test 2 digestive system Flashcards
mesoderm turns into
paraxial mesoderm → somites→
- dematome-dorsal skin dermis
- sclerotome- axial skelelton
- myotome- skeletal muscles
- syndetome- tendon cell progenitors
intermediate mesoderm
- urogenital/ repro → kidneys and gonads
lateral mesoderm
- splanchnic → structural components of respiratory tract and gut, hematopoietic system, endothelium
- somatic mesoderm → limb skeleton, body cavity, ventral skin dermis
what is the area in between the somatic and splanchnic mesoderm?
intraembryonic coelom
splanchnic mesoderm and endoderm
splanchnopleure
somatic mesoderm and ectoderm
somatopleure
somatopleure
somatic mesoderm and ectoderm
splanchnopleure
splanchnic mesoderm and endoderm
intraembryonic coelom
The epithelial components of the GI tract, including those of the associated glands, are derived from the ___ germ layer (along with the respiratory tract).
endodermal
The ___ components of the GI tract generate mucosal epithelium, mucosal glands, and submucosal glands (aka ____) of the intestine, liver, pancreas, stomach, trachea, esophagus, and gall bladder
- epithelial*
- Parenchyma*
the epithelial components of the GI tract generate the ___, ___ and ___ of the intestine, liver, pancreas, stomach, trachea, esophagus, and gall bladder
mucosal epithelium, mucosal glands, and submucosal glands (aka Parenchyma)
The connective tissue and muscle of the primitive gut are derived from the ____
splanchnic mesoderm
splanchnic mesoderm in the digestive tract gives rise to
lamina propria
muscularis mucosae (thin mucosal smooth muscle below epithelium) ,
submucosal connective tissue and blood vessels,
muscularis externa (smooth muscle of the GI tract),
adventitia/serosa (outermost connective tissue enveloping organs).
thin mucosal smooth muscle below epithelium
muscularis mucosae
outermost smooth muscle of the GI tract
muscularis externa
outermost connective tissue enveloping organs
adventitia/serosa
neural crest gives rise to what in the primitive gut?
neurons and nerves of the submucosal and myenteric plexes.
mucosa= ____ and ___
lamina propria and epithelium
what part of the primitive gut are formed by endodermal derivatives
all glands (glands in submucosa and lamina propria)
epithelial components of villi
part of the primitive gut formed by mesodermal derivatives
Mesoderm (via lateral plate mesoderm-splanchnic mesoderm):
lamina propria
muscularis mucosae
muscularis externa
basement membrane (submucosal connective tissue)
Serosa
Craniocaudal folding, or flexion, is driven by the rapid extension of the ____
neural plate
_____ cause the opening of the gut tube to the yolk sac to draw closed forming a pocket toward the head end of the embryo, which will form the foregut, and a posterior (or caudal) “intestinal portal” toward the tail of the embryo, which will form the hindgut.
Cranio-caudal and lateral folding
Cranio-caudal and lateral folding cause the opening of the gut tube to the yolk sac to draw closed forming a pocket toward the posterior (or caudal) “____” toward the tail of the embryo, which will form the ___
intestinal portal
hindgut.
The originally wide opening between the gut and yolk sac is reduced to a narrow passage called the ____
Vitelline duct
another name for Vitelline duct
yolk stalk
what happens when the vitelline duct closes off
vitelline duct is passage between gut and yolk sac (transient structure) when this is sealed off yolk sac will be sealed off and degrades
what is the name of the cranial membrane that seals the digestive tube
buccopharyngeal membranes
what is the name of the caudal membrane of that seals the digestive tube
cloacal membrane
what is this pointing too?
buccopharyngeal and cloacal membranes
what is the red point?
vitelline duct
what are these pointing too?
what are the three regions of the gut?
foregut
midgut
hindgut
what are the derivatives of the foregut?
Trachea
Esophagus
Stomach
Liver
Gallbladder/bile ducts
Pancreas
Upper duodenum
what are the derivatives of the midgut
Lower duodenum
Jejunum
Ileum
Cecum
Appendix
Ascending colon
Proximal 2/3 of transverse colon
what are the derivatives of the hind gut?
