Lecture 15: Fertilization and Implantation Flashcards
(201 cards)
1
Q
How many cells in the human body?
A
10 trillion
2
Q
How many different types of cells in the human body?
A
250
3
Q
What do we call cells that can continually renew tissues?
A
Stem cells
4
Q
What are the 4 types of stem cells?
A
- Skin 2. Intestinal 3. Bone marrow 4. Neuronal
5
Q
3 other names for fertilization?
A
Syngamy, fecundation and conception
6
Q
Where does normal fertilization happen within the fallopian tube?
A
The ampulla region
7
Q
What are fallopian tubes called in mammals other than humans?
A
Oviducts
8
Q
What is active-forward motility?
A
The way the sperm approaches the egg and then moves from the corona radiata to the zona pellicuda
9
Q
Describe the stages from sperm coming in contact with corona radiata to entry into ovum (7 steps).
A
- Release hyaluronidase by breaking down the plasma membrane of sperm to break down the hyaluronate covering the corona radiata cells: corona radiata breaks down and granulosa cells disperse
- Acrosome reaction: zona pellucida induces acrosome membrane of the sperm to break to release acrosin to break down the zona pellicuda: acrosin breaks down ZP1, ZP2, and ZP3 creating a channel through which the sperm can move via active-forward motility
- Sperm fuses to plasma membrane by its tip and then its side
- Fused sperm triggers intracellular Ca2+ wave and oscillations
- Cortical/Zona reaction: egg is activated which causes the cortical granules to release their contents through exocytosis into the perivitelline space
- Contents of cortical granules (1) inactivate ZP3 so it can’t bind to sperm membrane, (2) partially cleave ZP2 which hardens the zona pellicuda so that sperm cannot penetrate = block to polyspermy, and (3) activate PKC and CamKII enzymes that trigger the egg to resume meiosis
- Sperm injects its nucleus, tail, and other organelles into the egg’s cytoplasm, sperm plasma membrane is left behind
- Sperm nucleus decondenses and forms the male pronucleus and sperm tail degenerates
10
Q
What is the difference between totipotent and pluripotent cells?
A
Totipotent: cells can become all types of cells in the human body + cells of the placenta Pluripotent: cells can become all types of cells in the human body (but not the placenta cells)
11
Q
What are the 4 cell stages that are totipotent entirely?
A
- 2 cell stage 2. 4 cell stage 3. 8 cell stage 4. Morula
12
Q
Explain the formation of the blastocyst
A
Fluid filled cavity begins to form due to the blastomeres cells spreading out over each other to prevent fluid from exiting between cells
13
Q
How many sperm reach the ovum?
A
Thousands
14
Q
How are corona radiata cells held together?
A
Connective tissue of hyaluronic acid
15
Q
What is the zona pellicuda composed of?
A
3 glycoproteins: ZP1, ZP2, and ZP3
16
Q
What do the enzymes released by the sperm after attaching to the ovum precisely break down?
A
Extracellular adhesion molecules between the cells, not the actual cells
17
Q
How do the microvilli on the ovum plasma membrane contribute to fertilization?
A
They ensure the sperm is held firmly in place on the plasma membrane
18
Q
What are the 2 steps in fertilization that provide a block to polyspermy?
A
Contents of cortical granules inactivate ZP3 so it can’t bind to sperm membrane + cleave ZP2 which hardens the zona pellicuda so that sperm cannot penetrate
19
Q
What happens inside the ovum right when the sperm enters? What does this create?
A
Meiosis resumes at metaphase 2: Kinases (PKC and CamKII) activate other proteins to:
- PKC: pull chromosomes apart on the spindle
- CamKII: half the chromosomes deposited into the second polar body (life not possible without it) and half will form the female pronucleus
Creating the mature oocyte = ovum
20
Q
Describe restoration of the diploid state following fertilization. When does this occur?
