Lecture 11: Establishment Of Body Plan 3 And Extraembryonic Tissues Flashcards
The following is is not a transcription factor for endoderm formation A. Hex B. FGF -4 C. Cdx-2 D. Foxa-2
Ans: C
Endoderm
Initial signaling for endoderm formation occurs during gastrulation:
• Depends on nodal (SM) expression during gastrulation
• Anterior-posterior gradient: • Higher levels of nodal (SM) anteriorly
• Lower levels of nodal + presence of FGF-4 posteriorly (SM)
• Posterior gut expresses Cdx-2 (TF):
• Promotes hindgut development
• Suppresses formation of anterior gut structures
• Anterior gut expresses Hex, Sox-2, Foxa-2
• More refined differentiation of gut structures depends on Hox genes.
Posterior intestinal portal expresses A. Shh followed by BMP-4 B. Shh C. Foxa-2 D. Sox-2
Ans: A
Posterior intestinal portal Expression of Shh followed by BMP-4
Anterior intestinal portal expresses Shh
Both the oropharyngeal membrane and cloacal plate are formed by A. Endoderm only B. Endoderm and ectoderm C. Endoderm and mesoderm D. Ectoderm and mesoderm
Ans: B
Both the oropharyngeal membrane and cloacal plate are formed by
endoderm and ectoderm with no intervening mesoderm. • Instability created by lack of mesoderm results in perforations of these plates.
• Pockets created on ectodermal sides of these plates:
• Stomodeum = future oral cavity
• Proctodeum = future anal region
Note that Oral plate = oropharyngeal membrane
Rudiments for most of the major organ systems are
present (except limbs and kidneys) in the embryo at this week:
A. 1st week
B. 2nd week
C. 6th week
D. 4th week
Ans: D
Fourth Week Embryo
Major features to note: • Length of embryo = 4 mm
• Rudiments for most of the major organ systems are present (except limbs and kidneys).
• Prominent pharyngeal arches
• Wolffian ridge
Of the extraembryonic tissues this tissues is not formed from inner cell mass. A. Amnion B. Chorion C. Yolk sac D. Allantois
Ans: B
Extraembryonic Tissues
Extraembryonic tissues: • Amnion (Inner cell mass: epiblast derivative)
• Yolk sac (Inner cell mass: hypoblast derivative)
• Chorion (Part of fetal maternal interface)
• Allantois (Inner cell mass; interfaces with placenta via umbilical cord)
Fetal-maternal interface: • Placenta (Trophoblast derivative)
• Chorion (Trophoblast derivative)
Fetal maternal interphase has this tropoblast derivative. A. Amnion B. Chorion C. Allantois D. Yolk sac
Ans: B
Fetal-maternal interface: • Placenta (Trophoblast derivative)
• Chorion (Trophoblast derivative)
Amnion does not allows the:
A. Buffer against mechanical injury & allows normal movements
B. Accommodates growth
C. Protects fetus from adhesions
D. Relate to esophageal atresia and anencephaly
Ans: D
AmnionFunctions:•Buffer against mechanical injury•Accommodates growth•Allows normal movements•Protects fetus from adhesions
D- Hydramnios:•Relate to esophageal atresia and anencephaly
Renal agenesis: A. Oligohydramnios: B. Teratomas C. Genetic mutation D. Hydramnios
Ans : A
•Hydramnios: Relate to esophageal atresia and anencephal •Oligohydramnios: Relate to renal agenesis
This phase of amniotic fluid is formed with contributions from fetal urine and filtration from vessels associated with chorion laevae and other sources. Which phase? A. Phase 3 B. Phase 1 C. Phase 2 D. Phase 4
Ans: C
Formation of amniotic fluid:•Phase I:•First 20 weeks of pregnancy•Free diffusion of electrolytes through fetal ectoderm •Maternal serum •Secretion by amniotic membrane
•Phase II:•Contributions from fetal urine •Filtration from vessels associated with chorion laevae •Other sources?
Which structure concentrates folic acid and vitamins (A, B12, E)? A. Amniotic fluid B. Yolk sac C. Placenta D. Uterine walls
Ans: B
Possible Yolk Sac FunctionsMay concentrate:•Folic acid•Vitamins (A, B12, E)Other functions (relationships):•Site of origin of primordial germ cells•Location of blood islands:•Origin of initial blood cells (extraembryonic hematopoiesis)
Proximal part of allantois: A. umbilical vessels B. Urethra C. Urachus D. Fallopian tubes
Ans C
Allantois•Allantoic (umbilical) vessels:•Develop in the mesoderm of the allantois•Proximal part of allantois = urachus•Associated with the formation of the urinary bladder•Becomes median umbilical ligament
What is the correct sequence of the stages in placental development?
A. Previllous embryo -> Primary villous stage ->Secondary villous stage ->Tertiary villous stage ->Cytotrophoblastic columns -> Cytotrophoblastic shells &Anchoring villi
B. Primary villous stage ->Secondary villous stage ->Tertiary villous stage ->Previllous embryo->Cytotrophoblastic columns -> Cytotrophoblastic shells &Anchoring villi
C. Previllous embryo ->Cytotrophoblastic columns -> Cytotrophoblastic shells &Anchoring villi -> Primary villous stage ->Secondary villous stage ->Tertiary villous stage
Ans: A
Previllous embryo:•No villi have been formed on the trophoblast Primary villous stage: •Solid, cytotrophoblastic, ectodermal primary villi appear Secondary villous stage: •Mesodermal cores appear w/in the primary villi Tertiary villous stage:Characterized by the appearance of blood vessels within the mesenchymal core of the secondary villi Final development:•Cytotrophoblastic columns •Cytotrophoblastic shells: •Formed by expansion of the cytotrophoblastic columns over the maternal decidualcells •Anchoring villi: •Villi that are anchored to the cytotrophoblastic shell (as opposed to floating villi)
The pattern of Maternal blood flow pathway into the fetus?
Blood flow pathway (maternal):•Maternal blood enters intervillous spaces (trophoblastic lacunae) from spiral arteries.•Exchange of materials (respiratory gasses, nutrients, waste products) between maternal blood in lacunae and fetal blood in capillaries in the villi.•Maternal blood returns to maternal veins in the decidua basalis.
The pattern of blood flow pathway in the fetus?
Blood flow pathway (fetal):•Fetal blood is entirely enclosed within vessels.•Fetal blood travels to capillary beds within placental villi via umbilical arteries (usually two).•Fetal blood returns from capillary beds within placental villi via umbilical vein (usually one).
