Embryology S1 U1

gastrulation begins with the formation of this on the surface of the epiblast

Cells of the ________ migrate towards the primative streak; upon arrival in the region of the streak, they become flask-shaped, detach from the epiblast and slip beneath it.

Cell migation and specification are controlled by __________, which is synthesixed by streak cells themselves; this growth factor controls cell movement by downregulating the E-cadherin, a protein that normally binds epiblast cells together

growth factor controls cell movement by downregulating E-cadherin, a protein that normally binds epiblast cells together.

in gastrulation, once the cells of the epiblast have invaginated, some displace the hypoblast; creating the embryonic __________ and others come to lie between the epiblast and the newly creasted endoderm to form _____________; cells that remaining in the epiblast then form _______

where does the prechordial plate form?

As the hypoblast is replaced by endoderm cells moving in at the streak, cells of the notochordal plate proliferate and detach from the endoderm. They then form a solid cord of cells, the ___________________

the _______ is formed at the caudal end of the embryonic disc; This membrane, which is similar in structure to the oropharyngeal membrane, consists of tightly adherent ectoderm and endoderm cells with no intervening mesoderm.

when do the allantoenteric diverticulum (allantois) appear in development

the L-R development and D-V development occurs in early _____________ during the late morula and to blastocyst stages of development

By the blastocyst stage, the A–P axis is determined and cells that are destined to form the ________________________ at the cranial end of the endoderm layer of the bilaminar disc (Fig. 5.4) migrate toward what will become the head region

express genes essential for head formation, including the transcription factors OTX2, LIM1, and HESX1, and the secreted factors cerberus and lefty1 (members of the TGF-β family), which inhibit nodal (a member of the TGF-β family) activity, thereby establishing the cranial end of the embryo.

these secreted factors inhibit nodal and establish the cranial end of the embryo

absense of cerberus and leftyr at the caudal end of the embryo allows __ expression to continue and this signal establishes and maintains the primitive streak

is secreted throughout the embryonic disc (Fig. 5.4). In the presence of this protein and FGF, mesoderm will be ventralized to contribute to kidneys (intermediate mesoderm), blood, and body wall mesoderm (lateral plate mesoderm).

factors secreted by the node, including chordin, noggin, and gollistatin, antagonize the activity of ______

What activates chordin

expression of the ________________ gene antagonizes BMP4 to dorsalize mesoderm into notochord and paraxial mesoderm in caudal regions of the embryo.

a transcription factor secreted by the node and endoderm, maintains the node and primitive streak and later induces regional specificity in the forebrain and midbrain areas.

what happens without HNF-3B present?

what does over or under expressuon of GOOSECOID lead to?

this growth factor indices expressuon of NODAL; this restricts NODAL expresison to the left side of the embryo by the accumulation of _______- on the left side

High concentrations of 5-HT on the left activate expresison of TF ________ that restricts NODAL expression to the left side of the primitive node

TF that restricts NODAl expression to the left side of the primitive node

midline genes not only involved in establishing the midline but also involved in preventing NODAL expression from crossing over to the right side (x3)

nodal protein initiates a signal cascade that includes _______ tp upregulate ____

(L-R) a homeobox-containing transcription factor that is a “master gene” responsible for establishing left-sidedness, and its expression is repeated on the left side of the heart, stomach, and gut primordia as these organs are assuming their normal asymmetrical body positions.

Genes regulating right-sided development are not as well defined, although expression of the transcription factor _____________ is restricted to the right lateral plate mesoderm and probably regulates effector genes responsible for establishing the right side.

high doses of alcohol at this stage kill cells in the anterior midline of the germ disc, producing a deficiency of the midline in craniofacial structures and resulting in...

In caudal dysgenesis ______________, insufficient mesoderm is formed in the caudalmost region of the embryo.

remanants of the primitive streak can perist in the sacrococcygeal region; these clusters of pluriptent cells proliferate and form tumors known as ...

refers to the normal positioning of the internal organs.

refers to a condition in which the positioning of all organs is reversed in a mirror image arrangement; patients at low risk for other birth defects

discordant organ positioning with respect to symmetry, in which one or more organs are abnormally reversed in position or isomerisms; patients at high isk for having a wide variety of other birth defects

what does the connecting stalk later become

neural tube differentiation: Initially, _____________) secreted in the ectoderm overlying the neural tube establish a signaling center in the roof plate.

neural tbe differentiation: BMP4 in the roof plate upregulates a cascade of TGF-β proteins, including _____________ in this region.

