Midterm 1 Lectures 1-8 Flashcards
1
Q
How is embryology research done?
A
- Model Organisms
- Stem Cells
- Organoids
2
Q
Embryonic stem cells are removed from ______ stage embryo and are ________
A
Embryonic stem cells are removed from blastocyst stage embryo and are pluripotent
3
Q
What are two groups of stem cells?
A
- Embryonic stem cells
- removed from blastocyst stage embryo
- Induced Pluripotent stem cells
- isolate adult somatic cells
- Revert back to stem cell stage with factors:
- Oct4
- Sox2
- Klf4
- c-Myc
4
Q
Label the male reproductive system
A
5
Q
Label the testis
A
6
Q
Sperm develop while surrounded by _______ cells within the ___________
A
Sperm develop while surrounded by sertoli cells within the seminiferous tubules
7
Q
Label the diagram of Spermatogenesis
A
8
Q
Spermatogenesis takes ~ _________. Sperm then mature in the ________ for _______ months
As a final step, sperm undergo _______ in the female Reproductive tract
A
Spermatogenesis takes ~ 2 months. Sperm then mature in the epididymis for 2-3 months
As a final step, sperm undergo capacitation in the female Reproductive tract
9
Q
Label the coronal section of the female reproductive tract
A
10
Q
Ovaries contain many ________ follicles; a handful of which begin to develop each menstrual cycle
A
Ovaries contain many primordial follicles; a handful of which begin to develop each menstrual cycle
11
Q
What makes up the primordial follicle?
A
The primary oocyte and a single layer of follicle cells
12
Q
Primary oocyte is arrested in which stage?
A
Prophase I of meiosis (2N, 4C)
13
Q
One of the first steps in follicular development is the formation of a tough glycoprotein layer between the oocyte and follicle cells called the __________
A
One of the first steps in follicular development is the formation of a tough glycoprotein layer between the oocyte and follicle cells called the zona pellucida
14
Q
What produces the zona pellucida?
A
Secretions from both the oocyte and the follicle cells
15
Q
As the follicle cells produce fluid they form the _______ within the follicle
A
As the follicle cells produce fluid they form the antrum within the follicle
16
Q
When does the oocyte complete meiosis I? What is extruded after this completion?
A
Once the follicle is mature and in response to the LH surge the oocyte completes meiosis I (1N, 2C) and extrudes the first polar body
17
Q
After meiosis I is complete, the oocyte starts ______ but is arrested in ______ until fertilization
A
After meiosis I is complete, the oocyte starts meiosis II but is arrested in metaphase II until fertilization
18
Q
When does ovulation occur?
A
Day 14; dependent on LH surge (rapid rise in estrogen) When the follicle ruptures, releasing the oocyte with its loose covering of follicle cells. It is quickly swept into the fallopian tube by the actions of the fimbriae at the end of the tube
19
Q
After ovulation and the release of the oocyte, what happens to the remainder of the follicle?
A
It collapses into folds and becomes the corpus luteum which secretes estrogen, progesterone and inhibin
20
Q
How is the the capsule of the mature (graafian) follicle form?
A
Follicle cells (aka granulosa cells) recruit surrounding connective tissue cells to form a capsule (theca cells)
21
Q
Label the theca cells, cumulus oophorus, corona radiata and granulosa cells
A
22
Q
Describe the major hormones at play at the following stages and what they elicit:
- Menstrual phase
- Proliferative phase
- Ovulation
- Secretory Phase
A
Describe the major hormones at play at the following stages and what they elicit:
- Menstrual phase
- Low progesterone levels induce shedding of the stratum functionalis
- Proliferative phase
- Increasing estrogen levels cause the functionalis layer to re-develop.
- Glands are straight or moderately coiled
- Ovulation
- LH surge ; rapid rise in estrogen
- Secretory Phase
- Progesterone levels maintain functionalis and cause glands to become highly coiled and secretory
23
Q
Menstrual Cycle:
Developing follicles secrete _____ which drives regrowth of the _______
A
Developing follicles secrete estrogen which drives regrowth of the endometrium
24
Q
Menstrual cycle
After ovulation, corpus luteum secretes _______ which promotes maturation of the ________ such as:
A
Menstrual cycle
After ovulation, corpus luteum secretes progesterone which promotes maturation of the endometrium such as: increased vascularization and development of glands
25
Menstrual cycle:
In the absence of pregnancy, the ________ stops secreting progesterone after about 14 days. Effect on endometrium?
Menstrual cycle:
In the absence of pregnancy, the _Corpus Luteum_ stops secreting progesterone after about 14 days
Blood vessels constrict in endometrium leading to ischemia and shedding
26
In response to GnRH the pituitary gland secretes:
LH and FSH
27
What is the effect of FSH in the ovary?
FSH promotes development of follicles (including estrogen secretion) by follicle cells
Acts on theca cells to convert androgens to estrogen
28
What are the 3 functions of LH?
* stimulates resumption of meiosis (completion of meiosis I : primary oocyte → secondary oocyte)
* Stimulates ovulation
* Promotes progesterone production by corpus luteum
LH acts on theca cells to synthesize androgens which then diffuse into granulosa cells where FSH promotes conversion from androgens to estrogen
29
IMAGE SLIDE 27
Describe hormone cycle throughout the menstrual cycle (FSH, estrogen, LH, Progesterone)
FSH and estrogen are elevated during the first half of the menstrual cycle
LH spikes just prior to ovulation in response to high estrogen
Progesterone is elevated in second half of the menstrual cycle
30
What are three challenges sperm face within the female reproductive tract
* acidic vagina
* immune cells in vagina and uterus
* travel through cervical mucus (more watery ovulation)
31
Granulosa cells are connected to the oocyte surface through \_\_\_\_\_\_\_\_\_
Granulosa cells are connected to the oocyte surface through _granulosa cell processes_ which allow for cell-cell communication
32
Granulosa cells are surrounded by \_\_\_\_\_\_\_\_\_\_\_
Granulosa cells are surrounded by _extracellular matrix (mostly hyaluronic acid)_
33
Sperm penetrates corona through \_\_\_\_\_\_\_\_
Sperm penetrates corona through _mechanical action of the flagellum and action of enzymes on surface of acrosome_
34
Sperm have receptors (\_\_\_\_\_\_\_\_) that bind to _________ which results in breakdown of acrosomal membrane (acrosomal reaction)
Sperm have receptors (_SPAM1 (sperm adhesion molecule 1 - hyaluronidase on sperm head)_ that bind to _a zona pellucida glycoprotein_ which results in breakdown of acrosomal membrane (acrosomal reaction)
35
Once receptors from the sperm bind to ligands on the zona pellucida glycoprotein, the acrosome releases ________ which digest through the zona pellucida and allows sperm to enter the \_\_\_\_\_\_\_
Once receptors from the sperm bind to ligands on the zona pellucida glycoprotein, the acrosome releases _hydrolytic enzymes (hyaluronidases)_
Enzymes digest path through ZP and sperm enters the _perivitelline space_
36
what happens after sperm enters the Perivetelline space?
sperm plasma membrane fuses with egg plasma membrane and becomes incorporated into egg PM
Contents of sperm enter cytoplasm of oocyte
Oocyte resumes meiosis and extrudes another polar body
A Mature ovum (ootid) only exists once fertilized
37
Zona Pellucida is composed of glycoproteins \_\_\_\_\_\_\_\_\_
These act as specific ligands and bind to receptors on the head of the sperm triggering the ________ (species specificity)
The acrosome bursts and releases _______ that degrade the Zona pellucida
Zona Pellucida is composed of glycoproteins _ZP1-4_
These act as specific ligands and bind to receptors on the head of the sperm triggering the _acrosomal reaction_ (species specificity)
The acrosome bursts and releases _enzymes_ that degrade the Zona pellucida
38
How does the zygote prevent polyspermy?
