Exam #3 Flashcards Preview

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Flashcards in Exam #3 Deck (74):
1

Primitive gut closed at ends by?

Bilaminar membranes:
oropharyngeal membrane and cloacal membrane (made of endo and ectoderm)

2

Primitive gut suspended to body wall by?

dorsal mesentery (double fold) and ventral mesentery

3

Primitive gut temporarily connected to what?

yolk sac

4

primitive gut supplied blood by?

ventral branches of the aorta

5

digestive system is the main organ system derived from embryonic?

Endoderm

6

Parts of the dorsal mesentery?

stomach: greater omentum (dorsal mesogastrum)
mesoduodenum
jejunum/ileum: mesentery
descending colon: ascending mesocolon
Lesser omentum: heptogastric and hepatoduodenum

7

Falciform ligament

remnant of fetal ventral mesentery and connects liver to body wall

8

4 divisions of the primitive gut:

1. Pharynx (to GI and respiratory tract)
2. Foregut
3. Midgut
4. Hindgut

9

Components of the foregut?

esophagus, stomach, descending duodenum, liver and pancreas

10

Components of the midgut?

ascending duodenum ---> transverse colon

11

Components of the hindgut?

descending colon (distal 1/3), rectum and anal canal

12

Esophageal development

- cervical part not surrounded by coelom
- not suspended by mesentery
- maintains initial shape and position (above trachea, slight left from thoracic inlet to diaphragm)

13

Arteries to foregut, midgut, and hindgut?

1. Foregut: celiac a.
2. Midgut: cranial mesenteric a.
3. Hindgut: caudal mesenteric a., internal pudendal, and femoral in some

14

Stomach begins as a fusiform dilation of the?

caudal foregut

15

differential growth of the walls results in changes in position and appearance of?

Stomach
- Differential growth of walls also leads to compartments

16

dilations becoming curvatures?

dorsal dilation --> greater curvature
ventral dilation --> lesser curvature

17

Positional changes of the stomach

rotates 90 degrees clockwise along its axis and dorsal dilation shifts to the left (liver growing further pushes left and caudoventral)

18

Order of differentiation of compartments of ruminant stomach

1. Rumen: expansion of fundus
2. reticulum: as caudoventral pocket of fundus
3. omasum: expansion of lesser curvature
4. abomasum: dilation of the pyloric region

19

Adult size of stomach reached after?

1 year of age
- compartments change shape and relative capacities during growth (milk --> grasses)

20

Liver = the largest

GLAND of the body

21

Liver begins as?

hepatic diverticulum = ventral outgrowth of foregut

22

Formation of liver sinusoids?

endodermal cells proliferate into cords that anastomose around vitelline and umbilical veins

23

Formation of the common hepatic duct?

expansion of the liver narrows the connection with the foregut and the hepatic ducts merge

24

Gallbladder formation?

diverticulum of liver bud - cystic duct joins the hepatic duct to form the bile duct (opening at origin of liver bud)

25

No gallbladder in?

Horse, rat and birds - forms but quickly regresses

26

Septum Transversum

liver expands temporarily - forms the centrum tendineum of diaphragm

27

Liver remains connected to caudal vena cava by? and to the centrum tendineum by?

caudal vena cava -> coronary ligament
centrum tendineum --> triangular ligaments

28

Ventral mesentery divided by liver into 2 things?

lesser omentum and falciform ligament

29

Parts of the lesser omentum?

hepatogastric ligament and hepatoduodenal ligament

30

origin of the hepatic diverticulum shifted dorsally by?

differential growth of duodenum

31

Pancreas dual origin: left lobe

dorsal diverticulum from duodenum forms left lobe & accessory duct

32

Pancreas dual origin: Right Lobe

ventral diverticulum around greater curvature from hepatic diverticulum forms right lobe (along descending duodenum) with pancreatic duct

33

Species with both pancreatic and accessory ducts?

dog and horse

34

species with only a pancreatic duct?

cat and small ruminants

35

species with only an accessory pancreatic duct?

pig and ox (opens at minor duodenal papilla)

36

Midgut characteristics?

forms greater part of digestive tract, suspended by dorsal mesentery and temporarily connected to yolk sac

37

Physiological herniation of midgut causes?

rapid elongation in a small abdominal cavity

38

Result of physiological herniation?

herniation into umbilical cord in a U shaped loop with cranial (descending) and caudal (ascending) limbs

39

Rotation of the midgut?

loop rotates around the axis of the cranial mesenteric A. - determined by connection to yolk sac and uneven growth
- full rotation: 270 degrees counterclockwise around artery forming root of mesentery (180 than 90 during withdrawal)

40

withdrawal of loop:

sequence of withdrawal determines the final placement of intestines

41

Cranial limb of the midgut

returns first and passes to the L caudal to artery - forms duodenum and jejunum

42

Caudal limb of the midgut:

passes to right in from of cranial mesenteric A.