A
Occurs 6-10 hours post fertilization
- Both the hapoloid male and female pronuclei double their DNA
- The haploid female and male pronuclei come very close next to each other
- The pronuclei’s nuclear membranes dissolve, allowing their chromosomes to mix
- The spindle forms
- Microtubules line up chromosomes on the metaphase plate
- Cytokinesis (24 hours post-fertlization)
21
Q
What are the 8 developmental transitions?
A
- Fertilization 2. Induction of the zygotic genome 3. Morula formation 4. Blastocyst formation 5. Implantation 6. Gastrulation 7. Neuralation 8. Organogenesis
22
Q
What happens during the induction of the zygotic genome
A
Maternal genes begin to turn off and embryo genes begin to turn on
23
Q
What is the first embryo stage where there are 2 different cells types? What are they?
A
Blastocyst: intracellular mass (ICM) and trophectoderm
24
Q
When does organogenesis start?
A
8-9 weeks after fertilization
25
Describe blastocyst formation (3 steps). When does this happen?
4 days post-fertilization
1. Outer cells differentiate into trophectoderm and start expressing Na+/L+ ATPase pumps to set up an osmotic gradient for water to flow into the interstitial space (following Na+ out of the cells) to reach equilibrium
2. Cell junctions provide structural integrity and prevent water from escaping which allows for bastocoel formation
3. Fluid builds up and and pushes inner cell mass to one side (4.5 days post-fertilization)
26
What are the 3 types of cell junctions created by the blastomeres?
1. Occludens (tight) 2. Adherens (intermediate) 3. Desmosomes
27
When does the fluid filled cavity start to form?
4 days post fertilization
28
When does the bastocyst hatch out of the zona pellucida?
4.5-5 days post fertilization
29
When does embryonic implantation occur?
5-9 days post fertilization
30
What is the ratio of ions pumped by the Na+/K+ ATPase?
3 Na+ out/2 K+ in
31
What type of cells attach to the endometrial epithelium?
Trophectoderm at the embryonic pole
32
What type of epithelium is the endometrial epithelium?
Simple: 1 layer
33
How do the cells of the trophectoderm attach to the endometrial epithelium? 2 mechanisms
1. Selectins loosely attach to receptors on mucosa cells
2. Integrins strongly attach
34
Describe the steps of the Na+/K+ ATPase
1. 3 Na+ bind to protein channel 2. ATP provides energy to move them against gradient 3. Pi is left bound which causes the channel to change shape 4. 3 Na+ released 5. 2 K+ bind 6. Pi released and channel returns to prior shape 7. 2 K+ released in cell
35
List the 2 differentiations of the inner cell mass cells in the stroma.
1. Columnar cells = epiblast
2. Cuboidal cells = hypoblast
36
What happens to the trophoblast cells once they reach the uterine stroma?
They differentiate into syncytiotrophoblast (=syncytial trophoblast) and cytotrophoblast (=cellular trophoblast)
37
What types of cells make up the embryonic portion of the placenta?
1. Syncytiotrophoblast
2. Cytotrophoblast
38
Draw the embryonic tissues fate map
39
What is another name for the epiblast?
Primitive ectoderm
40
What is another name for the hypoblast?
Primitive endoderm
41
What do the epiblast cells form upon implantation?
The amniotic cavity by giving rising to amnioblasts: think layer of primary ectoderm cells
42
What do the hypoblast cells form upon implantation?
Heuser's membrane around the primitive yolk sac: they grow along the cytotrophoblast (along the "old" blastocyst cavity) and become squamous in this process
Heuser's membrane = primitive endoderm + the ECM it secretes.
43
What do the syncitiotrophoblast cells form upon implantation? How? Where is it?
It surrounds the embryo entirely and forms trophoblastic lacuna (fluid filled cavities)
44
What happens to the trophoblastic lacunae at days 8-12?
Syncytiotrophoblast produces digestive enzymes that eat away at arteriole and veniole capillaries which fills up the lacunae with maternal blood
45
When, where and how does the extraembryonic reticulum form?