After fertilization zygote develops a ZP block and a plasma membrane block to sperm entry
* Increase in intracellular Ca++ concentration triggers changes in ZP and PM
* Triggers release of cortical granules into perivitelline space
* Juno (egg ligand) is released from cell surface after fertilization
39
Chromosomal abnormalities most commonly arise because of _________ during \_\_\_\_\_\_\_\_
Chromosomal abnormalities most commonly arise because of _nondisjunction_ during _gametogenesis_
40
What is monosomy?
Only one copy of chromosome
Autosomal monosomies usually not viable
XO can survive
41
What is trisomy?
Three copies of chromosome
Doesn't have to be complete (ie can be only a portion of the extra chromosome (translocation) or only some cells have 3 copies (mosaicism)
42
What is trisomy 21?
* cause of down syndrome
* Typically, two copies of chromosome 21 fail to separate during meiosis
* Normal gamete fuses with one containing non-disjoined chromosomes 21
43
When does the zygote have one nucleus?
At no point do we have a zygote w/ one nucleus
Maternal and Paternal nuclei swell - Pronuclei Replicating their dna
44
What happens during the cleavage stage?
Rapid cell division (blastomeres) wherein cells become smaller and smaller but embryo remains same size
45
What is the difference between Epithelial and Mesenchymal Cells?
Epithelial cells:
* Stable adhesions
* Polarized (apical/basal)
* Arranged in layers
* Basal lamina (layer of ECM - reinforcing/stabilizing layer)
Mesenchymal cells:
* transient adhesions
* mobile
* unpolarized
* no basal lamina
46
What is the first cell differentiation even in the new embryo?
At ~16 cell stage
Compaction occurs
External cells and internal cells adopt different fates
47
What makes up the blastocyst?
Blastocyst is made of a thin outer layer of cells - trophoblast which gives rise to embryonic part of placenta and the inner cell mass/embryoblast that becomes the embryo and a blastocystic cavity (blastocoel)
48
What is the trophoblast?
Thin outer layer of cells that gives rise to embryonic part of the placenta
Tropho = to feed
49
What is the embryoblast (inner cell mass)?
Portion of the blastocytes that gives rise to embryo
50
What makes up the blastocyst?
Blastocyst is made of a thin outer layer of cells - trophoblast which gives rise to embryonic part of placenta and the inner cell mass/embryoblast that becomes the embryo
51
# Define:
Totipotent
Pluripotent
Multipotent
# Define:
* Totipotent
* cells that can give rise to any embryonic or extra-embryonic tissue (placenta/membrane) – blastomeres prior to differentiation
* Pluripotent
* Cells that give rise to any body tissue
* Multipotent
* Cells that can give rise to multiple tissue types
52
What is Hatching of the blastocyst? Why is it important
Hatching is the loss of the zona pellucida
* Hatching allows for growth of the embryo and attachment to the endometrial epithelium — allows implantation
53
When does implantation occur?
~ 6 days after fertilization
Blastocyst attaches to endometrial epithelium with embryoblast facing the the epithelium
54
Summary of First week:
Mature follicle → ruptures and releases oocyte → oocyte enters infundibulum of fallopian tube due to sweeping of fimbrae → cilia sweep oocyte to ampulla - fertilization typically occurs in distal ampulla) → Zygote travels through fallopian tube undergoing cleavage (2-cell stage - 4 cell stage - 8 cell stage - Morula (8-16cell)) → Enters uterus as early blastocyst → late blastocyst implants in uterine endometrium ~ day 6
55
What is a hydatidiform mole?
If sperm fertilizes an oocyte that has lost its nucleus, the cell can grow into a grape like mass called the hydatidiform mole
56
How is the endometrium prepped for implantation? (what stage is the endometrium in?)
* Endometrium is in the secretory phase of development at the same time the embryo is traveling down the fallopian tube and during implantation
* Corpus luteum secreting progesterone which maintain the stratum functionalis and cause glands to become highly coiled and secretory
* **Surface of epithelium changes to promote attachment of embryo**
* **Vascular supply increases**
* **Glands form - expand and fill with secretions to nourish embryo**
* **Immune cells invade - develop tolerance to embryo**
* **Stromal cells undergo the decidual reaction**
57
Describe what is happening in endometrial development during early/late proliferative phase and the secretory phase
* In proliferative phase, new cells and glands are made
* glands develop a coiled shape
* In secretory phase, glands expand and secrete abundantly - develop sawtooth appearance
* The spiral arteries become more and more tortuous - providing rich blood supply
58
What is decidualization (decidual reaction)?
* Occurs in response to progesterone from corpus luteum & signals from implanting embryo
* endometrial stromal cells (mesenchymal cells under epithelium) change gene expression, accumulate glycogen and lipids - become highly secretory)
* Stromal cells are now called **decidual cells** and the stroma is called the **decidua** (where embryo ends up after implantation)
* Secretions from decidual cells have multiple roles
* nourish
* promote implantation - limit extent
* regulate immune response
59
The ______ is the mothers tissue surrounding the embryo/fetus
The _decidua_ is the mothers tissue surrounding the embryo/fetus
60
How does epithelium change during decidual reaction?
* Apical surfaces of endometrial epithelial cells - **pinopodes**
* only present transiently during receptive period
* may have a role in blastocyst adhesion
* Epithelial cells secrete factors and express surface proteins that promote attachment and invasion of the embryo
61
In IVF, the hormone _______ is used in place of LH
In IVF, the hormone _hCG_ is used in place of LH
62
Difference between IVF and ICSI?
IVF spermatozoa and oocyte placed together in petri dish
ICSI spermatozoa injected directly into oocyte - important if theres a problem with sperm motility
63
Label:
Endometrial gland
Endometrial capillary
Endometrial epithelium
Trophoblast
Embryonic pole
Blastocyst
Abembryonic pole
Embryoblast
64
Approx day 7 - what happens to trophoblast cells contacting the endometrium?
