Lecture 11 Body Plan III and Extraembryonic tissues Flashcards
Which signaling factor is necessary for the formation of endoderm?
nodal expression during gastrulation
Describe the relationship of the expression of nodal and FGF-4 to the establishment of
the anterior-posterior gradient.
high levels of nodal anteriorly
lower levels of nodal and presence of FGF-4 posteriorly
Describe the role of Cdx-2 in the formation of the hindgut and foregut.
Promotes the handout and surpasses the formation of the anterior gut structures
Describe the relationship of Shh and BMP-4 in the formation of the anterior and posterior intestinal portals.
Expression of Shh followed by BMP-4 leads to the development of the posterior intestinal portal
Expression of Shh alone leads to the development of the anterior intestinal portal
Which series of Hox genes is involved in the refinement of the differentiation of gut structures?
Posterior expresses cdx2 and the anterior expresses Hex, Sox, and Foxa-2
List major features of the fourth week embryo.
Length- 4mm
rudiments for the major organ systems are present
prominent pharyngeal arches
List each of the three major circulatory arcs in the 4-week human embryo and the components and function of each.
- vitelline arc
- allantoic arc
- stomach ish - Embryonic arc
- all the heart and aorta and stuff
List and describe the four extraembryonic layers and the germ layers from which they are derived.
- amnion- from the inner cell mass and epiblast
- yolk sac- from the inner mass cells and hypoblast
- chorion- part of fetal maternal interface
- allantois- from the inner cell mass; interfaces with the placenta via the umbilical cord
List the two trophoblastic derivatives that comprise the fetal-maternal interface
Placenta and the chorion
List the functions of the amnion.
- buffer against mechanical injury
- accommodates growth
- allows normal movement
- prevents fetus from adhesions
Describe the following conditions and indicate what circumstances these are often
associated: hydramnios, oligohydramnios.
hydramnios: relate to esophageal atresia and anencephaly
oligohydramnios: relate to renal agenesis
Describe phase I and phase II formation of amniotic fluid. What is its source?
- electrolytes through fetal ectoderm
maternal serum
secreted by amniotic membrane - contributions from fetal urine
List known and possible functions of the yolk sac in mammals
concentrates folic acid and vitamins, including a site of origin for primordial germ cells
Describe the development of the allantoic vessels and the relation of the allantois to the urinary bladder and the median umbilical cord
develop in the mesoderm of the allantois
proximal part forms urinary bladder and becomes the median ligament
Describe each of the four stages in the development of the chorionic villi.
previllous embryo: no villi on trophoblast
primary villous stage: solid, cytotrophoblastic, ectodermal primary villi appear
secondary villous stage: mesodermal cores appear within the primary villi
tertiary villous stage: characterized by the appearance of blood vessels within the mesenchymal core of the secondary villi
