Embryology Of Fore Gut Flashcards
The GI tract is the main organ system derived from the ——— germ layer.
▪ This germ layer covers the ventral surface of the embryo and forms the —- of the yolk sac.
▪ With development and growth of the brain vesicles, the embryonic disc begins to fold ——.
The GI tract is the main organ system derived from the endodermal germ layer.
▪ This germ layer covers the ventral surface of the embryo and forms the roof of the yolk sac.
▪ With development and growth of the brain vesicles, the embryonic disc begins to fold cephalocaudally.
The folding is most pronounced in the regions of the — and —, where they form head and tail fold
▪ In the anterior part, the endoderm forms the —-; in the tail region, it forms the ——.
The folding is most pronounced in the regions of the head and tail, where they form head and tail fold
▪ In the anterior part, the endoderm forms the foregut; in the tail region, it forms the hindgut.
The part between foregut and hindgut is the ——. The midgut temporarily communicates with the yolk sac by way of a broad stalk, the ——-
▪ At its cephalic end, the foregut is temporarily bounded by an ectodermal-endodermal membrane called the —— membrane.
The part between foregut and hindgut is the midgut. The midgut temporarily communicates with the yolk sac by way of a broad stalk, the vitelline duct
▪ At its cephalic end, the foregut is temporarily bounded by an ectodermal-endodermal membrane called the buccopharyngeal membrane.
In the —- week, the buccopharyngeal membrane ruptures, establishing an open connection between the oral cavity and the primitive gut
▪ The hindgut also terminates temporarily at an ectodermal-endodermal membrane- the —- membrane, which breaks down in the ——week to create the opening for the anus.
In the 4th week, the buccopharyngeal membrane ruptures, establishing an open connection between the oral cavity and the primitive gut
▪ The hindgut also terminates temporarily at an ectodermal-endodermal membrane- the cloacal membrane, which breaks down in the 7th week to create the opening for the anus.
Extent of Foregut:
▪ Foregut starts from the —— and terminates at the level of ——— (the point where —— duct opens into —-)
Extent of Foregut:
▪ Foregut starts from the Oral cavity and terminates at the level of Ampulla of Vater (the point where common bile duct opens into Duodenum)
Gut-associated organs begin to form as buds from the ——-: (e.g., thyroid, lung, liver, pancreas)
Midgut opening to the yolk sac progressively ——
Gut-associated organs begin to form as buds from the endoderm: (e.g., thyroid, lung, liver, pancreas)
Midgut opening to the yolk sac progressively narrows
By the end of the first month:
The —— bulge is visible, ——pancreas has begun to bud
Connection of the midgut to the yolk sac is reduced to a ——-
By the end of the first month:
The stomach bulge is visible, Dorsal pancreas has begun to bud
Connection of the midgut to the yolk sac is reduced to a yolk stalk
A respiratory diverticulum develops from the —— of the foregut, divides the foregut into two parts:
▪ Part cranial to diverticulum - ——-
▪ Part caudal to diverticulum - ——-
A respiratory diverticulum develops from the floor of the foregut, divides the foregut into two parts:
▪ Part cranial to diverticulum - primitive pharynx
▪ Part caudal to diverticulum - foregut proper
List the derivatives of fore gut
Pharynx
Lower respiratory system
Oesophagus
Stomach
Proximal part of duodenum
Liver and biliary tree
Pancreas
Gut tube proper. Derivatives
Of gut tube
Fore :
Gut
Mid gut:
Hind gut:
Gut tube proper. Derivatives
Of gut tube
Fore : pharynx. Thyroid
esophagus. Parathyroid
stomach. Tympanic cavity
proximal duodenum. Trachea
Bronchi
Lungs
Liver,
gallbladder,
pancreas
Mid gut:distal duodenum
To right half of transverse
Colon
Hind gut:left half of. Urinary
Transverse colon. Bladder
To anus
The foregut derivatives except the pharynx, lower respiratory tract and most of esophagus are supplied by the ——— - the artery of the foregut
The foregut derivatives except the pharynx, lower respiratory tract and most of esophagus are supplied by the Celiac trunk- the artery of the foregut
Development of the Esophagus
▪ Esophagus develops from the foregut immediately caudal to the ——-
▪ The ——— septum separates it from the developing trachea
Development of the Esophagus
▪ Esophagus develops from the foregut immediately caudal to the primitive pharynx
▪ The tracheo-esophageal septum separates it from the developing trachea
Growth of
▪ Up to the —- week it is very short.