Embryonic implantation day 8-12
Between Heuser's membrane and cytotrophoblasts
The Heuser's membrane cells (hypoblasts) secrete a gellatenous material: ECM
46
What proteins in the extraembryonic reticulum?
Fibernectins, laminins
47
What happens to the epiblast after formation of the embryonic reticulum? How does this affect the embryonic reticulum? What day does this happen on?
It proliferates to form the extraembryonic mesoderm and completely surronds Heuser's membrane, which can no longer secrete the gellatenous substance in the embryonic reticulum, so it begins to break down and fluid cavities start forming in it and eventually it disappears
Day 12
48
When does the embryonic reticulum disappear?
Day 12-13
49
What happens to the extraembryionic reticulum once it disappears?
It becomes the chorionic cavity
50
Where is the embryo housed at days 12-13?
The chorionic cavity
51
What forms the yolk sac? What type?
The hypoblast: primary yolk sac
52
What happens to the primary yolk sac? When?
The inner layer of extraembryonic mesoderm pinches inward to form an 8-like structure that divides the primary yolk sac and pushes it to the Ebb embryonic pole in exocoelomic vesicles
Days 12-13
53
How is the secondary yolk sac formed?
The cavity that forms closest to the embryonic yolk sac is the secondary yolk sac
54
Where do the first embryonic blood vesseld form?
The secondary yolk sac: cytotrophoblast villi penetrated by extraembryonic mesoderm
55
From what is the extraembryonic mesoderm formed? When?
From the epiblast
Day 8-12
56
How does the syncytiotrophoblast form?
Once the trophoblast cells enter the stroma they proliferate and loose their membrane resulting in a confluent cytoplasm with many nuclei scattered throughout: the syncytiotrophoblast
57
Implantation of a blastocyst stage embryo first occurs between what two cell types?
Trophectoderm and mother's uterine epithelium
58
The chorionic cavity is lined by what type of tissue?
Extraembryonic mesoderm
59
What are the 2 types of skin stem cells? What does each regenerate?
1. Basal layer: regenerates a layer of skin that lacks any other structures of the epidermis
2. Hair follicle: regenerates sweat glands, sebaceous glands, hair follicles, etc.
60
What do the intestinal stem cells regenerate?
Villi/microvilli
61
How frequently is an entire body regenerated?
Every 7-10 years
62
What is the ultimate stem cell?
The one cell fertilized embryo
63
What 2 steps happen with the egg prior to fertilization?
1. Ovulation: once a month one of the follicles of the ovary matures and is released from the ovary as a secondary oocyte
2. Upon release, it makes its way to the fallopian tube
64
What type of cells make up the corona radiata?
Granulosa cells
65
What connects the zona pellicuda with the granulosa cells of the corona radiata? What is the purpose of these?
Gap junctions to facilitate communication between egg and corona radiata
66
What is the perivitelline space?
The space between the plasma membrane and the zona pellucida
67
In what stage of meiosis is the secondary oocyte?
Metaphase II
68
What are the 3 regions of the uterus?
1. Corpus: body
2. Fundus: portion above the oviduct entry point
3. Cervix: narrow portion below corpus that opens into the vagina
69
What is in between the vagina and the cervix?
The uterine ostium
70
What are the 3 wall layers of the uterus (from inner to outer)?
1. Endometrium
2. Myometrium (muscular layer)
3. Perimetrium (only a few cell layers thick)
71
What are the 3 layers of the endometrium during the secretory phase (from inner to outer)?
1. Basal layer
2. Spongy layer
3. Compact layer
72
What is special about the basal layer of the endometrium?
It has its own blood supply and isn't sloughed off during menstruation
73
How many of the thousands of sperm approaching the ovum in the ampulla actually come in contact with the corona radiata?
Hundreds
74
What is the exact adhesion mechanism between the sperm and the ovum's plasma membrane?
