Sonic hedgehog gene is produced at the...
base of the limbs in the zone of polarizing activity.
Sonic hedgehog gene is involved in..
patterning along the anterior posterior axis and CNS development.
Mutation of the sonic hedgehog gene can cause....
The Wnt-7 gene is produced at...
the apical ectodermal ridge (a thickened ectoderm at the distal end of each developing limb.
Wnt-7 gene is necessary for...
proper organization along the dorsal-ventral axis.
FGF gene is produced at the....
apical ectodermal ridge.
FGF gene stimulates....
mitotis of the underlying mesoderm providing for lengthening of limbs.
Homeobox (Hox) gene is involved in...
segmental organization of the embryo in a craniocaudlal direction.
Hox mutations lead to...
appendages in the wrong locations.
Day 0 of fetal development
fertilization by sperm, forming zygote, initiating embryogenesis
Fetal development within one week
hCG secretion begins around the time of implantation of the blastocyst
Fetal development within 2 weeks
bilaminar disc (epiblast, hypoblast) (2 weeks = 2 layers)
Fetal development within 3 weeks
trilaminar disc (3 wks = 3 layers) gastrulation primitive streak, notochord, mesoderm, neural plate begin to form
Fetal development during wks 3-8 (embryonic period)
neural tube formed by neuroectoderm and closes by wk 4; organogenesis **extremely susceptible to teratogens
Fetal development within within wk 4
heart begins to beat upper and lower limb buds (week 4 = 4 chambers, 4 limbs)
Fetal development within week 6
fetal cardiac activity is visible by transvaginal ultrasound
Fetal development within week 10
genitalia have male/female characteristics
Gastrulation is the process that...
forms the trilaminar embryonic disc. It establishes the ectoderm, mesoderm and endoderm germ layers.
Gastrulation starts with the....
epiblast invaginating to form the primitve streak.
Surface ectoderm derivatives (8)
-adenohypophysis -lens of eye -epithelial linings of oral -sensory organs of the ear -olfactory epithelium -epidermis -anal canal below pectinate line -parotid, sweat and mammary glands
A craniopharyngioma is...
a benign Rathke pouch tumor with cholesterol crystals and calcifications. (surface ectoderm derivative)
Neuroectoderm derivatives (3)
-brain (neurohypophysis, CNS neurons, oligodendrocytes, astrocytes, ependymal cells, pineal gland) -retina and optic nerve -spinal cord
Neural Crest derivatives (8)
-PNS (DRG, cranial nerves, celiac ganglion, Schwann cells, ANS) -melanocytes, -chromaffin cells of adrenal medulla -parafollicular cells of thyroid -pia and arachonid -bones of the skull -odontoblasts -aorticopulmonary septum
Mesoderm derivatives (15)
-muscle -bone -CT -serous linings -spleen -CV structures -lymphatics -blood -wall of gut tube -vagina -kidneys -adrenal cortex -dermis -testes -ovaries
Mesodermal defects =
VACTERL -Vertebral defects -Anal atresia -Cardiac defects -Tracheo-Esophageal fistula -Renal defects -Limb defects
-gut tube epithelium -most of urethra -luminal epithelial derivatives (lung, liver, gallbladder, pancreas, eustachian tube, thymus, parathyroid)
absent organ due to absent primordial tissue
absent organ despite presence of primordial tissue
incomplete organ development; primordial tissue present
extrinsic disruption; occurs after the embryonic period