Most defects of the spinal cord result from abnormal closure of the neural folds in the third and fourth weeks of development. The resulting abnormalities, _____________), may involve the meninges, vertebrae, muscles, and skin.

general term for NTDs affecting the spinal region. It consists of a splitting of the vertebral arches and may or may not involve underlying neural tissue

a defect in the vertebral arches that is covered by skin and normally does not involve underlying neural tissue (Fig. 18.15A). Most often, the defect occurs in the sacral region (S1–S2) and is sometimes marked by a patch of hair overlying the affected region

what causes spina bifida occulta

refers to NTDs in which the neural tube fails to close, resulting in spina bifida and exposure of neural tissue that often becomes necrotic

spina bifida: only fluid-filled meninges protrude through the defect

spina bifida: neural tissue is included in the sac

______________requiring intervention develops in 80% to 90% of children born with severe NTDs and is often related to the presence of an Arnold–Chiari malformation (herniation of part of the cerebellum into the foramen magnum), which obstructs the flow of cerebrospinal fluid (CSF) and causes this

herniation of part of the cerebellum through the foramen magnum

revention of many NTDs is possible if women take ________________ starting at least 1 month prior to conception and then throughout their pregnancy.

herefore, the critical period for causing most structural birth defects extends from _____________

result in morphologic alterations of already formed structures and are caused by destructive processes. Vascular accidents leading to transverse limb defects and defects produced by amniotic bands are examples of destructive factors that produce these

result from mechanical forces that mold a part of the fetus over a prolonged period. Clubfeet, for example, are caused by compression in the amniotic cavity

Strands of ________ may be swallowed or become wrapped around structures causing various disruption-type defects. The origin of the bands of amniotic tissue is unknown.

a group of anomalies occurring together that have a specific common cause. This term indicates that a diagnosis has been made and that the risk of recurrence is known.

the nonrandom appearance of two or more anomalies that occur together more frequently than by chance alone, but the cause has not been determined. An example is the VACTERL

Susceptibility to teratogenesis depends on the ______________ and the manner in which this genetic composition interacts with the environment.

Limb defects characterized by loss of the long bones of the limb

________________ is a serious threat. Often, the mother has no symptoms, but the effects on the fetus can be devastating. The infection can cause serious illness at birth and is sometimes fatal. On the other hand, some infants are asymptomatic at birth but develop abnormalities later, including hearing loss, visual impairment, and intellectual disability.

nduced abnormalities are rare, and usually, infection is transmitted to the child during delivery, causing severe illness and sometimes death

infection with _________- causes scarring of the skin, limb hypoplasia, and defects of the eyes and central nervous system.

Zika infection causes a unique pattern of birth defects in affected children including (x5)

cause fevers

Characteristically, ____________ is affected by elevated temperatures, and neural tube defects, such as anencephaly and spina bifida, are produced.

what does fetal toxoplasmosis infection cause?

kills rapidly proliferating cells, so it is a potent teratogen, producing virtually any type of birth defect depending on the dose and stage of development of the conceptus at the time of exposure.

an analogue of vitamin A, has been shown to cause a characteristic pattern of malformations known as the isotretinoin embryopathy.

produce a broad spectrum of abnormalities that constitute distinct patterns of dysmorphogenesis known as the trimethadione and fetal hydantoin syndromes. F

increases the risk for several defects, including atrial septal defects (ASDs), cleft palate, hypospadias, polydactyly, and craniosynostosis, but the highest risk is for the neural tube defect spina bifida.

linked by epidemiologic studies to multiple birth defects, presumably because of serotonin’s role in establishing the left–right axis

produce growth retardation, renal dysfunction, fetal death, and oligohydramnios if exposures occur during the second or third trimester

diagnosis of fetal alcohl syndrome must include...

refers to cases with evidence of involvement of the central nervous system that do not meet the diagnostic criteria for FAS

inked to an increased risk for orofacial clefts (cleft lip and cleft palate) and is a moderate risk factor for heart defects, including transposition of the great arteries (TGA), ASD, pulmonary stenosis, and common truncus arteriosus.

was used to prevent abortion, raised the incidence of carcinomas of the vagina and cervix in women exposed to the drug in utero.
-Male embryos exposed in utero can also be affected, as evidenced by an increase in malformations of the testes and abnormal sperm analysis among these individuals.

phenylketonuria (PKU), in which the enzyme phenylalanine hydroxylase is deficient or reduced, resulting in increased serum concentrations of phenylalanine, are at risk for having infants with (x3)

obsese mothers are more likely to have babies with..

a relatively noninvasive technique that uses high-frequency sound waves reflected from tissues to create images. The approach may be transabdominal or transvaginal, with the latter producing images with higher resolution

test involves measurement of the translucent space at the posterior of the baby’s neck, where fluid accumulates when Down syndrome and some other abnormalities, especially heart defects, are present.

involves inserting a needle transabdominally or transvaginally into the placental mass and aspirating approximately 5 to 30 mg of villus tissue. The technique is performed earlier in gestation (8 to 9 weeks) than amniocentesis (13 to 15 weeks), thereby providing an earlier diagnosis of genetic abnormalities.

conducted on a single blastomere obtained 3 days after the process of in vitro fertilization has been initiated when the embryo is at the three- to eight-cell stage. FISH analysis can determine the presence of aneuploidy and the cell’s DNA can be amplified by whole genome PCR to screen for genetic abnormalities.

whereby the uterus is exposed and opened to operate directly on the fetus;

surgery using small incisions through the mother’s abdominal wall and the uterus.