Mostly Human Development See pages 636 and 640 for overview of Phylogenetic tree Early Development Early Development Developmental Tissue Layers Sponges0 Gridera Centophores2 All other Phyla3 ID: 755804
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Slide1
Development
Chapter 21, 46, 47
Mostly Human Development
See pages 636 and 640
for
overview
of Phylogenetic treeSlide2
Early Development
Early Development: Developmental Tissue Layers, Sponges-0,
Gridera
/Centophores-2, All other Phyla-3
Hormones released in hypothalamus
FSH: Follicle Stimulating Hormone
LH: Luteinizing Hormone
At menstruation, there are multiple concurrent events
Estrogen and Progesterone (hormones from the ovaries) gone down its concentration
FSH increases in concentration
Menstruation is occurring. The endometrial lining of the uterus is flushed out.
When Estrogen levels drop, the brain monitors and produces FSH. The target of the increased at FSH is in the ovaries.
A cluster of cells in the back of the ovary. Each contains the germ line cell. Primary
oocye
that started meiosis before birth. But this was arrested in prophase.
After 2 or 3 days, usually only one Oocyte continues to matureSlide3
The maturing of
Oocyte
1. The
surrounding cells form the
Graffarian
Follicle.
2. Continues
into the first division of
meiosis
3. the
developing follicle moves down the Ovary and growing in cell
number
4. the
follicle continues to mature for about 14 days – it enlarges spatially and more
cells
the
meiotic dividing primary oocyte is in a cavity with some surrounding nursing
cells.
The
nursing cells are adding nutrients and other components to this meteoric cell to prepare for it to become an
egg
fully
developed follicle (
egg/ovary)
outer
follicle cells synthesis and release Estrogen (steroid) Maturing outer follicle becomes a hormone producer..
5. Increased
Estrogen stimulates the rebuilding of the Endometrium of the
uteral
wall and the decline of FSH
concentration.
6. The
brain monitors increased estrogen and as a feedback mechanism, it decreases the release of FSH
.Slide4
The maturing of Oocyte
7. The
developing follicle also can secrete inhibits, this is also a hormonal message to the hypothalamus and anterior pituitary to decrease the release of FSH.
An egg is being formed – both still requires 2
nd
meiotic division
the Estrogens and
Inhibins
decrease with equals FSH increases
Endometrium is rebuilding. The endometrium is continuing to form under hormonal direction and or stimulates currently estrogens. Mostly made of mucus, blood, glycogen. It's being formed in case of the pregnancy. If there is a pregnancy endometrium is the nutrient, food, 02 etc. source and will maintain the first part of the pregnancy.
This is for internal fertilization only not for things like fish as the ovarian follicle nears maturity, it's:
estrogenic output decreases
This is a signal to the brain or hypothalamus to cause anterior pituitary
release more FSH
release a very large amount of luteinizing hormone.
The estrogen decrease is not enough of drop to stop the endometrium from building
spike of LH stimulates to events to occur and a concurrent third eventSlide5
Ovulation
Ovulation: Oocyte sent to the
filopian
tubes and
ovaduct
with nursing cells (triggers 2
nd
meiotic division)
Remaining follicle cells collapse in and forms the Corpus
Luteum
.
Two possible concurrent events during ovulation
the released egg travels down the
ovaduct
by Cilia on
ovaduct
cells and contraction of smooth muscle cells, called
peristolsis
.
The Corpus
Luteum
becomes the new Hormone Factories:
prodcues
Estrogen and Progesterone. - causes LH and FSH to decrease, causes Endometrium to enlarge more
(possibility) the egg can be fertilized, but the egg is viable (able to function) for about 24 hours
to become fertilized
sperm must be present during
fallopion
tubes during 24 hours
sperms must contact, attach and release nucleus into
eggSlide6
Ovulation
Situation #1: if no sperm is present:
corpus
luteum
will function longer if pregnancy has occurred. There will be no message with no sperm. 10-11 days if not pregnant, corpus
luteum
deteriorates.
If both estrogen decreases and
inhibins
decreases, then FSH increases and LH increases. If estrogen decreases and progesterone decreases, more FSH increases then LH.
Situation #2: Sperms (high number of sperms and obstacles to sperms) meets, attaches and fertilizes egg
sperm must overcome obstacles (get lost, environment shock, go up wrong side, get through the nursing cells, Nona
Puluza
)
Multiple sperm must work to fertilize sperm, but if multiple sperm enter the egg (
polysperm
), then the egg is worthless and discarded.
