Week 3: Prenatal Development - Rotation Of Foregut, Dorsal And Ventral Mesenteries

Front 1

Describe gut tube formation

Back 1

-delineated from yolk sac during process of embryonic folding (ventral bending of cranial and caudal ends, lateral bending of body).
-gut tube closed at two ends by oropharyngeal membrane cranially and cloacal membrane caudally

Front 2

Three subdivisions of developing gut tube

Back 2

- foregut, midgut, hindgut

Front 3

Four main events for developing gut tube

Back 3

1. rotation of foregut 90 degrees in clockwise direction
2. development of the greater omentum and lesser peritoneal sac from the posterior (dorsal) mesentery
3. rotation of the midgut 270 degrees around the superior mesenteric artery
4. tremendous growth of the midgut loop

Front 4

Early differentiation of GI tract occurs in the __ week

Back 4

5th

Front 5

Foregut developmental (5 weeks)

Back 5

-short, extends from pulmonary outgrowth to liver outgrowth/hepatic diverticulum
-posterior to septum transversum

Front 6

Midgut development (5 weeks)

Back 6

-no ventral mesentery, communicates with yolk sac through vitello-intestinal duct (at umbilicus)
-continuous caudally with short hindgut. no distinct boundary between two parts

Front 7

Hindgut development (5 weeks)

Back 7

-joined caudally by allantois, forming common endodermal chamber or cloaca, which receives the Wolffian ducts

Front 8

What is the distinctive feature demarcating the two zones of the midgut and the hindgut

Back 8

There is none

Front 9

9-10 week differentiation of GI tract- what organs involved, starting to develop

Back 9

-stomach forming by fusiform dilatation of foregut dorsal to septum transversum
-increase in length of trachea, esophagus
-narrowing of hepatic diverticulum, forming tubular common bile duct from which gallbladder arises distally
-short diverticulum of bile duct proximal to gallbladder is rudiment of ventral pancreas
-dorsal to foregut at more cranial level is rudiment of dorsal pancreas

Front 10

What is the septum transversum ventral to in weeks 9-10?

Back 10

-terminal segment of esophagus
-stomach
-proximal part of duodenum as far caudally as bile duct

Front 11

foregut development weeks 9-10

Back 11

-suspended by septum transversum ventrally, dorsal mesentery dorsally
-will give rise to pharynx, thyroid gland, trachea, lungs, esophagus in thorax, terminal esophagus, stomach, 1 and 2 of duodenum, pancreas, liver, gallbladder in abd

Front 12

midgut development 9-10 weeks

Back 12

-begins caudally to septum transversum, no ventral mesentery
-comprises 3rd, 4th (distal) part of duodenum and midgut loop
-dorsal mesentery helps suspend it
-vitello intestinal duct arises from apex of loop
-caudal limb -localized dilitation is primordium of cecum, appendix
-elongation of midgut loop in later stages--> extra embryonic coelom, forming umbilical hernia

Front 13

Esophagus

Back 13

-muscular tube conveying food from pharynx to stomach
-develops from foregut caudal to primordial pharynx
-partitioning of common endodermal tube by tracheoesophageal septum
-4 histological layers
-T10 from thorax into abdomen
-LARP- vagal trunks

Front 14

Function of stomach

Back 14

-expanded part of digestive system bet esophagus and small intestine
-blender and reservoir as it performs enzymatic digestion, gastric juice coverts food into chime

Front 15

Stomach development, rotation

Back 15

4th week-->dilatation of foregut, enlargement of caudal part of foregut-->ventrodosral enlargement,-->posterior grows, greater curvature-->rotates 90 degrees clockwise around craniocaudal axis. dorsal convex faces left, ventral concave faces right--> minor tippiing of caudal end of stomach in cranial direciton

Front 16

Stomach is considered intraperitoneal (T/F)

Back 16

true

Front 17

Right surface of stomach becomes anterior surface, left surface of stomach becomes posterior surface (T/F)

Back 17

false, opposite

Front 18

What is omenta?

Back 18

-double layered fold of peritoneum that extends from stomach and proximal part of duodenum to an adjacent organ in either the anterior or posterior direction

Front 19

Greater omentum

Back 19

-left side, attach stomach to posterior abdominal wall
-3 portions: gastrophrenic ligament, gastrosplenic ligament, gastrocolic ligament

Front 20

Lesser omentum

Back 20

-right side, extends bet stomach/duodenum and liver
-two parts: hepatogastric ligament bet lesser curvature, hepatoduodenal ligament bet upper duodenum and liver

Front 21

What is the pancreas?

Back 21

-elongated, accessory digestive gland that has exocrine and endocrine functions

Front 22

Where is the pancreas located?

Back 22

-behind or posterior to stomach, is covered anteriorly by transverse mesocolon, is secondary retroperitoneal

Front 23

Pancreatic development

Back 23

begin as dorsal and ventral primordia/buds in mesenteries--> dorsal bud becomes larger-->duodenum rotates to right, carries ventral bud and bile duct behind it and into dorsal mesentery,-->ventral pancreas fuses with dorsal, superior mesenteric vein becomes trapped bet primoordia-->ventral bud gives rise to lower head of pancreas, uncinate process. dorsal bud gives rise to remaining part of adult pancreas

Front 24

Annular pancreas

Back 24

-failure of full rotation. descending portion of duodenum surrounded by pancreatic tissue, can become obstructed.

Front 25

Ductal rearrangements of pancreas

Back 25

-both buds possess large duct. main duct of ventral pancreas forms anastomotic connection with duct of dorsal bud
-duct of dorsal bud- tail- runs through substance of gland to head, turns into bile duct and joins it
-duct of ventral bud- drains uncinate process, inferior part of head of pancreas
-regression of portion of dorsal pancreatic duct bet anastomotic connection and duodenum- forming main pancreatic duct of wirsung. if no regression, then accessory duct of antorini

Front 26

Development of omental bursa (lesser sac)

Back 26

-develops within dorsal mesentery as divericulum
-dorsal mesentery bulgs to left
-stomach rotated in clockwise direction
-posterior wall of bursa?

Front 27

Boundaries of epiploic foramen

Back 27

i. Posterior: hepatocaval mesentery (IVC)
ii. Roof: caudate lobe
iii. Floor: first part of the duodenum
iv. Anterior: hepatoduodenal ligament (portal triad)

Front 28

Spleen development

Back 28

-proliferation of mesoderm in left wall of omental bursa- intraperiotneal
0inflitrated with lymphoid cells, by 4th month- vascular structure of red pulp takes place. 3rd-5th month important site of embryonic hematopoiesis
=suspended by splenorenal ligament, part of spleen to stomach becomes gastrosplenic ligament