Embryo - Fetal Membranes, Placenta, And Multiple Pregnancies

Front 1

Up to and including the 3rd week of development, what does the embryo consist of?

Back 1

flat disc

Front 2

What happens to the disk at the end of the 3rd week?

Back 2

it becomes three-layered

Front 3

What is the term when tissue of embryonic disk grows more rapidly than surrounding tissue?

Back 3

differential growth

Front 4

The embryonic disk folds into what two planes?

Back 4

median and horizontal

Front 5

What are the two types of folds in the median plane?

Back 5

head and tail fold

Front 6

What is the fastest growing tissue in the developing fetus?

Back 6

ectoderm of the developing nervous system

Front 7

Continued growth of the forebrain results in folding of the head region such that the _____________________ overhangs the developing heart and will lie ________ to it.

Back 7

oropharyngeal membrane

cranial

Front 8

What is the endoderm of the yolk sac incorporated into during a head fold?

Back 8

foregut

Front 9

Continued growth of the distal neural tube (future spinal cord) results in folding of the caudal end of the embryo such that the tail of the embryo lies ventral to the ___________.

Back 9

cloacal membrane

Front 10

Umbilical cord is cranial to what membrane?

Back 10

cloacal membrane

Front 11

What is the endoderm of yolk sac incorporated into during tail fold?

Back 11

hindgut

Front 12

What does rapid growth of the spinal cord and somites result in?

Back 12

lateral folding of the embryo

Front 13

What is the endoderm of yolk sac incoporated into during lateral folding?

Back 13

midgut

Front 14

What attaches to the endoderm of yolk sac to the midgut?

Back 14

yolk stalk

Front 15

What happens to the region of attachment of the amnion when the umbilical cord forms?

Back 15

it narrows

Front 16

What is the amnion composed of?

Back 16

amniotic ectoderm and amniotic mesoderm (extraembryonic mesoderm)

Front 17

What does the amniotic cavity contain?

Back 17

amniotic fluid

Front 18

Where does the amniotic fluid come from?

Back 18

maternal interstitial fluid and the developing fetus through amniotic ectoderm, fetal respiratory tract and fetal urine

Front 19

How much amniotic fluid should be present at10 weeks?

Back 19

30 ml

Front 20

How much amniotic fluid should be present at 20 weeks?

Back 20

350 ml

Front 21

How much amniotic fluid should be present at 37 weeks?

Back 21

1000 ml

Front 22

How is amniotic fluid removed?

Back 22

- via diffusion into maternal tissue via amniochorionic membrane
- umbilical cord
- via swallowing by the fetus

Front 23

What are the functions of the amniotic fluid?

Back 23

- cushion and protect
- prevent adhesions
- allow freedom of movement
- control body temperature

Front 24

What is oligohydramnios?

Back 24

Lower than normal levels of amniotic fluid

Front 25

What is polyhydramnios?

Back 25

Higher than normal levels of amniotic fluid

Front 26

When can you perform an amniocentesis?

Back 26

Earliest - 14 weeks LMP
- 12 weeks of embryonic development

* usually not possible until 15-16 weeks LMP

Front 27

When can you perform chorionic villi sampling?

Back 27

- 8.5-11 weeks LMP
- 6.5 - 9 weeks of embryonic development

Front 28

What makes up the trophoblast?

Back 28

- cytotrophoblast
- synchtiotrophoblast

Front 29

What are the three types of chorionic villus?

Back 29

-primary villus
- secondary villus
- tertiary villus

Front 30

When does the primary villus form?

Back 30

day 13

Front 31

When does the secondary villus form?

Back 31

15-18 day

Front 32

When does the tertiary villus form?

Back 32

18-19 day

Front 33

When does utero-placental circulation occur and how does blood flow??

Back 33

between day 9 - 11

- maternal blood flows into syncytial lacunae

Front 34

When does feto-placental circulation occur and how does blood flow?

Back 34

between day 21-22

- fetal blood circulates through tertiary villus

Front 35

What is nonfunctional for storage of yolk in the human?

Back 35

yolk sac

Front 36

Where does blood development first occur?

Back 36

- in the extraembryonic mesoderm covering the yolk sac

Front 37

When does blood development first occur?

Back 37

3-6th week

Front 38

When does the primoridal germ cells appear and migrate to developing sex organs?

Back 38

3rd week

Front 39

When is the endoderm of yolk sac incorporated into the primitive gut?

Back 39

4th week

Front 40

What do the allantoic blood vessels persist as?

Back 40

umbilical vein and arteries

Front 41

What is the fetal component of the placenta?

Back 41

villous chorion

Front 42

What is the maternal component of the placenta?

Back 42

decidual basalis

Front 43

What are the features of the mature placenta?