Still unknown, but here is what we know:
* Sperm's membrane protein fertilin: alpha/beta subunits that are glycosylated and attached noncovalently (they can move apart)
* Integrins on the ovum's membrane (look a lot like fertilin)
THEY BIND and pulls them together allowing MEMBRANES TO FUSE!
75
What is the purpose of blocked polyspermy?
Secures the zygote's diploid phenotype
76
Can you discern the female and male pronuclei right after fertlization?
NOPE
77
What is a blastomere?
Each cell of the 2-cell embryo
78
When does the 4-cell stage occur?
26 hrs post-fertilization
79
When does the 8-cell stage occur?
48 hrs post-fertilization
80
When does the early morula occur? How many cells?
72 hrs post-fertilization
8-12 cells
81
Describe compaction. When does this happen?
Blastomeres use adhesion to flatten onto one another: 1 inside cell and outside cells which is important for differentiation because of the difference in environments 3.5 days post fertilization at the morula stage
82
Describe cell growth from fertilized zygote to morula. How is this made possible?
No cell growth so division forms smaller and smaller blastomeres
83
What happens to the polar bodies from fertilization to morula?
They disentegrate
84
What is a chimeric mouse?
A mouse with blastomeres from two different mice (had to be separated before the morula stage)
85
What is the fate of the 2 cell types produced through compaction?
1. Outside: trophoblast: placenta
2. Inside: pluripotent cells: inner cell mass: embryo
86
What are the 2 poles of the trophectoderm?
1. Embryonic (where the ICM is)
2. Ebb embryonic pole (opposite pole)
87
How does the blastocyst invade the endometrium? When does this happen?
7 days post-fertilization
1. Trophoblast cells secrete matrix metallopeptidases (MMPs) that digest cell-cell junctions of the endometrial epithelium
2. MMP 2 and 9 break down epithelial cells and underlying basement membrane
88
Where and how does the endometrial stroma differentiate? What do these new cells secrete and why?
The endometrial stroma near the implanted embryo differentiaes into decidual cells (decidua basalis and decidua capsularis) under the influence of progesterone
Decidual cells secrete proteins (eg: prolactin) and growth factors to support embryonic growth
89
What does the inner cell mass differentiate into after the invasion of the blastocyst? 2 parts
1. Epiblast
2. Hypoblast: flattened cell layer facing into the blastocoel
90
What kind of cells is the epiblast made of?
Columnar
91
What kind of cells is the hypoblast made of?
Cuboidal cells
92
What is the name of the phase when the embryo is completely implanted into the mother's decidual tissue?
Gravid Phase
93
What constitutes the initial establishent of the uteral-placenta circulation?
The trophoblastic lacunae filling up with mom's blood
94
Where is the bilaminar disk at days 14-15? How is it attached?
Suspended in the chorionic cavity and attached to the extraembryonic mesoderm by the connecting stalk
95
Describe the early follicular phase of the menstrul cycle (3 steps). What does uterus phase does this correspond to?
1. FSH stimulates development of 10-20 preantral follicles = primary follicles = **RECRUITMENT**
2. One of the follicles (the one receiving the most FSH b/c closest to blood supply, but sometimes too) is selected to become the dominant secondary follicle
3. Day 7: follicle secretes estrogen, which exerts (-) feedback on FSH secretion and enduces the proliferation of endometrial cells
**MENSUS PHASE**
96
Describe the mid-follicular phase (4 steps). What uterus phase does this correspond to?
1. Estrogen levels reach and stay at 150 pg/mL (10-12g/mL) for ~36 hrs
2. Estrogen (+) feedback, **large LH surge** and slight FSH surge
3. LH stimulates ovulation and the follicle to secrete progesterone
4. Progesterone induces ovulation by stimulating collagenolytic enzymes that weaken the wall of the secondary follicle cause rupture and release of ovum
**PROLIFERATIVE PHASE**
97
How do the rising estrogen and progesteron levels affect the woman's temperature during the menstrual cycle? What phase does this correspond to?
Increase in temp!
