Lecture 11 Body plan III

Question 1

Which signaling factor is necessary for formation of endoderm?

Answer 1

Depends on nodal expression during gastrulation. A gradient occurs between anterior and posterior gut

Question 2

Describe relationship of expression of nodal and FGF-4 to establishment of anterior posterior gradient.

Answer 2

High levels of nodal anterior and low levels of nodal posteriorly with presence of FGF-4

Question 3

Describe role of Cdx-2 in formation of hindgut and foregut.

Answer 3

• The posterior gut expresses Cdx-2 which promotes hindgut formation and suppresses structures of anterior gut formation

Question 4

Describe relationship of Shh and BMP-4 in formation of anterior posterior intestinal portals.

Answer 4

• Endodermal edges of anterior and posterior intestinal protals express Shh signaling molecule.
• In posterior portal the Shh expression is followed by BMP-4 creating a gradient in the mesoderm of Hox-9-Hox-13.

Question 5

Which series of hox genes is involved in refinement of differentiation of gut structures.

Answer 5

Hoxa-d9 is expressed most cranially and Hoxa-d13 is expressed most caudally. The distribution of the hox gene expression is associated with hindgut formation.

Question 6

List major features of fourth week embryo

Answer 6

• Length of embryo is 4mm
• Rudiments for most of major organs are present except limbs and kidneys
• Prominent pharyngeal arches
• Wolffian ridge

Question 7

What are the three major circulatory arcs in four week human embryo and components/fxn of each?

Answer 7

1. Intraembryonic circulatory arc organized similar to fish
2. Vitelline arc principally an extraembryonbic circulatroy loop that supplies yolk sac
3. Allantoic arc, also extraembryonic. Consists of umbilical vessels

Question 8

List and describe four exttarembryonic layers and germ layers from which they are derived.

Answer 8

1. Amnion: inner cell mass epiblast derivitive endoderm
2. Yolk sac: ICM, hypoblast derivitive,
3. Chorion: part of fetal maternal interface
4. Allantois: ICM, interaces with placenta via umbilical cord

Question 9

List the two trophoblastic derivitives that compromise the fetal maternal interface

Answer 9

1. Placenta: trophoblast derivative
2. Chorion: Trophoblast derivative

Question 10

List functions of the amnion.

Answer 10

• Buffer against mechanical injury
• accommodates growth
• allows normal movements
• protects fetus from ahdhesion

Question 11

Describe hydramnios and what circumstances are associated?

Answer 11

• Hydramnios: excessive amniotic fluid greater than 2000 mL.
• Condition si frequently associated with multiple pregnancies and esophageal atresia or ancephaly.
• Plays an important role in fetal swallowing

Question 12

Describe oligohydramnios and associated circumstances.

Answer 12

• Oligohydramnios is too little amniotic fluid, less than 500 mL.
• This condition is associated with bilateral renal angenesis (absence kidneys) and points to the role of fetal urinary excretion in amniotic fluid dynamics

Question 13

What information is learned from testing for creatine?

Answer 13

Fetal maturity

Question 14

What info is learned by testing for A-fetoprotein

Answer 14

A-Fetoprotein is a protein of central nervous system. In high concentrations in the amniotic fluid it indicates a neural tube defect.

Question 15

What information is learned by testing for lecithin to sphingomyelin ratio?

Answer 15

Fetal maturity of the lungs

Question 16

Describe phase I and phase II formation of amniotic fluid and its source.

Answer 16

1. Phase 1: first 20 weeks of pregnancy, free diffusion of electrolyrtes through fetal ectoderm, maternal serum, secretion by amniotic membrane
2. Phase II: contributions from fetal urine, filtration from vessels associated with chorion laevae

Question 17

List known and possible functions of yolk sac in mammals.

Answer 17

• May concentrate folic acid Vitamins A, B12, or E
• Site of origin of primordial germ cells
• location of blood islants origin of intitial blood cells

Question 18

Describe the development of allantoic vessels and their relation of allantois to urinary bladder and median umbilical ligament.