▪ Then, it elongates rapidly due to the descent of developing —- and —-.
▪ By the —- week it reaches its final position.
▪ Its lumen is completely or partially obliterated due to proliferation of its ——.
Growth of
▪ Up to the 4th week it is very short.
▪ Then, it elongates rapidly due to the descent of developing heart and lungs.
▪ By the 7th week it reaches its final position.
▪ Its lumen is completely or partially obliterated due to proliferation of its epithelial lining.
Duodenum
▪ The epithelial cells proliferate and obliterate the lumen (partly or completely) but ———-
▪ Recanalization normally occurs by the end of the —— period (—- wk)
▪ Failure of proper recanalization leads to narrowing of the lumen (also called—-)
▪ The epithelial cells proliferate and obliterate the lumen (partly or completely) but temporarily
▪ Recanalization normally occurs by the end of the embryonic period (8th wk)
▪ Failure of proper recanalization leads to narrowing of the lumen (stenosis)
▪Re-canalization of the oesophagus–errors in this process lead to ——-
▪Re-canalization –errors in this process lead to esophageal stenosis
▪ Epithelium & glands:
Derived from —-
▪ Striated muscles (mainly in the —-):
Derived from the ——-
▪ Smooth muscles (mainly in the —-):
Derived from the surrounding ——-
▪ Epithelium & glands:
Derived from endoderm
▪ Striated muscles (mainly in the superior third):
Derived from the mesenchyme in the caudal pharyngeal arches
▪ Smooth muscles (mainly in the inferior third):
Derived from the surrounding splanchnic mesoderm
Congenital malformations of
Esophagus
▪ Errors in forming the esophagotracheal septa and/or re-canalization- ———- and/or ——-, respectively.
▪ Atresia of Esophagus prevents the normal passage of amniotic fluid into the intestinal tract
leading to (———- accumulation of excess fluid in the amniotic sac)
▪ Short esophagus resulting in ——
Congenital malformations of
Esophagus
▪ Errors in forming the esophagotracheal septa and/or re-canalization- tracheoesophageal fistulas and/or esophageal atresia, respectively.
▪ Atresia of Esophagus prevents the normal passage of amniotic fluid into the intestinal tract
leading to (Polyhydroamnios)- accumulation of excess fluid in the amniotic sac
▪ Short esophagus resulting in hiatal hernia
▪Region of foregut just caudal to lung bud develops into ——
▪Endodermal lining is ——and proliferates such that the lumen is obliterated; patency of the lumen established by
▪Region of foregut just caudal to lung bud develops into esophagus –
▪Endodermal lining is stratified columnar and proliferates such that the lumen is obliterated; patency of the lumen established by
▪Region of foregut just caudal to lung bud develops into ——
▪Endodermal lining is ——and proliferates such that the lumen is obliterated; patency of the lumen established by
▪Region of foregut just caudal to lung bud develops into esophagus –
▪Endodermal lining is stratified columnar and proliferates such that the lumen is obliterated; patency of the lumen established by
Development of the Stomach
▪ In the middle of the —-
week, a fusiform
dilatation appears in the
caudal part of the foregut
(indicating site of future ——)
▪ This dilatation (oriented in the midline), enlarges and broadens ——
Development of the Stomach
▪ In the middle of the 4th
week, a fusiform
dilatation appears in the
caudal part of the foregut
(indicating site of future stomach)
▪ This dilatation (oriented in the midline), enlarges and broadens ventrodorsally
During next —- weeks:
The —- border grows much faster and forms the greater curvature
The —- border forms the lesser curvature
During next 2 weeks:
The dorsal border grows much faster and forms the greater curvature
The ventral border forms the lesser curvature
As stomach enlarges, it slowly rotates —- degrees, clockwise around its —- axis
As a result, the:
▪ The ventral border moves to the —- and the dorsal border to the —-
▪ The original left side becomes the —- surface and the original right side becomes the —- surface
As stomach enlarges, it slowly rotates 90 degrees, clockwise around its longitudinal axis
As a result, the:
▪ The ventral border moves to the right and the dorsal border to the left
▪ The original left side becomes the ventral surface and the original right side becomes the dorsal surface
Left vagus nerve- innervates —- wall
▪ Right Vagus nerve- innervates —- wall
Left vagus nerve- innervates anterior wall
▪ Right Vagus nerve- innervates posterior wall
▪ Initially the two ends of the stomach lie in the —-. During further growth:
the cranial end moves to the — and slightly ——
the caudal end moves to the —- and ——
▪ After rotation, stomach assumes its final position with its long axis almost transverse to the long axis of the ——
▪ Initially the two ends of the stomach lie in the midline. During further growth:
the cranial end moves to the left and slightly inferiorly
the caudal end moves to the right and superiorly
▪ After rotation, stomach assumes its final position with its long axis almost transverse to the long axis of the body
Formation of the Lesser sac/Omental Bursa
▪ During its dev, the stomach is suspended in the midline with the help of double-layered mesenteries (——-),
▪ The Dorsal mesogastrium connects it to the —— body wall.