Trophoblast cells contacting the endometrium begin to divide. some separate from blastocyst - fuse together and form a new layer
* Cytotrophoblast - inner layer
* Syncytiotrophoblast - outer layer, a syncytium of fused cells with no cell boundaries
65
Approx day 8
Happens to Syncytiotrophoblast?
Cytotrophoblast?
* Syncytiotrophoblast gradually increases in volume and invades underlying endometrium (secreting enzymes to breakdown endometrial tissue)
* villus processes actively migrate into tissue
* Cells detach from proliferating cytotrophoblast and fuse with the syncytium
66
What are the lacunae?
Cavities that develop in the syncytiotrophoblast approx day 9 - breakdown and phagocytose cells of decidua for nourishment by embryo
67
What is the coagulation plug?
At ~day 9 the endometrial epithelium nearly covers the embryo
68
Day 9 cont
* Maternal capillaries enlarge to form ________ - anastamose with the \_\_\_\_\_\_\_\_
* Synctiotrophoblasts produce _____ which enters maternal blood via the ____ and maintains the _______ (pregnancy test hormone)
Day 9 cont
* Maternal capillaries enlarge to form _sinusoids_ - anastamose with the _trophoblastic lacunae - blood flows from maternal sinusoids into lacunae to supply metabolic needs of developing embryo_
* Synctiotrophoblasts produce _hCG_ which enters maternal blood via the _lacunae_ and maintains the _corpus luteum_ (pregnancy test hormone)
69
Day 12
The lacunae grow and anastomose to form:
Day 12
The lacunae grow and anastomose (fuse) to form: a network to supply the increasing metabolic needs of the growing embryo
* form pools of blood around the embryo
* Syncytiotrophoblast surrounds entire embyro
70
Embryo at Day 8
2nd differentiation event:
* The second differentiation event: Embryoblast differentiates into two layers (*bilaminar disc)*
* epiblast
* “on top”
* Columnar epithelial
* Hypoblast
* “under”
* Cuboidal epithelium
* Amniotic cavity between cells of embryoblast and overlying cytotrophoblast
71
What makes up the bilaminar disc? what does it give rise to?
The epiblast and hypoblast
Gives rise to the embryo
\*first evidence of an axis
Top → dorsal (surface epiblast) embryo
Bottom → ventral embryo
72
What gives rise to the fetal portion of the placenta?
Derivatives of trophoblast
73
How is the amnion formed?
Cells migrate from the epiblast and line the amniotic cavity = amnion
74
Embryo and Day 8 cont
How is the primary yolk sac (umbilical vesicle) formed?
Cells migrate from the hypoblast and line the blastocystic cavity/blastocoel (this cavity is now the primary yolk sac or umbilical vesicle)
75
What new tissue forms beneath the cytotrophoblast layer?
Extraembryonic mesoderm
Between cytotrophoblast and amnion/yolk sac
Originates mainly from cells of the hypoblast and yolk sac
76
By day 12, fluid-filled spaces begin to form within the extraembryonic mesoderm (CT layer) and split this CT layer to form the \_\_\_\_\_\_\_\_
By day 12, fluid-filled spaces begin to form within the extraembryonic mesoderm (CT layer) and split this CT layer to form the _extraembryonic coelom/ Chorionic cavity_
* Some extraembryonic mesoderm left surrounding the embryo = inner coat
* Not a complete split as a connecting stalk remains which holds embryo within the cavity
77
Embryo at day 12
Development of the extraembryonic coelom splits the mesoderm into two layers:
Outer layers lines the \_\_\_\_\_\_\_
inner layer covers the \_\_\_\_\_\_\_
Embryo at day 12
Development of the extraembryonic coelom splits the mesoderm into two layers:
Outer layers lines the _cytotrophoblast_
inner layer covers the _surface of the yolk sac and amnion_
78
Embryo at Day 13
Three multi-layered membranes can now be distinguished:
* CHORION
* composed of cytotrophoblast, syncytiotrophoblast and extraembryonic mesoderm
* Yolk sac (within chorionic cavity)
* Cells derived from hypoblast and extraembryonic mesoderm
* Amnion (within chorionic cavity)
* Cells derived from epiblast and extraembryonic mesoderm
79
Day 13
Bilaminar disc with dorsal ______ and ventral ______ suspended in the ______ by a connecting stalk of \_\_\_\_\_\_\_\_
Day 13
Bilaminar disc with dorsal _amnion_ and ventral _yolk sac_ suspended in the _chorionic sac_ by a connecting stalk of _extraembryonic mesoderm_
80
How is the definitive yolk sac formed?
Hypoblast cells
Second wave → Divide and migrate laterally (over inside of the extraembryonic mesoderm) → displace original lining of primary yolk sac → definitive yolk sac
Between days 12 and 13
81
Once the definitive yolk sac is complete, what happens to the primary yolk sac?
Day 14
Primary yolk sac becomes displaced to the abembryonic pole and degenerates
82
Development of Utero-Placental Circulation:
* During first week of development, embryo exchanges nutrients and wastes by \_\_\_\_\_\_\_
* As embryo grows, more efficient mechanism required
* __________ is the system by which maternal and fetal blood come into close proximity in the placenta for the exchange of gasses and metabolites
* During first week of development, embryo exchanges nutrients and wastes by simple diffusion
* As embryo grows, more efficient mechanism required
* Utero-placental circulation is the system by which maternal and fetal blood come into close proximity in the placenta for the exchange of gasses and metabolites
83
What is the first step in the development of uteroplacental circulation?
Formation of lacunae (filled with maternal blood) in the syncytiotrophoblast
84
Development of Utero-Placental circulation
Day 11-13
Fingerlike clusters of cytotrophoblasts protrude into _syncytiotrophoblast_ form the \_\_\_\_\_\_\_
Development of Utero-Placental circulation
Day 11-13
Fingerlike clusters of cytotrophoblasts protrude into _syncytiotrophoblast_ form the _primary chorionic villi_
85
How is the secondary chorionic villus formed?
Extraembryonic mesoderm grows into core of primary villus
→ mesodermal cells can make blood vessels (mesenchymal cells)
86
How is the tertiary chorionic villi formed?
Blood vessels form within the mesoderm = tertiary chorionic villus
Embryonic blood in tertiary villi come near maternal blood for exchange (no direct exchange)
87
What are the anchoring (stem) villi?
Some villi, the cytotrophoblast cells grow through the syncytiotrophoblast past the lacunae to the endometrial tissue = anchoring villi
Some of the cytotrophoblasts grow around the lacunae creating a **cytotrophoblast shell** lining the endometrium
88
What are the four layers of the placental barrier? Which two of these layers are lost as pregnancy progresses?
1. Vascular endothelium
2. Extraembryonic mesoderm
3. Cytotrophoblast layer
4. Syncytiotrophoblast
Much of the cytotrophoblast and mesoderm layers will be lost = placental barrier thins
89
What is the normal site of implantation?
