Fetal Development Flashcards
1
Q
Lasts for 8 weeks, organogenesis takes place
A
Embryonic period
2
Q
Chorionic sac 1cm
True intervillous space formed
Fetal BV in chorionic villi appear
A
3rd week after ovulation
3
Q
Chorionic sac 2-3cm
Embryo 4-5cm
Arm and leg buds present
Formed: PUC
Primitive heart
Umbilical cord
Cardiovascular system
A
4th week
4
Q
Embryo 22-24mm
Head larger than trunk
Finger toes present
Complete:
Heart
Upper lip
A
6th week
5
Q
External ears form definitive elevations on either side of head
A
6th wk
6
Q
Earliest synapses in the spinal cord develop
A
6th
7
Q
Consist of growth and maturation of structures that were formed during the embryonic period
A
Fetal period
8
Q
8 weeks after fertilization or 10 weeks after onset of last menses
A
Fetal period
9
Q
Embryo-fetys is nearly
A
4 cm long
10
Q
UCC
Uterus is palpable (above symphysis pubis)
Crown-rump length 6-7cm
Centers for ossification appear
A
12 weeks
11
Q
Fingers toes have become differentiated
Skin and nails develop
A
12 weeks
12
Q
External genitalia start to show definitive signs of gender
Fetus begin to make spontaneous movements
A
12th
13
Q
CRL (crown rump length) 12cm
Weight: 110g
A
16th week
14
Q
Eye movement begin at
A
16-18 weeks with midbrain maturation
15
Q
Weight >300g
Fetal skin = less transparent
Downy lanugo covers entire body
Developed scalp hairs
A
20 weeks
16
Q
Weight 630g
Skin is wrinkled
Fat deposition
Eyebrows and eyelashes recognize
A
24th week
17
Q
Canalicular period of lung development
A
24th week
18
Q
CRL: 25cm
Weight: 1,100g
Thin skin is red and covered w vernix caseosa
90% chance of survival
A
28 weeks
19
Q
CRL: 28cm
Weight: 1,800g
A
32 weeks
20
Q
CRL: 32cm
Weight: 2,500g
Body more rotund bcs of deposition of subcutaneous fat
A
36 weeks
21
Q
CRL: 36cm
Weight: 3,400g
Fully developed
A
40 weeks
22
Q
Thickened disk-shaped growing to a diameter of 20cm
A
Placenta
23
Q
Fetal portion is derived from
A
Chorion
24
Q
One of the surrounding extraembryonic membranes of conceptus
A
Chorion
25
Derived from the region of endometrium that underlies the implantation site (the deciduas basalis)
Maternal portion
26
Development of the placenta: the EARLY blastocyst consists of a single layer of
Ectoderm
27
What consists of an inner cell mass that gives rise to the embryo and outer, single layer of trophoblast cells that encloses the blastocyst cabity
Late blastocyst
28
Blastocyst implants high up on the
Posterior wall of uterus
29
Following implantation, these become highly invasive and erode the endometrium
Trophoblast cells
30
As the blastocyst buries itself in the endometrium, it is covered by both
Trophoblast and decidua (the endometrium of the preg uterus)
31
One pole of the buried blastocyst extends towards the endometrial cavity and is covered by
Chorion frondosum and deciduas capsularis
32
The innermost pole ultimately forms the
Placenta
33
Contiguous with maternal decidua (and later maternal blood)
Syncytiotrophoblast
34
Outer layer
Syncytiotrophoblast
35
Syncytiotrophoblast has no individual cells instead it had an
Amorphous cytoplasm
| without cell borders, and nuclei that are multiple and diverse
36
Innermost layer (embryonic side)
Cytotrophoblast
37
Cells nearest the intervillous space; well-demarcated cell border and a single nucleus
Cytotrophoblast
38
After implantation is complete, trophoblast further differentiates into:
- Villous trophoblasts
- Extravillous trophoblasts
• Interstitial
• Endovascular
39
Give rise to chorionic villi which transport oxygen and nutrients between fetus and mother
Villous trophoblasts
40
Invades deciduas and penetrates myometrium to form placental bed giant cells
Interstitial trophoblasts
41
Surrounds spiral arteries and prepare these vessels for endovascular trophoblast invasion
Interstitial trophoblasts
42
Surrounds spiral arteries and prepare these vessels for endovascular trophoblast invasion
Interstitial trophoblasts
43
Penetrates lumen of spiral arteries by intially forming cellular plugs then destroying vascular endothelium via an apoptosis mechanism then invading vascular media
Endovascular trophoblasts
44
Trophoblasts only invade
Spiral arteries
NOT VEINS
45
Endovascular invasion proceeds into 2 waves/stages
First wave (BEFORE 12 WKS POSTFERTILIZATION)
Second wave (BETWEEN 12 AND 16 WEEKS)
46
Consists of invasion and modification of spiral arteries up to the border between decidua and myometrium
First wave
47
Involves invasion of intramyometrial segments of spiral arteries
Second wave
48
Endovascular invasion of trophoblasts converts narrow-lumen muscular spiral into
Dilated, low resistance uteroplacental vessels (also important in pathogenesis of pre eclampsia and fetal growth restriction
49
Invades most superficial portion of endometrium, spiral arteries and arterioles are invaded and destroyed
Cytotrophoblasts
50
As endometrial invasion proceeds, maternal BV are trapped to form
Lacunae (lakes) - which soon fill w maternal bld
51
Invades the endometrium and become surrounded by lacunae
Irregular protrusions of syncytiotrophoblast
52
Finger-like extensions of the cytotrophoblast grow into these protrusions forming structures called
Primary placental villi
53
Distinguished on about 12th day after fertilization
Chorionic villi
54
When the solid trophoblastic column is invaded by a mesenchymal core, these are formed
Secondary villi
55
After angiogenesis occurs in situ from mesenchymal core, the villi are
Tertiary
56
Maternal arterial blood enters the intervillous space by day