▪ The Ventral mesogastrium attaches the gut tube to the —- abdominal wall
▪ Rotation around the longitudinal axis pulls the ‘dorsal mesogastrium’ to the —-.
▪ This move leads to the formation of ‘Omental
Bursa’ (a pouch of peritoneal cavity located behind the ——).
Formation of the Lesser sac/Omental Bursa
▪ During its dev, the stomach is suspended in the midline with the help of double-layered mesenteries (mesogastrium),
▪ The Dorsal mesogastrium connects it to the post/dorsal body wall.
▪ The Ventral mesogastrium attaches the gut tube to the ant abdominal wall
▪ Rotation around the longitudinal axis pulls the ‘dorsal mesogastrium’ to the left.
▪ This move leads to the formation of ‘Omental
Bursa’ (a pouch of peritoneal cavity located behind the stomach).
Formation of Greater & Lesser Omenta
▪ With the rotation of stomach, the greater curvature along with the attached dorsal mesogastrium becomes the ‘——’
▪ While the ventral mesogastrium lying between the lesser curvature of stomach & the inferior surface of liver- ‘———
Formation of Greater & Lesser Omenta
▪ With the rotation of stomach, the greater curvature along with the attached dorsal mesogastrium becomes the ‘Greater Omentum’
▪ While the ventral mesogastrium lying between the lesser curvature of stomach & the inferior surface of liver- ‘Lesser Omentum’
Formation of Greater & Lesser Omenta
▪ With the rotation of stomach, the —- curvature along with the attached —-/ becomes the ‘Greater Omentum’
▪ While the —- mesogastrium lying between the lesser curvature of stomach & the —- surface of liver- ‘Lesser Omentum’
Formation of Greater & Lesser Omenta
▪ With the rotation of stomach, the greater curvature along with the attached dorsal mesogastrium becomes the ‘Greater Omentum’
▪ While the ventral mesogastrium lying between the lesser curvature of stomach & the inferior surface of liver- ‘Lesser Omentum’
Stomach Abnormalities
▪ ——— occurs when musculature of the stomach in the region of the pylorus hypertrophies.
▪ Is one of the most common abnormalities of the stomach in infants- believed to develop during fetal life.
▪ There is an extreme —— of the pyloric lumen, passage of food is obstructed which causes——-
▪ Other malformations of the stomach, such as ——- are rare
Stomach Abnormalities
▪ Pyloric stenosis occurs when musculature of the stomach in the region of the pylorus hypertrophies.
▪ Is one of the most common abnormalities of the stomach in infants- believed to develop during fetal life.
▪ There is an extreme narrowing of the pyloric lumen, passage of food is obstructed- severe vomiting.
▪ Other malformations of the stomach, such as duplications are rare
Pyloric stenosis is Characterized by very forceful (aka “—-”), —— vomiting approximately—-hr. after feeding (when pyloric emptying would occur).
▪NOTE: the presence of bile would indicate ——- blockage of some sort.
•Hypertrophied sphincter can often be palpated as a ——-; peristalsis of the sphincter seen/felt under the ——
•Stenosis is due to ——-of pyloric sphincter… NOT an error in ——-
•More common in —- than —-, so most likely has a genetic basis which is as yet undetermined.