## Footnote
**Mid-follicular phase = proliferative phase**
98
Describe the luteal phase (4 steps). What uterus phase does this correspond to?
1. Remaining follicular remnant becomes corpus luteum
2. Corpus luteum takes over secreting estrogen and progesterone
3. High progesterone levels inhibit FSH and any new follicular development
4. 2 scenarios depending on whether fertilization happens
**SECRETORY PHASE**
99
What cells of the corpus luteum secrete estrogen? Progesterone?
Theca lutein cells: estrogen
Granulosa lutein cells: progesterone
100
Describe what happens during the luteal phase of the menstrual cycle if fertilization does not takes place.
1. Corpus luteum degenerates (12 days after ovulation)
2. Decrease of estrogen and progesterone lead to mensus and no more (-) feedback on pituitary so FSH increases
3. New round of follicle stimulation in the ovary
101
Describe what happens during the luteal phase of the menstrual cycle if fertilization takes place.
1. Mensus inhibited
2. Trophectoderm secretes placental hCG, which replaces LH (binds to same receptors) **and rescues corpus luteum**
3. Corpus luteum continues to supply progesterone to the placenta
102
What kind of cells secrete hCG?
Syncitiotrophoblasts
103
What is the role of gonadotropin releasing hormone (GnRH)? What secretes it?
Secreted by the hypothalamus and stimulates the **anterior** pituitary gland to release FSH and LH
104
How does Ru486 manipulate fertilization? When is it used?
It's a competitive antagonist to the progesterone receptors on the uterus (it binds but does not activate) so the uterus behaves as if no progesterone is present causing the mensus
Used if plan B is not used or unsuccessful **IF OVULATION HAS ALREADY OCCURED**
105
How does levonorgestrel manipulate fertilization? Describe both types of prescriptions.
Synthetic progestin that prevents ovulation:
1. 2 mg daily: general prevention
2. 10 mg dose: day after pill that blocks ovulation **if it hasn't already happened**
106
What does the extraembryonic mesoderm line?
1. Amnion
2. Chorion
3. Yolk sac
107
How many sperm swimming up female reproductive tract?
250 million
108
For how long can the oocyte be stuck in metaphase II before it looses its integrity?
5-7 days
109
What allows the formation of the male and female pronuclei?
Ca2+
110
What are 2 different theories regarding where the Ca2+ wave comes from?
1. Sperm releases the Ca2+
2. Vacuolar tubes close to the membrane of the egg that release the Ca2+
111
What does the Ca2+ wave look like?
First initiated and then bounces on all sides of the cell (see with calcium dyes that fluoresce)
112
What does the primary oocyte divide into?
1 egg + 3 polar bodies (just a place for the chromosomes to go into) because the division of the egg is not done equally
113
What stage is the endometrium in when the blastocyst implants?
Luteal
114
What is another name for Ru486?
Mifepristone
115
Is it bad if the blastocyst implants on the Ebb embryonic pole?
NOPE
116
Why do ectopic pregnancies pose a risk for the mother?
Because the embryo employs maternal blood vessels to provide nutrients which are not designed to support an embryo like the endometrium is and can rupture leading to internal bleeding and death
117
What is another name for luteal phase of endometrium?
Progestational phase
118
What is another name for the ICM?
Embryoblast
119
How often does pre-eclampsia occur?
5% of all pregnancies
120
How does the amniotic cavity form?
Na+/L+ ATPase pumps on the epiblast
121
Where do ectopic pregnancies occur? 7 spots
1. Ovarian
2. Fimbrial (right outside the ovary)
3. Ampullary
4. Isthmic (at the beginning of the oviduct)
5. Interstitial (above fundus)
6. Cervical
7. Abdominal (intestinal or rectal)
122
Should mom and embryo blood ever mix?
NOPE
123
What causes pre-eclampsia?
