Lecture 4 - Embryo (Reep!) Flashcards Preview

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Flashcards in Lecture 4 - Embryo (Reep!) Deck (48):
0

when does regionalizationof endodermal gene expression occur?

early - prior to gut tube formation

1

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

surrounding mesenchyme and splanchnic mesoderm

2

what does transverse folding of tilaminar embryo form?

gut tube

3

head fold and tail fold create what?

foregut and hindgut

4

lateral body folds create what?

closure at midline

5

what are the major components of gut development

endoderm, splanchnic mesoderm and neural crest

6

how does the trachea begin?

as an outgrowth of the esophagus

7

when does the esophagus elongate?

during growth of cervical and thoracic regions

8

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

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

9

describe the develoment of the compound stomach

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

10

describe the development of the liver

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

11

where do hepatocytes derive from?

endoderm of foregut

12

where does the gall bladder originate from

buds off hepatic diverticulum

13

which animals do not have a gall bladder?

horse and rat

14

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

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

15

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

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

16

how do the hepatic buds develop into hepatoblasts?

the hepatic buds interact with surrounding mesenchyme and proliferate as hepatoblasts

17

what does Notch signaling do?

it transforms some hepatoblasts into biliary epithelial cells.

without the presence of Notch signaling, they develop into hepatocytes

18

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

presence of Notch: hepatoblasts differentiate into biliary epithelial cells

absence of Notch: hepatoblasts become hepatocytes

19

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

they develop independently initially and eventually anastomose

20

what two things seen together imply a common genetic dysfunction?

1. biliary cysts
2. polycystic kidneys

21

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

arises from duodenum to form left lobe and accessory pancreatic duct

22

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

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

23

describe the development of the small intestine

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

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

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

25

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

volvulus - a twisting of the intestine; constriction and atrophy

26

what separates the cloaca into the rectum and urogenital sinus?

the urorectal septum

27

define stenosis

local narrowing of gut lumen

28

define atresia

closure of gut lumen; becomes critical at birth

29

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

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

30

where is atresia most commonly seen in the cow?

jejunum, colon, rectum

31

where is atresia most commonly seen in the pig?

rectum

32

where is atresia most commonly seen in the cat?

colon

33

where is atresia most commonly seen in the foal?

colon

34

where in the dog is stenosis rarely seen?

the jejunum

35

where in the cow is stenosis rarely seen?

the jejunum

36

where in the lamb is stenosis rarely seen?

the colon

37

where in the cat is stenosis rarely seen?

the colon

38

describe and define blind diverticulum

its an outpocketing of the gut tube

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

39

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

usually involve neural crest and enteric nervous system

two examples: megaesophagus and lethal white syndrome

40

what is a fistula?

an opening with another system

41

what are 3 examples of fistulas?

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

42

what happens in a urorectal (rectourethral) fistula?

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

43

what happens in an umbilical fistula?

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

44

what are two examples of hernias?

1. omphalocele
2. umbilical hernia

45

what is an omphalocele?

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

46

what is an umbilical hernia?

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

47

what is situs inversus?

1. lateral transposition of viscera (right/left reversal)
2. often accompanied by "immotile cilia syndrome"

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