Lesson 4 - Early Craniate Morphogenesis Flashcards
(161 cards)
1
Q
bilaterally symmetrical chordates with indeterminate cleavage with mouth not arising from blastopore
A
deuterostomes
2
Q
closes relatives of chordates
A
- Hemichordates
- Echinoderms
3
Q
- believed to be closer relatives of chordates but still being debated on
- believed to have branched off
A
Cephalochordates or Tunicates
4
Q
show resemblance to each other in neuroanatomy and biochemistry
A
- cephalochordates
- vertebrates
5
Q
Egg types: amount of yolk
A
- microlecithal
- mesolecithal
- macrolecithal
6
Q
- very little yolk
- amphioxus, therian mammals
A
microlecithal
7
Q
microlecithal example
A
- amphioxus
- therian mammals
8
Q
- moderate amount of yolk
- amphibians
A
mesolecithal
9
Q
mesolecithal example
A
amphibians
10
Q
- large amount of yolk
- reptiles, monotremes
A
macrolecithal
11
Q
macrolecithal example
A
- reptiles
- monotremes
12
Q
Egg types: yolk distribution
A
- isolecithal
- telolecithal
13
Q
- yolk is evenly distributed in the cytoplasm
- seen in microlecithal egg
A
isolecithal
14
Q
where is isolecithal seen
A
microlecithal egg
15
Q
- yolk is concentrated in one pole (vegetal pole)
- seen in mesolecithal and macrolecithal eggs
- opposite pole contains the nucleus and relatively yolk free cytoplasm
A
telolecithal
16
Q
where is telolecithal seen
A
- mesolecithal
- macrolecithal eggs
17
Q
two pole in telolecithal
A
- vegetal pole
- animal pole
18
Q
where yolk is concentrated
A
vegetal pole
19
Q
opposite pole containing the nucleus and relatively yolk free cytoplasm
A
animal pole
20
Q
Ways offsprings are produced by interal fertilization
A
- oviparity
- viviparity
21
Q
- animals that lay eggs (spawn)
- eggs contain sufficient amount of yolk and albumen to support the development into a free-living organism that is able to take food orally
A
oviparous
22
Q
fully formed when hatched
(birds)
A
oviparous macrolecithal
23
Q
example of fully formed when hatched
A
birds
24
Q
young hatch in larval stage
(frog)
A
oviparous mesolecithal
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example of young hatch in larval stage
frog
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young hatch in a free-living and self-nourising stage
(amphioxus)
oviparous microlecithal
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example of young hatch in a free-living and self-nourising stage
amphioxus
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animals that give birth to offsprings
viviparous
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different types of viviparity
1. ovoviviparity
2. euviviparity
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- mother provides only protection and oxygen
- nourishment stored in the egg
ovoviviparity
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example of ovoviviparous animal
spiny dogfish shark
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embryos are dependent on maternal tissues for all nourishment, oxygen, excretion of wate products of metabolism
euviviparity
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- egg may be fertilized and the young may develop in the ovarian follicle or ovarian cavity
- trophotaeniae
viviparous teleosts
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where do viviparous teleosts develop
- ovarian follicle or
- ovarian cavity
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- External, umbilical cord-like structure present in members of the family Goodeidae and some other fish groups responsible for transfer of nutrients between an adult female and her internally-developing young.
