Chapter 4-6 Flashcards
(115 cards)
1
Q
The series of divisions of the early embryo is called
A
Cleavage
2
Q
The resulting cells are called
A
blastomeres and blastoderm
3
Q
What type of cleavage has animal and vegetal poles?
A
Meroblastic
4
Q
contains a little yolk material that undergo the segmentation division first
A
Animal pole
5
Q
contains much of the yolk material which is the last to be segmented.
A
Vegetal pole
6
Q
Types of yolks Based on the amount of yolk
A
• Oligolecithal/miolecithal
• Mesolecithal/medialecithal
• Polylecithal/megalecithal
7
Q
Types of yolks Based on the distribution of yolk
A
• Isolecithal
• Centrolecithal
• Telolecithal
8
Q
Commonly called “ball of cells”, after the Latin name for mulberry. Cellular mass of the embryo occupies most of the perivitelline space.
A
Morula
9
Q
form tight junctions destined to become trophoblast or trophoectoderm
A
Outer blastomeres
10
Q
form gap junctions destined to become inner cell mass
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Inner blastomeres
11
Q
when water osmotically flow inside, fluid accumulates making some of the blastomeres flattened and a cavity is formed called blastocoele.
A
Early Blastocyst
12
Q
The outer cells become the trophoblast and the inner cells are destined to be the _____ that becomes the embryonic disc. Still the embryo is confined inside the zona pellucida.
A
inner cell mass (ICM)
13
Q
diameter of the embryo dramatically increased with concurrent thinning of the zona pellucida.
A
Expanded blastocyst
14
Q
is best done on blastocyst stage (early to expanded blastocyst).
A
Embryo Transfer (ET)
15
Q
zona pellucida ruptures, blastocyst leaves the zona pellucida and attaches (adheres) to the uterine mucosa, followed by the implantation/nidation and placentation of the embryo.
A
Hatching blastocyst
16
Q
Other term for inner cell sheet
A
Hypoblast
17
Q
ICM differentiates into two cell populations:
A
Hypoblast and epiblast
18
Q
Blastocyst Elongation- varies among species of animals:
marked round to oval expansion of the blastocyst
A
Horses, dogs, cats and rabbits
19
Q
Blastocyst Elongation- varies among species of animals
marked thread-like expansion
A
Cattle, sheep, pig-
20
Q
Blastocyst Elongation- varies among species of animals
little expansion occurs because blastocyst invades the endometrium
A
Primates, rodents, guinea pigs
21
Q
Consists of a thin layer of cells and overlies the subgerminal cavity and with no yolk material attached
A
Area pellucida
22
Q
Consists of a layer of large cells and overlies the unaltered yolk
A
Area opaca
23
Q
comes from a greek term “Gaster” which mean “stomach
A
Gastrulation
24
Q
It is a developmental stage in placental mammals which begins with the formation of ____?
A
primitve streak
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outer layer gives rise to the epidermis and nervous system, and connective tissue of the head
Ectoderm
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inner layer gives rise to the primitive gut or “archenteron” , (gk.
Arche, “origin”, enteron “gut”.
Endoderm
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divides into paraxial or dorsal mesoderm, intermediate mesoderm and lateral mesoderm.
Mesoderm
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gives rise to the vertebral bones muscles and skeletal connective tissues of the trunk;
paraxial mesoderm
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Gives rise to the urogenital system, heart and blood vessels
intermediate mesoderm
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subdivides into lateral and splanchnic mesoderm and a cavity in between called coelom.
lateral mesoderm
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In avian, development starts in a whitish disc area on the surface of the yolk called ___?
blastodisc/ embryonic disc/ germinal disc.
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During gastrulation the central portion of the blastoderm, the area pellucida is separated from the yolk via
subgerminal cavity
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A cavity between hypoblast and epiblast?
blastocoele
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gives rise to the three germ layers
Epiblast
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gives rise to extraembryonic endoderm.
hypoblast
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Within the posterior half of the epiblast, cells rearrange by moving first to the caudal midline and then anteriorly forming a fountain like flow and the cells which aggregate into solid median ridge is called the
primitive streak
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the epiblast assumes a pear shape. The stage of embryo development then is called
primitive streak stage.