Back 43

umbilical cord and its insertion

Battledore placenta

Front 44

What does the fetal surface of the mature placenta consist of?

Back 44

-amnion
-chorionic plate
-chorionic vessels

Front 45

What does the maternal surface of the mature placenta consist of?

Back 45

-decidual (placental) septa
-cotyledons

Front 46

What does the placental membrane consist of up to 20 weeks? (maternal --> fetal)

Back 46

-syntrophoblast
-cytotrophoblast
-connective tissue in core of villus
- endothelium of fetal capillaries

Front 47

What does the placental membrane consist of after 20 weeks? (maternal --> fetal)

Back 47

- syntrophoblast
- connective tissue in core of villus
- endothelium of fetal capillaries

Front 48

In some cases the syncytiotrophoblast comes into direct contact with the endothelium of the fetal capillaries to form a ___________________?

Back 48

vasculosyncytial membrane

Front 49

How does a vasculosyncytial membrane form?

Back 49

syncytiotrophoblast comes in direct contact with endothelium of the fetal capillaries

Front 50

What are Hofbauer cells?

Back 50

macrophage in connective tissue core of branch villus

Front 51

What mechanisms are used in placental transfer?

Back 51

- simple diffusion
- facilitated diffusion
- active transport
- pinocytosis

Front 52

What is simple diffusion?

Back 52

substances move from high to low concentration

Front 53

What is facilitated diffusion?

Back 53

transport mediated via electrical charges

Front 54

What is active transport?

Back 54

against a concentration gradient; requires energy

Front 55

What is pinocytosis?

Back 55

endocytosis of extracellular fluid

Front 56

How do some materials pass abnormally?

Back 56

- small defects of breaks in placental membrane (leaking)
- diapedesis
- bacteria and protozoa create lesions and cross

Front 57

What material primarily crosses by simple diffusion?

Back 57

Gas exchange: O2, CO2, and CO

lipids

Front 58

What material primarily crosses via facilitated diffusion?

Back 58

carbohydrates: glucose

Front 59

What material primarily crosses via active transport?

Back 59

amino acids
-water-soluble vitamins

Front 60

What material primarily crosses via pinocytosis?

Back 60

proteins (slowly)

e.g. Antibodies - IgG passes readily via pinocytosis

Front 61

How are lipid soluble vitamens transfered?

Back 61

generally by diffusion

Front 62

What is essential for normal fetal development?

Back 62

lipid-soluble vitamins

Front 63

What should we be cautious about with lipid-soluble vitamins?

Back 63

take only physiological amounts, megadoses may be teratogenic (e.g. Vitamin A)

Front 64

How are electrolytes and water transferred through the placenta?

Back 64

simple diffusion

Front 65

Protein hormones normally do not reach fetus except _________________.

Back 65

- thyroxine
- triiodothyronine

Front 66

What kind of hormones freely cross the placental membrane?

Back 66

steroid hormones (estrogen and progesterone)

Front 67

What materials should be considered to freely cross the placenta?

Back 67

- drugs (steroids, cocaine, agents used during labor)
- infectious agents

Front 68

What type of infectious agents can pass through the placenta?

Back 68

- viruses (rubella and HIV)
- pathogenic bacteria (treponema pallidum - syphilis)

Front 69

What are the 3 types of hormones involved in the endocrine function of placenta?

Back 69

- steroid hormones
- prostaglandins
- protein hormones

Front 70

What are the types of steroid hormones involved in placenta endocrine function?

Back 70

- progesterone
- estrogen

Front 71

What are the types of protein hormones used in endocrine function of placenta?

Back 71

- human chorionic gonadotropin (hCG)
- human placental lactogen (hPL) (=human chorionic somatommotropoin (hCS))
- human chorionic thyrotropin (hCT)
- human chorionic corticotropin (hCACTH)

Front 72

What occurs during the first stage of parturition?

Back 72

- dilatation of cervix
- uterine contractions
- rupture of amniochorionic membrane

Front 73

What occurs during the second stage of parturition?

Back 73

delivery of baby

Front 74

What occurs during the third stage of parturition?

Back 74

- delivery of placenta

Front 75

How does delivery of placenta occur?

Back 75

- fetal prtion of placenta separates from decidua basalis
- uterus continues to contract
- spiral arteries are constricted

Front 76

What forms deep to fetal portion of placenta?

Back 76

hematoma

Front 77

What is the diameter and thickness of the placenta?

Back 77

diameter = 15-20cm
thickness = 2-3 cm

Front 78

What is the maternal surface of fetal placenta covered with?

Back 78

cotyledons separated by grooves formed from septa of decidual basalis

Front 79

What is the fetal surface of placenta covered by?

Back 79

amnion

Front 80

What percentage of newborns have only one umbilical artery and what percentage of these individuals have cardiovascular anomalies?

