Development Of Digestive System Flashcards

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1
Q

What is the primitive gut

A

Part of endoderm-lined yolk sac cavity incorporated into the embryo

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2
Q

3 parts of the primitive gut?

A

Foregut, midgut and hindgut

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3
Q

Foregut and hindgut are blind ended, what about midgut

A

Temporarily connected to yolk sac by vitelline duct

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4
Q

Two parts of the foregut

A

Pharyngeal gut and caudal to pharyngeal gut up to the hepatic diverticulum (so from proximal part of duodenum and up)

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5
Q

Pharyngeal gut (part of foregut) extends from where to where

A

Oropharyngeal membrane to respiratory diverticulum

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6
Q

Where does midgut begin and end

A

Caudal to liver bud and extends to junction of proximal and distal transverse colon

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7
Q

Hindgut extends from where to where

A

Distal transverse colon to cloacal membrane

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8
Q
  1. What arises from endoderm

2. What arises from visceral (splanchnic) mesoderm

A
  1. Epithelial lining of GI tract and glands

2. Muscle, connective tissue, and peritoneal components of wall of gut (and stroma of glands)

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9
Q

Ventral mesentery exists for what 3 organs

Derived from?

A

Esophagus, stomach, and initial part of duodenum

Septum transversum (mesodermal plate between pericardial cavity and stalk of yolk sac)

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10
Q

Function of tracheoesophageal septum

A

Completely separates esophagus from respiratory diverticulum

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11
Q

What is esophageal atresia?

What does this cause

A

Distal esophagus becomes connected to trachea just above bifurcation

Accumulation of excess amniotic fluid (polyhydramnios)

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12
Q

Where does esophageal stenosis usually occur

A

In lower 1/3

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13
Q

What is a congenital hiatal hernia caused by

A

Failure of esophagus to lengthen causes stomach to be pulled up through esophageal hiatus of diaphragm

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14
Q

What part of the stomach do both vagus nerves innervate

A

Right vagus nerve innervates posterior wall of stomach
Left vagus nerve innervates anterior wall of stomach

~left side of stomach becomes anterior side

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15
Q

What creates the omental bursa/lesser peritoneal sac?

A

Rotation of stomach pulls dorsal mesogastrium to the left and ventral mesogastrium to the right creating a space behind stomach

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16
Q

What causes ventral mesogastrium to divide into 2 regions

What are these regions

A

Development of liver

Liver to ventral body wall (forms falciform ligament) and stomach to upper duodenum to lover (forms lesser omentum)

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17
Q

Free margin of lesser omentum contains what 3 things

A

Bile duct, portal vein, and hepatic artery (portal triad)

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18
Q

What causes pyloric stenosis

What does it cause

A

When musculature of stomach (usually circular fibers) hypertrophies in the pyloric region

Obstructs passage of food resulting in severe vomiting

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19
Q

What part of the gut is the duodenum

A

Terminal part of foregut and initial part of midgut

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20
Q

Duodenum rotates __

What does this contribute to

A

To the right with the pancreas

Contributes to these two organs being retroperitoneal (fuse with posterior body wall)

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21
Q

What forms the bile duct

A

Narrowing of connection between liver bud and foregut

22
Q

Hematopoietic cells, Kupffer cells and connective tissues cells originate from?

A

Mesoderm of septum transversum

23
Q

Cells of hepatic diverticulum give rise to?

A

Liver parenchyma (hepatocytes) and epithelial lining of biliary ducts

24
Q

Importance of the liver between months 2-7 of development

A

Produces RBCs and WBCs

25
Q

What is extrahepatic biliary atresia

A

Biliary ducts fail to recanalize leading to death unless liver transplant. Few of these cases result in a patent proximal ducts which is correctable without transplant

26
Q

What is the communication between the primitive gut and the yolk sac

A

Vitelline duct

27
Q

Location of septum transversum (made of mesoderm)

A

Between pericardial cavity and vitelline duct

28
Q

What is the pancreas formed by

A

Ventral and dorsal pancreatic buds that originate from endodermal lining of duodenum

