Lecture 2 Flashcards
which germ layer is rolled upwards to create the neural tube (and neural plate) during neurulation?
ectoderm
what germ layer is rolled down to create the gut tube?
endoderm
what two structures are important for instructing neurulation?
notochord
prechordal mesoderm
the ectoderm forms that neural plate, which is induced by the up regulations of ______ while the node (organizer), notochord, and prechordal mesoderm will block _____ activity.
up regulation of FGFs
block BMP-4 activity
up-regulation of FGFs and blocked BMP-4 activity during neurulation activates neural pathway in what 2 regions of the brain?
fore and midbrain only
hind brain and spinal chord induction are dependent upon increased _____ and ____ as well as increased BMPs, which are only secreted at the midline
increased FGF and WNT
the neural plate will form neural folds that will elevate and fuse in the midline to form the neural tube, a primitive form of the ____
central nervous system
cells of the neuroepithelium that form at the tips of the neural folds and then migrate to other regions to form many structures, including: spinal ganglia, bones and connective tissue of the face, septa for the outflow tract of the heart, some cranial nerve ganglia, ganglia for the guy tube (enteric ganglia), melanocytes, etc.
vulnerable to teratogenic insult and provide a rationale for why many children with facial clefts also have cardiac defects
like a “fourth germ layer”
neural crest cells
layer of the ectoderm where neural crest cells form
located at top of neural tube where the crests of the tubes come together
neuroectoderm layer
neural crest cells will migrate out of the spinal cord when the cord is _____
closed
neural crest cells will migrate out of the head region while the neural tube is still open and forms _____-
the bones of the face
rolling of the middle portion of the ectoderm to form the neural tube starts _____ and moves ____
cranially (head) and moves caudally (toward body)
formed from the mesoderm
eventually form vertebrae
head forms first then rest forms
somites
what happens if the primitive streak goes too far caudally?
sacrococcygeal teratoma
what happens if the primitive streak stops short?
caudal dysgenesis (mermaid syndrome)
closing of the neural tube begins in the ____ then zippers up and down
occurs around 22 days
neck region
derived from the medodermal germ layer
mesoderm
any loose connective tissue
may be derived from mesoderm, neural crest, etc.
mesenchyme
defect due to lack of closure at different regions of the neural tube
Ex: Anencephaly, Spina Bifida, Spina Bifida Occulta
neural tube defects
NTD
failure of cranial neural folds to close causing brain tissue to generate
fatal
folic acid is a preventative measure
anencephaly
NTD
open neural tube anyhwere from cervical to lumbosacral area (most common)
70% prevents by taking folic acid for 3 months prior to conception and throughout pregnancy
spina bifida
NTD
tube closes but vertebra does not
covered by skin (and often, patch of hair)
very common
increased risk of having a child w/ NTD if you already have a child or family history with NTD
spina bifida occulta
during formation of the lateral plate mesoderm, the ______ grows downward and around the yolk sac, pinching off what will become the gut tube
leads to creation of intra-embryonic cavity
amnion
double mesoderm layer formed during formation of lateral plate meoderm
similar to connecting stalk
suspends the guy and allows a pathway for blood vessels, nerves, and lymphatics
mesentery
mesoderm derived from somites
leads to creation of vertebral column, muscles, and dermis
paraxial (dorsal) mesoderm
form in the head region and contribute ot the skull and muscles of the face
not quite somites
somitomeres
mesoderm that leads to urogenital structures
intermediate ventral mesoderm
mesoderm that splits into splanchnic (visceral-organs) and somatic (parietal-lines body cavity)
lateral plate (ventral) mesoderm
duct that keeps the gut connected w/ the yolk sac
vitelline duct
will become the umbilical cord
allantois
mesoderm tissue originally lying cranial to the heart but repositioned b/w the heart and connecting stalk by cranial folding of the embryo
gives rise to the central tendon of the diaphragm, connective tissue for the liver, and ventral mesentery
as the embryo grows and curves in fetal position, the heart gets tucked into thoracic cavity
some mesoderm around the heart proliferates and creates the _____
septum transversum
programmed cell death is necessary to cause the ____ to fall away so folding can finish
yolk sac
defect due to abnormal closure of one or more of the body folds
ventral body wall defects
ventral body wall defect usually located on right side more common defect in infants from young mothers intestines outside of body abnormal closure of abdomen
gastroschisis
ventral body wall defect not due to abnormal closure
caused by faulure of bowel loops to return to abdominal cavity following umbilical hernation
omphalocele
created by proliferation of tissue around the heart
fills up a lot of space from sternum to the back
separates thoracic cavity and peritoneal cavity due to cranial folding that curved the heart into the thoracic region
contributes to central tendon of the diaphragm
septum transversum
what part of the spine innervates the diaphragm?