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As primitive streak elongates, a furrow called
primitive groove
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Terminate anteriorly in a thickening
Primitive ridge/hensen’s node
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The node has a funnel shape depression, called
primitive pit
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Organ development
organogenesis
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Is an example of organogenesis marked by the establishment of the CNS, initial development of the gut and heart and the segmentation of the paraxial mesoderm At this stage the body of the embryo begins to delienate from the three germ layers.
Neurulation
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There are two major ways of forming a neural tube
Primary and Secondary neurulation
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is first indicated by thickening (columnation of cells ) of the surface ectoderm along the dorsal midline called neural plate. This is then followed by infolding (depressed) at the midline to form the neural groove causing a slight elevation on either side of the neural folds. Subsequently, neural folds converge, meet and fuse towards the dorsal midline to form the neural tube.
Primary nerulation
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formation of the neural tube in the posterior portion is without folding
secondary neurulation
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The cells which are not incorporated during the closure of the neural tube are called
neural crest cells.
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undergo an epithelio-m transition as they leave the neuroectoderm by active migration into the underlying mesoderm.
Neural crest
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closure defect of the brain
Cranioschisis
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closure defect of the spinal cord
Rachioschisis
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abnormalities in which the vertebral arches fail to close dorsal to the spinal cord to form the vertebral canal
Spina bifida-
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cranial neuropore fails to fuse properly or even remains open
Dysraphia
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meninges herniate and become distended by fluid accumulation.
Meningocoele
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protrusion involves both meningeal and brain tissue.
Meningoencephalocoele
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brain tissue containing part of the ventricular system.
Meningohydroencephalocoele
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complete failure of the cephalic part of the neural tube to close. In this condition, the vault of the skull does not form, leaving the malformed brain exposed.
Exencephaly
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absence of the telencephalon and much of the diencephalon, although the brainstem remains intact
Anencephaly
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Causes of multiple births
*Fertilization of separately ovulated egg
*Complete or partial separation cleavage/blastocyst blastomeres
*Duplication during gastrulation
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are monozygotic (identical) derived from a single ovulated egg fertilized by a single spermatozoon that separates or duplicate at different stages of development:
Free, symmetrical twins
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are dizygotic (fraternal) twins • derived from two ovulated eggs, each fertilized by separate spermatozoa during a single breeding cycle
Free /separate / symmetrical twins
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may originate from a monozygotic or dizygotic embyros, one member is normal and the other is rudimentary surviving by sharing the blood supply of the normal one.
Free, asymmetrical twins
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are monozygotic in origin and generally termed diplopagus but popularly known as siamese twin.
Cojoined or fused symmetrical twins
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fused at the thorax facing each other
Thoracopagus
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joined at the abdomen with often partially fused intestines
Abdomonopagus
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fused back to back at the pelvic or sacral region
Pygopagus
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joined at the head region.
Cephalopagus
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two heads
Dicephalus
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two faces
Diprosopus
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two tails
Dicaudatus
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2 pairs of thoracic limbs
Tetrabrachius
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2 pairs of pelvic limbs
Tetrascelus
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are unequal in size, consisting of one normal individual, the autosite and an extra body part only, the parasite such as extra limbs attach at the back or at the schial region projecting caudally
Cojoined, asymmetrical twins
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usually happens when the specific organ forming regions are already established ( limb, heart,eye etc. fields)
Asymmetrical twinning
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Soon after successful fertilization, the zygote undergoes cleavage or segmentation division (type of cleavage depends on the amount of yolk material) and moves along the uterine tube and enters the uterus.
Implantation/Nidation
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It occurs in three stages in domestic animals:
• Apposition of the blastocyst or foetal membranes to the uterine epithelium
• Adhesion
• Firm attachment or invasion of the endometrium
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Blastocyst implants itself interstitially by passing through the uterine epithelium and becoming completely cut off from the uterine lumen. This is true in primates, guinea pigs and human.
Interstitial/Invasive Implantation
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blastocyst remains small and becomes lodged in the fold of the uterine lumen, where it implants itself. Example of this form of implantation are rodents.
Eccentric Implantation
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Blastocyst elongates and enlarges until it fills a good part of the uterine cavity. This form of placentation occurs in ungulates, carnivores, swine,sheep, cattle and horse.
Centric/Superficial Implantation
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Blastocyst implants in the endometrium on the same side as the attachment of the mesometrium.
MesometriaL Implantation
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implantation occurs at a site opposite to the attachment of the mesometrium.
