exam review Flashcards
Folding of neural plate
Results in formation of neural groove flanked by neural folds; Median hinge point: induced by notochord, Involves changes in shape of columnar cells to pyramidal-shaped
cells via apical constriction, Requires synthesis of actin filaments at apical ends of cells; Lateral hinge points: Also involve apical constriction by actin filaments; Elevation of neural folds: Due to pushing inward by expanding non-neural epithelium
Anterior neural ridge signaling center:
Important in organizing telencephalon, parts of diencephalon,
olfactory area, and pituitary gland - Secretes Shh and FGF-8
zona limatns signaling center
Organizes border between dorsal and ventral thalamus - Secretes Shh
increase in FGF-8 concentration in the wavefront mechanism leads to?
mitosis in mesenchymal cells in posterior primitive streak
increase in RA concentration in the wavefront mechanism leads to?
more anteirorly opposes action of FGF-8
what results in a cessation of somitogenese?
the balance b/w the opposing gradients of RA and FGF-8 (also causes expression of Mesp-2
what molecule become concentrated at the furture anterior border of a somite and what at the future posterior border in the segmentation clock?
anterior border - lunatic fringe
posterior border - c-hairy
what do cells at the anterior and posterior border of a somite express in the segmentaiton clock?
anterior: express Eph A
posterior: express Eph B
in somite differntiation, what drive the change from mesenchymal cells to epithelial cells?
paraxis + decrease in snail
role of noggin and BMP-4 in the dermomyotome of somite organization
Noggin inhibits BMP-4 which is produced by the lateral plate and suppresses myogenesis in ventrolateral dermomyotome and stimulates cells from here to migrate into the limb bud
role of FGF in somite organization
FGF from myotome signal sclerotme to produce scleraxis which causes ant. and post. borders of each somite to from the syndetome (precursor of tendons)
intermediate mesoderm
responds to BMP from lateral ecto and activin from paraxial meso and become intermediate meso and starts to express pax-2
cranial and caudal extent of the intermediate meso is dependent on expression of what genes?
Hox-4 - Hox-11
where do early hear forming cells arise from?
epiblast then migrate through primative streak (anterior = outflow tract middle = ventricles posterior = atria)
HCG
secreted by syncytialtrophoblast cells; measurable 8-9 days after ovulation but max secretion at 10-12 weeks; functions to prevent involution of CL, increase progesterone/estrogen secretion from CL, increase growth of CL, stimulate male testes (testosterone)
estrogens
Secreted by syncytiotrophoblast cells of placenta; Placental estrogens are formed almost entirely from androgenic steroid compounds: found in mother’s and fetal’s adrenal glands; converted by trophoblast cells into estradiol, estrone, and estriol; fns: Uterine and breast enlargement; growth of breast ductal structure; enlargement of maternal external genitalia; relaxation of pelvic ligaments; may also affect aspects of fetal development
progesterone
Secreted in small quantities by corpus luteum early and secreted in large quantities by placenta; Causes decidual cells to develop in the endometrium; decreases contractility of pregnant uterus; increases secretions of Fallopian tubes and uterus; may work w/ estrogen to prepare breasts for lactation
human chorionic somatomammotropin
secreted by placenta beginning in 5th week of pregnancy; function: decreased insulin sensitivity and decreased utilization of glucose by mother; general metabolic hormone
disruptions
disturbances in otherwise normal morphgenetic processes. (amniotic bands)
deformations
disturbances in otherwise normal morphogenetic processes typically caused by abnormal biomechanical forces (uterine contraints - club foot)
sequences
cascade of events triggered by one initiating factor (complement) (oligohydramnios)
syndromes
contellatoins of congenital anomalies that are thought to be pathologically related but cannot be explained on the basis of a signle local initial event; often caused by single event like viral infection
effects of thalidomide
limb defects, ear defects, cardiovascular anomalies
effects of alcohol
growth/mental retardation, microcephaly, malformations of face/trunk
effects of RA
defects related to cranial neural crest ; facial structures, outflow tract, thymus
when do fetal blood cells reach the maternal blood stream?
during last trimester or during childbirth itself
what is the major factor of immune hydrops?
D ag of Rh group
melanoblast
from neural crest; migrate into dermis then epidermis; stain w/ HMB-45; produce pigment by mid-pregnancy
langerhans are derived from?
bone marrow
merkel cells
from neural crest, slow-adapting mechano-receptors
progesterone in mammary gland stimulates?
formation of secretory alveoli
prolactin
stimulates synthesis of milk protein and fats
origin of skeletal tissue?
mesenchymal in origin
what happens when all Hox10 paralogues are knocked out?
ribs form on the lumbar and sacral vert.
mesodermal scleretome derivatives
vertebral column, ribs, sternum
derivatives of lateral plate meso, head meso and neural crst.
lateral plate meso: limb bones and girdles; head: calvaria and bas of skull; nc: facial bones
Neurocranium
Part of the skull that surrounds the brain; has cartilaginous portion and membranous portion; base formed from chondrocranium - origin of occipital, sphenoid, ethmoid, and parts of temporal; membranous part - origin of occipital, parietal so, frontals, part of temporals
Viscerocranium
(Refers to pharyngeal arches); surrounds oral cavity and pharynx; cartilagenous portion - forms pharyngeal arch I and II; membranous portion forms - temporal, zygomatic, maxillary, nasal, lacrimal, alanine, vomer, pterygoid plates, mandible, tympanic ring
the mesenchyme that formst the viscerocranium is mostly from ?
neural crest
what cranial nerves are the pharyngeal arches associated w?