14 or 15 postfertilization
57
Fetal and maternal BV of the embryo are fxnal and placental circulation is est
By about 17th day
58
The feto-placental circ is completed when BV of embryo are connected w the chorionic vessels wc are formed in situ from
cytotrophoblasts
59
Chorionic plate
Roof of intervillous spaces
60
Basal plate
Floor of intervillous spaces
61
Are villi of the chorion frondosum extending from the chorionic plate to the deciduas
Anchoring villi
62
most villi arbores and end freely in the
intervillous spaces
63
supplied w a chorionic artery and vein
cotyledon
64
consist of decidual tissue w trophoblasts and are of fetal and maternal origin
placental septa
65
through the 2 umbilical arteries, then into the capillaries of the villi and finally back thru a single umbilical vein into the fetus
fetal blood flow
66
branches of the umbilical vessels that traverses along the surface of the placenta
placental surface or chorionic vessels
67
Chorionic ___ always cross over chorionic _____
Chorionic artery always cross over chorionic veins
68
what are perforating branches of the surface arteries that pass thru the chorionic plate
truncal arteries
69
placental circulation
intervillous spaces --> chorionic plate --> basal plate --> uterine veins --> placenta
70
maternal blood enters intervillous spaces in spurts propelled by
maternal blood pressure
71
this force blood in discrete streams towards the chorionic plate until the head of pressure is
reduced then lateral spread then occurs
72
arterial bld exits basal plate and drains thru
uterine veins
73
TO the uterine wall, what are the arteries and veins
arteries are perpendicular to uterine wall
| veins are parallel to uterine wall
74
6 components of placental barrier lying between the maternal and fetal circulations are:
1. syncytiotrophoblasts
2. cytotrophoblast
3. trophoblastic basement membrane
4. fetal loose CT
5. endothelium of fetal capillaries
6. its surrounding basement membrane
75
at full term, the cytotrophoblast is represented only as
fragments (hence the placental barriers consists only 5 fetal compo)
76
early months of pregnancy, placental mem is still
thick and not fully dev
therefore, permeability is low
surface area is slight
77
later pregnancy
increase permeability
thinning mem
SA expands
increase placental diffusion
78
dissolved O2 in bld of large maternal sinuses passes into fetal bld by
simple diffusion, driven by an O2 pressure gradient
79
3 reasons why fetus is able to obtain sufficient O2 to maternal blood
1. HbF carry more O2 (20-50%)
2. Hb conc of fetal is 50% greater than mom's (enhancing the amount of O2 transported to fetal tissues)
3. Bohr effect (Hb can carry more oxygen at a low pCO2 than it can at a high pCO2)
80
loss CO2 makes FETAL blood
more alkaline
81
increased CO2 in MATERNAL blood makes it:
more acidic
82
diffusion of CO2
thru simple diffusion
83
diffusion of food stuff
thru facilitated diffusion
84
before 5 weeks, HCG is produced in
both syncytio and cytotrophoblasts
85
later, whne maternal serum is at its peak
HCG prod in syncytiotrophoblast onlee hehehehehekapoyaperolabanlaaaaaaang
86
HCG detected in plasma of preggy
7-9 dayz (after the midcycle surge of LH that precedes ovulation
87
HCG maximal lvls attained at abt 8-10 weeks
(peak 100,000 mIU/mL between 60th and 80th days after menses)
88
levels begin to decline by
10-12 wks and nadir by 16 wks
89
if corpus luteum is removed before approx 7th week of preg (sometimes 12th wk)
spontaneous abortion
90
the corpus luteum involutes slowly after
13th-17th week
91
has GH-like bioactivity; demonstrable in placenta within 5-10 days after conception in maternal serum as early as 3 wks after fertilization
HPLactogen or HCS
92
It is demonstrated in cytotrophoblasts and later concnted in syncytiotrophoblast
Before 6 weeks
93
Rate of secretion is proportional to placental mass
Therefore lvls rise steadily until 34-36 weeks
94
HPL actions
1. Lipolysis
2. Anti insulin
3. Potent angiogenic hormone
95
Demonstrated in CL, decidua and placenta
Relaxin
96
Rise jn maternal circulating relaxin
Early pregnancy
97
May act on myometrium to promote relaxation and quiescence of early pregnancy
Relaxin
98
Enhancement of GFR
Relaxin
99
Large amnts secreted by syncytiotrophoblast during pregnancy
Estrogen
100
Serve as estrogen precursors
C19 steroids (DHEA-S dehydroepiadrosterone and its sulfate)
101
Quantitatively the most important source of placental estrogen precursors in preg
Fetal adrenal gland
102
Effects of estrogen
1 enlarge maternal uterus, breast and ductal structures, external genitalia
2 relax the pelvic ligaments (prep for delivery)
3 may affect fetal dev (rate of cell reprod in early embryo)
103
Principal precursor of progesterone biosynthesis
Maternal plasma CHOL
104
Progesterone effects
1 causes decidual cells to develop (embryo nutrition)
2 decrease uterus contractility
3 dev and conceptus even b4 implantation by increasing secretions of fallopian tubes and uterus to provide appropriate nutritive matter for developing morula and blastocyst
4 helps estrogen prepare mom'$ breasts for lactation
105
By _______, amniotic fluid consists largely of extracellular fluid that diffuses thru fetal skin and thus reflects compo of fetal plasma
2nd trimester
106
After _____, composed largely of fetal urine ew ans smol proportion of pulmonary fluid
20wwwks
107
Volume increases from 10mL/week at 8 weeks to
60mL/week at 21 weeks ans peaks at 34 weeks
