Endoderm Development - Lecture 16 Flashcards
Which signalling factor is necessary for the formation of endoderm?
Original signalling of nodal happens during gastrulation
how does the expression of nodal and FGF-4 relate to the establishment of the anterior-posterior gradient/
theres a higher level of nodal expressed anteriorly and the posterior end there’s lower levels of nodal and expression of FGF-4
This gradient allows expression of other transcription factors
What is Cdx-2’s role in hindgut and foregut formation?
Cdx-2 promotes hindgut development and suppresses the formation of anterior gut structures
What is the role of shh and BMP-4 in the developing intestine?
The endodermal edges of the anterior intestinal portal expresses shh, the posterior intestinal portal expressed shh followed by BMP-4
Which series of Hox genes is involved i nthe refinement of the differentiation of the gut?
After shh and BMP-4 a gradient of Hox gene groups 9 to 13 is expressed
Hox-d9 more cranial and hox-d13 caudally
Oralpharyngeal membrane/oral plate and cloacal plate are formed how?
Formed by endoderm and ectoderm only, lack of mesoderm makes them unstable and leads to perforations.
The stomedeum pocket - future oral cavity
The proctodeum pocket - future anal region
Desscribe the basic development of the digestive system by the end of the forth week.
From endoderm you get the anterior gut, foregut, and the posterior gut, hind gut. With an open midgut in between that eventually forms the allontois - which is the umbilicial cord in mammals.
What does the four week embryo look like?
Four week embryo: length - 4mm
- established rudaments of most organ systems except the limbs and urogenital system.
- C-shaped with prominant somites and paryngeal arches
- featureless head with rudimentary eyes and eyes and the oropharyngeal membrane
- wolffian ridge: marked by a wnt pathway and spans the nose, inner ear, eye, payrngeal arches and limbs- thickened ectoderm
- two chambered heart with 3 separate circulatory arcs
What are the 3 circulatory arcs in the 4-week embryo?
Viteline arc: made of the vitelline vessels - extraembryonic circulatory loop
Allantoic arc: allantoic (umbilical) vessels - through body stalk and into placenta and chorionic tissues
Embryonic arc: dorsal aorta, aortic arches, anterior cardinal vein, common cardinal veins, posterior cardinal veins, aatrium, ventricle, ventral aorta
EA: Aortic outflow tract -> aortic arches -> pharyngeal arches -> paired dorsal aorta -> rest of body -> cardinal veins -> common inflow tract
What basic embryonic structure forms from embryonic endoderm
Allantois -> urinary bladder
Gut -> trachea, lungs, pancreas, liver, digestive, parynx -> thyroid and pharyngeal pouches
Pharyngeal pouches -> middle ear, auditory tube, tonsils, thymus, parathyroids, superior parathyroids, posterior branchial bodies
What forms from embryonic mesoderm?
Intermediate mesoderm
- > gametes, gonads
- > pronephros -> mesonephros -> metanephros
- > paramesonephric ducts -> vagina, uterus, uterine tubes
- > mesonephric ducts -> ductus epididymis, ductus deferens
Lateral plate mesoderm
- > splanchnic mesoderm -> visceral, mesenteries, blood cells, endothelium of vessels, heart tissues, wall of respiratory tract and of gut
- > somatic mesoderm -> limb skeleton, paritial (pleura/cardiums),
Paraxial mesoderm -> myotomes (limb muscles and axial muscles), sclerotomes (axial skeleton), and dermatones
What structures from from the embryonic endoderm?
Neural tube
- > optic vesicle and retina, posterior pituitary, spinal cord and brain
- > neural crest -> trunk neural crest and cranial neural crest
Other epithelium
- > glands, hair, nails, auditory vescicle and inner ear, cornea, and lens
- > protodeal epithelium -> anal canal
- > stromdeal epithelium -> oral epithelium and teeth enamel
