Lecture 3 - Gut Development

Question 1

Foregut extends from?

Answer 1

Pharynx -> proximal 1/2 duodenum

Question 2

Midgut extends?

Answer 2

Distal 1/2 duodenum -> Proximal 2/3 Transverse colon

Question 3

Hindgut Extends?

Answer 3

Distal 1/3 Transverse Colon -> Proximal 2/3 Anal Canal

Question 4

Early development 3 layer disc?

Answer 4

Ectoderm, Mesoderm, Endoderm

Question 5

Lateral Folding of 3 layers?

Answer 5

Ectodem and mesoderm fold medially and ventrally, closing off the endoderm to form a seperated gut-tube structure

Question 6

Disc layers become?

Answer 6

Endoderm: epithelial lining of tube; Mesoderm: supporting structures and smooth muscle (space is body cavity -> grater sac)

Question 7

Longitudinal Folding of endoderm?

Answer 7

Endodem pulls yolk sac purse-like fashion making splits of gut (midgut remains open w yolk sac)

Question 8

Extremity Tube Membrane Formation?

Answer 8

Oropharyngeal and Anal membrnaes open at cranial and caudal ends respectively

Question 9

Lumen of Tube development?

Answer 9

Initially patent (open), epithelium then proliferates and blocks the tube, then recanalisation occurs to clear space within the filling

Question 10

Arterial Supply in Gut Differentiation?

Answer 10

Fore: Celiac Trunk; Mid: Sup. Mesenteric; Hind: Inf. Mesenteric

Question 11

Oesophagus formation?

Answer 11

Tracheoesophageal ridge forms, trachea partitions ventral to leave oesophagus, which starts short then rapidly elongates

Question 12

Incomplete partitioning problems?

Answer 12

Tracheoesophangeal Fistula (connection) and Atresia (blockage)

Question 13

Congenital Hiatal Hernia?

Answer 13

Hindered oesophageal elongation leads to stomach displacement and herniates into thorax

Question 14

Stage 2 of Stomach formation? (Stage 1 being initial dilation)

Answer 14

Dilation continues, roation on long axis (0 degrees clockwise, ant. mesogastrium moves right, post. mesogastrium moves left

Question 15

Stage 3 of Stomach formation?

Answer 15

Dilation continues, rotation on coronal axis 90 degrees clockwise, right boundary becomes superior (lesser curvature), left boundary becomes inferior (greater curvature)

Question 16

Greater Omentum formation?

Answer 16

Dorsal mesogastrium hangs as result of stomach rotation, both sides fuse to dform 4 layered peritoneal structure

Question 17

Congenital Hypertropic Pyloric Stenosis?

Answer 17

Thickening of pylorus muscular wall, blocks exit of stomach to duodenum (non-bilias vomiting)

Question 18

Liver origin?

Answer 18

Subsection from the duodenum within ventral mesogastrium, then splits into two compartments: liver and gall bladder

Question 19

Pancreatic formation?

Answer 19

Ventral pancreatic bud is connected to the bile duct, rotates with the duodenum to meet the posterior pancreatic bud forming the pancreas with 2 ducts to the gut

Question 20

Midgut Elongation & herniation?

Answer 20

U-Shaped midgut loop, with cranial and caudal limb formation; loops migrate into umbilical cord (still in contact w yolk sac

Question 21

Midgut Rotation?

Answer 21

Rotates 270 degrees counterclockwise, herniation retracts after embryonic growth, loop returns to abdominal cavity, at cecum level (top right) rotates and goes down (bottom right)

Question 22

Urorectal Septum?

Answer 22

Divides what will be the Hindgut from the Allantois which becomes GU structures

Question 23

Rectal Atresia?

Answer 23

Anal canal and rectum seperate, fistulas from large intestine to either urethra, bladder or vagina

Question 24

Hirschprung’s Disease?

Answer 24

Absence of ANS ganglion cells in wall of gut leading to failure to relax and build up of fecal content