Only one sperm fertilize, protection to avoid
polysperm
. - but its dependent on species.Slide7
Sea Urchins (
polysperm
)
Sea Urchins (
polysperm
)
Sperm releases acrosomes. Acrosomes are hydrolytic digestive enzymes. That digests the
zona
peluza
up to the
vitealie
layer. Actin fibers of sperm attaches to receptors on the egg membrane and pulls it in. Receptors are very specific
the membrane of both cells fuse. Consequences:
sodium pathways open up and let sodium in. The egg becomes positively charged. No more sperm can attach.
Cortical vesicles are all around inside the egg. Calcium
rugles
out of the cell and cortical vesicles release and pushes the membrane and
vitealine
layer apart. Water does the job.
Vitealine
stiffens and becomes the fertilization. Envelope plasma membrane returns to normal charge.
Slow box 3
polysperm
takes about .5 – 1 min. but is long lasting the egg plasma membrane returns to its condition. The texture of the
vitalin
layer of egg changes. The plasma membrane re-polarizes
.Slide8
Sea Urchins (
polysperm
)
The cytoplasmic increases in concentration calcium also initiates the metabolic and functional changes with the egg cell.
Increases cellular respiration
and increases ATP in cell
increases in protein synthesis
DAG, intracellular messenger molecule activates its output of the cell, so the cytosol becomes more basic. When these two events is occurring the sperm's nuclear starts to swell and in about 20 min. after entering the egg, the two nuclei fuse together. Now a to end
nuclear's
, fertilization, and the zygote.
Male and female genetic info come
togetherSlide9
Zygote
Mammals
extra coating around the populated egg. It is a surrounding corona of the formal nursing cell. They surrounded the egg in the follicle and continue to surround the related egg.
Zona
Pellucida
extracellular matrix woven with glycoproteins that cross-link into a 3-D network.
One of these three glycoproteins, ZP3 (
zona
pellucida
glycoprotein #3) also functions as the sperm's receptor
binding of plasma membranes cause
depolorazation
of cell membrane (fast block)
corticle
vesicles,
corticle
reaction, changes the
zona
pellucida
and rigid (slow block)
zona
pellucida
does not separate from egg
events change inside the ovum, 2
nd
meiotic divisions occurs in mammalsSlide10
Zygote
the egg doesn't go through second meiotic division unless sperm
perpetrates,
it forms a second polar body due to uneven
cytokenesis
.
The female nucleus and male do not fuse
both
separately
replicate DNA, still
separate
as mitosis occurs
both nuclei lose the nuclear envelope
all chromosomes line up in metaphase in one plane, then fertilization. The cell finishes mitosis including
cytokenesis
.
This is now:
2 cell zygote, each has a 2n nucleus
the initiation of cleavage
the genetic identity of the offspring is established,, unique
sex chromosomes determine sexual
determination
the
next events are in the mammalian zygote traveling through the
ovaducts
4 days to reach the uterus.
Meanwhile, corpus
luteum
is fully formed, this produces estrogen and progesterone; endometrium is growing, cleavage happens while traveling in
ovaduct
.Slide11
Cleavage
number of cells increases, mitosis with
cytokenisis
cells grow in number, not in size.
Cells are genetically identical to each other.
Egg must contain many organelles to fuel all these cells may grow.
the cytosol and all non-nuclear organelles of the egg just one cell have now become the cytosol and non-nuclear organelles in many different descendent cells. The organelles especially the mitochondria of the developing offspring came only from the egg. Mitochondrial inheritance is from the mother.
2 types of cleavage
Spiral cleavage
by 8 cells stage, the cells do not align. The upper for cells are shifted upward from the lower 4 cells.
A pattern in
protesostome
, mouth opens first in the digestive tract, very early cell differentiationSlide12
Cleavage
Spiral
cleavage (cont.)
Organisms
with spiral cleavage tend to have early differentiation only certain cellular identities in the future and possible as development progresses.
cellular differentiation for
multiorganism
SL's progress through this differentiation of development, the types of cells they can end up being in the final organism fully developed becomes more and more limited.
During this process, various potential genetic info is being turned on and off. Many that are turned off, stay off and all descendent cells. Consequently, there are many types of expressions that may make the descendent cells can never perform.
