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Undeleted > Lecture 4 - Embryo (Reep!) > Flashcards

Lecture 4 - Embryo (Reep!) Flashcards

0
Q

after regional specification, the gut endoderm interacts with what two things to form specific structures?

A

surrounding mesenchyme and splanchnic mesoderm

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1
Q

when does regionalizationof endodermal gene expression occur?

A

early - prior to gut tube formation

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2
Q

what does transverse folding of tilaminar embryo form?

A

gut tube

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3
Q

head fold and tail fold create what?

A

foregut and hindgut

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4
Q

lateral body folds create what?

A

closure at midline

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5
Q

what are the major components of gut development

A

endoderm, splanchnic mesoderm and neural crest

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6
Q

how does the trachea begin?

A

as an outgrowth of the esophagus

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7
Q

when does the esophagus elongate?

A

during growth of cervical and thoracic regions

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8
Q

what are the 3 mechanisms of development of the stomach and describe each one briefly

A

displacement: caudally, due to elongation of esophagus
reorientation: rotation of stomach; creates greater and lesser omenta
differential enlargement: formation of fundus

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9
Q

describe the develoment of the compound stomach

A

initially develops like a simple glandular stomach

by the end of the first month:
rumen and reticulum develop from the fundic region
omasum and abomasum develop from the lesser curvature

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10
Q

describe the development of the liver

A

the hepatic diverticulum is an outgrowth of the foregut into the mesenchyme os the septum transversum

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11
Q

where do hepatocytes derive from?

A

endoderm of foregut

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12
Q

where does the gall bladder originate from

A

buds off hepatic diverticulum

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13
Q

which animals do not have a gall bladder?

A

horse and rat

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14
Q

what induces the hepatic diverticulum to begin branching? what does the branching form?

A

under the inductive influence of the surrounding mesenchyme.

the branching forms hepatic buds that differentiate into hepatocytes and biliary cells that form the biliary duct system

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15
Q

endoderm is induced to become hepatic buds by what 3 structures and associated signals

A
  1. cardiac mesoderm via FGF
  2. septum transversum mesoderm via BMP
  3. endothelial cells via an unknown signal
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16
Q

how do the hepatic buds develop into hepatoblasts?

A

the hepatic buds interact with surrounding mesenchyme and proliferate as hepatoblasts

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17
Q

what does Notch signaling do?

A

it transforms some hepatoblasts into biliary epithelial cells.

without the presence of Notch signaling, they develop into hepatocytes

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18
Q

what do hepatoblasts differentiate into with the presence of Notch signaling?
absence of Notch signaling?

A

presence of Notch: hepatoblasts differentiate into biliary epithelial cells

absence of Notch: hepatoblasts become hepatocytes

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19
Q

describe the development of the intra and extra hepatic portions of the biliary system?

A

they develop independently initially and eventually anastomose

20
Q

what two things seen together imply a common genetic dysfunction?

A
  1. biliary cysts

2. polycystic kidneys

21
Q

what does the dorsal pancreatic diverticulum arise from? what does it form?

A

arises from duodenum to form left lobe and accessory pancreatic duct

22
Q

what does the ventral pancreatic diverticulum arise from? what does it form?

A

arises from hepatic diverticlum and forms the right lobe and pancreatic duct

23
Q

describe the development of the small intestine

A
  1. loss of yolk sac
  2. evagination of cecum
  3. rapid elongation of small intestine into umbilical stalk
  4. rotation of intestinal loop about cranial mesenteric artery
  5. withdrawal of small and large intestines from umbilical stalk
24
Q

describe the shape of the large intestine, ascending colon for the dog, horse, cattle, and pig

A

dog: straight
horse: sharply bent (volvulus can occur at bend)
cattle: flatly coiled
pig: spiral

25
Q

what can occur at the bend of the horse’s large intestine, ascending colon?

A

volvulus - a twisting of the intestine; constriction and atrophy

26
Q

what separates the cloaca into the rectum and urogenital sinus?

A

the urorectal septum

27
Q

define stenosis

A

local narrowing of gut lumen

28
Q

define atresia

A

closure of gut lumen; becomes critical at birth

29
Q

what are the 4 most common examples of stenosis and atresia?

A

atresia ani (imperforate anus)
rectal atresia
esophageal stenosis or atresia - often accompanied by tracheoesophageal fistula
intestinal stenosis or atresia

30
Q

where is atresia most commonly seen in the cow?

A

jejunum, colon, rectum

31
Q

where is atresia most commonly seen in the pig?

A

rectum

32
Q

where is atresia most commonly seen in the cat?

A

colon

33
Q

where is atresia most commonly seen in the foal?

A

colon

34
Q

where in the dog is stenosis rarely seen?

A

the jejunum

35
Q

where in the cow is stenosis rarely seen?

A

the jejunum

36
Q

where in the lamb is stenosis rarely seen?

A

the colon

37
Q

where in the cat is stenosis rarely seen?

A

the colon

38
Q

describe and define blind diverticulum

A

its an outpocketing of the gut tube

often see diverticulum of yolk stalk - an outpocketing of intestine into patent yolk stalk

39
Q

what do neuromuscular abnormalities usually involve and what are two examples of such conditions?

A

usually involve neural crest and enteric nervous system

two examples: megaesophagus and lethal white syndrome

40
Q

what is a fistula?

A

an opening with another system

41
Q

what are 3 examples of fistulas?

A
  1. tracheosophageal fistula - often accompanies esophageal atresia
  2. urorectal (rectourethral) fistula
  3. umbilical fistula
42
Q

what happens in a urorectal (rectourethral) fistula?

A
  • urorectal septum fails to complete development.
  • fecal material gets into urogenital system.
  • females may survive
  • often accompanied by rectal atresia - always critical
43
Q

what happens in an umbilical fistula?

A

entire yolk stalk remains patent, connecting intestinal lumen with opening at navel

44
Q

what are two examples of hernias?

A
  1. omphalocele

2. umbilical hernia

45
Q

what is an omphalocele?

A

failure of gut to return to abdominal cavity from umbilical cord; covered by amnion

46
Q

what is an umbilical hernia?

A

gut returns, but then herniates again through defect in muscular wall around umbilicus; covered by amnion AND peritoneum

47
Q

what is situs inversus?

A
  1. lateral transposition of viscera (right/left reversal)

2. often accompanied by “immotile cilia syndrome”

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