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Flashcards in Animal Development Deck (113):
1

a series of mitotic divisions and cell migrations that transform the zygote into a blastula

cleavage

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blastula

"hollow ball" of cells

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hallow center of blastula

blastocoel

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there is little increase in the overall volume during cleavage because the -- become progressively smaller

blastomeres

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the cells of a blastula

blastomeres

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the amount of -- influences cleavage

yolk

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fertilization stimulates -- across the egg membrane

ion fluxes

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fertilization sets up blocks to the entry of -- into the egg

additional sperm

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fertilization changes the --of egg cytoplasm

pH

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fertilization increases egg -- and stimulate protein synthesis

metabolism

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fertilization initiates the rapid series of -- that produce a multicellular embryo

cell divisions

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-- is well stocked with organelles, nutrients, transcription factors, and mRNA

egg cytoplasm

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sperm contributes --

DNA (haploid nucleus) and centriole (origin of primary cilia)

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centriole becomes the zygote's --

centrosome which organizes the mitotic spindles for subsequent cell divisions

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molecules in the cytoplasm of amphibian egg are -- distributed

not homogenously

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sperm entry establishes -- of the zygote

polarity

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the nutrients in an unfertilized frog egg are dense yolk granules that are concentrated by gravity in the lower half of the egg called

vegetal pole

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the haploid nucleus of egg is located at

animal pole

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the animal cortical cytoplasm is

pigmented

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frog egg is -- symmetrical

radially

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when a sperm binds to and enters a frog's egg the radial symmetry turns into a -- symmetry

bilateral

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cortical cytoplasm rotates toward

the site of sperm entry

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in amphibian eggs, cortical rotation and rearrangement of the cytoplasm after fertilization create the -- opposite the point of sperm entry

gray crescent

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gray crescent marks the location of

important developmental events

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the centriole from sperm initiates

cytoplasmic reorganization (causes microtubules in vegetal pole to form a parallel array that guides movement of the cortical cytoplasm)

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sequence of early cell divisions that transform the diploid zygote into a mass of undifferentiated cells that will develop as the embryo

cleavage

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occurs in most eggs that have little yolk

complete cleavage

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frogs undergo -- complete cleavage

unequal

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occurs in species in which the egg contains a lot of yolk and the cleavage furrows do not penetrate it all

incomplete cleavage

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is a type of incomplete cleavage common in fishes and birds in which the embryo forms a disc of cells (blastodisc) that sits on top of the dense yolk mass

discoidal cleavage

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variation of incomplete cleavage that occurs in fruit flies

superficial cleavage

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a single cell with many nuclei

syncytium

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the nuclei eventually migrate to the periphery of the egg, after which the plasma membrane grows inward, creating a -- by partitioning the nuclei into individual cells surrounding a core of yolk

blastoderm

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what influences the pattern of cleavage

amount of yolk and orientation of mitotic spindle (determined by maternal genome)

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-- cleavage occurs in mammals

rotational

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mammalian cleavage is slow and asynchronous because

blastomeres do not undergo mitosis at the same time

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when the zygote reaches the 8-cell stage, the blastomeres change shape to maximize their surface contact with each other forming -- and become a compact mass of cells

tight junctions

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At the 32-cell stage, cells separate into two groups:

inner mass and trophoblast

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will become embryo

inner mass

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surrounding outer cells become an encompassing sac that secretes fluids to create the blastocoel cavity with the inner cell mass at one end

trophoblast

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at the 32-cell stage the embryo is called a

blastocyst

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specific blastomeres generate specific

tissues and organs

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loss of blastomeres results in loss of later structures

mosaic (determinate) development

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loss of blastomeres doesn't deleteriously affect the development because the remaining cells compensate for loss

regulated (undeterminate) development

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cells move to new positions adn form the three germ layers from which differenitated tissues develop

gastrulation

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inner most germ layer, digestive tract, respiratory tract, pancreas, thyroid, liver

endoderm

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outer germ layer, nervous system and epidermis of skin

ectoderm

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middle layer, skeletal muscle, circulatory system, kidneys, gonads, blood cells, dermis of skin

mesoderm

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embryonic or unspecialized cells that migrate to other tissue layers

mesenchyme cells

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sea urchin gastrulation, some cells change shape and move inward to form the -- other cells break free becoming primary --

archenteron, mesenchyme

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opening created by the invagination of the vegetal pole

blastopore

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blastopore becomes anus

deuterostomes (sea urchins and vertebrates)

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blastopore becomes mouth

protostomes (earthworm and insects)