Fundus of the uterus
90
What is placental previa?
When embryo implants in lower part of the uterus - close to and possible covering the internal os of the cervix
91
What is litopedion?
Stone fetus
Rare
When unknown abdominal pregnancy progresses too far but the fetus dies - too large for body to absorb - tissues become calcified
92
SUMMARY OF WEEK THREE
* process of gastrulation converts the bilaminar embryonic disc to a \_\_\_\_\_\_\_
* Establishment of \_\_\_\_\_\_\_
* Origin of the nervous system appears with the creation of the \_\_\_\_\_\_\_
* the _________ starts to differentiate
SUMMARY OF WEEK THREE
* process of gastrulation converts the bilaminar embryonic disc to a _trilaminar disc = all three germ layers_
* Establishment of _body axes_
* Origin of the nervous system appears with the creation of the _neural plate_
* the _intraembryonic mesoderm_ starts to differentiate
93
What is the primitive streak and when does it appear?
A beginning of third week, a thickening containing a midline groove forms along midsagittal plane of epiblast = the primitive streak
Cranial end of streak is round with pit = primitive node
94
The _____ establish the dorsal-ventral axis
The formation of the _____ establishes cranial-caudal, medial-lateral, left-right
The _epiblast/hypoblast_ establish the dorsal-ventral axis
The formation of the _primitive streak_ establishes cranial-caudal, medial-lateral, left-right
95
What is gastrulation?
Epiblast cells proliferate and migrate medially to the primitive streak
At the primitive streak the cells undergo **EMT** and migrate *ventrally* into the interior of the embryo
Produces three basic germ cell layers:
Ectoderm
Mesoderm
Endoderm
96
Formation of Endoderm:
Early 3rd week, cells from the epiblast begin to migrate through the \_\_\_\_\_\_\_\_
First ingressing cells invade ______ and replace to form \_\_\_\_\_\_\_
Endoderm gives rise to \_\_\_\_\_\_\_
Formation of Endoderm:
Early 3rd week, cells from the epiblast begin to migrate through the _primitive streak_
First ingressing cells invade _hypoblast_ and replace hypoblast cells to form _endoderm_
Endoderm gives rise to _lining of future gut/respiratory systems_
97
Formation of Mesoderm:
A second wave of epiblast cells migrates through the ______ and enters space between the ______ and \_\_\_\_\_\_
Ingressing cells migrate laterally and cranially to form loose mat of cells between _____ and \_\_\_\_\_
Form the \_\_\_\_\_\_\_\_\_\_
Formation of Mesoderm:
A second wave of epiblast cells migrates through the _primitive streak_ and enters space between the _epiblast_ and _definitive endoderm_
Ingressing cells migrate laterally and cranially to form loose mat of cells between _epiblast_ and _endoderm_
Form the **_intraembryonic mesoderm_**
98
WHich germ layer gives rise to Connective tissue, skeletal tissue, muscle tissue, cardiovascular system, reproductive system, kidneys?
Mesoderm
99
Formation of Ectoderm:
* Once formation of endoderm and mesoderm is complete, epiblast cells \_\_\_\_\_\_\_\_\_\_
* Ectoderm gives rise to:
Formation of Ectoderm:
* Once formation of endoderm and mesoderm is complete, epiblast cells _cease migrating through the primitive streak - remaining epiblast cells form the ectoderm_
* Ectoderm gives rise to: _epidermis and neural tissue_
100
Migration of mesoderm during gastrulation:
* ingressing mesoderm cells migrate _____ and \_\_\_\_\_\_
* Ectoderm and endoderm fuse in the regions of the ______ and ______ creating bilaminar membranes that *exclude mesoderm*
* Membranes become blind ends of developing ______ that rupture later in development
Migration of mesoderm during gastrulation:
* ingressing mesoderm cells migrate _laterally_ and _cranially_
* Ectoderm and endoderm fuse in the regions of the _cloacal_ and _oropharyngeal membranes_ creating bilaminar membranes that *exclude mesoderm*
* Membranes become blind ends of developing _gut tube_ that rupture later in development
101
What is an organizer region?
Region or group of cells in an embryo that can both induce and pattern adjacent embryonic cells
102
What is the embryos first organizer?
The node
Raised group of cells with a central pit - sits at cranial end of primitive streak
* establishes the body plan so that tissues adopt different fates along all axes
103
In what three ways does the node act as an organizer?
* Secretion of morphogens/morphogen antagonists
* Left-right ciliary flow
* Origin of notochord
104
What is a morphogen? (Morphogen signalling)
“A morphogen is a molecule that emanates from a specific set of cells, that is present in a concentration gradient and that specifies the fate of each cell along this gradient”.
105
What are the 5 most common morphogen families?
* Bone morphogenetic proteins (BMPs)
* Sonic Hedgehog (Shh)
* Fibroblast growth factors (FGFs)
* Wnts
* Retinoic acid
106
What morphogen is important in the node to induce surrounding ectoderm to thicken and differentiate into neuroepithelial cells of the neural plate?
BMP antagonists
Trilaminar disk has high ubiquitous expression of BMPs
BMP antagonists secreted by the node induce the surrounding ectoderm to thicken and differentiate into neuroepithelial cells of the neural plate (neural induction) (Mid gastrulation)
107
The neural plate extends \_\_\_\_\_\_\_
Becomes broad ______ and tapers \_\_\_\_\_
Which part forms the brain and which the spinal cord?
Neural plate extends cranially
Becomes broad _cranially (_**_brain_**_)_ and tapers _caudally (spinal cord)_
Which part forms the brain and which the spinal cord?
108
What happens to the primitive streak as the neural plate expands?
it regresses
109
What do the motile cilia on the nodal cells create?
Nodal flow - establishes left-right axis
* morphogen particles in the fluid are swept from right to left
* Different concentrations of morphogen on right and left - triggering different gene expression on left and right
110
What is the defining feature of all chordates?
Notochord
111
What is the notochord?
Acts as a temporary backbone in all chordate embryos
Kept as adult backbone in non-vertebrate species
112
How is the notochord formed?
During latter half of gastrulation, cells migrate through the primitive node to create a midline structure = notochordal process
Notochordal process → notochordal plate → definitve notochord
113
What is the prechordal plate?
Cells at leading edge of notochord - mesenchymal and contribute to head structures
114
The notochord is an important source of _______ in embryo
The notochord is an important source of _signalling cues_ in embryo
115
What are the three layers of the notochord?
* inner cells of notochord expand and fill with a large vacuole
* outer cells form epithelial sheath
* tough sheath of extracellular matrix surrounds the rod
\*inside pressure against tough exterior creates a stabilizing rod that forms the backbone of the early embryo
116
What is a key morphogen secreted by the notochord?
Which tissues does the notochord pattern?
