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DAT Embryology Continued Flashcards

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1
Q

Animal embryos follow four stages in growth
and development:

A

gametogenesis (sperm/egg
formation), embryonic development (fertilization
of egg until birth), reproductive maturity
(puberty), and aging process to death.

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2
Q

Stages of embryonic development
(sea urchin, echinoderm)

A

Fertilization - sperm penetrates
plasma membrane of secondary
oocyte
a. Recognition - before
penetrating, the sperm secretes
proteins that bind with
receptors that reside on a
glycoprotein layer surrounding
the plasma membrane of the
oocyte. In non-mammals, this
layer is called the vitelline
membrane. In mammals, this
layer is the zona pellucida. In
both organisms, the layer
ensures same species
fertilization.

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3
Q

Zona pellucida

A

external glycoprotein
membrane surrounding the plasma
membrane (jelly coat) of an oocyte. This
first appears in unilaminar oocytes, and
is secreted by both the oocyte and
follicular cells. At puberty, FSH
stimulates growth of granulosa cells
around the primary oocyte that secrete
the viscous zona pellucida.

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4
Q

Fertilization cannot occur until

A

capacitation and
acrosomal reaction have taken place.

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5
Q

capacitation,

A

secretions from the uterus’ wall and
uterine tube destabilize the plasma membrane
surrounding the head of the sperm (acrosome),
making the head more fluid, which helps prepare
it for fertilization and makes the sperm
hyperactive (faster and wiggle more).

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6
Q

Penetration

A

plasma membrane of
sperm and oocyte fuse, and the sperm
nucleus enters the oocyte

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7
Q

Formation of fertilization membrane

A

the vitelline layer forms a fertilization
membrane that blocks additional sperm

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8
Q

Completion of meiosis II in secondary
oocyte

A

sperm penetration triggers
meiosis II to complete.

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9
Q

Fusion of nuclei and replication of DNA

A

sperm and ovum nuclei fuse → diploid
zygote forms.

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10
Q

cleavage stage involves

A

rapid cell division of
the zygote without cell growth.

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11
Q

Embryo polarity

A

an egg has
an upper, animal pole and lower, vegetal
pole. Depending on the species, the
vegetal pole can contain more yolk
material, which is denser than the
cytoplasm and settles at the bottom. In
general, the vegetal pole differentiates
into extra-embryonic membranes that
protect and nourish the embryo. Polarity
is critical in setting up body axes.

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12
Q

Polar and equatorial cleavages

A

early
cleavages are polar, and divide the egg
into segments that stretch from pole to
pole, like the segments of an orange.
Others are parallel with the equator.
Note that in frogs, the horizontal
cleavage is closer to the animal pole.

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13
Q

Radial and spiral cleavages

A

occurs in deuterostomes. Radial
cleavage forms indeterminate cells at
animal and vegetal poles that are aligned
together, with top cells directly above
bottom cells. In protostomes, spiral
cleavage occurs, and determinate cells
are formed on top and are shifted
relative to those below.

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14
Q

Indeterminate and determinate
cleavages

A

in indeterminate cleavage,
blastomeres can individually complete
normal development if separated. In
determinate cleavage, blastomeres
cannot develop into a complete embryo
if separated; each is differentiated into
part of the embryo.

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15
Q

Morula

A

successive cleavage results in a
solid ball of ~8 cells, where the first 8
cells are totipotent, meaning the cells are
capable of giving rise to any cell type or
embryo

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16
Q

Blastula

A

cell division continues, and
liquid fills the morula and pushes cells
outward to form a circular cavity
surrounded by a single layer of cells. The
blastocoel is the fluid filled cavity.

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17
Q

Gastrula

A

formation of
the gastrula occurs with the invagination
of a group of cells into the blastula,
forming a two-layered embryo with an
opening from the outside into a center
cavity. forms 14 days post fertilization

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18
Q

Three germ layers

A

ectoderm,
mesoderm, and endoderm.

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19
Q

Ectoderm -

A

skin cells of epidermis, neuron on brain, pigment cells

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20
Q

Mesoderm

A

cardiac muscle cells, skeletal muscle cells, tubule cells of kidney, red blood cells, smooth muscle cells ( in the gut)

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21
Q

endoderm

A

lung cells, thyroid cells, digestive cells

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22
Q

Archenteron

A

the center cavity
formed by gastrulation that is
completely surrounded by
endoderm cells and gives rise to the
gut

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23
Q

Blastopore

A

opening into the
archenteron, becomes the mouth in
protostomes or the anus in
deuterostomes

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24
Q

Extra-embryonic membrane
development

A

in birds, reptiles, and
humans (collectively, amniotes),
membranes develop outside of the
embryo proper.