Characterized by very forceful (aka “projectile”), non-bilious vomiting ~1hr. after feeding (when pyloric emptying would occur).
▪NOTE: the presence of bile would indicate POST-duodenal blockage of some sort.
•Hypertrophied sphincter can often be palpated as a spherical nodule; peristalsis of the sphincter seen/felt under the skin.
•Stenosis is due to overproliferation / hypertrophy of pyloric sphincter… NOT an error in re-canalization.
•More common in males than females, so most likely has a genetic basis which is as yet undetermined.
Development of the Duodenum
▪ Duodenum begins to develop early in —— week, from the caudal part of the —— and cranial part of the ——
▪ Grows rapidly, forms a —–shaped loop that projects —-
▪ Has dual arterial supply
Development of the Duodenum
▪ Duodenum begins to develop early in 4th week, from the caudal part of the foregut and cranial part of the midgut
▪ Grows rapidly, forms a C-shaped loop that projects ventrally
▪ Has dual arterial supply
Development of the Duodenum
▪ Duodenum begins to develop early in —— week, from the caudal part of the —— and cranial part of the ——
▪ Grows rapidly, forms a —–shaped loop that projects —-
▪ Has dual arterial supply
Development of the Duodenum
▪ Duodenum begins to develop early in 4th week, from the caudal part of the foregut and cranial part of the midgut
▪ Grows rapidly, forms a C-shaped loop that projects ventrally
▪ Has dual arterial supply
Development of the Duodenum
▪ Duodenum begins to develop early in —— week, from the caudal part of the —— and cranial part of the ——
▪ Grows rapidly, forms a —–shaped loop that projects —-
▪ Has dual arterial supply
Development of the Duodenum
▪ Duodenum begins to develop early in 4th week, from the caudal part of the foregut and cranial part of the midgut
▪ Grows rapidly, forms a C-shaped loop that projects ventrally
▪ Has dual arterial supply
Duodenum=“tit bits”
▪ Dual origin- Caudal part of foregut & Cranial part of midgut
▪ Dual blood supply- —— and ——
▪ Opening of —-duct separates the 2 parts derived from the foregut and midgut
▪ Grows rapidly to form a C-shaped loop
Duodenum=“tit bits”
▪ Dual origin- Caudal part of foregut & Cranial part of midgut
▪ Dual blood supply- coeliac trunk & superior mesenteric artery
▪ Opening of bile duct separates the 2 parts derived from the foregut and midgut
▪ Grows rapidly to form a C-shaped loop
Duodenum
▪ Rotation of stomach pulls it to the —- , bringing it in a ——position
▪ During — to —th weeks, its lumen obliterates due to proliferation of epithelial cells
▪ Recanalization is complete by the end of ——
▪ Most of the —- mesentery disappears by this time
▪ Iniatially ventral, it then rotates to the right during the rotation of the stomach
▪ It loses its dorsal mesentary =——
▪ — to — th week the lumen is obliterated
▪ —-th week lumen recanalized
▪ Ventral mesentary disappears
▪ Rotation of stomach pulls it to the right , bringing it in a retro-peritoneal position
▪ During 5-6th weeks, its lumen obliterates due to proliferation of epithelial cells
▪ Recanalization is complete by the end of embryonic period
▪ Most of the ventral mesentery disappears by this time
▪ Iniatially ventral, it then rotates to the right during the rotation of the stomach
▪ It loses its dorsal mesentary =retroperitoneal
▪ 5-6th week the lumen is obliterated
▪ 8th week lumen recanalized
▪ Ventral mesentary disappears
Congenital abnormalities
▪ Duodenal stenosis-incomplete recanalization involves —- & —- parts of duodenum
▪ Duodenal atresia- complete occlusion of lumen involves — & — parts of duodenum
▪ Clinical presentation is — vomiting in infants
▪ “——” sign on X-ray or USS
Congenital abnormalities
▪ Duodenal stenosis-incomplete recanalization involves 3rd & 4th parts of duodenum
▪ Duodenal atresia- complete occlusion of lumen involves 2nd & 3rd parts of duodenum
▪ Clinical presentation is bilous vomiting in infants
▪ “Double bubble” sign on X-ray or USS
Congenital abnormalities
▪ Duodenal ——-incomplete recanalization involves 3rd & 4th parts of duodenum
▪ Duodenal ——– complete occlusion of lumen involves 2nd & 3rd parts of duodenum