Notochord secretes Sonic Hedgehog (SHH)
patterns neural tube, mesoderm and gut tube
117
Notochord and Neural plate:
Notochord extends cranially along with (and just below) the neural plate
Notochord is physically connected to neural plate
Eventually neural plate extends cranially beyond the notochord
Notochord reaches future midbrain-hindbrain boundary
118
What is the fate of the primitive streak after the fourth week?
* Primitive streak actively forms mesoderm until early fourth week
* Once it reaches the mid-disk, begins to regress caudally
* Becomes insignificant structure in sacrococcygeal region
* Normally degenerates and disappears by end of fourth week
119
Primitive streak that fails to degenerate becomes a \_\_\_\_\_\_\_\_
Sacrococcygeal teratoma
tumor derived from pluripotent primitive streak cells
contains various types of tissues derived from the three germ layers - tissues are poorly differentiated but sometimes fully differentiate into tissues like teeth and hair
120
Summary of fourth week:
* neurulation is completed and converts the _______ into a hollow \_\_\_\_\_\_\_
* Neural crest cells differentiate from the \_\_\_\_\_\_\_\_
* Embryonic disc folds to create \_\_\_\_\_\_\_
Summary of fourth week:
* neurulation is completed and converts the _neural plate_ into a hollow _neural tube_
* Neural crest cells differentiate from the _neural folds_
* Embryonic disc folds to create _the basic body form_
* _tube within a tube_
121
What is neural induction
Specification of region of ectoderm as neural tissue
Gives rise to neural plate
122
What is neurulation?
formation of neural tube from neural plate
123
Development and fusion of the neural tube:
* by the end of the third week, what is happening to the neural plate:
The neural plate has started to fold
Should be completely closed by end of fourth week
124
Neural induction and neurulation:
The cells of the neural plate adopt a _____ morphology making the neural plate a visible structure on the ____ side of the embryo
Neural induction and neurulation:
The cells of the neural plate adopt a _columnar_ morphology making the neural plate a visible structure on the _dorsal_ side of the embryo
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Neurulation:
The median hinge point forms above the \_\_\_\_\_\_
The neural plate bends to form the _____ with the _____ between them
Neurulation:
The median hinge point forms above the _notochord_
The neural plate bends to form the _neural folds_ with the _neural groove_ between them
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Neurulation:
The neural folds meet in the midline where the ______ is brought together
Neurulation:
The neural folds meet in the midline where the _surface ectoderm_ is brought together - forms continuous layer
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Fusing of the neural folds forms a ______ with a central \_\_\_\_\_\_\_
Fusing of the neural folds forms a _neural tube_ with a central _neural canal_
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The neural tube becomes the \_\_\_\_\_\_\_\_
the neural canal will form the \_\_\_\_\_\_\_\_
The neural tube becomes the _brain and spinal cord_
the neural canal will form the _ventricular system of the brain and the central canal of the spinal cord_
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How does closure of the neural tube occur?
Neural tube fusion begins at hindbrain/spinal cord junction early 4th week and then proceeds cranially and caudally
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What are three of the most severe neural tube defects that can occur if the neural tube fails to completely close
* Anencephaly
* failed closure in the brain region
* Open spina bifida (aka rachischisis)
* failed closure in the spinal cord region
* Failure to initiate closure: craniorachischisis
131
What are the neural crest cells?
Population of neuroectoderm cells at the lateral edges of the neural plate begin to differentiate into cells with a different fate = neural crest cells
* Undergo EMT - delaminate from the epithelium and migrate into the embryo
* Form all neurons and glia of PNS
* Form melanocytes
* Contributes to the heart
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During folding, neural crest cells are brought \_\_\_\_\_\_\_
toward the midline (dorsally)
133
What are the three neural crest derivatives in the trunk?
* all neurons and glia (schwann cells) of PNS
* Dorsal root ganglia
* Chain ganglia
* Preaortic (prevertebral) ganglia
* Melanocytes (skin pigment)
* Contributes to the heart (dorsal aorta)
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Patterning of Mesoderm:
The intraembryonic mesoderm forms ________ extending laterally on either side of the \_\_\_\_\_\_\_\_
Patterning of Mesoderm:
The intraembryonic mesoderm forms _three contiguous regions_ (**paraxial mesoderm, lateral plate mesoderm, intermediate mesoderm**) extending laterally on either side of the _notochord_
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Where do the somites come from?
Somites: cuboidal bodies
The paraxial mesoderm forms two longitudinal columns of cells along the lateral edges of the notochord
Near the third week, the paraxial mesoderm begins to segment into paired cuboidal bodies - somites
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The intermediate mesoderm forms only in the _____ and gives rise to \_\_\_\_\_\_\_
The intermediate mesoderm forms only in the _trunk_ and gives rise to _tissues of the urinary and reproductive systems_
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LATERAL PLATE MESODERM:
As the neural folds form, the lateral plate mesoderm splits into two layers creating a space called the \_\_\_\_\_\_\_\_
The lateral plate mesoderm is continuous with the \_\_\_\_\_\_\_\_
Some of the lateral plate mesoderm extends into the cranial region forming a crescent shape around the \_\_\_\_\_\_\_\_
As the neural folds form, the lateral plate mesoderm splits into two layers creating a space called the _intraembryonic coelum_
The lateral plate mesoderm is continuous with the _extraembryonic mesoderm_
_Some of the lateral plate mesoderm extends into the cranial region forming a crescent shape around the_ oropharyngeal membrane
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What is the splanchnic mesoderm and what does it give rise to?
The layer of mesoderm associated with the endoderm is the splanchnic mesoderm
Gives rise to the muscle and mesothelial lining of the viscera
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What is the somatic mesoderm? What does it give rise to?
Layer of mesoderm associated with the ectoderm
Gives rise to inner mesothelial lining of the body cavities and connective tissue of the limbs
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The cranial lateral plate mesoderm is called the _______ and forms the \_\_\_\_\_
The cranial lateral plate mesoderm is called the _cardiogenic mesoderm_ and forms the _heart_
\*originates from some of the earliest cells to migrate through the primitive streak
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Development of the intraembryonic coelom:
The primordia of the intraembryonic coelom form as isolated spaces in the _______ and \_\_\_\_\_\_\_\_
Developing coelomic spaces begin to \_\_\_\_\_\_\_
By the end of the 3rd week the coelomic spaces have fused to form a single horse-shoe shaped cavity within the \_\_\_\_\_\_\_
At this stage the intraembryonic coelom is continuous with \_\_\_\_\_\_\_\_\_\_
Development of the intraembryonic coelom:
The primordia of the intraembryonic coelom form as isolated spaces in the _lateral plate mesoderm_ and _cardiogenic mesoderm_
Developing coelomic spaces begin to _coalesce_
By the end of the 3rd week the coelomic spaces have fused to form a single horse-shoe shaped cavity within the _intraembryonic mesoderm_
At this stage the intraembryonic coelom is continuous with _extraembryonic coelom_
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In the future head region, the paraxial mesoderm forms _____ that disperses throughout the region and gives rise to \_\_\_\_\_\_\_
Paraxial mesoderm in the trunk first segments into transient blocks of tissue called \_\_\_\_\_\_
In the future head region, the paraxial mesoderm forms _mesenchyme_ that disperses throughout the region and gives rise to _striated muscles of face, jaw and throat_
## Footnote
Paraxial mesoderm in the trunk first segments into transient blocks of tissue called *_somites_*
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Somites form from ________ in _____ to ______ succession at regular intervals in pairs beginning at the end of the third week
Somites form from _paraxial mesoderm_ in _cranial_ to _caudal_ succession at regular intervals in pairs beginning at the end of the third week
144
Formation of somites is a ____ event
MET
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At approx day 30 we have ____ pairs of somites, the \_\_\_\_\_\_-most pairs degenerate so we're left with _____ pairs.