Answer 18

• Allantoic vessels develop into mesoderm of allantois
• Proximal part of allantois becomes median umbilical ligament that extends up from bladder

Question 19

Describe stages in development of chorionic villi.

Answer 19

Supported by the extraembryonic mesoderm and arises from trophoblastic tissues

• Previllous embryo: trophoblastic tissues have no consistent morphological features
• Primary Villi take place in the second week and are defined
• Secondary Villus when a mesenchymal core appears surrounding the villus
• Tertiary villus occurs when blood vessels penetrate mesenchymal core, during third week of pregnancy

Question 20

What are Hofbauer cells?

Answer 20

Fetal macrophages

Question 21

Describe cytotrophoblastic column in relation to palcental development.

Answer 21

• part of final development of the placenta
• Formed by the expansion of the cytotrophoblastic oclumns over the maternal decidual cells

Question 22

Describe cytotrophoblastic shell in relation to placental development.

Answer 22

• Formed by the expansion of cytotrophoblastic columns over maternal decidual cells

Question 23

Describe anchoring cilli in relation to placental development.

Answer 23

• Villi that are anchored to cytotrophoblastic shell

Question 24

Describe floating villi in relation to placental development.

Answer 24

Not attached to cytotrophoblastic shell

Question 25

Describe chorionic plate in relation to placental development.

Answer 25

d

Question 26

Describe hemochporial type placenta in relation to placental developement.

Answer 26

d

Question 27

What tissue in mature placenta directly interfaces with maternal uterine CT?

Answer 27

Synctiotrophoblast

Question 28

What is decidual reaction?

Answer 28

Occurs within days of implantation of the embryo. Stromal cells swell as result of glycogen and lipid. The reaction spreads throughout stromal cells in the endometrium.

Question 29

what does the term decidua refer to?

Answer 29

Shedding of Basal layer

Question 30

Describe layers from amnion out to outer layer of endometrium.

Answer 30

• Amnion surrounds the fetus
• The chorionic cavity surrounds the amnion
• The chorionic plate (extraembryonic mesoderm) surrounds the chorionic cavity

Question 31

What is the fate of the decidua capsularis?

Answer 31

• Baby breaks through this layer at birth as well as amnion

Question 32

What maternal tissues are lost at childbirth?

Question 33

Trace maternal-fetal blood flow pattern and where does exchange occur?

Answer 33

• Maternal blood enters the (trophoblastic lacunae) intervillous spaces from the spiral arteries
• Exchange of materials occurs between maternal blood in the lacunae and fetal blood in capillaries in the villi
• Maternal blood returns to maternal veins in the decidua basalis
• Fetal blood enclosed within vessels and travels t ocapillary bed within placental vili via two umbilical arteries (deox)
• Fetal blood returns from capillary beds within placental vilia via one umbilical vein

Question 34

Describe FAS in relation to placental transfer.

Answer 34

• Alcohol can cross the placental barrier

Question 35

Describe etiology of erythroblastosis and how it relates to hydrops fetalis.

Answer 35

Erythroblastosis fetalis is when Rh- mothers attach Rh + fetuses and the biliruben released from the lysed red blood cells causes water accumulation in fetus which is known as hydrops fetalis.

Question 36

Describe hydatidiform mole and relation to placenta.

Answer 36

Paternal imprinting characterized by overdevelopment of trophoblastic tissues and extreme under development of the embryo. Can results from fertilization of an egg by two sperm. Paternal imprinting favors trophoblast over embryo development.

Question 37

Describe placenta previa in relation to structure of placenta.

Answer 37

The placenta forms a partial covering over the cervical canal because hte embryo implants too close to the cervix. This can result in hemorrhage during late pregnancy and if untreated will most likely cause death. Very rare.

Question 38

What is the genetic basis for hydatiediform mole?

Answer 38

d