Distal 1/3 of transverse colon
Descending colon
Sigmoid colon
Rectum
Upper anal canal
how is the gut divided?
divided by the nerve that innervates them
hox code is controlled by
cranio-caudal retinoic acid gradient
what controls what is formed along the primitive gut
hox code
controlled by cranio-caudal retinoic aid grandient
___ forms lining/epithelia and secretory elements of the digestive tube and glands (___)
- Endoderm*
- Parenchyma*
___ forms connective tissue, smooth muscles for peristalsis, ___ of liver and pancreas.
- Mesoderm*
- Stroma*
most mesoderm derivative are ___ in nature and are called the ___
mesenchyme
stroma
most derivatives of the endoderm are ___ in nature and are called ___
epithelial
parenchyma
The region of the foregut just caudal to the pharynx develops two longitudinal ridges called the ___
tracheoesophageal folds
tracheoesophageal folds that divide the tube ventrally into the ___ (and subsequent lung buds), and dorsally into the ___
trachea
esophagus.
The esophagus is initially____ and must grow in length to keep up with the overall growth in length of the embryo.
short
when tracheosophageal folds form the rest of the gut tube, the lumen of the esophagus becomes temporarily ___ around the 5th week of development and ___ by around the 9th week.
OCCLUDED
recanalizes
lung buds turn into
bronchial bubs
Esophageal atresia
(abnormal closure) occurs when the tracheoesophageal ridges deviate too far dorsally causing the upper esophagus to end as a closed tube. Often accompanied by a tracheoesophageal fistula, in which case gut contents can be aspirated into the lungs after birth causing inflammation (pneumonitis) or even infection (pneumonia).
Esophageal stenosis
occurs when the esophagus fails to recanalize. (doesn’t open back up_
Congenital hiatal hernia
occurs when the esophagus fails to grow adequately in length. As a result, the esophagus is too short and therefore pulls the cardiac stomach into the esophageal hiatus in the diaphragm. The resulting compromised structure of the hiatus can allow other gut contents (usually loops of small bowel) to herniate up into the thoracic cavity.
disorder when esophagus doesn’t open up again (__)
Esophageal stenosis
recanalize
esophageal atresia can lead to
esophagus not connected to each other
or
esophagus and trachea fused (fistula)- in which case gut contents can be aspirated into the lungs after birth causing inflammation (pneumonitis) or even infection (pneumonia).
proliferation of mesoderm-derived smooth muscle in the caudal end of the stomach forms the ___
pyloric sphincter.
Developing stomach attached to body walls by ___
dorsal/ventral mesentery
dorsal/ventral mesentery turn into
greater and lesser omenta (folds of the peritoneum that connect the stomach with other abdominal organs).
formation of the stomach appears first as a dilation of the foregut endoderm which undergoes a 90° rotation such that the left side moves ___ and the right side moves ___
ventrally
dorsally
the vagus nerves follow the rotation of the forming stomach which is how the left vagus becomes ___ and the right vagus becomes ___.
anterior
posterior
differential growth on the left and right sides of the stomach establishes the ___ and ___
greater and lesser curvatures
cranio-caudal rotation of the stomach tips the pylorus ___
superiorly
the liver grows ___ then the rest of the primitive gut
faster
greater curvature (___border) and the lesser curvature (___ border)
dorsal
ventral
pyloric stenosis
Congenital defect (dogs, humans).
1/350 live births in humans, 80% males, familial incidence.
Defect in innervation causes hypertrophy of the circular smooth muscle and projectile vomiting and poor growth. Can be corrected with resection of the sphincter.
what are the four chambers of the ruminant stomach
Rumen-Reticulum-Omasum-Abomasum
which chamber of a ruminant stomach is used for digestion?
abomasum
Mesoderm of the ___ (& developing heart (also mesoderm) signal endoderm to form liver
septum transversum
septum transversum
(the mesoderm of the septum transversum and developing heart send out signals that induce this region of endoderm to become liver).
the parenchyma of the liver (___ and branched tubules of bile ducts) intercalates within the tissue of the ___ and the plexus of vitelline vessels, accounting for the overall architecture observed in the adult (plates of hepatocytes, which are endoderm derived, surrounded by vascular sinusoids, which are mesoderm derived).
cords of hepatocytes
septum transversum
in an adult liver the structure is
plates of hepatocytes, which are endoderm derived,
surrounded by vascular sinusoids, which are mesoderm derived
The cardiac mesoderm signals a competent endoderm to become liver…the endoderm is ___
pre-patterned.