They flank the _______ from the occipital region to the tip of the embryonic tail
At approx day 30 we have _42-44_ pairs of somites, the _caudal_-most pairs degenerate so we're left with _37_ pairs.
They flank the _notochord/neural tube_ from the occipital region to the tip of the embryonic tail
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Shortly after forming, the somites subdivide:L
* Ventromedial portion becomes \_\_\_\_\_\_\_
* Dorsolateral part forms the \_\_\_\_\_\_\_\_
Shortly after forming, the somites subdivide:L
* Ventromedial portion becomes _sclerotome_
* Dorsolateral part forms the _dermomyotome_ (dermis muscle)
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The sclerotome cells undergo _____ so can migrate around notochord and neural tube, creating \_\_\_\_\_\_\_
The sclerotome cells undergo _emt_ so can migrate around notochord and neural tube, creating _vertebral column and ribs_
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The dermamyotome will initially produce individual _______ that undergo \_\_\_\_\_\_
The dermamyotome will initially produce individual _myoblasts (muscle progenitors)_ that undergo _EMT_
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The dermamyotome will subsequently divide into:
1. ______ - makes dermis
2. _____ - makes skeletal muscle
The dermamyotome will subsequently divide into:
1. Dermatome - makes dermis
2. _myotome_ - makes skeletal muscle
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What causes the embyro to fold?
Growth of the embryonic disc
151
The cranial end of the embryonic disk with the developing heart and oropharyngeal membrane folds ______ and \_\_\_\_\_\_
The caudal end folds ______ and ______ taking the cloacal membrane, connecting stalk and allantois
The cranial end of the embryonic disk with the developing heart and oropharyngeal membrane folds _ventrally_ and _caudally_
The caudal end folds _ventrally_ and _cranially_ taking the cloacal membrane, connecting stalk and allantois
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As the head and caudal region fold ventrally, the underlying endoderm layer folds into the _______ of the \_\_\_\_\_\_\_
As the head and caudal region fold ventrally, the underlying endoderm layer folds into the _blind ends_ of the _primitive gut tube_
153
Folding of the embryo constricts the proximal region of the _____ into a narrow _______ duct
Folding of the embryo constricts the proximal region of the _yolk sac_ into a narrow _vitelline_ duct
154
The vitelline duct connects the _____ with the \_\_\_\_\_\_\_
The vitelline duct connects the _gut tube_ with the _remaining yolk sac_
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Folding of the embryo brings the \_\_\_\_\_\_\_, _______ and ______ together in a ventro-medial position
The amnion expands, it envelops the \_\_\_\_\_\_, ______ and ____ to form the epithelial covering of the umbilicus
Folding of the embryo brings the _connecting stalk_, _vitelline duct_ and _allantois_ together in a ventro-medial position
## Footnote
The amnion expands, it envelops the _connecting stalk_, _vitelline duct_ and _allantois_ to form the epithelial covering of the umbilicus
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Lateral folding of the embryo:
* the right and left sides of the _____ flex ventrally constricting the proximal yolk sac
* ____ brings the lateral edges of the embryonic disc into contact with each other
* when the edges meet, the \_\_\_\_\_, ______ and _____ layers on each side fuse with the corresponding layers on the opposite side
* the two _______ fuse together to create a single _______ enclosed within the body
Lateral folding of the embryo:
* the right and left sides of the flex ventrally constricting the proximal yolk sac
* _flexion_ brings the lateral edges of the embryonic disc into contact with each other
* when the edges meet, the _ectodermal_, _mesodermal_ and _endodermal_ layers on each side fuse with the corresponding layers on the opposite side
* the two _intraembryonic coeloms_ fuse together to create a single _intraembryonic coelom_ enclosed within the body
157
Fusion of the lateral folds establishes a _______ body plan
Fusion of the lateral folds establishes a _tube within a tube_ body plan
Outer ectodermal tube - epidermis
inner endodermal tube - gut
158
What is the most critical period of development?
Weeks four to eight
* disturbance of development during this period gives rise to major congenital anomalies
159
The placenta is the primary site of __________ between fetus and mother.
* Also a site of ________ production
* Consists of two components:
* fetal portion which develops from the \_\_\_\_\_\_\_
* Maternal portion derived from the \_\_\_\_\_\_\_\_\_\_
The placenta is the primary site of _nutrient, gas and waste exchange_ between fetus and mother.
* Also a site of _hormone_ production
* Consists of two components:
* fetal portion which develops from the _chorion_
* Maternal portion derived from the _endometrium (decidua)_
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Label:
* Secondary chorionic villi
* cytotrophoblast
* extraembryonic mesoderm
* Syncytiotrophoblast
* Primary chorionic villi
A. Syncytiotrophoblast
B. Primary chorionic villi
C. Cytotrophoblast
D. Secondary Chorionic Villi
E. Extraembryonic mesoderm
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By the end of the third week, the chorion has numerous _____ villi and is completely surround by the \_\_\_\_\_\_\_\_\_\_\_
By the end of the third week, the chorion has numerous _stem_ villi and is completely surround by the _cytotrophoblast shell_
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The cytotrophoblast shell surrounding the chorion attaches the ______ to the \_\_\_\_\_\_
The cytotrophoblast shell surrounding the chorion attaches the _chorion_ to the _decidua_
163
Whata are the 4 layers between embryonic/fetal blood and maternal blood?
* Endothelium of blood vessels
* Extraembryonic mesoderm
* Cytotrophoblast
* Syncytiotrophoblast
ALL THESE TISSUES CAME FROM THE EMBRYO
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During the first half of pregnancy, the placental barrier has ____ layers
During the second half of pregnancy, the oxygen demand increases and the placental barrier \_\_\_\_\_
Which layers are lost?
During the first half of pregnancy, the placental barrier has _four_ layers
* 1) endothelium of blood vessels
* 2) extraembryonic mesoderm
* 3) cytotrophoblast
* 4) syncytiotrophoblast
During the second half of pregnancy, the oxygen demand increases and the placental barrier _thins_
Which layers are lost?