Congenital abnormalities
▪ Duodenal stenosis-incomplete recanalization involves 3rd & 4th parts of duodenum
▪ Duodenal atresia- complete occlusion of lumen involves 2nd & 3rd parts of duodenum
Development of the Liver
▪ Liver appears in —th week, as a ventral bud called —-, from the caudal part of the foregut
▪ The bud grows into the septum transversum and divides into two parts:
▪ Larger cranial part which forms- ———
▪ Smaller caudal part which forms—— and —-
▪ The proliferating endodermal cells give rise to ——- which anastomose around endothelium lined spaces- ——
Development of the Liver
▪ Liver appears in 4th week, as a ventral bud called hepatic diverticulum, from the caudal part of the foregut
▪ The bud grows into the septum transversum and divides into two parts:
▪ Larger cranial part - primordium of liver;
▪ Smaller caudal part- gall bladder and cystic duct
▪ The proliferating endodermal cells give rise to Hepatic cords which anastomose around endothelium lined spaces- Hepatic sinusoids
The liver grows rapidly and in —- to—th weeks fills a large part of the abdominal cavity
▪ By —-th week, the liver forms about —% of total body weight
▪ Initially the right and left lobes are of the same size, later —- lobe grows larger
The liver grows rapidly and in 5-10th weeks fills a large part of the abdominal cavity
▪ By 9th week, the liver forms about 10% of total body weight
▪ Initially the right and left lobes are of the same size, later right lobe grows larger
Development of the liver
▪ The hepatic cords and the epithelial lining of the intrahepatic portion of the biliary system are derived from —-
▪ The fibrous tissue, hematopoeitic tissue and Kupffer cells are derived from the ————-
▪ The hepatic sinusoides derived from ———-
▪ Hematopoiesis begins during——th week, giving dark color to liver
▪ The hepatic cells begins to form bile during the —-th week
▪ The hepatic cords and the epithelial lining of the intrahepatic portion of the biliary system are derived from endoderm
▪ The fibrous tissue, hematopoeitic tissue and Kupffer cells are derived from the mesenchyme of the septum transversum
▪ The hepatic sinusoides derived from vitelline veins
▪ Hematopoiesis begins during 6th week, giving dark color to liver
▪ The hepatic cells begins to form bile during the 12th week
Development of the Biliary Apparatus
▪ The small caudal part of the hepatic diverticulum becomes the ——, and the stalk of the diverticulum forms the —-
▪ The stalk connecting the hepatic & cystic ducts to the duodenum becomes the —- duct, and opens on the — aspect of the duodenum.
▪ Later due to rotation of duodenum, the opening comes to lie —-
▪ The ducts become occluded initially, but are later canalized
▪ Bile formation commences about the —th week,
(After —th week bile entering the duodenum gives a dark green color to the intestinal contents (——)
Development of the Biliary Apparatus
▪ The small caudal part of the hepatic diverticulum becomes the gall bladder, and the stalk of the diverticulum forms the cystic duct
▪ The stalk connecting the hepatic & cystic ducts to the duodenum becomes the bile duct, and opens on the ventral aspect of the duodenum.
▪ Later due to rotation of duodenum, the opening comes to lie dorsally
▪ The ducts become occluded initially, but are later canalized
▪ Bile formation commences about the 12th week,
(After 13th week bile entering the duodenum gives a dark green color to the intestinal contents (meconium)
Development of the Pancreas
▪ Pancreas begins to appear as two buds, —- and —-, from the —- part of the foregut
▪ The —- bud is larger, appears first and lies cranial to the smaller —- bud
▪ The rotation of stomach and duodenum carry the —- bud dorsally along with the bile duct.
▪ The ventral bud comes to lie post to the dorsal bud and later fuses with it and their ducts anastomose
Development of the Pancreas
▪ Pancreas begins to appear as two buds, dorsal and ventral, from the caudal part of the foregut
▪ The dorsal bud is larger, appears first and lies cranial to the smaller ventral bud
▪ The rotation of stomach and duodenum carry the ventral bud dorsally along with the bile duct.