Organisms with spiral cleavage have early cell
differitiation
Radio Cleavage
by the eight cell stage, upper four cells aligned with lower four cells
Deuterostomes
. No differentiation yet (cell division starts later)
all cells are still aligned
anus opens first, mouth secondSlide13
Morula
we have radio cleavage. At this point the developing offspring is traveling through
ovaduct
. Cleavage is
occurring.
While still in the over duct, one of the cells no longer has any of its surface in contact with the outer
zona
pellucida
. No cell
differentiation
yet. It is in intercell, cells in contact with
zona
pellucida
or outer surface are outer cells.
Once this occurs, both inner and outer cells have developmental stage is now called a
morula
. Still a solid ball of cells. The zygote has become a
morula
.
In organisms like us:
still no cell differentiation. The cells
aretotspotent
:
intercell can be exchanged with any outer cell and still have all cellular potentials ahead of it.
The
zona
pellucida
remains intact through
themorula
stage. It is still in the cleavage
stage
it
is the
morula
that enters the uterus. 4-5 days since ovulation. Likewise, it would be in on fertilized egg entering the uterus at the same time. The
morula
cells are still
totipotent.
Totipotent:all
cells possible, not differentiated, any inner cells can be exchanged with any outer cellSlide14
Morula
Upon
morula
entering the uterus, several events occur relatively simultaneously:
the
zona
pellucida
starts to disappear. Consequently the volumes can now expand without much restrictions
the
zona
pellucida
stops a tube pregnancy
a forms in this developing offspring. It is no longer a solid ball of cells. The cavity is the
blastocystic
cavity.
This is a new stage in development
the outer cells form a single layer around the blastula. The cells have become
trophoblasts
(protect and support tissues). They were in contact with the
zona
pellucida
the inner cells are pushed to one cluster within the cavity at a whole. The inner cells have become a single
embryoblasts
(forms the embryo)
those two cells are not exchangeable because it is the first differentiated cells
The location of a cell highly affects its differentiation. Environment for a cell is important
.Slide15
Morula
The
trophoblasts
that are in contact with the embryo blasts within a succession of events, do the following:
release a sticky substance
form
microvili
on the plasma membrane outside the blastula.
Both help with attachment of the endometrium. The two entities try to assure attachment of blastula to the endometrium has a embryo blast facing the endometrium.
The endometrium also form microvilli in its later stages
These
trophoblast
in contact with the embryo blasts, once attachment has occurred, it will release a hormone called human
chonionic
Gondotrophin
.(
hCG
). The target for
hCG
ourselves of the Corpus Lutein in the mothers ovary. Without this hormonal message between mom and partially developed offspring the corpus lutein will degenerate within 10 to 11 days. With the
hCG
, the corpus lutein last several months. Without it menstruation follows
.Slide16
Morula
However, in corpus
luteum
receiving
hCG
, the corpus lutein stays for several more months. Estrogen and progesterone levels stays high concentration. Consequently:
the endometrium continues to enlarge instead of
demostrating
.
No new cycle starts. No further start of eggs in the follicles. No at SH is released.
This is the starter pregnancy. Due to
hCG
the corpus
luteum
now lasts about 10 to 8 weeks past ovulation.
HCG is the development and offspring's message to the mother not to flush out the developing offspring. It is the support for material, food, nutrients, 02, etc. for the first part of the pregnancy. This is about 6 to 7 days after ovulation for the attachment. There is no menstruation.Slide17
Second week (7-14 days
since
ovulation)
implantation; shifting of
Embryoplast
into two cell layers; growth of
trophoblasts
.
Implantation
the blastula is completely covered with endometrium material
trophoblasts
release enzymes that digest into the endometrium
carves a place for the blastula
opens cavities that increase blood flow (pools of internal blood), lacunae
to start implantation,
trophoblasts
next to the endometrium search release enzymes that digest into the endometrium
endometrium grows around the blastula – continues all week
trophoblasts
not touching
embryoblasts
, starts to touch endometrium
more enzyme release
fibrin coagulum: “scabs” over the blastula – completing implantation, blastula is completely coveredSlide18
Second week (7-14 days
since ovulation)
meanwhile, the
trophoblasts
grow and divide into the endometrium (cellular differentiation, will later become the placenta) / the support develops faster than the offspring, take nutrients from mother
meanwhile, the
embryoblasts
change location, go through one major differentiation
embryoblasts
in contact with
trophoblasts
become
Epiblasts
Epiblasts
move away from the
trophoblasts
embryoblast
not in contact with
trophoblasts
become hypoblasts
amniotic cavity formsSlide19
Third Week
formation of Primitive Steak (depression by cells folding in)
cellular differentiation of
Epiblasts
into Ectoderm and Endoderm and then Mesoderm.