Back 80

0.5% of newborns w/ only one umbilical artery, 15-20% of these have cardiovascular anomalies

Front 81

What is the fourth stage of parturition?

Back 81

recovery

Front 82

What is involved in recovery from parturition and how long does it last?

Back 82

- constriction of uterine spiral arteries
- usually last 2 hours

Front 83

What is the frequency of multiple births in the natural cycle?

Back 83

- twins - 1:90
- triplets - 1:90^2
- quadruplets - 1:90^3

Front 84

How does the frequency of multiple births increase?

Back 84

use of fertility drugs and in vitro fertilization

Front 85

What percentage of twins are dizygotic (fraternal)?

Back 85

66.6% or 2/3

Front 86

What phenomenon results in dizygotic twins?

Back 86

- fertilization of 2 secondary oocytes by 2 spermatozoa

Front 87

What structures develop as a result of dizygotic twins?

Back 87

- formation of 2 amnions
- 2 chorionic cavities
- 2 placentas

(chorionic cavities and placentas may be fused)

Front 88

What is the first scenario that results in monozygotic twins (identical) and by how many percent?

Back 88

65%

- fertilization 1 secondary oocye
- twinning in blastocyst stage
-inner cell mass divides --> two embryos
- each embryo has its own amniotic sac, but common chorionic cavity and placenta

Front 89

How do conjoined twins occur?

Back 89

inner cell mass does not completely divide

Front 90

What is the 2nd scenario that results in monozygotic twins (identical) and by how many percent?

Back 90

35%
-fertilization of 1 secondary oocyte
-twinning occurs during cleavage
- two morulas are formed --> two embryos
- each embryo has its own amniotic sac, chorion, and placenta (similar to dizygotic twins)

Front 91

What does the primary villus contain?

Back 91

contains core of cytotrophoblast

Front 92

What does the secondary villus contain?

Back 92

contains core of mesenchyme

Front 93

What does the tertiary villus contain?

Back 93

contains fetal capillaries

Front 94

What is a cytotrophoblastic shell?

Back 94

cytotrophoblasts extensions that anchor the chorionic sac to endometrium

Front 95

During feto-placental circulation, embryonic blood vessels differentiate from ___________________and ______________.

Back 95

mesenchyme in villi and connecting stalk

Front 96

What is the chorion frondosum?

Back 96

(villous chorion)
- where embryo implants into uterien wall
- participates in making placenta **

Front 97

What is the chorion levae?

Back 97

(smooth chorion)
- on abembryonic side of embryo

Front 98

What is the allantois?

Back 98

extension of yolk sac into connecting stalk

Front 99

Blood development (hemoatopoietic) begins in allantois when?

Back 99

3-5 weeks

Front 100

What do the umbilical vein and arteries eventually form in the adult (they are nonfunctional)?

Back 100

-froms urachus (thick tube) which will eventually come the medial umbilical ligament

Front 101

What is the decidua?

Back 101

functional part of endometrium

Front 102

What happens to the decidua capsularis?

Back 102

degenerates

Front 103

What happens to decidua parietalis?

Back 103

fuses with chorion

Front 104

What happens to decidua basalis?

Back 104

becomes maternal component in the placenta

Front 105

What are the components of the tertiary villus?

Back 105

-cytotrophoblastic shell
-mainstem villus (trunk)
-free floating villi
-anchoring villus
-branch villi

Front 106

What are cotyledons?

Back 106

groups of placental villi with grooves due to placental septum (dividing them up)

Front 107

What is the function of branch villus?

Back 107

exchange between fetal and maternal blood

Front 108

What happens in the velamentous insertion of the umbilical cord?

Back 108

- umbilical cord inserts into chorion laeve away from placental edge, so that the vessels pass between the amnion and the chorion to reach the placenta (not protected)
- occurs in 1% of single births (more frequent in twins and common in trips)

Front 109

What is the hormones of the placental synthesized by?

Back 109

syncytiotrophoblast

Front 110

What is the function of the human chorionic gonadotropin (hCG)?

Back 110

"initial maintenance"
- allows rescue of corpus luteum of ovary
- continued production of progesterone by ovary

Front 111

What is the function of human placental lactogen (hPL) (=human chorionic somatomammotropoin hCS)?

Back 111

converts mother's metabolism from primarily carbohydrate user to fatty acid, diabetogenic metabolism
- fetus = 1st glucose user
- mother = secondary glucose user

Front 112

What hormones are human chorionic thyrotropin (hCT) and human chorionic corticotropin (hCACTH) similar to?

Back 112

thyroxin and ACTH

Front 113

What happens during delivery of baby?

Back 113

uterine contractions and increased intraabdominal pressure