Genetic predisposition and shallow implantation of embryo:
1. Flt-1 (on endothelial cells): Vascular endothelial growth factor (Also in blood as sFlt-1): VEGF receptor
2. Placental growth factor (PLGF): binds to Flt-1 to enhance blood vessel growth and only made during pregnancy (**during 3rd trimester**)
⇒5 week before disease: sFlt-1 rose and PLGF dropped: sFlt-1 in bloodstream hijacks PLGF leading to deterioration of blood vessels in placenta (and liver, kidneys)
124
What are normal implantation sites?
Lateral sides of uterus (but top wall is fine too)
125
What is the effect of pre-eclampsia on the fetus?
Premature birth
126
What are the 7 abonormal ectopic implantation sites? Provide their relative frequencies.
1. Ampulla: 54%
2. Isthmus: 25%
3. Fimbria: 17%
4. Interstitial space: 2%
5. Abdomen: 1.2% (intestine or rectum)
6. Ovary: 0.5%
7. Cervix: 0.3%
127
What is the 2 treatments for pre-eclampsia?
Future treatment: flood mother with PLGF (phase 1 and 2 trials)
Present treatment: early detection to delay premature birth (delivery when appropriate) and parenteral magnesium to prevent convulsions (during labor, delivery, and post-partum)
128
What happens if you do not get rid of hydatiform moles?
Mother will die
129
What is a hydatiform mole made of?
No fetus, only placental membranes = hidatis-cyst or cyst-like, mole fleshy growth
130
Describe morula formation (2 steps)
1. 12 to 16 rounded blastomeres begin to expression adhesion junction proteins
2. Adhesion proteins used by blastomeres to flatten on top of each other: inner and outer environments
131
Are the trophectoderm cells pluripotent or totipotent?
Totipotent
132
Are the ICM cells pluripotent or totipotent?
Pluripotent
133
What is often the needed treatment for ectopic pregnancies? What about if the implantation happens in the fallopian tube?
Surgical removal
May need to remove fallopian tube too
134
What are the 2 symptoms of ectopic pregnancies?
1. Vaginal bleeding
2. Abdominal pain
135
What % of serious pregnancy complications are pre-eclampsia?
20%
136
What is another name for ectopic pregancy?
Tubal pregnancy
137
What are the 3 risk factors for pre-eclampsia?
1. First pregnancy
2. Overweight
3. IVF w/ donor egg
138
What are the 6 symptoms of pre-eclampsia in pregnant women?
1. Hypertension
2. Proteinuria
3. Liver inflammation
4. Edema
5. Platelet depletion
6. Brain swelling, convulsions and possible coma (severe cases) **= ECLAMPSIA**
139
What is another name for ampulla region of fallopian tube?
Bulge
140
What is a hydatiform mole?
Placental membranes (no fetus) that form a hydatis-cyst or mole-fleshy growth
141
What is the incidence of hydatiform moles?
0.1-0.5% of pregnancies
142
For what women are hydatiform moles more common?
Women under the age of 25
143
What does it mean for a hydatiform mole to be complete?
The placental membrane remains in the uterus without the fetus
144
What is the cause of complete hydatiform moles? 2 different types
Fertilization of an egg lacking a female pronucleus ⇒ embryo cannot develop properly because paternal and female genomes are regulated differently even though they contain virtually identical chromosomes
1. Monospermic fertilization: sperm enters second polar body instead of female pronucleus and duplicates its own genome (XX zygote)
2. Dispermermic fertilization: two sperm fertilize the polar body and mix their genetic material (XX or XY zygote)
145
What are 4 symptoms of hydatiform mole?
1. Vaginal bleeding
2. Hypertension
3. Edema
4. High levels of hCG
146
How can one identify hydatiform moles?
Cytogenetic analysis: the study of chromosomes and their abnormalities
147
What usually happens to complete hydatiform moles?
They abort by week 10 (remanants may remain)
148
What happens if there is residual trophoblastic tissue in the uterus?
It'll cause persistent trophoblastic disease which may develop into a tumor, which could be malignant
149
What is the cause of incomplete hydatiform mole? How many chromosomes?
