Embryology Flashcards
What two cells are required for zygote formation?
“Activated” sperm and secondary oocyte
What happens during cleavage of a zygote? What is the resulting name of a multicellular zygote with an inner cell mass and outer cell mass?
Cells in the zygote proliferate but the zygote does not expand volume
Morula is the result
What two differentiated cell types arise from zygote proliferation? What is the cavity that forms? What is this new cell called?
- Trophoblast and Embryoblast
- Blastocoele
- Blastocyte
What happens to the inner cell mass as it further differentiates (right after the blastocoele is formed)?
A cavity forms inside the ICM (amniotic cavity)
Another layer of differentiation forms: embryoblast turns into the epiblast and hypoblast
What two cells types does the trophoblast turn into?
Cytotrophoblast and syncytiotrophoblast
What two sacs are formed from the embryoblast?
Amniotic sac (inside the “inner cell mass” space)
Yolk Sac (surrounded by hypoblast cells)
What does the cytotrophoblast do?
Defends embryo against maternal immune response
What does the syncytiotrophoblast do?
Expands into the endometrium to gather nutrients and starts to form a vascular network to supply the embryo
What is the cell type that determines ventral orientation? Dorsal?
Ventral = hypoblast
Dorsal = epiblast
What is a differentiation of the hypoblast that clumps together and forms cranial/caudal distinction?
AVE (anterior visceral endoderm)
What is the covering of the gap in the endometrial epithelium that prevents blood loss from the embedded embryo? What can disruption of this formation result in?
Fibrin coagulum
Blood loss through vaginal canal, mistaken period
What does the extraembryonic mesoderm derive from? What do the cavities that form in it result in?
Trophoblast and hypoblast cells; chorionic cavity
What is another name for the extra-embryonic somatic mesoderm?
Chorionic plate
What are all the cell types that arise from the epiblast?
Extraembryonic ectoderm (amnioblast)
Embryonic germ layers
What are all the cell types that arise from the hypoblast?
Extraembryonic mesoderm (somatic and splanchic)
Extraembryonic Endoderm
What are all the cell types that arise from the trophoblast?
Syncytiotrophoblast; cytotrophoblast
What weeks present the biggest potential for birth defects?
3-8 (with week 5 being the highest risk)
What are the three embryonic germ layers?
Ectoderm, mesoderm, endoderm
What are the early differentiations of the ectoderm?
Surface ectoderm, neural ectoderm
What does the neural ectoderm diff into?
Neural tube and neural crest
What tissue type does the surface ectoderm differentiate into?
Lining and secretory epithelium (epidermis, oral, nasal, distal anal mucosa)
What tissues are formed from the neural tube?
CNS
What tissues are formed from the neural crest?
Nervous (PNS)
Non-nervous (facial bones, melanocytes, face and ant neck dermis, iris/ciliary smooth muscle, etc)
What are the early differentiations of the mesoderm?
Paraxial, intermediate meso, lateral plate (somatic and splanchic meso)
What are the tissues that result from the paraxial mesoderm?
Connective (proper and supportive), skeletal muscle
What are the adult derivatives of the paraxial mesoderm?
CT Proper: dermis of back, tendons and ligs of axial skeleton (vert and rib)
Support CT: axial skeleton bones and cart
Skeletal Muscle: trunk, limbs, head
What are the tissues that result from the intermediate mesoderm?
Surface and glandular epithelium
Smooth muscle
CT proper
What are the adult derivatives of the intermediate meso?
Sec/Gland epithelium: lining of excretory and collecting epi of kidney and ureter; GI tract lining
Smooth muscle: GU smooth muscle
CT proper: GU connective tissue proper
What are the tissues that result from the lateral plate?
Epithelial: meso and edothelium
Cardiac and smooth muscle
CT: proper, support, fluid
What are the adult derivatives of the lateral plate?
Mesothelium: parietal and visceral serous lining of body cavities
Endothel: lining of blood/lymph vessels & cardiac chambers
Myocardium
Smooth musc: blood vessels, resp and GI tract walls; erector pili of skin
CT Proper: CT of GI and resp tract, dermis of anterolateral trunk & appendages
CT support: appendicular bones and cart; sternum
Fluid CT: hemopoietic stem cells to form fluid CT
What are the tissues that result from the endoderm (Lining of primitive gut tube and allantois)?
Lining and secretory epithelium
What are the adult derivatives of the endoderm?
GI and resp tract lining, bladder and urethra lining
Parenchymal cells of lungs and accessory digestive glands
Endocrine glands (except adrenal)
What is gastrulation?
The formation of the trilaminar germ layers
T or F: Gastrulation, neurolation, etc happen chronologically.
False; there is a large degree of overlap in embryonic development
What does the development of the primitive streak activate?
Gastrulation
What do the first epiblast cells that invade through the primitive streak become? How?
Endoderm; replace hypoblast cells
Where is the mesoderm on the embryonic disc? Ectoderm?
Middle set of cells
Original remaining epiblast cells
What are the three germ layers derived from?
Epiblast cells
What germ cells go through primitive streak and node?
Meso and endoderm
Location of passing through the primitive streak determines what?
What kind of endo/mesoderm the cells become
What do primordial germ cells do?
Give rise to oocytes/sperm eventually
What does insufficient caudal mesoderm formation cause? (Give rise to limbs and GU system)
Caudal dysgenesis (fused lower legs)
During gastrulation, what is an important step established by the notochord for organ development, placement, and function?
Laterality
Where do signals accumulate of the trilaminar germ disc?
Left side to establish LT-RT asymmetry
What is situs solitus? Situs inversus? Situs ambiguous?
Normal symmetry
Flipped symmetry
Only a few organs have flipped laterality
What week does gastrulation and neurulation start?
Wk3
What happens to the neural plate during neurulation?
Folds from center out
What develops as a result of neural plate folding?
Neural tube
What are the two ends of the neural tube called?
Anterior/posterior neuropore (should fuse eventually)
What does posterior neuropore non-fusion cause?
Spina bifida
Where do neural crest cells go when the neural tube is closed off?
They go full mesenchymal and flow outward (think: they give rise to PNS, so they need to go forth)
Where do the cell bodies of the PNS derive from?
Neural tube; neural crest derivatives are axons
What are a lot of facial deformities caused by?
Bad migration of neural crest cells
What type of mesoderm lies right next to neural tube and notochord?
Paraxial
What is the most lateral mesoderm?
Lateral plate
What derives into dermatome, sclerotome, and myotomes? What are the structures of these three?
Paraxial mesoderm
Dermatome: back dermis
Sclerotome: bones/CT of vertebrae and ribs (NOT sternum)
Myotome: trunk/limbs/diaphragm muscles
What are the two directions of folding?
Lateral: amniotic sac gets folded inward at multiple points to envelop the embryo (tube within a tube)
Cephalocaudal: inward folding of head and tail regions
What results from folding?
3D fetus surrounded by yolk sac
Where do the three body cavities derive from?
Coelomic cavity (formed from lateral and craniocephalic folding)