43

Species differences:

formation of secondary loop of ascending colon
1. spiral colon: pig and ruminants
2. bend colon: horse

44

Cloaca

common chamber for digestive and urogenital systems (persists in adult birds, reptiles and amphibians)

45

Urorectal septum

anal canal and urogenital sinus

46

Allantois

diverticulum of the hindgut with yolk sac from the umbilical cord -> forms part of the urinary bladder and urachus

47

Physiological Gut Atresia

temporary occlusion of the gut by epithelial proliferation - recanalization occurs by degeneration of the central epithelium
- not simultaneous events and anomalies occur at any level

48

Meconium

product of fetal digestion (amniotic fluid/embryonic debris) - sticky semisolid green feces

49

When should meconium be completely eliminated?

by day 4 postnatally - should start 6-8 hrs post birth

50

Meconium retention

common cause of colic in equine neonates (treat with enema)

51

4 possible causes of gut atresia/stenosis

1. fetal vascular accidents: vessels dont form/regress
2. lack of re-canalization
3. gut rotation defects (clockwise or lack of rotation)
4. other causes: cattle rough manipulation of fetal membranes during preg Dx)

52

Gut atresia/stenosis genetic condition in?

horses, jersey cows and some dog breeds

53

Pyloric stenosis

rare in domestic animals - commonly due to hypertrophy of wall

54

Anal atresia

(imperforated anus)
- due to persistent anal membrane - Tenesmus (distension/straining)
- surgical corrected

55

Urorectal septal defects - fistulas

errors in separating cloaca - ectopic anal opening (named for site of communication)

56

Types of Urorectal Septal defects (7)

1. persistent cloaca
2. anal stenosis
3. persistent anal membrane
4. anoperineal fistula
5. rectovaginal fistula
6. Rectourethral fistula
7. rectal atresia

57

Congenital megaesophagus

neural reflex defect - lack of motor function - absent peristalsis
Result: lack of relaxation of sphincter, esophageal distension throughout

58

Symptoms of megaesophagus

postprandial regurgitation of undigested food

59

Incidence and management of megaesophagus

breed predilection in dogs
symptomatic tx: bailey feeding chair or PEG tube
most common cause of regurge in cats and dogs
- can also be caused by vascular ring anomalies (persistent right aortic arch)

60

Congenital Megacolon

lack of motor function due to absence of myenteric ganglia
result: hypertrophic dilation of gut cranial to constricted area (compaction)

61

symptoms of congenital megacolon:

tenesmus (strain), constipation, abdominal distension

62

Megacolon details?

- genetic defect
- white foals with overo parents (painted and pinto ponies)
- Mx: surgery difficult (manx cats)
- predisposing factors: stenotic pelvic canal, foreign bodies, tumors, lumbosacral cord inj.

63

Mega conditions involve lack of migration of what embryonic cells and is absence of what type of innervation?

- Neural crest cells
- Autonomic ganglia

64

Congenital umbilical hernia

- incomplete closure of abdominal wall at umbilicus
result: herniation of viscera under skin - can be genetic or not - pigs highest incidence - sugical correction

65

Vitelline duct anomalies

persistent patent ductus - intestinal-umbilical communication (horses) - fecal material evacuated through umbilicus (or meckel's diverticulum/ vitelline cyst)

66

Urinary and repro systems develop from?

intermediate mesoderm (kidneys, gonads and genital duct system)

67

Urinary and genital ducts share a common cavity

urogenital sinus

68

Urinary system formation:

intermediate mesoderm migrates ventrally and proliferates - forms nephrogenic cords (cranial portion segmented and caudal portion not)

69

Pronephros

clusters of cells connected to the pronephric duct - transitory and non-functional
- its duct is taken over by the mesonephros

70

Mesonephros

consists of excretory tubules and mesonephric duct (renal corpuscle) - temporary function in some species (birds and reptiles) - becomes adult kidney in fish and amphibians

71

Metanephros

- dual origin
- ureteric bud: arises from dorsal evagination of mesonephric duct
- forms the collecting system when distal end expands to form renal pelvis, calyces, collecting tubules and proximal part of ureters

72

Metanephric blastema

- from intermediate mesoderm surrounding ureteric bud - forms excretory system

73

Nephrogenesis stops when?

At birth (kidney cannot regenerate) - grow postnatally due to growth in tubule size
- migrate from sacral to lumbar region
- metanephric kidney begins to function in fetal stage

74

the 2 kidney primordia promote?

reciprocal differentiation