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25
Chorion
outer membrane
26
Chorion birds and reptiles
functions as a membrane for gas exchange
27
Mammals chorion
chorion implants into endometrium, and later, the chorion and maternal tissue (which is modified endometrial tissue called deciduas basalis) form the placenta.
28
Allantois
sac that buds off from archenteron that eventually encircles the embryo, forming below the chorion.
29
Allantois birds and reptiles
initially stores waste products as uric acid, and later fuses with the chorion to form a membrane for gas exchange with blood vessels beneath it
30
Allantois mammels
allantois functions to transport waste products to placenta, and eventually forms the umbilical cord between the embryo and placenta.
31
Amnion
encloses the amniotic cavity, and is a fluid-filled cavity that cushions the developing embryo, much like the coelom that cushions internal organs in coelomates. Amphibians do not have an amnion.
32
Yolk sac birds and reptiles
digests enclosed yolk, and blood vessels transfer nutrients to embryo
33
yolk sac mammals
is empty and contains no yolk as the umbilical cord and placenta deliver nutrients instead.
34
Organogenesis
cells continue to divide after gastrulation → differentiate into specific tissues and organs.
35
Notochord
cells along the dorsal surface of the mesoderm layer form the notochord, a stiff cartilaginous rod that provides support in lower chordates.
36
Neural tube
develops into the CNS, and additional cells roll off the top of the neural tube and form neural crest cells, which form teeth, bones, muscles of skull, pigment cells in skin, and nerve tissue.
37
Gray crescent (frog)
sperm penetrates frog egg → reorganization of cytoplasm → pigmented cap of animal pole rotates towards the point of penetration while a gray crescent shape region forms opposite of the point of penetration.
38
Gastrulation (frog)
blastopore forms at the border between the gray crescent and the vegetal pole. During gastrulation, cells migrate over the top edge of, and into, the blastopore through a process called involution, forming the dorsal lip in the same region previously occupied by the gray crescent.
39
Yolk (frog)
cells from the vegetal pole rich in yolk material form a yolk plug near the dorsal lip
40
Blastodisc (bird)
flattened, disc shaped region that sits on top of the yolk; cleavage occurs here.
41
Blastocyst (humans and most mammals
- the blastula stage consists of two parts: an outer ring of cells (trophoblast) and inner cell mass (embryonic disc)
42
Trophoblast
accomplishes implantation by embedding into the endometrium.
43
Embryonic disc
within the cavity created by the trophoblast, the inner cell mass clusters at one pole and flattens into the embryonic disc, analogous to the blastodisc of birds and reptiles.
44
Influence of egg cytoplasm
cytoplasmic material is distributed unequally in the egg (think gray crescent in frogs and yolk in bird eggs), which results in embryonic axes, such as animal and vegetal poles. When cleavages divide the egg, daughter cells have different quality of cytoplasmic substances, or cytoplasmic determinants. These determinants are unique substances that influence subsequent development of each daughter cell.
45
Embryonic induction
influence of one cell/group of cells over neighboring cells. Organizers (controller cells) secrete chemicals that diffuse among neighboring cells, and influence their development. The dorsal lip of the blastopore, functioning as a primary organizer, induces notochord development in nearby cells.
46
Homeotic (Hox) genes
control development by turning on/off other genes that code for substances that directly affect development of body segments. An experiment in fruit flies found that mutant homeotic genes resulted in wrong body parts in wrong places.
47
Homeobox (unique DNA segments of 180 nucleotides)
identifies a particular class of genes that control development (encodes homeodomain of protein that can bind DNA). The homeobox sequence is highly preserved across species.
48
Embryonic lethals
mutations that affect a process as fundamental as segmentation, and cause death at embryo/larval stage
49
Apoptosis
programmed cell death that is part of normal cell development. Apoptosis is essential for development of the nervous system, operation of immune system, and destruction of tissue (webbing) between fingers and toes.
50
Labor (three stages)
a series of strong uterine contractions... i. Cervix thins out and dilates, amniotic sac ruptures and releases fluids ii. Rapid contractions followed by birth iii. Uterus contracts and expels umbilical cord and placenta
51
Fraternal/dizygotic twins
two separate eggs are fertilized by two different sperm, so the eggs are not genetically identical, and are no more related than ordinary siblings
52
Identical/monozygotic twins
result from indeterminate cleavage; a single fertilized egg splits into two, forming two genetically identical offspring
53
notochord is derived from
mesoderm
54
Totipotent stem cells
can give rise to any and all human cells, and even an entire functional organism
55
Pluripotent
can give rise to all tissue types, but not an entire organism
56
Multipotent
can give rise to limited range of cells within a tissue type
57
Unipotent
just one single cell type
58
External development
fish and amphibians have external fertilization (ovuliparity) in water, to prevent gametes from drying out, and to allow sperm to swim to the egg. This requires cooperative mating behaviors to ensure simultaneous egg and sperm release.
59
Ovuliparity
external fertilization
60
Internal development -
reptiles, birds, and some mammals (monotremes) have internal fertilization, which requires cooperative behavior leading to copulation.
61
Viviparity
birth to live young that was given nutrients during development
62
Oviparity
egg is laid and hatches later
63
Ovoviviparous
eggs are internal and birthed as live young, but the egg is not nourished in any way by the parent
64
Non-placental internal development
certain animals like marsupials and tropical fish spend a short time in the uterus as embryos, then crawl out and complete development attached to a mammary gland in the mother’s pouch!
65
Placental internal development
major components of this development in humans include the umbilical cord and placenta system. The oxygen is received directly from the mother (as fetal lungs are not functional until birth), as well as nutrients. CO2 and metabolic wastes are removed.
66
Placenta formation
begins with chorion, and blood vessels of allantois wall enlarge and become umbilical vessels that connect the fetus with the developing placenta.
67
Amniotes
group of tetrapods, four- limbed animals with backbones or spinal columns that have terrestrially adapted eggs that are supported by several extra embryonic membranes.
68
Monotremes
mammals that lay leathery eggs, lack nipples, and are endothermic (but have an unusually low body temperature and metabolic rate compared to other mammals)
69
In vitro
looks at cells and biological molecules outside their normal biological context, such as in a lab.
70
In vivo
normal biological environment
71
first trimester,
Organs of the fetus develop (critical development period)
72
second trimester
fetus is very active during the second trimester and the uterus grows enough for the pregnancy to be noticeable.

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