The cytotrophoblast layer is lost (as well as extraembryonic mesoderm) and the fetal vessels can be directly in contact iwht the syncytiotrophoblast layer
165
Stem chorionic villi develop side branches; why are these important?
Increase the surface area available for exchange between fetal and maternal blood
166
Label the:
* Ovarian artery
* Uterine artery
* Intervillous pool of maternal blood
* acruate artery
* maternal vein
* Spiral artery
* basal artery
* myometrium
* trophoblasts
* umbilical artery
* umbilical vein
* chorion frondosum
* umbilical cord
167
What stimulates the cytotrophoblasts to invade the ends of the spiral arteries?
The cytotrophoblasts invade the ends of the spiral arteries (become new wall at distal portion), creating temporary plugs. This causes hypoxia which stimulates the cytotrophoblasts to invade further
168
As the cytotrophoblasts invade they replace the _______ and ________ of the spiral arteries
The spiral arteries lose their ______ and their opening in the lacunae expands
Creates higher _______ and lower \_\_\_\_\_\_\_
As the cytotrophoblasts invade they replace the _endothelium_ and _smooth muscle_ of the spiral arteries
The spiral arteries lose their _elasticity_ and their opening in the lacunae expands
Creates higher _blood flow_ and lower _blood pressure_
169
What happens if the spiral artery remodelling is defective?
Not enough Blood flow → intrauterine growth restriction (IUGR) in baby and preeclampsia in mom (hypertension and swelling)
170
Why might spiral artery remodelling be defective?
Immune cells play a role in driving remodelling, the defect may arise from an altered immune response of mother to embryo
171
Preeclampsia is characterized by ______ and ______ during later half of pregnancy
Associated with damage to _______ and high risk of \_\_\_\_\_\_
Eclampsia=
Cause is unclear but the risk of morbidity/mortality is high for both mother and fetus and the only cure is \_\_\_\_\_\_
Preeclampsia is characterized by _hypertension_ and _proteinuria_ during later half of pregnancy
Associated with damage to _maternal organs (esp liver and kidney)_ and high risk of _stroke_
**Eclampsia**= seizure, so preeclampsia means that the disease can progress to cause seizures
Cause is unclear but the risk of morbidity/mortality is high for both mother and fetus and the only cure is _delivery_
172
At first, embryo and chorion are embedded within the _____ in wall of uterus
At first, embryo and chorion are embedded within the _endometrium (decidua)_ in wall of uterus
173
Chorion becomes asymmetrical:
What happens as the embryo and associated sacs grow?
they bulge out into the lumen of the uterus, covered by a thin layer of endometrium (decidua)
174
The side of the chorion bulging into the lumen becomes ______ and the \_\_\_\_\_\_\_
The side of the chorion bulging into the lumen becomes _compressed_ and the _villi degenerate_
175
Chorion becomes asymmetrical with __________ facing the uterine lumen and the ________ facing the placenta
Chorion becomes asymmetrical with _smooth chorion/chorion laeve_ facing the uterine lumen and the _villous chorion/chorion frondosum_ facing the placenta
176
Regionalization of decidua:
\_\_\_\_\_\_\_\_\_ cover protruding embryo
\_\_\_\_\_\_\_\_ to side of embryo
\_\_\_\_\_\_\_\_\_ deep to the embryo
Regionalization of decidua:
_decidua capsularis_ cover protruding embryo
_decidua parietalis_ to side of embryo
_decidua basalis_ deep to the embryo, underlying the embryonic pole
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Which portion of the decidua forms the maternal part of the placenta?
Decidua basalis → in contact with chorion villi
178
The placenta is composed of the ______ and \_\_\_\_\_\_\_
The maternal side of the placenta (decidua basalis) is termed the \_\_\_\_\_\_\_
The fetal side of the placenta (villous chorion) is termed the \_\_\_\_\_\_\_\_\_\_
The placenta is composed of the _villous chorion_ and _decidua basalis_
The maternal side of the placenta (decidua basalis) is termed the _basal plate_
The fetal side of the placenta (villous chorion) is termed the _chorionic plate_
_Placenta takes on discoid shape_
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Maternal placenta:
As chorionic villi grow and cytotrophoblasts invade decidua basalis, the decidual tissue becomes \_\_\_\_\_\_.
• Leaves wedge-like walls of decidual tissue, extending from basal plate into the intervillous space.
- Called _\_\_\_\_\_\_\_\_\_\_\_\__
• Separate villi into groups called _\_\_\_\_\_\__
• Placental septa do not fuse with _\_\_\_\_\_\_ \_\_\_\_\_\__
- Maternal blood flows freely from one _\_\_\_\_\_\__ to another
Maternal placenta:
As chorionic villi grow and cytotrophoblasts invade decidua basalis, the decidual tissue becomes _eroded_.
• Leaves wedge-like walls of decidual tissue, extending from basal plate into the intervillous space.
- Called _placental septa_
• Separate villi into groups called _cotyledons_
• Placental septa do not fuse with _chorionic plate_
- Maternal blood flows freely from one _cotyledon_ to another
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Maternal septa would insert into \_\_\_\_\_\_\_\_\_
Maternal septa would insert into _intervillous spaces_
181
Label the
* smooth chorion
* cotyledon
* villous chorion
* intervillous space
182
Label the
* smooth chorion
* cotyledon
* villous chorion
* intervillous space
183
Once formed, how does the placenta change?
Placenta continues to increase in surface area (diameter, thickness and complexity of branching) until near end of pregnancy (Grows with baby)
* placenta stops functioning near term (induce birth)
184
Which portion of the placenta comes out as the after birth? Which portion comes out as bleeding afterwards?
Amnion surrounding the baby + layers on placenta
The portion in contact with the basalis comes out laters as bleeding
185
What happens if placenta previa occurs?
Placenta may be partially or completely overlying internal os of cervi
Late term bleeding frequently occurs
Placenta obstructs cervical canal and fetus often must be delivered by Caesarean section
186
# Define:
* Placenta Accreta
* Placenta Increta
* Placenta Percreta
# Define:
* Placenta Accreta
* Placenta contacts/attaches to myometrium
* Placenta Increta
* placenta invades myometrium
* Placenta Percreta
* placenta grows through myometrium to serosa and sometimes attaches to other organs
High risk of bleeding and risk for uterine rupture
187
What is the difference between monozygotic and dizygotic twins?
