Midterm 1 Lectures 1-8 Flashcards
How is embryology research done?
- Model Organisms
- Stem Cells
- Organoids
Embryonic stem cells are removed from ______ stage embryo and are ________
Embryonic stem cells are removed from blastocyst stage embryo and are pluripotent
What are two groups of stem cells?
- 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
Label the male reproductive system
Label the testis
Sperm develop while surrounded by _______ cells within the ___________
Sperm develop while surrounded by sertoli cells within the seminiferous tubules
Label the diagram of Spermatogenesis
Spermatogenesis takes ~ _________. Sperm then mature in the ________ for _______ months
As a final step, sperm undergo _______ in the female Reproductive tract
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
Label the coronal section of the female reproductive tract
Ovaries contain many ________ follicles; a handful of which begin to develop each menstrual cycle
Ovaries contain many primordial follicles; a handful of which begin to develop each menstrual cycle
What makes up the primordial follicle?
The primary oocyte and a single layer of follicle cells
Primary oocyte is arrested in which stage?
Prophase I of meiosis (2N, 4C)
One of the first steps in follicular development is the formation of a tough glycoprotein layer between the oocyte and follicle cells called the __________
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
What produces the zona pellucida?
Secretions from both the oocyte and the follicle cells
As the follicle cells produce fluid they form the _______ within the follicle
As the follicle cells produce fluid they form the antrum within the follicle
When does the oocyte complete meiosis I? What is extruded after this completion?
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
After meiosis I is complete, the oocyte starts ______ but is arrested in ______ until fertilization
After meiosis I is complete, the oocyte starts meiosis II but is arrested in metaphase II until fertilization
When does ovulation occur?
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
After ovulation and the release of the oocyte, what happens to the remainder of the follicle?
It collapses into folds and becomes the corpus luteum which secretes estrogen, progesterone and inhibin
How is the the capsule of the mature (graafian) follicle form?
Follicle cells (aka granulosa cells) recruit surrounding connective tissue cells to form a capsule (theca cells)
Label the theca cells, cumulus oophorus, corona radiata and granulosa cells
Describe the major hormones at play at the following stages and what they elicit:
- Menstrual phase
- Proliferative phase
- Ovulation
- Secretory Phase
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
Menstrual Cycle:
Developing follicles secrete _____ which drives regrowth of the _______
Developing follicles secrete estrogen which drives regrowth of the endometrium
Menstrual cycle
After ovulation, corpus luteum secretes _______ which promotes maturation of the ________ such as:
Menstrual cycle
After ovulation, corpus luteum secretes progesterone which promotes maturation of the endometrium such as: increased vascularization and development of glands
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
In response to GnRH the pituitary gland secretes:
LH and FSH
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
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
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
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)
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
Granulosa cells are surrounded by ___________
Granulosa cells are surrounded by extracellular matrix (mostly hyaluronic acid)
Sperm penetrates corona through ________
Sperm penetrates corona through mechanical action of the flagellum and action of enzymes on surface of acrosome
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)
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
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
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
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
Chromosomal abnormalities most commonly arise because of _________ during ________
Chromosomal abnormalities most commonly arise because of nondisjunction during gametogenesis
What is monosomy?
Only one copy of chromosome
Autosomal monosomies usually not viable
XO can survive
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)
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
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
What happens during the cleavage stage?
Rapid cell division (blastomeres) wherein cells become smaller and smaller but embryo remains same size
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
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
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)
What is the trophoblast?
Thin outer layer of cells that gives rise to embryonic part of the placenta
Tropho = to feed
What is the embryoblast (inner cell mass)?
Portion of the blastocytes that gives rise to embryo
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
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
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
When does implantation occur?
~ 6 days after fertilization
Blastocyst attaches to endometrial epithelium with embryoblast facing the the epithelium
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
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
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
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
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
The ______ is the mothers tissue surrounding the embryo/fetus
The decidua is the mothers tissue surrounding the embryo/fetus
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
In IVF, the hormone _______ is used in place of LH
In IVF, the hormone hCG is used in place of LH
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
Label:
Endometrial gland
Endometrial capillary
Endometrial epithelium
Trophoblast
Embryonic pole
Blastocyst
Abembryonic pole
Embryoblast
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
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
What are the lacunae?
Cavities that develop in the syncytiotrophoblast approx day 9 - breakdown and phagocytose cells of decidua for nourishment by embryo
What is the coagulation plug?
At ~day 9 the endometrial epithelium nearly covers the embryo
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)
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
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
- “under”
- epiblast
- Amniotic cavity between cells of embryoblast and overlying cytotrophoblast
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
What gives rise to the fetal portion of the placenta?
Derivatives of trophoblast
How is the amnion formed?
Cells migrate from the epiblast and line the amniotic cavity = amnion
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)
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
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
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
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
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
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
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
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
What is the first step in the development of uteroplacental circulation?
Formation of lacunae (filled with maternal blood) in the syncytiotrophoblast
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
How is the secondary chorionic villus formed?
Extraembryonic mesoderm grows into core of primary villus
→ mesodermal cells can make blood vessels (mesenchymal cells)
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)
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
What are the four layers of the placental barrier? Which two of these layers are lost as pregnancy progresses?
- Vascular endothelium
- Extraembryonic mesoderm
- Cytotrophoblast layer
- Syncytiotrophoblast
Much of the cytotrophoblast and mesoderm layers will be lost = placental barrier thins
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
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
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
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
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
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
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
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)
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?
What happens to the primitive streak as the neural plate expands?
it regresses
What is the notochord?
Acts as a temporary backbone in all chordate embryos
Kept as adult backbone in non-vertebrate species
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
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
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
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
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
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
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
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
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
Fusing of the neural folds forms a ______ with a central _______
Fusing of the neural folds forms a neural tube with a central neural canal
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
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
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
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
During folding, neural crest cells are brought _______
toward the midline (dorsally)
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)
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
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
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
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
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
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
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
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
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
Paraxial mesoderm in the trunk first segments into transient blocks of tissue called somites
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
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
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)
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
The dermamyotome will initially produce individual _______ that undergo ______
The dermamyotome will initially produce individual myoblasts (muscle progenitors) that undergo EMT
The dermamyotome will subsequently divide into:
- ______ - makes dermis
- _____ - makes skeletal muscle
The dermamyotome will subsequently divide into:
- Dermatome - makes dermis
- myotome - makes skeletal muscle
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
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
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
The vitelline duct connects the _____ with the _______
The vitelline duct connects the gut tube with the remaining yolk sac
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
The amnion expands, it envelops the connecting stalk, vitelline duct and allantois to form the epithelial covering of the umbilicus
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
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
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
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
The cytotrophoblast shell surrounding the chorion attaches the ______ to the ______
The cytotrophoblast shell surrounding the chorion attaches the chorion to the decidua
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
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
Stem chorionic villi develop side branches; why are these important?
Increase the surface area available for exchange between fetal and maternal blood
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
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
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
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)
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
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
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)
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
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
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
Which portion of the decidua forms the maternal part of the placenta?
Decidua basalis → in contact with chorion villi
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
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
Maternal septa would insert into _________
Maternal septa would insert into intervillous spaces
Label the
- smooth chorion
- cotyledon
- villous chorion
- intervillous space
Label the
- smooth chorion
- cotyledon
- villous chorion
- intervillous space
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
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
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
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
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
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
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
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
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
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
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
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
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
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
What embryonic tissues are sites of hematopoiesis?
Ventral area of aorta has clusters of hematopoetic stem cells
Liver - primary source prenatally
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
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