C3, 4, 5
C 3, 4, 5 keeps the diaphragm alive!
what fold grows out toward the septum transversum to make the pericardio-peritoneal canals?
pleuroperitoneal fold
most common type is a hole on the left side (probably bc liver is on the right)
can push on developing heart and lungs and cause spontaneous abortion
fetal surgery can patch hole and save baby
diaphragmatic hernia
mesoderm that grows around lungs to cover them
visceral mesoderm
membrane that eventually covers the heart
pleuropericardial membrane
what nerve is located in the pleuropericardial membrane and runs down both sides of pericardial sac?
phrenic nerve
the visceral mesoderm creates the ______ pericardium during formation of the pleural and pericardial cavities
fibrous pericardium
what are the four body folds?
cephalocaudal (Head and tail folds) lateral folding (2 lateral folds close the gut tube around umbilcal region) vitelline duct (connects yolk sac to gut)
what are the 2 ways in which blood vessels are formed?
vasculogenesis
angiogenesis
blood vessels formed in situ
form blood islands then these cells coalesce into endothelial tubes and establish major vessels (aorta, cardinal veins)
regulated by vascular endothelial growth factor and its receptors
vasculogensis
blood vessels formed from sprouting from existing vessels
regulated by vascular endothelial growth factor and its receptors
angiogenesis
for divisions of the gut
pharyngeal, fore, mid, and hind gut
two closures of the gut
cranial (buccopharyngeal)
caudal (cloacal membrane)
expanded portion of the hind gut
later forms the urogenital sinus and part of anal canal
cloaca
three cavities derived from the space between the two layers of the lateral plate mesoderm
cardiac
pleural
peritoneal
layer of mesoderm that surrounds the gut tube, heart, and lungs
splanchnic (visceral) layer of lateral plate mesoderm
layer of mesoderm that lines the body wall
somatic (parietal) layer
2 layers of lateral plate mesoderm form ______ that secrete fluid for lubrication
2 layers are continuous at the root of each system
serous membranes
suspends the gut
double layer of peritoneum
2 layers are continuous
mesentery
genes that contain conserved DNA binding motifs from the homeotic gene complex of Drosphilia
grouped into 4 clusters and regulate anterior-posterior (craniocaudal) patterning of the embryo
Homeobox genes (HOX genes)
period of organogenesis most sensitive to teratogenic insults b/c organ primordia are forming
3-8th week
posterior to septum transversum
connect primitive pleuropericardial and peritoneal cavities
pericardioperitoneal canals
membranes that close pericardiperitoneal canals
pleuroperitoneal membranes
membranes that grow around hte heart and separate the pleural and pericardial cavities
form fibrous pericardium
pleuropericardial folds
what forms the diaphragm?
pleuroperitoneal membranes
septum transversum (central tendon)
muscular components from cervical myotomes (C 3,4,5) carrying phrenic nerve
mesentery of the esophagus (crura)
dorsal portion of each somite that forms the dermis of the skin of the back
segmented and supplied by spinal nerves from the segments at which they originated
segmental pattern maintained as they migrate over the body–each region that they occupy on the skin is also called a ____ and is innervated by the same spinal nerve that originally supplied the __ region of the somite
(each blank is the same word)
dermatome
???
epimere
branch of a spinal nerve that innervates intrinsic back muscles
derived from primaxial muscle cells
skin over the back
dorsal primary ramus
ventral branch of a spinal nerve that innervates limb and trunk muscles except the intrinsic (“true”) back muscles
ventral primary ramus
an extended column of midline cells lying immediately ventral to the floor plate of the central nervous system
extends from the hypophysis to the end of the spinal cord
important for inducing the neural plate and the sclerotome portion of the somites to form vertebrae
major signal molecule is sonic hedgehog (SHH)
notochord
the ventral (motor) region of the brain and spinal cord
neural plate
cranial and caudal openings in the neural tube that exist from the time that closure of the neural folds is initiated until it is complete, i.e. unclosed portions of the closing neural tube
neuropores
mesoderm-derived tissue along the axis of the embryo
responsible for forming somites and somitomers
paraxial mesoderm
a thickened region of ectoderm that forms sensory organs and ganglia
Ex: nasal, otic, lens, epibranchial
placodes
mesoderm-derived layer lying between the paraxial and lateral plate layers
responsible for forming much of the urogenital system
intermediate mesoderm
mesoderm-derived tissue that splits into visceral and parietal layers surrounding the organs and body cavity
lateral plate mesoderm
epithelia balls of cells formed in segmental pairs along the neural tube from paraxial mesoderm
differentiate into vertebrae, muscles of the back and body wall, and dermis of the skin
somites
ventromedial part of each somite that forms the vertebrae
sclerotome
formation of blood vessels from blood islands in situ (i.e. in its original place)
vasculogenesis
formation of blood vessels by sprouting from existing vessels
angiogenesis
common chamber for the hindgut and urinary systems
anterior portion forms the urogenital sinus
posterior portion forms the anus
cloaca
connection b/w the yolk sac and the primary intestinal loop of the midgut through the connecting stalk
failure of this duct to degenerate results in fistulas and diverticula (Meckel’s diverticulum) from the small intestine to the umbilicus
Vitelline duct
layer of lateral plate mesoderm associated with ectoderm
forms parietal pleura, parietal peritoneum, etc.
somatic (parietal) mesoderm
transcription factors that contain a a specific DNA-binding motif (sequence) within a region called the homeodomain
important for patterning the embryonic axis, establishing different regions of the brain, determining the origin and type of guy derivatives, patterning the limbs, etc.
Homeobox genes
