Embryology Flashcards
What is another name for the inner cell mass?
Embryoblast
What is another name for the outer cell mass?
Trophoblast
What is the beginning of implantation?
When the blastocyst attaches to the endometrial epithelium at the embryonic pole
What 2 layers does the trophoblast give rise to?
1) Cytotrophoblast
2) Syncytiotrophoblast
What is the new layer of cells that form on the surface of the inner cell mass at the end of the first week?
Hypoblast
By what day(s), is implantation complete by?
11-12
When can primary villi first be seen?
9 days
When can secondary villi be seen?
11-12 days
Where does implantation normally occur?
Posterior wall of the uterus
How often do ectopic pregnancies occur?
.25-1%
Where is the most likely place for ectopic pregnancies?
Within the uterine tube
What hormone when giving in large doses prevents preganancies from occurring by 1) inhibiting implantation b/c the uterus isn’t ready 2) delaying ovulation 3) inhibiting ovulation 4) preventing fertilization?
Progestin compounds
At what day is there an advanced morula?
4 days
At what day is there a blastocyst?
5 days
What is a transgenic mouse?
Created by injecting the pronucleus with a DNA fragment that then becomes RANDOMLY incorporated into the cell’s genome
What is a gene-targeted mouse?
Created by constructing the DNA fragment in a way that the gene is not only incorporated into the genome but also replaces part of the endogenous gene that matches specific regions of the DNA fragment. “Transfection”
The inner cell mass/embryoblast forms these 2 things?
1) Epiblast
2) Hypoblast
Cells from the yolk sac endoderm and the primitive streak give rise to?
Extraembryonic mesoderm (surrounds the amnion and yolk sac)
What cavities are formed from the syncytiotrophoblast invading the endometrial stroma?
Amniotic and chorionic cavities
What is another term for the hypoblast?
Bilaminar embryonic disc
What cells begin to produce hCG?
Syncytiotrophoblast cells
Where do lacunae appear?
Syncytiotrophoblast
At early stages in development, how do nutrients pass to the embryonic disc?
Diffusion
At what day is the conceptus completely embedded in the endometrium?
Day 10
What days are the lacunar networks establishing the primitive uteroplacental circulation?
12-12.5
The extraembryonic coelom splits the extraembryonic mesoderm into:
1) Somatic Mesoderm
2) Splanchnic mesoderm
Where do primary villi originate from?
Cytotrophoblast and induced by extraembryonic somatic mesoderm
What 2 layers constitue the chorion?
1) Extraembryonic somatic mesoderm
2) 2 layers of the trophoblast
At day 13, what develops from the hypoblast cells?
Prechordal plate
The prechordal plate is the future site of what?
1) Mouth
2) (Important organizer of the head)
When can hCG be assayed in the blood?
Day 8 post fertilization
When can hCG be assayed in the urine?
Day 10 post fertilization
High HcG levels can suggest?
1) multiple pregnancies
2) hydatidiform mole
3) gestational trophoblastic neoplasia
What are the 2 forms of hydatidiform moles?
1) Complete
2) Partial
What is a complete hydatidiform mole?
1) Trophoblast develops over embryoblast
2) Pregnancy without embryo
3) Placental villi become swollen/vesicular
4) trophoblastic tissue high level of hCG
5) Diploid embryo but all parental
6) female pronucleus lost or absent
7) polyspermia
8) diploid sperm
Pregnancy spontaneously aborted
What is a partial hydatidifrom mole?
Usually some evidence of embryonic development
1) Triploidy (dbl dose of paternal, polyspermia, diploid sperm)
Typically spontaneously abort
What is the main difference btw a complete vs partial hydatidiform mole?
Partial H. moles have some evidence of embryonic development.
What is gastrulation?
Process by which the bilaminar embryonic disc (hypoblast) is converted into a trilaminar embryonic disk
What does gastrulation MARK?
morphogenesis
Gastrulation begins with the formation of?
The primitive streak at caudal end
This process and what cell type result in the 3 germ layers?
Gastrulation; epiblast
During gastrulation the cells of the epiblast undergo this type of transformatios?