- May still be attached to fry at birth
trophotaenia
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meaning of word trophotaenia
trophe = nutrition
taenia = band
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Different types of fertilization
1. internal fertilization
2. external fertilization
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- fertilization takes place within the body of the female (viviparous craniates)
- intromittent organ is needed to introduce sperm into the female reproductive tract
- eggs are covered by impenetrable shell before being extruded (reptiles)
internal fertilization
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what is needed in internal fertilization in order for the sperm to be introduced into the female reproductive tract
intromittent organ
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- millions of sperm cells are shed over the eggs as the eggs are being extruded
- oviparous fishes, frogs, and toads
external fertilization
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example of external fertilization
oviparous fishes, frogs, toads
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describes sexually reproducing fishes that develop mature gonads containing oocytes and spermatozoa
Hermaphroditism
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considerably different from juveniles and adults
larvae
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Stages in Early Development
1. gamete formation
2. fertilization
3. cleavage
4. gastrulation
5. organ formation
6. growth, tissue specialization
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- repeated mitotic cell division of the zygote initiated by the union of two mature sex cells or gametes
- embryo experience little or no growth in size
cleavage or segmentation
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- formed during cleavage
- multicelled and hollow sphere
blastula
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cells resulting from the early cleavage division of the ovum
blastomeres
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fluid filled cavity in a blastula
blastocoele
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cells of the blastula form an epithelial (covering) layer
blastoderm
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Types of Cleavage
1. holoblastic cleavage
2. meroblastic cleavage
3. discoidal cleavage
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- entire egg undergoes cellularization, and yolk platelets are either absent (e.g., in mammals) or present as cytoplasmic inclusions that partition among cells (e.g., in amphibians)
- mitotic furrow pass through the entire zygote from animal to vegetal pole
holoblastic cleavage
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mitotic furrow in holoblastic cleavage
pass through the entire zygote from animal to vegetal pole
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holoblastic cleavage in microlecithal eggs
blastomeres are approximately of equal size
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holoblastic cleavage in mesolecithal eggs
yolk laden cells in vegetal pole divide more slowly and are larger
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- where yolk is plentiful macrolecithal)
- cleavage furrows form, but do not progress into the yolk.
- mitotic furrow is slowed and only a portion of the cytoplasm in the animal pole is cleaved
- Species that exhibit this type of cleavage are birds, insects, fish, and reptiles
meroblastic cleavage
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mitotic furrow in meroblastic cleavage
- slowed
- only a portion of the cytoplasm in the animal pole is cleaved
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- extensive yolk material at the vegetal pole remains undivided by mitotic furrows
- cleavage restricted to a cap of dividing cells at the animal pole
discoidal cleavage
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mitotic furrow in discoidal cleavage
do not divide extensive yolk material at vegetal pole
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where is discoidal cleavage restricter to
cap of dividing cells at animal pole
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Mechanisms of cleavage
1. localized expansion of cortex
2. increased stiffness of the cortical cytoplasm
3. increased tangential force activity in the cortex
4. contractile nature of regions near the cortex
5. formation of new cell membrane from the subcortical sytoplasm
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cleavage follows __
fertilization
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when is the cleavage called blastula
after it produced over 100 blastomeres
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- continued cleavage produces this
- it is a microscopic ball or cluster of cells formed through cell division very early in the embryonic development that occurs after the formation of a zygote through fertilization but before the blastocyst stage.
morula
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no. of cells in morula
16 cells
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no. of cells in blastocyst
70-100 cells
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two-cell, four-cell, eight-cell
occurs in uterine tube
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morula and blastocyst
occurs in uterus
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make use of the abundant cytoplasm of the fertilized egg as the cells rapidly divide without changing the total volume
pre-embryonic cleavages
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what results in the rearrangment of the cells in the mammalian bastula to two layers
blastocyst
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parts of the blastocyst
1. trophoblast
2. inner cell mass
3. blastocoel
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give rise to extraembryonic structures, including the placenta
trophoblast
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gives rise to the embryo
inner cell mass
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very early stage of development when the zygote becomes a ball of cells with a fluid filled center, and an inner mass of cells.
blastulation
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next step in which the inner mass of cells forms three distinct germ layers.