29
Q

What forms the main pancreatic duct

Fate of proximal part of dorsal pancreatic duct

A

Distal part of dorsal pancreatic duct and entire ventral pancreatic duct

Either obliterated or becomes accessory pancreatic duct

30
Q

What forms pancreatic connective tissue

A

Visceral mesoderm surrounding pancreatic buds

31
Q

What is annular pancreas

What happens if it is compressed

A

Pancreatic tissue that surrounds the duodenum

Causes complete obstruction of duodenum

32
Q

What is the physiological umbilical herniation

A

Abdominal cavity becomes temporarily too small to accommodate the rapidly growing intestines, so they enter umbilical cord during 6th week-10th week (gives abdominal cavity time to grow)

33
Q

What is the last part of the midgut to reenter the abdominal cavity

A

Cecal bud

34
Q

As cecal bud descends into right iliac fossa, what does it cause

A

The ascending colon to be on the right side of abdominal cavity

35
Q

What is an omphalocele

A

Herniation of abdominal viscera through an enlarged umbilical ring
(Failure of the organs to return to the abdominal cavity) - high fatality rate because usually have chromosomal abnormalities as well

36
Q

What is gastroschisis?

A

Protrusion of intestinal loops into the amniotic cavity (so on the outside of umbilical cord) due to abnormal closure of body wall

37
Q

Other differences between omphalocele and gastroschisis

A

Omphalocele- high mortality rate; herniated viscera is covered by amnion
Gastroschisis- lower mortality rate because it is not associated with other abnormalities, common in babies of young moms who use cocaine during pregnancy; not covered by amnion so exposed and can be damaged easier

38
Q

What is/what causes Meckel’s/ileal diverticulum

Symptoms?

A

Small portion of vitelline duct persists forming outpocket of ileum- usually asymptomatic

Can cause ulcers/bleeding; symptoms mimic appendicitis

39
Q

What is enterocystoma/vitelline cyst

What can it cause

A

When both ends of vitelline duct transform into fibrous cords and middle portion forms a cyst (can compromise blood supply)

40
Q

What is a vitelline fistula

Symptom

A

Vitelline duct remaining patent which forms a communication between umbilicus and intestinal tract

Fecal discharge may be found at umbilicus

41
Q
  1. If primary intestinal loops only rotate 90 degrees COUNTERCLOCKWISE what happens
  2. What happens if 90 degrees CLOCKWISE
A
  1. Cecum and colon will end up on left side instead of right side; jejunum and ileum will be on left side
  2. Transverse colon will pass behind duodenum and lie behind SMA
42
Q

Where in the midgut are you most likely to have atresias and stenoses?

A

Duodenum

43
Q
  1. Atresia’s in upper part of duodenum are most likely from?

2. Distal duodenum and other parts of midgut?

A
  1. Lack of recanalization

2. Vascular accidents (will lead to blood loss and eventual transformation into a fibrous cord)

44
Q

Hindgut endoderm gives rise to

A

Internal lining of urinary bladder and urethra

45
Q

Caudal end of hindgut is called __

This is connected to

A

Cloaca

Allantois (which connects to umbilical cord)

46
Q

Cloacal membrane is derived from

A

Ectoderm and endoderm

47
Q

Urorectal septum divides cloaca into

A

Primitive urogenital sinus (anteriorly) and anorectal canal (posteriorly)

(These both rupture to form anal opening)

48
Q

What can cause rectourethral/rectovaginal fistulas?

A

Abnormalities in formation of cloaca and/or urorectal septum

49
Q

Most likely causes of rectoanal atresia?

A

Vascular accidents (may leave fistula, or cause loss of segment of rectum/anal canal)

50
Q

What causes an imperforate anus

A

Failure of anal membrane to breakdown

51
Q

What causes congenital megacolon (aka aganglionic megacolon/Hirschprungs disease)

How does it present

A

Scarce or absent parasympathetic neurons in distal colon (leaves this region permanently constricted - and causes proximal region to be dilated

Hypertrophy of sigmoid and descending colon, constipation, abdominal distention