Turns out, ___derived from cardiac mesoderm are necessary and sufficient to induce liver formation
FGFs
explain competence vs specification
competence has to come first
Liver:
spectum transversum produces Bmps which binds to endoderm and makes it competent to bind with Fgfs (competence get it ready to bind to something)
once the endoderm is competent cardiac mesoderm produces Fgf and the competent endoderm binds to these signals which triggers the competent endoderm to specify into liver
___ from Septum Transversum provide ___, subsequently Cardiac mesoderm-derived ___ drive ____
BMPS Competence
FGFs specification
explain competence and specification at a molecular level
competence opens chromatin and gets it ready to bind to transcription factors which will activate/specify a gene
Competence and specification at the molecular level:
binding of pioneer transcription factors Foxa/Gata4 to repressed chromatin at the Albumin enhancer signifies competence. Subsequent binding of Nf1 and C/EBP transcription factors activate transcription post-specification.
pancreas formation
The endodermal lining of the foregut forms TWO outgrowths caudal to the forming liver: ___
ventral pancreatic bud and the dorsal pancreatic bud.
pancreas formation
ventral pancreatic bud and the dorsal pancreatic bud.
within each bud, the endoderm develops into branched tubules attached to secretory acini (the exocrine pancreas). The endocrine pancreas (islets of Langerhans) arise from stem cells at the duct branch points that then develop into discrete islands of vascularized endocrine tissue within the parenchyma of the exocrine glandular tissue.
Primary rotation of the gut tube causes the ventral and dorsal buds to merge together into what is usually a SINGLE organ in the adult
The endocrine pancreas (____) arise from stem cells at the duct branch points that then develop into discrete islands of vascularized endocrine tissue within the parenchyma of the exocrine glandular tissue.
islets of Langerhans
the endoderm develops into branched tubules attached to secretory acini (___).
the exocrine pancreas
Primary rotation of the gut tube causes the ventral and dorsal buds of the pancreas to ___
merge
SINGLE organ in most adult species
pancreas
Shh is ___ and ___ is active
inactive/repressed
The pancreas is specified by interactions with blood vessels and notochord that repress endodermal Shh
Pdx1
Signaling molecules FGF and Activin bind cell surface receptors on epithelial cells to activate transcription factors including ___ and __ to specify pancreatic cell fate.
Isl-1
Pdx1
how are islet formed?
in pancreas beta- cells leave epithelium- EMT like
form islet
beta islet formation is by migration of ___ and adhesion by ___
TGF beta, MMPs, Timps, Integrins
Cadherins, CAMs
As liver growth accelerates, the midgut loop cannot be contained in the peritoneal cavity and it herniates into the umbilical cord (___).
Physiological Umbilical Hernia
Physiological Umbilical Hernia
As liver growth accelerates, the midgut loop cannot be contained in the peritoneal cavity and it herniates into the umbilical cord
•Proximal limb of the midgut loop grows faster and gives rise to the ___ coils.
jejunal and ileal
Distal limb of the midgut loop grows slower and gives rise to the ____
cecum and colon.
•Small intestinal coils sink back into the peritoneal cavity, ___ rotates .
midgut loop
•Jejunum withdraws from the hernia, then ileum, then cecum and transverse colon and the yolk stalk ___
normally degenerates
Intestinal development involves ___, ___ and __
looping, rotation, and herniation.
The developing vertebrate gut tube forms a ___ pattern as it grows into the body cavity
reproducible looped
Gut looping morphogenesis is driven by forces that arise from the relative growth between the ___ and the anchoring dorsal ___, tissues that grow at different rates.
gut tube (grows fast)
mesenteric sheet (grows slow)
the developing gut tube folds are ___ and are similar between animals of the ___ species
predictable
same
4 things normal in embryo by abnormal for baby
- Physiological Umbilical Hernia*
- Yolk Stalk/Meckel’s Diverticulum (remnant of vitteline duct)*
- Lack of intestinal lumen*
- Cloacal Membrane*
___ is a defect in neural crest-derived neurons innervating the submucosal and myenteric plexes
White Foal Lethal (Ileocolonic aganglionosis)
fatal defect
end of intestine not innervated, unable to digest and dies