gastrulation
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cells that have the capacity to self-renew by dividing and to develop into the three primary germ cell layers of the early embryo and into extra-embryonic tissues such as the placenta
Totipotent stem cells
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consists of totipotential cells
epiblast layer
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visible feature which represents the site of cell migration to form the additional layers
primitive streak
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gastrulation rearranges the embryo into a __ __
triploblastic gastrula
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what are the embryonic germ layers
1. ectoderm
2. mesoderm
3. endoderm
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produces a triploblastic embryo with an archenteron
frog gastrulation
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- digestive cavity of an embryo during the gastrula stage
- will eventually develop into the complete gastrointestinal (GI) tract
archenteron
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“germinal localization” and it is a marker of the dorsal side of the fertilized egg, the future embryo, and the adult
gray crescent
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what is formed in the invagination during frog gastrulation
dorsal lip of blastopore
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cells on the dorsal surface roll over the edge of the dorsal lip and into the interior of the embryo
involution
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patch of vegetal cells (endoderm) that remains exposed in the blastopore after the formation of the ventral lip during gastrulation.
yolk plug
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when is the primitive streak visible
during week three
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stimulates neurulation in the ectoderm after its development
notochord
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process that leads to the development of the central nervous system, starting around 21 days postfertilization in humans
neurulation
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the process by which the neural tube, the precursor of the brain and spinal cord, is shaped from the neural plate.
Primary neurulation
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form the neural tube
folds of the groove
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what is formed from the anterior portion of neural tube
basal plate
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what is formed from the posterior portion of neural tube
alar plate
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what is formed from the center of neural tube
neural canal
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when do the ends of the neural tube close
conclusion of fourth week of gestation
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either of the openings to the exterior at the anterior and posterior ends of the neural tube of a vertebrate embryo
neuropore
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how to know dorsal blastopore lip
where archenteron is
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how to know ventral blastopore lip
where blastocoel is
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what is formed when the neural plate folds outward
neural groove
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what is known as the 4th germ layer
neural crest cells
100
what is formed from neural crest cells
components of the PNS
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separates neural plate and ectoderm
neural plate border
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referred to the neural plate once its joined
neural crest
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what disconnects the neural crest from the epidermis or ectoderm
closure of neural tube
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what happens to the notochord
- degenerates
- persists as nucleus pulposus
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precursor of axial skeleton and skeletal muscles
somites
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- mesoderm found lateral to the neural tube
- distinct from the mesoderm found more internally in the embryo
paraxial mesoderm
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somites develop into what
- dermis
- skeletal muscle
- vertebrae
108
four components of somites
1. sclerotome
2. myotome
3. dermatome
4. syndetome
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the part of each somite in a vertebrate embryo giving rise to bone or other skeletal tissue
sclerotome
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forms some of the skeletal muscle
myotome
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forms the connective tissues, including the dermis
dermatome
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- gives rise to the axial tendons of the body
- located between neighboring sclerotome and myotome, at the future site of connection between bone and muscle
syndetome
113
process of formation of organs from three germ layers
Organogenesis
114
ectoderm layer contributes to
1. epidermis of skin, and derivatives
2. epithelial lining of mouth and rectum
3. cornea and lens of eyes
4. nervous system
5. adrenal medulla
6. tooth enamel
7. epithelium of pineal and pituitary glands
115
endoderm layer contributes to
1. epithelial lining of digestive tract (except mouth and rectum)
2. epithelial lining of respiratory system
3. pancreas
4. thyroid, parathyroid
5. thymus
6. lining of urethra, urinary bladder, and reproductive systems
116
mesoderm layer contributes to
1. notochord
2. skeletal and muscular systems
3. circulatory and lymphatic systems
4. excretory systems
5. reproductive system (except germ cells)
6. dermis of skin
7. lining of body cavity
8. adrenal cortex
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solution to reproduction in a dry environment
amniote embryo
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what do amniote embryo have
extra amniotic membrane
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shelled eggs
reptiles and birds
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uterus
placental mammals
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cleavage in avian development
meroblastic, or incomplete
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embryo-forming portion of an egg with discoidal cleavage usually appearing as a small disc on the upper surface of the yolk mass.
blastodisc
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will keep embryo attached to the yolk
yolk stalk
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- occurs at the eight-cell stage of mammalian development
- results to cells tighlty adhering to one another
compaction
125
Mammalian development
Step 1: about 7 days after fertilization
- blastocyst reaches the uterus
- inner cell mass is surrounded by the trophoblast
126
Mammalian development:
surrounds the inner cell mass
trophoblast
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what does the inner cell mass form
- epiblast
- hypoblast
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where does the embryo develop almost entirely
from epiblast
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Organogenesis begins with the formation of what?