Anti-mesometrial Implantation
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• Sites of abnormal implantation
• Ovary
• Uterine tube
• Peritoneal cavity
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Of what When single oocyte is fertilized, the blastocyst attaches to the middle or upper third of the uterine horn adjacent to the ovulating ovary.
Cattle
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Of what two blastocysts are derived from one ovary, one blastocyst usually migrates to the contralateral (opposite) horn where it becomes implanted.
Sheep
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Blastocyst implants in either the left or right horn close to the body of the uterus.
Horse
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• Blastocysts are evenly spaced within the uterine horns.
• Mechanism underlying the equal spacing of embryo is unclear although estrogen produced by the developing blastocyst is considered to have an important role in embryo spacing.
Polytocous (litter bearing) animals
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tissues derived from the developing embryo that enclose and contribute to the support of the developing embryo.
Extra embryonic membranes
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There are four Extra Embryonic Membranes
yolk sac, allantois, amnion, and chorion
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The amnion and chorion are derived from the _____ (fused mesoderm and ectoderm).
somatopleure
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The allantois and yolk sac are from the _____ (fused mesoderm and endoderm).
splanchnopleure
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The remnant after birth is known as
Meckel’s diverticulum.
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In avian the perimeter of the yolk sac is marked by a blood vessel called
sinus terminalis or marginal vein
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is the outermost membrane surrounding the embryo in mammals, birds and reptiles (amniotes).
CHORION
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It develops from an outer fold on the surface of the yolk sac, which lies outside the zona pellucida (in mammals), known as the
vitelline membrane
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It produces ______ which serve to cushion and protect the embryo.
chorionic fluid
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is the fetal part of the placenta
Chorion
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maternal component of the placenta is known as
decidua basalis
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begin to elevate towards the head region and then progresses caudally.
chorioamniotic folds
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The site where the folds fuse forms a scar-like thickening known as the ____which remains throughout development in reptiles and birds.
chorioamniotic raphe
98
is a hollow sac-like structure filled with clear fluid that forms part of a developing amniote's conceptus (which consists of all embryonic and extra-embryonic tissues).
ALLANTOIS
99
Shapes of the allantois vary among animals, it is anchor shaped in what animals?
Cattle, sheep, and pig
100
Shapes of the allantois vary among animals, it is tube shaped in what animals?
Dogs, cats, and horses
101
is the connecting stalk between the fetus and the placenta. In cattle, sheep and pigs, the cord ruptures as the fetus passes through the birth canal. In horses, dogs and cats, the cord normally breaks as a result of the action of the dam after the fetus has been born
UMBILICAL CORD
102
is a structure formed by the apposition of the fetal and maternal tissues
Placenta
103
The formation, type and structure, or arrangement of the placenta is called ____?
Placentation
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the yolk sac placenta, fused vascular choriovitelline membranes become attached to the endometrium
choriovitelline placenta
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membrane becomes attached to the endometrium
chorioallantoic placenta
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CLASSIFICATION OF CHORIOALLANTOIC PLACENTA
• Based on gross distribution of the chorionic villi
• Based on the degree of contact between fetal and uterine mucosa
• Based on the number of tissue layers interposed between the fetal and maternal bloodstream
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BASED ON GROSS DISTRIBUTION OF THE CHORIONIC VILLI
• Diffuse
• Cotyledonary
• Zonary
• Discoidal
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• Characterized by uniform distribution of villi on the outer surface of the chorion
• Occurs in horses and pigs
DIFFUSE
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• Equidae
• Principal source of the equine chorionic gonadotrophin (formerly known as the pregnant mare serum gonadotrophin).
• ENDOMETRIAL CUPS
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• Chorionic villi are restricted to cotyledons
• Occurs in ruminants
• 90-100 in sheep, 70-120 in cattle
COTYLEDONARY
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• Chorionic villi are confined to a girdle-like structure around the middle of the chorionic sac
• Occurs in carnivores
ZONARY
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• Chorionic villi are restricted to disc-shaped areas on the chorionic sac
• Occurs in humans, monkeys and rodents
Discoidal
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Apposed, non-deciduat Conjoined, deciduate
MUCOSA
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• Loose apposition
• Separation is easily achieved at parturition without damage to maternal tissue.
• Horses, ruminants and pigs
APPOSED, NON-DECIDUATE
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• Intimate connection is formed between maternal and embryonic tissue.
• Some maternal tissue is lost with the fetal tissue at birth.
• Humans, dogs, cats and rodents
CONJOINED, DECIDUATE