Triploid karyotype (2 paternal and 1 maternal) which can elevate their embryonic development beyond that of complete hydatiform moles (XXX, XXY, XYY).
69 chromosomes
150
How have the mortality rates due to hydatiform moles changed since 1980? Why?
1. Invasive: used to be 60%, now 0%
2. Choriocarcinoma: used to be 100%, now 20%
Because:
1. Highly sensitive assays for plasma hCG
2. Cytogenetics to identify chromosomes within the trophoblast
3. New chemotherapies
151
What usually happens to incomplete hydatiform moles?
They usually abort in the second trimester and some rare fetuses survive
152
What are the 6 symptoms of Prader-Willi syndrome?
1. CNS malformations
2. Impaired body control
3. Mental retardation
4. Short stature
5. Insatiable appetite (starting at 2-5 trs and leading to obesity)
6. Behavioral difficulties (temper tantrums and stubborness)
153
What is the incidence of Prader-Willi syndrome?
1:15,000 births
154
What are the 4 symptoms of Angelman's syndrome?
1. Developmental delay
2. Little/no language skills
3. Movement/balance disorders
4. Happy demenor
155
What is the incidence of Angelman's syndrome?
1:15,000 births
156
What do PWS and Angelman's syndromes result from?
Chromosome deletion at 15q11-q13
* PWS: paternal deletion (genes 1 and 3 are not methylated): genes 1 and 3 not expressed
* Angelman's: maternal deletion (genes 2 and 4 are not methylated): genes 2 and 4 not expressed
157
What is genomic imprinting?
The ability to mark a gene as coming from either the fatger or mother
158
What is the role of methylation during gametogenesis?
It regulates paternal and maternal genes differently
159
What is an example of the gene regulation via methylation?
Epsylon-globin gene is active at 6 weeks due to an unmethylated promoter while gamma-globin is inactive due to a methylated promoter. At 12 weeks that switches.
160
Describe the formation of the amniotic cavity and its membrane
**1.** Na+K+ ATPase pumps located on the basolateral membranes of primary ectoderm (epiblast) drive 3 sodium into intercellular spaces and 2K**+** in the cell. Water follows to intercellular spaces to balance out the high salt gradient. The result is expansion of the amniotic cavity. The fluid becomes Amniotic fluid
## Footnote
**2**. Amnioblasts: Thin layer of primary ectoderm that separate the cavity from the cytotrophoblast cells
**3**. Amniotic membrane: thin layer of amnioblasts
161
What is gestational diabetes due to?
**Excess somatomammotropin = human placental lactogen (HPL) leads to maternal hyperglycemia**
Somato decreases maternal insulin sensitivity and decreases maternal glucose utilization (to ensure fetal nutrition), which in turn raises maternal blood glucose levels.
162
What are symptoms of gestational diabetes? What do these resemble?
1. Weight gain
2. Excessive hunger/thirst
3. Frequent urination
4. Recurrent vaginal infections
Resemble Type 2 diabetes symptoms
163
What are the risk factors of gestational diabetes?
1. Pre-diabetic mother
2. Overweight mother
164
What is the treatment for gestational diabetes? Why is this dangerous?
Insulin (sometimes 2-3x the amount given to a non-pregnant patient)
Dangerous because can lead to hypoglycemia and diabetic coma
165
What initial test should be done when gestational diabetes is suspected?
Hyperglycemia blood glucose test
166
How does gestational diabetes affect the fetus?
High glucose in mother will enter the fetus bloodstream and child may develop macrosomia = kid becomes fat and may become diabetic because pancreas is heavily taxed to deal with the high level of blood glucose
167
How is the calcium wave in other animals?
Unidirectional
168
Where does meiosis 1 occur?
In the ovaries
169
Where does the third polar body come from?
From the first polar body
170
What happens to the second polar body? When?
It's released after fertilization
171
Do the membranes of the female and male pronuclei fuse in humans?
NOPE
172
What phase of meiosis is it called when chromosomes are pulled apart?
