Extra Embryonic Membranes

Question 1

what 2 parts does the somites differentiate into?

Answer 1

ventral part - sclerotome (gives rise to ribs and vertebrae)
dorsal- dermomyotome (gives rise to dermis and skeletal muscle)

Question 2

what does the intermediate mesoderm give rise to?

Answer 2

embryonic kidney and the urogenital tract

Question 3

what is the junction between the embryonic tissue and extra embryonic tissue?

Answer 3

umbilical vein

Question 4

what does the somatic lateral plate mesoderm form?

Answer 4

the body wall of the embryo, this will help close the body wall and so the lateral body wall folds have happened, separates the embryo from the extra embryonic fluid (happens at the end of week 4)

Question 5

what is the role of the umbilical vein?

Answer 5

returns oxygenated blood from the placenta

Question 6

what membranes have continuity with the yolk sac?

Answer 6

endoderm and splanchnic mesoderm

Question 7

what is the function of the yolk sac in gut development?

Answer 7

gut will poke into yolk sac to give it space to grow

Question 7

what are the 4 extra-embryonic membranes?

Answer 7

-amnion
-chorion
-yolk sac
-allantois

Question 8

generally how much amniotic fluid surrounds the foetus?

Answer 8

1.5L

Question 9

what are the contributions of the yolk sac?

Answer 9

small nutritional involvement of the provisions of vitamins A, B and E
main function is the production of blood
plays an important role in the production of GI tract

Question 10

where does extra embryonic haematopoesis occur?

Answer 10

yolk sac from week 4 to 6 until the feel liver develops and that will take over production of blood cells

Question 11

when does the yolk sac disappear completely?

Answer 11

between 18 and 20 weeks

Question 12

where is the chorion?

Answer 12

outside the amnion

Question 13

what is the chorion?

Answer 13

the fetal part of the placenta, combines with the maternal side
layer of trophoblasts which have implanted into the uterine wall plus a layer of extra embryonic mesoderm
forms a complete covering around the embryo and the amnion

Question 14

where is the allantois?

Answer 14

lies below the chorion

Question 15

what is the allantois?

Answer 15

the extra embryonic kidney
placenta actually gets rid of waste in human so it becomes redundant but it does have some vasculature

Question 16

where does the decidua come from?

Answer 16

come from the endometrium of the uterus

Question 17

what effect does progesterone have on endometrium?

Answer 17

causes stroll cells to become enlarged and accumulate glycogen

Question 18

what happens when a pregnancy occurs?

Answer 18

progesterone levels rise which causes the stroll cells and endometrium to enlarge and accumulate glycogen

Question 19

what is the decidual reaction?

Answer 19

endometrial vessels start to become dilated around the implantation site
esentially the uterus becoming receptive to the pregnancy

Question 19

what are the 2 components to the placenta?

Answer 19

chorionic frondosum (fetal)
decidua basalis (maternal)

Question 20

what are the 3 sections of the decidua?

Answer 20

decidua basalis
decidua capsularis
decidua parietalis

Question 21

what is the decidua basalis?

Answer 21

the area that interacts with the fetal membranes

Question 22

what is the decidua capsularis

Answer 22

the area of the decidua that grows around the embryo that’s bulging into the uterine lumen

Question 23

which 2 membranes of the placenta fuse at around 20 weeks?

Answer 23

capsularis and pareitalis

Question 24

what structures emerge from the chorion?

Answer 24

chorionic villi

Question 25

what is the area that becomes the placenta essentially?

Answer 25

chorion frondosum

Question 26

which cells do the burying in to the endometrium?

Answer 26

trophoblast cells

Question 27

what is the layer of trophoblasts closest to the embryo called?

Answer 27

cytrophoblast

Question 28

what is the outer layer of the trophoblasts?

Answer 28

syncytiotrophoblast cells

Question 29

which layer of the trophoblasts is driving the invasion?

Answer 29

syncytiotrophoblast cells

Question 30

what happens around day 12 after fertilisation?

Answer 30

syncytiotrophoblasts are becoming very invasive and invading into the uterine mucosa, we start to see small spaces called lacunae

Question 31

where do the growing blood vessels form?

Answer 31

the fill the lacunae with causes the mixing of material and metal circulation which is how we establish a good blood supply so nutrients and waste can be passed

Question 32

when do the primary villi appear from the cytotrophoblast?

Answer 32

day 13 stal

Question 33

when does the mesoderm invade and start to branch and invade the core of the primary villi?

Answer 33

day 16

Question 34

when are they called secondary villi?

Answer 34

when they have a mesenchymal core

Question 34

what are tertiary villi?

Answer 34

when the blood vessels develop in the mesenchyme of the secondary villi these blood vessels connect to the umbilical vessels of the embryo

Question 35

what is the placental barrier?

Answer 35

-partition between the maternal and fetal circulation in the placental membrane or placental barrier -usually 4 layers thick the barrier reduces to 3 layers from the 4th month

Question 36

what are the 4 layers of the placental barrier?

Answer 36

-fetal capillary endothelium -connective tissue of the villi -cytotrophoblast -syncytiotrophoblast

Question 37

which layer of the placental barrier is lost at around moth 4?

Answer 37

cytrophoblast cells

Question 38

what are the functions of the placenta?

Answer 38

-metabolism (synthesised glycogen, fatty acids, cholesterol) -produces energy for the embryo -transfer of O2 and CO2 (diffusion) -transfers urea, uric acid and bilirubin (diffusion) -transfers electrolytes and carbs (diffusion)

Question 39

how are amino acids transferred across placenta?

Answer 39

by a carrier mechanism against their conc gradient (facilitated diffusion)

Question 40

what vitamins can cross the placenta readily?

Answer 40

B, C and D

Question 41

how much water is transferred in Laye pregnancy?

Answer 41

3.5L per hour

Question 42

how do antibodies cross the placenta?

Answer 42

pinocytosis

Question 43

what are the darker stained area around the villi?

Answer 43

cut-trophoblasts and syncytiotrophoblasts

Question 44

what do syncytiotrophoblasts look like on histology?

Answer 44

darker stained, many nuclei fused together and no clear boundaries

Question 45

what do the cytotrophoblast cells look like?

Answer 45

larger nucleus quite basophilic cytoplasm

Question 46

what differences can be seen later in placenta histologically?

Answer 46

villi diameter have massively decreased much more villi much larger vessels appearing reduction in cytotrophoblast layer smaller diameter to reach blood supply much easier

Question 47

where is the zone pellucid on the blastocyst?

Answer 47

the outside edge

Question 48

what tissue does the notochord induce to start the process of neural tube development?

Answer 48

ectoderm

Question 49

in which area of the uterine tube does fertilisation normally take place?

Answer 49

ampulla

Question 50

all of the essential features of the organ systems are laid down by the end of week X?

Answer 50

8

Question 51

What system has the longest critical period of development, and therefore is most susceptible to a wide range of teratogenic insults?

Answer 51

CNS

Question 52

Which molecule is responsible for inactivating BMP4 during neural tube development?

Answer 52

noggin

Question 53

Which extra embryonic membrane consists of extra embryonic ectoderm and extra embryonic mesoderm?

Answer 53

amnion

Question 54

what does the antibiotic tetracycline cause defects in babies?

Answer 54

teeth

Question 55

After fertilisation, the embryo travels down the uterine tube and undergoes division. At around day 4, it will reach a stage called a morula. What process occurs when an embryo reaches the morula stage?

Answer 55

compaction