▪ The ventral bud comes to lie post to the dorsal bud and later fuses with it and their ducts anastomose
Development of pancreas
▪ The duct of ventral bud and distal part of the duct of the dorsal bud form the ———duct that opens on the ——-
▪ The proximal part of the duct of the dorsal bud often persists as the ——- duct that opens separately on the ——-
▪ The —- bud forms most of the pancreas
▪ The ventral bud gives rise to the —— and ——-
▪ The duct of ventral bud and distal part of the duct of the dorsal bud form the main pancreatic duct that opens on the major duodenal papilla
▪ The proximal part of the duct of the dorsal bud often persists as the accessory pancreatic duct that opens separately on the minor duodenal papilla
▪ The dorsal bud forms most of the pancreas
▪ The ventral bud gives rise to the uncinate process and part of the head of the pancreas
Development of the pancreas
▪ Finally pancreas comes to lie horizontally along the ——- abdominal wall in a retroperitoneal position
▪ Insulin production begins -——th week
▪ Glucagon —-th week
▪ Finally pancreas comes to lie horizontally along the posterior abdominal wall in a retroperitoneal position
▪ Insulin production begins -10th week
▪ Glucagon 15th week
▪ Spleen develops from the mesenchyme within the —- mesogastrium
▪ Begins to develop in—th week and attains its shape early in fetal life
▪ Is —- initially but lobules normally disappear before birth
▪ Spleen functions as a ——-until late fetal life, but retains its potential for blood cell formation even in adult life
▪ Spleen develops from the mesenchyme within the dorsal mesogastrium
▪ Begins to develop in 5th week and attains its shape early in fetal life
▪ Is lobulated initially but lobules normally disappear before birth
▪ Spleen functions as a hematopoeitic organ until late fetal life, but retains its potential for blood cell formation even in adult life
▪ Spleen develops from the mesenchyme within the —- mesogastrium
▪ Begins to develop in—th week and attains its shape early in fetal life
▪ Is —- initially but lobules normally disappear before birth
▪ Spleen functions as a ——-until late fetal life, but retains its potential for blood cell formation even in adult life
▪ Spleen develops from the mesenchyme within the dorsal mesogastrium
▪ Begins to develop in 5th week and attains its shape early in fetal life
▪ Is lobulated initially but lobules normally disappear before birth
▪ Spleen functions as a hematopoeitic organ until late fetal life, but retains its potential for blood cell formation even in adult life
Derivatives of the Mesenteries of the Foregut
▪ Dorsal Mesoesophagus: —-
▪ Ventral Mesoesophagus: ——
▪ Dorsal Mesogastrium: —-
▪ Ventral Mesogastrium:——
▪ Dorsal mesentery of the duodenum: ———-
▪ Ventral mesentery of the duodenum: ———
Derivatives of the Mesenteries of the Foregut
▪ Dorsal Mesoesophagus: Crura of the diaphragm
▪ Ventral Mesoesophagus: disappears completely
▪ Dorsal Mesogastrium: Greater omentum
Lienorenal ligament
Gastrosplenic ligament
▪ Ventral Mesogastrium:
Lesser omentum
Visceral peritoneum of the liver Falciform ligament of the liver
▪ Dorsal mesentery of the duodenum: persists in the proximal part (one inch) as hepatoduodenal ligament
▪ Ventral mesentery of the duodenum: disappears almost completely
Anomalies Related to the Development of the Liver & Gall Bladder
▪ Anomalies of liver are rare.
▪ Variations in hepatic ducts, cystic and bile ducts are common and clinically significant
▪ ——- is the most common serious anomaly. Jaundice develops soon after birth. If uncorrected surgically leads to death
Anomalies Related to the Development of the Liver & Gall Bladder
▪ Anomalies of liver are rare.
▪ Variations in hepatic ducts, cystic and bile ducts are common and clinically significant
▪ Extrahepatic biliary atresia is the most common serious anomaly. Jaundice develops soon after birth. If uncorrected surgically leads to death
List Anomalies Related to the Development of the Pancreas & Spleen
Anomalies Related to the Development of the Pancreas & Spleen
▪ Accessory pancreatic tissue
▪ Annular pancreas
▪ Accessory splenic tissue
Duodenal atresia is found in how many births
1:10000-1:15000