Hypoblasts reproduce and make one cell layer and makes a yolk sac.
The
Blastocistic
Cavity has membranes dividing it
The
epiblasts
on the
aminotic
side differentiate into ectoderm but they are limited by the walls of the blastula.
The cells that push into the hypoblasts turn into
endoerm
.
Endoerm
begins to divide themselves – lines the yolk sac, one layer think.
Once Endoderm lines the egg sac and ectoderm on the amniotic side, a cavity forms between the cell. Mesoderm fills the cavity
Folded in cells form Endoderm then Mesoderm
Primitive streak is formed (depression by cells folding in): the crease in the Ectoderm cell
Trilaminar
disk formed or three developmental layersSlide20
Third Week
the process is now called Gastrulation (Gastrula)
zygote –
morula
– blastula – gastrula
Invagination
the folding in of cells from an outer surface to an interior. Environment = invagination
Mesoderm begins migrating toward the
ephalic
end (head); it does not migrate in
procordial
plate
Migrating Mesoderm
it travels from primitive node toward the
Prochordial
plate. These cells turn into (differentiate) cells of the
Notocord
. The Notochord is the first characteristic that appears for
chordata
.
It travels beyond the
procordial
plate develops into Cardiogenic tissue, forms the muscles and values of the heart
.Slide21
Third Week
The notochord tissue is the first developed tissue that is still present in an adult. All other cells (mesoderm, ectoderm,
etc
) do not stay.
Toward the end of the 3
rd
week, the mesoderm next to the notochord differentiates into somite cells.
Somites
are structures made of
somitic
cells. They form in pairs on either side of the notochord. The first pair is between the primordial node and the
pricordial
plate.
Somites
continues to form about 3 pairs a day
til
the end of the 5
th
week. Each pair alternates on the cephalic end to the caudal end.
The Gastrula continues to grow and the primitive streak gets shorter. The streak totally disappears by the 4
th
week.
Once the
somites
appear, the Embryo stage begins.
Gastrulization
(folding) continues into the Embryo stage.
Zygote –
morula
–
blatula
– gastrula – embryoSlide22
Fourth Week
42-44 somite pairs have names
starting from the cephalic end
4 Occipital pairs – skull
8 cervical pairs
12 thoracic pairs – rib cage
5 lumbar pairs – lower back
5 sacral pairs – lower back
8-10 coccygeal
paris
– only 3 remain after development; tail for 4-5
th
week of development (Apoptosis)
as
somites
grow, the Neural Crests grow closer and closer, they eventually connect.
The trapped Ectoderm turn into neurons and Glial cells
The neural tube becomes the spinal chord, hollow dorsal nerve tube
organogensis
, starting of organ forming
the widest part of the
nureral
take at the cephalic end becomes the brain
Notochord = axis of symmetry, bilateral symmetrical
organizational locate for somite formation
the location of a cell determines what the cell differentiates into.
Cells around the notochord receive
horomones
that cause cell
differentiationSlide23
Somite dispersal 4-5th
week
Somite cells differentiate into other cells; they “fall apart”
the
somites
near the notochord proliferate an disperse.
The migrating cells differentiate into
osteoblasts – bone forming cells
chondroblasts
– cartilage forming cells
fibroblasts – connective tissue
one
somitic
pair = one vertebra, encases neural tube and notochord
the other remaining somite cells migrate and differentiate slightly later
differentiate –
myotome
(forms skeletal muscle) – follows osteoblasts,
chondroblats
dermatome – dermis, subcutaneous (form under/inner layer of skin)
Neural crest cells disperse and differentiate into front face, nose, teeth, dermis of skin, upper jaw.
In abdominal region,
adrenal medulla and some neurons, lots of differentiation (gene regulation
)Slide24
Somite dispersal 4-5
th
week
Meanwhile, growth an folding (ectoderm, mesoderm); endoderm so far has been a barrier from yolk sac but not much else, get trapped and passively move around and become internal
the upper cells (mesoderm) have been pushing the endoderm cells
2 major folding types
longitudinal – head and tail forming (cephalic, caudal)
½ of yolk sac is inside the fold
heart has swung down, cardiogenic cells migrate to below the head
amniotic cavity eventually surrounds the embryo dragged by
growing
Mesoderm cells
transverse/lateral folding – side folding
side to side folding – contemporary to longitude folding and somatic dispersal
in the
thoray
bones wrap around to form rib cage (
ostcoblasts
,
chordroblasts
)
longitudinal folding is complete before lateral folding is complete. Heart must be captured.