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the embryo develops only partially in the uterus then finishes outside in a pouch (marsupium)

non Eutherian mammals

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nutrient and waste exchange in eutherian mammals occur via the

placenta

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surround the vertebrate embryo

extraembryonic membranes

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encloses yolk within egg

yolk sac

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yolk is -- by cells of the yolk sac and the nutrients are transported to the embryo

digested

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a sac for waste storage

allantois

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surrounds the embryo, forming the fluid-filled amniotic cavity that protects the embryo

amnion

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forms a continuous membrane just under the eggshell; reduces water loss and exchanges gases

chorion

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the amniotic egg provides an -- environment for development of the embryo

aqueous

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the yolk sac is the -- and -- layers that surround the yolk to absorb its nutrients

mesoderm and endoderm

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the -- forms the umbilical cord in eutherian mammals

allantois

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chorion layers

ectoderm and mesoderm

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amnion layers

mesoderm and ectoderm

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allantois layers

mesoderm and endoderm

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in placental mammals, the first extraembryonic membrane to form is the --

trophoblast

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the inner cell mass consists of -- and --

hypoblast and epiblast

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trophoblast cells interact with the -- and adhesion molecules and adhesion molecules attach them to the --

endometrium, uterine wall

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the trophoblast -- into the uterine wall and sends out -- to increase contact with maternal blood

burrows, villi

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hypoblast cells form the

chorion

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the placenta develops from the -- and -- tissues

chorion and uterine

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the epiblast produces the --

amnion

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rupturing of the amnion and chorion and loss of the -- = water break

amniotic fluid

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the process of embryonic/fetal development from fertilization to birth (parturition)

gestation or pregnancy

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first trimester =

"embryonic" development

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in the first trimester the embryo becomes a --

fetus

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heart begins to beat by week

four

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limbs form by week

eight

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first trimester is a time of -- cell division and tissue differentiation

rapid

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second trimester

limbs elongate
fingers, toes, and facial features form
nervous system develops rapidly
first fetal movements are felt

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third trimester

internal organs mature
brain goes through sleep-wake cycles
birth occurs when lungs are mature

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increased ratio of -- to -- at the end of 3rd trimester

estrogen to progesterone

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human chorionic gonadotropin is produced by the chorion during

first trimester

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During the first trimester, hCG keeps the -- functional which keeps producing high E and P levels to prevent ovulation from occuring

corpus luteum

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Due to its highly negative chard, hCG may repel the -- of the mother, protecting the fetus during the first trimester

immune cells

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hormonal changes during the first trimester cause

"morning sickness"

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rapid fetal development occurs during the -- trimester

second

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during the second trimester, the placenta produces lots of E and P from -- (eg the steroid biosynthetic pathway) which continues to inhibit ovulation and menstruation

circulating androgens

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during the third trimester the -- ratio increases

E/P

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amniotic fluid is withdrawn

amniocentesis

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amniocentesis - chromosomal abnormalities, sex determination, week --, risk 0.5% miscarriage

14-16

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not as invasive as amniocentesis during week -- risk 0.5-1% miscarriage

chorionic villus sampling, 10-12

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ultrasound early week 6-10 = / week 10-13 =

vaginal, belly

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ultrasound measures

nuchal translucency

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an accumulation of fluid at the base of the baby's neck that is expected to be seen in all pregnancies

nuchal translucency

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a nuchal translucency measurement above -- is considered abnormal

3.0 - 3.5mm

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an increased nuchal translucency is associated with a higher risk for --

chromosome abnormality or structural defect

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absence of testosterone and MIH -->

mullerian duct system (fallopian tubes and uterus)

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presence of testosterone and MIH -->

wolffian duct system (epididymis and vas deferens)

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during the first trimester in humans, embryonic gonadal tissue (the mesoderm) develops into -- due to the expression of the gene on the Y chromosome

testes

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5-alpha DHT promotes the development of -- into male genitalia

undifferentiated external genitalia

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XY gonads produce androgen -->

male

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XX no androgen -->

female

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XY but androgen receptor defect -->

inside testes outside female

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XY 5-alpha reductase deficient -->

internal male, external micropenis

108

XY no androgen -->

fertile female

109

XX androgen production

oversized clitoris and fused labia

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XY androgen/no-androgen

fertile male, micropenis

111

Later in fetus XY no androgen

baby boy with micropenis

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a general term used for a variety of conditions in which a person is born with a reproductive or sexual anatomy that doesn't seem to fit the typical definitions of female or male

intersex

113

consequences of normalizing procedures

loss of sensory tissue, memories of child sexual trauma, surgeries intensify the feeling of shame and alienation they are meant to eliminate