunological privilege)

Front 25

What is gastrulation?
Describe each step.

Back 25

Establishment of 3 germ layers from bilaminar embryonic disc

Heralds beginning of morphogenesis

1) Formation of primitive streak which establishes axial orientation of embryo (cranial/caudal, dorsal/ventral, right/left)

Front 26

Primitive Streak

Back 26

Establishes axial orientation and marks beginning of gastrulation

Cells form mesenchyme, some of which will form mesoblast, which forms embryonic mesoderm

Some cells displace hypoblast to form embryonic endoderm in roof of umbilical vessel

Remaining epiblast cells form ectoderm

Note: primitive streak undergoes degeneration by end of 4th week

Front 27

Fate of epiblast.

Back 27

Gives rise to all three germ layers in embryo via gastrulation

Front 28

Ectoderm derivatives

Back 28

CNS, PNS
Epidermis
Sensory epithelia of eye, ear, nose
Mammary, pituitary, subcutaneous glands
Tooth enamel
NCCs

Front 29

Mesoderm derivatives

Back 29

CT
Cartilage, Bone, Muscle
Heart, blood, LVs
Kidneys, ovaries/testes, genital ducts, spleen
Seroud membranes lining body cavities
Adrenal Cortex

Front 30

Endoderm derivatives

Back 30

Epithelium of GI, resp tract
Parenchyma of thyroid, parathyroid, thmus, liver, pancreas
Epithelium of bladder and most of urethra