Epithelial-mesenchymal transformation invaginating btw the epiblast and hypblast all along primitive streak DAY 16
This develops from invaginating mesenchymal cells along the central axis of the embryonic disk?
notochordal process
What is forming in all direction from the primitive streak?
mesoderm
From gastrulation, the primitive streak actively forms what until the early 4th week and diminishes by the end of the 4th week?
Mesenchyme
What forms the neural plate?
Ectoderm
What are the functions of the notocord?
1) Primordial axis-ridigity
2) basis for axial skeleton
3) future site of vertebral bodies
4) induces overlying ectoderm and form neural plate
5) forms the nucleus pulposus in the adult
6) specifies cells in the ventral aspect of neural tube
Notocord: condensed group of mesenchymal cells
What is the process of neuralation?
Formation of the neural plate and neural folds and closure of these folds to form the neural plate (neuralectoderm)
The neural plate gives rise to what?
The CNS: brain and spinal cord
What are the 1st signs of brain development?
Neural groove and lateral neural folds in the neural plate
These structures fuse to form the neural tube?
Neural folds
These cells that arise from neuroectodermal cells migrate on either side of the neural fold to form the sensory ganglia of the spinal and cranial nerves?
Neural crest cells
As neuralation is taking place, the paraxial, intermediate, and lateral mesoderm forms from what?
Intraembryonic mesoderm
The paraxial mesoderm gives rise to?
Somites
What days are the somite period of development?
20 to 30
The somites give rise to?
1) Axial skeleton (e.g. bones ribs, sternum)
2) Associated axial skeleton musculature
3) Adjacent dermis
At day 24 of development, the condensed mesechyme differentiates into what 2 structures?
1) Dermomyotome
2) Sclerotome
The dermomyotome by day 26 gives rise to ?
Dermotome and myotome
The dermotome gives rise to?
Dermis
The myotome gives rise to?
Myoblasts that give rise to muscle
The sclerotome gives rise to?
Axial skeleton
The intermediate mesoderm gives rise to?
Urogenital system
What 2 regions are the lateral plate mesoderm divided into?
1) Somatic mesoderm
2) Splanchnic mesoderm
The somatic mesoderm and the overlying ectoderm are referred to as?
Somatopleure
The Somatopleure form what structure?
Embryonic body wall
The splanchnic mesoderm and the underyling endoderm are referred to as?
Splanchonopleure
Splanchonopleure forms what strucutre?
1) Embryonic guy wall
2) Cardiovascular system HEART
When do the intraembryonic and extraembryonic coelom begin to form?
Days 21-28 (week 4)
The intraembryonic coelom divides the lateral mesoderm into two layers?
1) Parietal/intraembryonic somatic mesoderm
2) Visceral or intraembryonic splanchnic mesoderm
What 3 structures does the intraembryonic coelom ultimately form?
1) Pericardial cavity
2) Pleural cavity
3) Peritoneal cavity
When does the cardiovascular system begin to develop (blood islands/blood vessels)?
17 days or 3rd week
Where does the cardiovascular system formation occur from (formation of extraembryonic blood islands)?
Extraembryonic mesoderm of the yolk sac, connecting stalk, and chorion
This is the formation of blood vessels from hemangioblasts, cells that have differentiated from the splanchnopleuric mesoderm?
Vasculogenesis
Blood islands to epithelium is what kind of transformation?
Mesechemal to Epithelial
What is angiogenesis?
Budding and sprouting of new vessels from exisitng angioblastic cords.
What original structure is the heart descended from?
Cardiogenic plate or crescent which represents the primary heart field
Does the early embryonic heart have chambers?
No
What day is the heart forming around?
20 days (3rd week)
What day does the heart start to beat?
22 days (immediately after the heart tube forms)
When does blood formation in the embryo begin?
Weeks 5-6
What does embryonic blood form from?
Mesoderm chiefly in liver, spleen bone marrow, and lymph nodes
Mesenchymal cells that surround the primordial blood vessels differentiate into what structure(s)?
Muscular and connective tissue elements of the vessels.