Dizygotic twins occur when splitting occurs at 2-cell of 4 cell stage (early)
Monozygotic twins occur when splitting occurs in early blastocyst (two inner cell masses) OR later splitting yields two embryos from one inner cell mass
188
In twin pregnancy:
If splitting occurs in early blastocyst: yields \_\_\_\_\_\_\_\_; embryos share _______ = these are _______ twins
If splitting occurs later, yields ______ from \_\_\_\_\_\_\_; share _______ = these are ______ twins
If splitting occurs in 2Cell or 4Cell stage the embryos share _______ = these are ______ twins
In twin pregnancy:
If splitting occurs in early blastocyst: yields _two inner cell masses_; embryos share _uterus, chorion and placenta_ = these are monozygotic twins
If splitting occurs later, yields _two embryos from one inner cell mass_; share _amnion, chorion and placenta_ = these are _monozygotic_ twins – highest risk of conjoined twins
If splitting occurs in 2Cell or 4Cell stage the embryos share _uterus only (separate amnions, chorions and placenta)_ these are _dizygotic_ twins
189
Growth of amniotic cavity:
The amniotic cavity expands faster than the _______ filling it completely
The ______ and ________ fuse to form the _________ membrane
Growth of amniotic cavity:
The amniotic cavity expands faster than the _chorionic cavity_ filling it completely
The _amnion_ and _smooth chorion_ fuse to form the _amniochorionic_ membrane
190
Growth of amniotic cavity:
The amniotic cavity expands faster than the _______ filling it completely
The ______ and ________ fuse to form the _________ membrane
Growth of amniotic cavity:
The amniotic cavity expands faster than the _chorionic cavity_ filling it completely
The _amnion_ and _smooth chorion_ fuse to form the _amniochorionic_ membrane
191
During the 3rd month, the ________ becomes pressed against the decidua parietalis and the uterine cavity is \_\_\_\_\_\_
By the 5-6th month the _______ degrades and th e\_\_\_\_\_\_\_\_ membrane adheres directly to the decidua parietalis
During the 3rd month, the _decidua capsularis_ becomes pressed against the decidua parietalis and the uterine cavity is _obliterated_
By the 5-6th month the _decidua capsularis_ degrades and the _amniochorionic_ membrane adheres directly to the decidua parietalis
192
At term, the fetus is enclosed within the ________ which is pushed against the \_\_\_\_\_\_\_\_\_
What ruptures during labor to allow expulsion of the fetus?
At term, the fetus is enclosed within the _amniochorionic membrane_ which is pushed against the _decidua pareitalis_
What ruptures during labor to allow expulsion of the fetus? The amniochorionic membrane
193
What is an en caul birth?
When fetus is born still enclosed in the intact amniochorionic membrane – usually just covers the head
194
Four functions of the amniotic cavity and amniotic fluid:
* cushion embryo/fetus and protect against impact
* Help maintain a uniform temperature for development
* Allow fetus to mvoe freely, important for joint/muscle development
* Help maintain homeostasis of fluid and electrolytes
* practice breathing
195
The expansion of the amniotic cavity is due to: \_\_\_\_\_\_\_\_\_\_\_\_
Composition of amniotic fluid similar to \_\_\_\_\_\_
Initially, amniotic fluid produced by transport of fluid from \_\_\_\_\_\_\_\_
During 11th week, fetus begins to contribute to amniotic fluid by \_\_\_\_\_\_\_\_
Fluid also excreted by fetal ______ and _______ tracts
The expansion of the amniotic cavity is due to: _increase in volume of amniotic fluid_
Composition of amniotic fluid similar to _blood plasma_
Initially, amniotic fluid produced by transport of fluid from _maternal tissues_
During 11th week, fetus begins to contribute to amniotic fluid by _excreting uring_ (fetus has functioning urinary system)
Fluid also excreted by fetal _gastrointestinal_ and _respiratory_ tracts
196
Because amnitoic fluid is constantly secreted, must also be continually resorbed, how is this accomplished?
Fetus drinks amniotic fluid which is absorbed by fetal gut
Excess fluid returned to maternal circulation via the placenta
197
What is oligohydramions? Risks to fetus?
Production of too little amniotic fluid
* can occur late in pregnancy from decrease in placental efficiency (less fluid - not as big deal in late pregnancy)
* Restricts fetal growth
* May cause congenital malformations
* Pulmonary hypoplasia
* limb defects
* Because baby can't practice breathing/movement
198
What is polyhydramnios?
Complications?
* overabundance of amniotic fluid
* Can cause pregnancy complications
* increased pressure
* separation of placenta
* premature birth
* Often may block GI → baby cant swallow fluid
199
Where does embryonic casculatrue and blood come from?
* Formation of blood vessels begins in the *extraembryonic mesoderm* of the yolk sac at start of 3rd week
* *Embryonic* blood vessels begin to form two days later in the *intraembryonic mesoderm*
* Development of blood vessels is required to conduct nutrients, waste and gases between embryo and developing placenta
200
Blood vessels always come from \_\_\_\_\_\_\_
mesoderm
201
Blood vessel formation starts by _______ in the _________ (same tissue that gives rise to heart early on)
Vasculature will expand into other tissues mainly through \_\_\_\_\_\_\_\_
Blood vessel formation starts by *_vasulogenesis_* in the _splanchnic lateral plate mesoderm_ (same tissue that gives rise to heart early on)
Vasculature will expand into other tissues mainly through _angiogenesis_
202
Along with vasculogenesis in splanchnic lateral plate, Vasculogenesis also happens in ______ to create an extensive vascular network
Vasculogenesis also happens in _yolk sac_ to create an extensive vascular network
* important because 1st blood cells form in yolk sac
203
What are blood islands?
Extraembryonic mesodermal cells aggregate to form blood islands in the yolk sac wall - clusters of extraembryonic mesodermal cells that are in the process of differentiation
204
What are the two possible fates of blood islands?
* Angioblasts
* differentiate into endothelial cells and form blood vessels
* Hematopoeitic stem cells
* Form red and white blood cells
Soruce of blood cells is wall of yolk sac - embryo takes over in 5th week
205
The hematopoietic stem cells prduce _______ RBCs
Once vessels connect between yolk sac and embryo, the RBCs can be transport from _____ to \_\_\_\_\_
Blood cells are not made by the embryo itself until ______ week
The hematopoietic stem cells prduce _nucleated_ RBCs
Once vessels connect between yolk sac and embryo, the RBCs can be transported from _yolk sac_ to _embryo_
Blood cells are not made by the embryo itself until _5th_ week
206
What embryonic tissues are sites of hematopoiesis?
Ventral area of aorta has clusters of hematopoetic stem cells
Liver - primary source prenatally
207
Postnatally, the site of hematopoiesis is the \_\_\_\_\_\_
Postnatally, the site of hematopoiesis is the _bone marrow_
208
What are the 3 major vessels of the umbilical cord?
2 placental arteries → transport waste from fetus to placenta → transferred to maternal blood and disposed of my maternal kidneys
1 placental vein → carries oxygenated blood from placenta to embryo
209
What is the Allantois?
The allantois, along with the amniotic membrane and chorionic membrane help in the development of the embryo. They are **the other outer embryonic membranes**, that are present in humans and other mammals and reptiles including birds
Along with part of the urogenital sinus, the dilated base of the allantois continues to expand to form **the urinary bladder**, and its attenuated distal end solidifies into the cordlike urachus, which ultimately forms the median umbilical ligament that leads from the bladder to the umbilical region