- neural tube
- notochord
- somites
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mesoderm underneath the neural tube
chordamesoderm
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paraxial mesoderm is called what in vertebrates
unsegmented mesoderm
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paraxial mesoderm is called what in chick embryos
segmented mesoderm
133
comparison of chordates and non-chordates:
notochords
chordates: present
non-chordates: absent
134
comparison of chordates and non-chordates:
dorsal hollow nerve cord
chordates: dorsal hollow single nerve cord
non-chordates: ventral, solid, double
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comparison of chordates and non-chordates:
pharyngeal gill slits
chordates: present
non-chordates: absent
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comparison of chordates and non-chordates:
heart
chordates: ventral
non-chordates: dorsal
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comparison of chordates and non-chordates:
post anal tail
chordates: present
non-chordates: absent
138
embryos possess extraembryonic membranes
amniotes (reptiles, birds, mammals)
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embryos without extraembryonic membranes
anamniotes (fishes, amphibians)
140
- composite organ formed from maternal and fetal tissues
- functions as a site for exchange between parent and embryo
placenta
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chief extraembryonic membrane
1. yolk sac
2. amnion
3. chorion
4. allantois
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- surrounds the yolk, empties into the midgut and usually lines the endoderm
- highly vascular, vitelline arteries and veins are continuous with the circulatory channel within the embryo
yolk sac
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- inner sac next to the fetus
- make up the amniotic sac
amnion
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- surrounds the embryo withtin the amniotic sac
- metabolic water from embryonic tissuse
- buffers the fetus against mechanical injury
- helps prevent dessication in embryos
amniotic fluid
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- outer sac next to uterine wall
- lies in intimate relationship with either the eggshell or the lining of the mother's uterus
- keeps the fetus in communication with its source of oxygen and in viviparous animals, its source of nutrients
chorion
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very thin, soft, usually unpigmented hair that is sometimes found on the body of a fetus or newborn
Lanugo
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- extension of the hindgut of the amniote embryos
- function in excretion and sometimes in respiration
allantois
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- when allantois comes in contact with the inner surface of the chorion
- respiratory organ in reptiles and monotremes
chorioallantoic membrane
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- when the allantois comes in direct contact with the lining of the maternal uterus
- respiratory organ, site of transfer of nutrients and metabolic waste
chorioallantoic placenta
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kinds of placenta based on composition
1. yolk sac placenta
2. choriovitelline placenta
3. chorioallantoic placenta
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- yolks sac serves as part of a placenta because of the absence of amnion, chorion, or allantois
- viviparous amphibians and fishes
yolk sac placenta
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yolk sac and chorion in direct contact with maternal uterus
choriovitelline placenta
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- chorion and allantois in direct contact with maternal uterus
- mammals have umbilical cord connecting the fetus with the placenta
chorioallantoic placenta
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Kinds of placenta based on intimacy of relationship between fetal and maternal tissues
1. nondeciduous or contact placenta
2. deciduous placenta
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- in simple contact with the uterine lining (endometrium)
- no shedding of the lining at birth
contact or nondeciduous placenta
156
- chorionic villi becomes rooted into the endometrium
- at birth, the fetal parts of the placenta disengages and the deciduas (invaded part of the uterine lining) is shed
deciduous placenta
157
Kinds of placenta based on chorionic villi distribution
1. cotyledonary placenta
2. zonary placenta
3. discoidal placenta
4. diffuse placenta
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- in isolated patches
- sheep, cow
cotyledonary placenta
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- in a band encricling the sac
- cat, dog, seal
zonary placenta
160
- in a single large discoidal area
- brown bear, human
discoidal placenta
161
- diffuse over the entire surface of the chorion
- pig
diffuse placenta