I: CN V
II: CN VII
elongation of primary ossification centers is due to?
Shh
what is expressed in all sutures?
Noggin; it suppresses BMP which otherwise would lead to the sutures closing
what does actual morphogensis of muscles depend on?
associated CT framework
epaxial muscles and tendons arise from ?
epaxial muscle: dorsal lip of myotome
epaxial tedons: syndetome layer w/i somites
hypaxial muscles and tendons arise from ?
hypaxial muscles: ventral buds of myotome
hypaxial tendosn :lateral plate mesoderm
limb muscles and tendons arise from?
ventrolateral dermomyotome
extraocular muscles arise from?
prechordal plate
some cranial musculature like lower jaw is derived from?
splanchnic mesoderm
remove half limb disc and ?
remaining half will form a complete limb
vertically divide limb disc into 2 halves and physically separate the 2 halves and ?
each half will form a normal limb
fuse 2 limb discs together and ?
a single normal limb will form
transplant a limb disc to the oposite side ?
AP axis is reversed but not DV axis but normal limb will form
rotate limb disc 180 degrees
both AP and DV axis will be reversed but norma limb will form will only AP axis reversed
transplant a strip of flank tissue from just posterior to the limb disc to an ectopic site just anterior to limb disc and ?
resulting limb consists of 2 posterior halves arranged in a mirror-image fashion meaning a strip of flank tissue just posterior to the limb organizes the posterior edges of the disc
what determines postition of ZPA via highest concentration?
Hoxb8 - induced by RA
Shh role in formation of anterior - posterior axis
maintain strucutre and function of AER, induces expression of gremlin, and inhibits Gli-3 in posterior limb bud
Gli-3 role in formation of AP axis
active in anterior part of limb bud; inhibits Shh in anterior limb bud
Formation of DV axis
Dorsal limb bud ecto signal Wnt-7a which induces dorsal limb meso to express Lmx-1b; ventral limb bud ecto produces En-1 which inhibits Wnt-7a
Formation of Proximodistal axis
AER (if removed limb would stop growth) uses FGFs and Wnts to keel cells in underlying mesenchyme in a proliferative state; cells that get left behind as limb bud grows distal become postmitotic and differentiate in to a part of the limb;
morphology of the limb is due to?
expression of Hox genes
the structure of the developing limb in every case is determined by what?
the nature of the mesodermal components
what maintains AER in healthy state?
apical ectoderm maintenacne factore (AEMF) produced by mesoderm
what do hypertrophic cells express?
ihh
limb muscle development
migrating premuscle cells express Pax-3 and Ncadherin; before migrating to limb bud, they express c-met which is the receptor for scatter factor; differentiation of premsucle cells into muscle in limb bud depend on Wnt-6 expressed by ectoderm; Tcf-4 is expressed by the CT associted w/ the muscle masses
axons originating from more medial locations in the spinal cord grow into ?
ventral muscle mass
axons originating in more lateral locations grow into?
dorsal muscle
ant. muscles will be inn by axons originating where?
anterior form spinal cord (and posteiror muscles by axons post. to spinal cord)
If the forelimb rudiment of a salamander embryo is removed so that the limb fails to develop:
The nerves of the brachial plexus remain smaller (thinner) than they would have been if the limb were still there; spinal ganglia three, four, and five (associated with the brachial plexus in the salamander) are also smaller. The number of cells in each ganglion may be reduced by as much as 50 percent.
If an additional limb rudiment is transplanted to the flank of a salamander embryo:
The local spinal nerves supply the innervation to the transplanted limb and these local nerves increase in thickness; Ganglia associated with these nerves increase in size; the increase in number of cells may be as much as 40 percent.
If the forelimb rudiment of an amphibian embryo, prior to the outgrowth of nerves, is cut out and transplanted to a position very near the original one:
The brachial nerves will deviate from their normal paths and will be deflected in the direction of the transplanted limb. If the distance of the transplanted limb from the original position is not too great, the brachial nerves will penetrate into the limb and ramify. The limb becomes fully functional.
If an additional limb is transplanted into the immediate
vicinity of the host limb:
The brachial nerves will develop branches running out to the additional limb and will supply it.
If the normal path of the nerves is blocked by some obstacle
The outgrowing nerves may avoid the obstacle, go around it, and still reach their normal destination; Hamburger inserted a piece of mica into a frog embryo between the spinal cord and the region where the hindlimb rudiments were to develop. The nerves formed loops around the mica plate and still reached the hindlimb rudiments.
If the limb rudiment transplant is placed farther away from
the normal limb site, or if the obstacle between the spinal
cord and the limb rudiment is too great:
The nerve fibers fail to be attracted to the limb; If the limb rudiment is placed on the flank of the embryo, it will attract the local spinal nerves. These nerves will grow into the limb, but they cannot provide for the normal limb function; It appears that only the areas of the spinal cord from which the nerves of the brachial and lumbar plexuses originate possess the properties necessary for controlling the functioning of the limbs.
