developmental biology final

Koller’s sickle

thick layer of cells found in posterior region of marginal zone

marginal zone

separates area opaca and area pellucida

what does the primitive streak form from?

koller’s sickle

what is the koller’s sickle analogous to?

dorsal lip of blastopore

primitive streak

major structure in avian, reptilian, and mammalian gastrulation

what does the primitive streak define?

the axis of the embryo

primitive groove

depression formed within the primitive streak

what does the primitive groove serve as?

opening through which migrating cells pass into blastocoel

henson’s node

forms at anterior end of primitive streak

where do the first group of cells move to (through primitive streak)

anterior portion of embryo

what do the first group of cells moving through PS produce?

notochord and anterior somites

cells in middle of embryo will form…

somites and heart and kidneys and organs

cells near the streak will form…

medial structures aka somites

cells further will form…

distal structures

primary hypoblast

formed when area pellucida cells migrate individually into subgerminal cavity

secondary hypoblast

sheet of cells from posterior margin of the blastoderm

what do hypoblast cells form

external membranes (yolk sac)

what do hypoblast cells do to epiblast cells

induce them to migrate

what do the inducing signals activate (3 things)

1. actin assembly

2. downregulation of cell adhesion molecules

3. change in shape

subgerminal cavity separates…

blastoderm from underlying yolk

yolk sac links…

underlying yolk proteins to developing digestive tube

germinal crescent

anterior region in which hypoblast cells are confined to

how is the germinal crescent formed?

when epiblast cells enter the primitive streak

cells once in blastocoel…

will displace hypoblast cells

how do cells migrate? (2)

1. cells lose adhesion for neighboring cells

2. cells undergo a change in shape

what are germinal crescent cells precursors to?

germ cells

germinal crescent cells form embryonic structures (t/f)

false

next group of cells in the blastocoel form…

head mesoderm and notochord

notochord is a — tissue

inducing

what does the notochord induce?

the migration path of neural crest

what does the neural crest produce?

neurons

neural tube is the precursor to what

spinal cord

formation of notochord is controlled by what pathway?

FGF signalling pathway

FGF8 is…

an inhibitor

FGF4 is…

a signalling molecule that promotes migration

What does FGF4 do in the notochord mechanism?

acts as a paracrine signalling molecule to initiate a pathway for actin formation

what does FGF8 do in the notochord pathway?

acts as a paracrine factor to initiate a pathway that inhibits contraction of actin filaments (no cell migration)

FGF4 causes…

downregulation of cell adhesion molecules

Sclerotome becomes…

cartilage of vertebrae and part of the ribs

sclerotome is located

closest to the neural tube (furthest from the back)

dermamyotome is located

on dorsal side

dermamyotome becomes…

dermatome=dermis, myotome=muscle precursor cells

when the primitive streak regresses, what happens to Henson’s node?

it moves to a more posterior region

what is the gradient for avian development

anterior-posterior, anterior faster development

in late gastrulation, cell migration occurs how?

epiboly

primary oocyte stalls in which phase

late prophase i

primary oocyte forms 2 things…

1. small first polar body

2. large secondary oocyte

small polar body…

undergoes meiosis ii to produce 2 smaller polar bodies

secondary oocyte…

arrests in metaphase ii and is ovulated

how long can sperm remain alive in the female reproductive tract?

1-6 days

why is it difficult to study mammalian fertilization

internal fertilization, ethical issues, sperm need to travel long time to get to egg

first event in mammalian fertilization

sperm released

newly released sperm cannot fertilize egg (t/f)

true

cumulus cells

surround oocyte, nourish the oocyte

graafian follicle

whole structure including cumulus cells

zone pellucida

surrounds egg cell membrane, lifts off cell following fertilization

second event in mammalian fertilizaton

capacitation

capacitation

sperm undergo a set of physiological changes to become competent to fertilize egg

sperm cell membrane has

phospholipid bilayer, chloresterol

chloresterol makes the sperm cell membrane more fluid (t/f)

false

why does capacitation occur?

albumin proteins

what does capacitation remove

chloresterol from sperm cell membrane

why does membrane fluidity matter?

membrane proteins are less compacted + able to be recognized easier

where does capacitation occur?

in female reproductive tract

calcium moves…potassium moves…with the head of the sperm

IN, OUT

the movement of ions in and out of the sperm head initiates…

acrosome reaction

third event in mammalian fertilization

binding of the sperm to the zona pellucida

fourth event in mammalian fertilization

induction of the acrosomal reaction

what initiates acrosome reaction?

binding of the capacitated sperm to the ZP3 receptor on the zona pellucida

what does the ZP2 receptor do?

interacts with sperm that have undergone the acrosomal reaction

fifth event of mammalian fertilization

gamete fusion

sixth event of mammalian fertilization

cortical granule reaction

how are ZP3 receptors modified during the cortical granule reaction?

they become ZP2, which can’t interact with capacitated sperm

what does the cortical granule reaction do?

blocks polyspermy

seventh event of mammalian fertilization

fusion of genetic material

how does the sperm pronuclei move

microtubules and motor proteins

eighth event of mammalian fertilization

egg activation - protein synthesis in egg cell cytoplasm

rotational cleavage

the first cleavage is vertical, the second cleavage horizontal

what does rotational cleavage result in

an odd number of cells (asynchronous division)

features of cleavage (3)

1. occurs slowly

2. asynchronous division

3. genome activated

compaction

when blastomeres group together to form tight ball

e cadherin

cell adhesion molecule produced by blastomeres responsible for compaction

what is e cadherin dependent on ?

calcium

tight junctions

tight interactions between neighboring cells

gap junctions

allows for cell-cell communication + exchange of materials

opening and closing of gap junctions regulated by

calcium

trophoblast cells

do not form structures, form tissues of chorion

first function of chorion

transports o2 and nutrients from mother to embryo

second function of chorion

secretes hormones to cause uterus to retain embryo

third function of chorion

regulators of immune response (so mother doesn’t reject fetus)

fourth function of chorion

induce uterine cells to form maternal portion of placenta

chorion

fetal tissue of placenta

decidua

maternal tissue of placenta

inner cell mass

frormed from internal cells of morula stage

inner cell mass gives rise to…

embryo, yolk sac, allentois, amnion

amniocentesis

amnionic fluid shed fetal cells

chorionic villi sampling (CVS)

villi suctioned off for study in procedure

OCT4

blocks some early embryonic cells from taking trophoblast fate - cells become inner cell mass cells

stat3 and nanog

cause inner cell mass cells to grow and divide

inner cell mass can give rise to all cell types except trophoblast

true