Some endometrium is captured in a interior environment. This differentiates into digestive tracts, also lungs, pancreas, liver.
The amniotic cavity is enlarged as surrounds the embryo. Cellular differentiation occurs mostly in embryonic cells. Few types of cells become many cells. (organogenesis)Slide25
During fourth week
the heart forms from
cardiogenetic
material
begins to contract even before there is blood.
Cardiac muscles differentiate from gene
cardiogenetic
material
fish – 2 chambers, mammals – 4 chambers
chambers form in the thorax cavity
invaginations (folding)
form various tissue on the outside that are captured on the inside (
otic
pit, lens
placode
, hair follicle)
intestines form outside of embryo and are folding into our gut via yolk sac folding
the yolk sac and connecting stalk twist, umbilical chord.Slide26
During fourth week
Aptoptosis
planned cell death
plays port in development and life
Gradients in the development of Embryos; blood cell and blood vessel formation – 4 areas
formation of blood system all over the embryo
inside the embryo, outside the yolk sac, connecting stalk, in the stem villi that will become the placenta
mesoderm –
angioblats
– form blood vessels –
pluribotential
– any type of blood cell
blood cells connect into the placenta via
ambilical
chord and this allows nutrients to be passed from mother to child. Blood never touchesSlide27
Eight weeks
Eight weeks after ovulation the Embryo stage is over, and the fetal stage begins.
Zygote –
morula
–
blatula
– gastrula – embryo – fetus
the placenta begins to fully functions
exchanges with circulatory system (nutrients, food, gases, water)
Elimination of waste
maintains the rest of pregnancy by releasing hormones (
estogen
and progesterone)
Corpus
Luteum
dies and
regeneartion
hCG
when the placenta begins to function.
Many outward characteristics are
noticable
½ of mass and size is in the head
eyes aren't rotated
foreward
all organs have started to form (organogenesis)
most of cellular differentiation has already formed, not allSlide28
Eight weeks
Placenta
develops before the embryo
by the 10
th
week, the placenta is fully functioning
umbilical cord is transferring nutrients
the fetus is entirely encased in the amniotic cavity
the placenta is as big as the developing offspring mass-wise
lots of folding in placenta – more surface area – more exchange
the circulatory system must not be exchanged – fatal
membranes keep the systems separate
the membranes are semi-permeable
Electrolytes
neural and muscle function needs these
calcification of bones
osmotic pressure
cellular integrity (co-factors)
enzymatic
co-enzymesSlide29
The Fetal Stage
A time of major growth (some cell differentiation)
embryo stage – cellular differentiation and organogenesis
sex differentiation occurs at this time (9
th
-10
th
week), (Early fetal stage)
the
Genetulia
will develop male characteristics if testosterone is present (TDF present) ,XY
if no testosterone female characteristics will form XX (TDF absent)
the product of TDF is a regulatory protein that turns on the genes for making testosterone among others
ovaries or testes come from the same
tissueSlide30
What Can Go Wrong?
Genetic Incompatibility – mother and father don't fit
Chromosomal Abnormalities – trisomy
some can make. Most do not it to birth
most problems happen in the first two weeks after fertilization. 42 % of
evolutated
eggs and sperms present do not survive in the 2 weeks.
Teratogens
begins to have impact after the first 2 weeks
any outside agent that influences malformations or debilitating problems
have a major impact in the embryonic stage (major cellular differentiation)
Rubella (German Measles) Virus, Alcohol (heart problems, growth deficiencies, mental/learning disorders, joint problemsSlide31
What Can Go Wrong?
Hormones
effective at low concentrations
masculinity hormones (testosterone)
estrogen and progesterone imbalance causes termination
endocrine disruptor
carcinoma of vagina.
Alkaloids (
Nicotin
) – cigarettes, antibiotics (tetracycline, streptomycin)
anticoagulants (causes fetus to hormone) not
Heprin
– doesn't cross the placenta
pathogens (Rubella,
Cytomegavirus,HIV
)
Radiation (X-rays,
radioacitivy
), and cause cancer
chemicals –
murcury
, LSD, tranquilizers, agent Orange
not all effects are immediate, some present themselves over time.