Telophase
173
What is another name for the dominant follicle?
Graafian follicle
174
What kind of enzyme is hyaluronidase?
Hydrolytic enzyme
175
What are the fimbria of the uterus?
The end of the fallopian tubes that kinda look like fingers
176
What is formation of the second polar body subject to?
Biological variation: could be 1-2% the size of the egg or less than 1%
Can even continue to divide to form up to 12 additional polar bodies
177
Which pronuclei larger: female or male?
Female
178
What can circumvention of male infertility by ICSI bypass?
1. Passage of sperm through corona radiata
2. Penetration of zona pelucida
3. Fusion of oocyte and sperm plasma membranes
4. Exclusion of sperm membrane from cytoplasm
179
What allows the blastocyst to grow in size?
Zona pellucida degeneration
180
How does the blastocyst obtain nutrients prior to implantation?
Uterine glands
181
What can spontaneously happen to ectopic pregnancies that are not treated? Why?
Spontaneous abortions due to chromosal and developmental abnormalities that would have resulted in congenitally malformed babies
182
What is a preantral follicle?
Follicles being stimulated by FSH in the ovary prior to ovulation
183
What causes the - feedback of estrogen to become +?
The number of pituitary estrogen receptors occupied by estrogen
184
Other than progesterone, what also indirectly influence the uterine preparation for pregnancy?
FSH, LH, and estrogem
185
Until when does the corpus luteum secrete progesterone for the uterus? What secretes it after that?
Until middle of first trimester
Chorion secretes it after that
186
What is the purpose of the extraembryonic reticulum?
Provide space for formation of extraembryonic mesoderm
187
What is the extraembryonic mesoderm the major site of?
Hematopoesis
188
What is the purpose of the cells of the secondary/definitive yolk sac?
Help metabolize embryonic nutrients
189
What happens to the secondary yolk sac during pregnancy?
Disappears before birth
190
What is Meckel's diverticulum?
Anomaly of digestive track resulting from non-dissolution of definitive yolk sac
191
How does gene methylation occur?
DNA methyltransferase adds a methyl group onto a cytosine (usually next to guanine)
192
What are the 2 effects of the hydatiform mole on the mother?
1. Lack of fetal vasculature causes lack of fluid being taken up by maternal vasculature
2. Villi becone swollen and vesicular
193
What genetic diseases' severity depend on parent from whom the gene was inherited?
* Wilm's tumor
* Huntington's
* Spinocerebellar ataxia
* Myotonic dystrophy
* Neurofibromatoses
* PW
* Angelman's
194
What should the plasma hCG level be after hydatiform mole removal?
0!!!
195
When does gestational diabetes most commonly develop?
2nd trimester
196
What is the difference between an egg and an oocyte?
An egg can be fertilized, an oocyte cannot
197
Can one take morula stage blastomeres apart without killing them?
NOPE
198
When is an embryo considered a morula? What cell stage can this happen at?
An embryo is considered a morula when the blastomeres flatten onto each other. That can happen at early as the 8 cell stage.
199
When do we call an embryo a blastocyst?
When a blastocoelic cavity is visible.
200
What is the difference between the secondary oocyte and the egg?
Egg is fertilized and seconday oocyte might still be in the ovary
201
What is X chromosome inactivation? Purpose? How is this inactivation achieved? At what stage in embryo development does this happen? When do they go back to both being active?
Another example of the inequality of genetic expression during early development: one of the two X chromosomes in the cells of females is inactivated by extreme condensation. The purpose of X-chromosome inactivation is dosage compensation, or preservation of the cells from an excess of X-chromosomal gene products.
In the inactivated X chromosome, the XIST gene is unmethylated and expressed (producing a long uncoding RNA that wraps around the X chromosome), whereas in the active X chromosome, this gene is methylated and silent.
This happens when the inner cell mass differentiates into the epiblast and hypoblast: permanent in somatic cells and back to normal in germ cells after the first mitotic division
