Early Craniate Morphogenesis Flashcards
Egg types according amount of yolk
a. microlecithal
b. mesolecithal
c. macrolecithal
-very little yolk
- amphioxus, therian mammals
microlecithal
- moderate amount of yolk
- amphibians
mesolecithal
- large amount of yolk
- reptiles, monotremes
macrolecithal
Egg types according to yolk distribution
a. isolecithal
b. telolecithal
- yolk is evenly distributed in the cytoplasm
- seen in microlecithal egg
isolecithal
- yolk is concentrated in one pole (vegetal pole_
- seen in mesolecithal ang macrolecithal eggs
telolecithal
opposite pole containing the nucleus and yolk free cytoplasm
animal pole
- animals that lay eggs (spawn)
- eggs contain sufficient amount of yolk and albumen
Oviparous
Oviparous
- eggs contain sufficient amount of yolk and albumen
to ___ the ___ into a free living
organisms that is able to take food orally
support, development
Oviparous macrolecithal
fully formed when hatched (birds)
Oviparous mesolecithal
young hatch in a larval stage (frog)
Oviparous microlecithal
young hatch in a free-living and self-nourishing stage (amphioxus)
animals that give birth to offspring
viviparous
type of viviparity
- mother only provides protection and oxygen, while nourishment stored in the egg (viviparous shark)
ovoviviparity
Type of viviparity where embryos are dependent on maternal tissues for nourishment, oxygen, secretion (placentals)
euviviparity
Trophotaeniae (trophe= ___, taenia= ___)
nutrition, band
- fertilization takes place within the body of the female
(viviparous craniates) - Eggs are covered by impenetrable shell before being
extruded (reptiles)
internal fertilization
___ ___ is needed to introduce sperm into the
female reproductive tract.
intromittent organ
- millions of sperm cells are shed over the eggs as the eggs
are being extruded - Oviparous fishes, frogs and toads
external fertilization
Process of Life
Gamete formation > Fertilization > Cleavage > Gastrulation > Organ formation > Growth, Tissue Specialization
Repeated mitotic cell division of the zygote
Cleavage or segmentation
Cleavage and blastula
* embryo experience little or no
___ in size
* multicelled
and hollow sphere
or ___ is formed
growth, blastula
cells resulting from the early cleavage division of the ovum
blastomeres
cavity of blastula
blastocoele
Types of Cleavage
- Holoblastic cleavage
- Meroblastic cleavage
- Discoidal cleavage
cleavage where yolk is sparse (microlecithal)
Holoblastic cleavage
Holoblastic cleavage
*mitotic furrow ____ from animal to
vegetal pole
* microlecithal
* mesolecithal
- pass through the entire zygote
- blastomere are equal size
- yolk-laden cells in vegetal pole divide slower and larger
cleavage where yolk is plentiful (macrolecithal) cell division is impeded by the presence of yolk
Meroblastic
extensive yolk material at vegetal pole remains undivided by mitotic furrows
discoidal cleavage
Mechanism of cleavage (LIICF)
- localize expansion of cortex
- increased stiffness of cortical cytoplasm
- increased tangential force
- contractile nature of region near cortex
- formation of new cell membrane
____ follows fertilization
cleavage
zygote is partitioned into ___
blastomeres
After the cleavage has produces over 100 blastomeres, the embryo is called a ___
blastula
Continued cleavage produces __
morula
The blastoderm surrounds a fluid filled or yolk filled cavity called
blastocoel
Blastulation
- Pre embryonic cleavages make use of the abundant ___ of the fertilized egg as the cells rapidly divide without changing the ___ ___.
cytoplasm, total volume
Blastulation
- The rearrangement of the cells in the mammalian blastula to two layers, the ____and the ____, results in the formation of the blastocyst
inner cell mass and trophoblast
The formation of gut, but in a broader sense
gastrulation
Gastrula = ___
belly
gastrulation leads to formation of
trilaminarembryo
Gastrulation
- the ____ ____ is the visible feature which represents site of cell migration to form more layers
primitive streak
formation of neural tube from the ectoderm of the embryo
neurulation
Organogenesis
- Alongside the neural tube, the mesoderm develops distinct paired
structures called ___ that develop into dermis, skeletal muscle, and
vertebrae.
somites
Four compartments of somites
sclerotome, myotome, dermatome, and syndetome
Derivative of ectoderm
- epidermis of skin
- epithelial lining of mouth and rectum
- cornea and lens of the eyes
- nervous system
Derivative of endoderm
- epithelial lining of digestive tract
- epithelial lining of respiratory system
- pancreas, thyroid and parathyroid, thymus, urogenital
derivatives of mesoderm
- notochord
- skeletal and muscular system
- circulatory and lymphatic
- excretory system
Solution to reproduction in a dry environment
amniote embryo
develop in a fluid-filled sac within shell or uterus
amniote embryo
avian version of blastula
blastodisc
blastodisc, when becomes arranges into
epiblast and hypoblast
during gastrulation some cells of the epiblast migrate towards the ___ of the embryo through the primitive streak
towards
In early organogenesis the ___ is formed as lateral folds pinch the embryo away from the yolk.
archenteron
The ___ (formed mostly by hypoblast cells) will keep
the embryo attached to the yolk.
yolk stalk
Mammalian development
- Blastocyst reaches uterus
- Blastocyst implants
- Extraembryonic membranes starts to form
- Gastrulation produces three-layered embryo
Begins with formation of the neural tube, notochord, and somite
organogenesis
Masses of mesoderm that can be found distributed among the two sides of the neural tube
Somites
Vertebrates whose vertebrates possess extraembryonic membrane
Amniotes (reptiles, birds, mammals)
Embryos without extraembryonic membrane
Anamniotes (fishes, aphibians)
Four extraembryonic membranes
- yolk sac
- amnion
- chorion
- allantois
Most primitive membrane that surrounds the yolk, empties into the midgut
yolk sac
Yolk sac
- highly vascular, ___ arteries and veins are continuous with the
circulatory channel within the embryo
vitelline
Innermost layer that make up the amniotic sac
Amnion
Surrounds the embryo within the amniotic sac
Amniotic fluid
Amniotic fluid
- Metabolic water from ____
- buffers the fetus against ____
- help prevent ___ in embryos (oviparous)
embryonic tissues, mechanical injury, dessication
Lies in intimate relationship with eggshell or lining of mother’s uterus
Chorion
Extension of the hindgut of amniote embryos
Allantois
When allantois comes in contact with inner surface of the chorion
chorioallantoic membrane
When the allantois comes in direct contact with the lining of the maternal uterus
Chorioallantoic placenta
Composite organ formed of maternal and fetal tissues serves as site for exchange between parent and embryo
placenta
Placenta based on composition
- yolk sac placenta
- choriovitelline placenta
- chorioallantoic placenta
yolk sac serves as part of a placenta, due to absence of amnion, chorion or allantois
yolk sac placenta
yolk sac and chorion in direct contact with maternal uterus
choriovitelline placenta
chorion and allantois in direct contact with maternal uterus
chorioallantoic placenta
Placenta based on intimacy
- Contact or nondeciduous placenta
- deciduous placenta
In simple contact with the uterine lining (endometrium), no shedding of lining at birth
contact placenta
chorionic villi becomes rooted to endometrium, fetal part of placenta disengages (shed)
deciduous placents
Placenta based on chorionic villi
- Cotyledonary placenta
- Zonary placenta
In isolated patches, commonly found in sheep and cows
cotyledonary placenta
In a band encircling the sac. Commonly found in cat, dog, or seal
zonary placenta
