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Flashcards in Exam 2 Deck (123):
1

Cardiovascular system first to?

become functional
--> Nervous first to differentiate

2

Cardiogenic fields

paired condensations of splanchnic mesoderm

3

endocardial tubes

cells proliferate and differentiate into angiogenic cell clusters, then cords, then paired tubes

4

inductive influences from what layer are essential for formation of heart function?

endoderm

5

endocardial tube (singular)

body folding causes tubes to fuse

6

cardia bifida

lack of fusion of the endocardial tubes (forms 2 non-functional hearts)

7

dorsal mesocardium

temporary connection of endocardial tube to foregut

8

Four parts of first differentiated endocardial tube

1. bulbis cordis
2. ventricle
3. atrium
4. sinus venosus

9

formation of cardiac loop determined by: (3) things

1. elongation - of tube within restricted pericardium
2. degeneration of dorsal mesocardium
3. anchorage of tube at both ends

10

Cardiac loop portions:

cranial portion: ventrocaudally and to right
caudal portion: dorsocranially and to the left

11

R: Dextocardia

heart on right side instead of left

12

R: Sinus Invertus

organs reverse sides

13

formation of cardiac chambers indicated by:

local expansions, direction of blood flow, and formation of cardiac septa

14

formation of AV canal

endocardium between 2 chambers proliferates to form endocardial cushions - divide AV canal into right and left canals

15

coronary groove

external constriction between common atrium and ventricle

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Septum Primum

ridge from roof of atrium extending towards cushions

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ostium primum

temprorary communication between atria

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ostium secundum

before fusing with cushions, the dorsal part of septum primum degenerates to form

19

septum secundum

dorsal: from roof of atrium
ventral: from cushions

20

Foramen Ovale

two parts of septum secundum do not fuse - leave opening

21

complete separation of two atria occurs when?

AFTER birth - when two septa fuse (due to pressure from left side)
--> Fossa ovalis in adult

22

Muscular septum (in ventricle partitioning)

formation of myocardial ridge between ventricles and bulbus cordis extending towards cushions

23

Membranous septum

completion of separation of ventricles from cushions

24

Bulbus cordis initially consists of two parts:

1. dilated part = bulbus cordis
2. narrow = conus cordis

25

Development of conus arteriosus

dilated part of bulbus cordis is incorporated into the right ventricle as origin of pulmonary trunk arteries

26

partitioning of conus cordis

initially maintains communication with both ventricles: divided eventually

27

conotruncal ridges

paired ridges that fuse on midline to form aorticopulmonary septum dividing it into two main channels: aortic and pulmonary

28

Sinus venosus

R - persists as sinus venarum (smooth part of right atrium)
L - coronary sinus

29

Blood vessels form

at the same time as heart

30

angiogenic cells that form the extraembryonic vessels?

yolk sac and allantois
--> allantois forms umbilical vessels

31

Vasculogenesis

formation of vascular plexuses

32

blood islands

hemangioblasts of splanchnic mesoderm

33

when blood islands connect?

form vascular plexuses
--> extraembryonic plexuses in yolk sac
--> intraembryonic plexuses around forming organs

34

angiogenesis

sprouting of blood vessels and remodeling of vascular plexuses - organs produce angiogenic factors for vessel formation

35

arterial and venous differentiation depends on?

amount and direction of blood flow (pressure differences)
--> large vessels receive alot of blood and capillaries a small amount
--> veins develop when receive low pressure
--> arteries high pressure so develop muscle around

36

embryonic arterial system:

PAIRED:
aortic arches, dorsal aorta, vitelline A, and umbilical A (from allantois)

37

embryonic venous system:

cranial and caudal cardinal v (turn into vena cavas)
vitelline v and umbilical v.

38

vitelline veins:

-blood from yolk sac to heart
- form hepatic sinusoids within liver
- cranial patent portions form hepatic veins and caudal patent portions form portal vein

39

vitelline arteries

distribute blood from dorsal aortae to yolk sac
-- in adult: right ones form ventral unpaired branches of aorta: bronchoesophageal, celiac, and cranial and caudal mesenteric aa.

40

umbilical veins:

convey oxygenated blood from placenta
--> right umbilical vein is obliterated and persists as falciform ligament

41

umbilical arteries

return fetal blood to placenta - if remains patent will supply urinary bladder as cranial vesical a. & if collapsed will form round ligament of bladder

42

Aortic Arches

represent arterial components of pharyngeal arches (core of mesoderm)
--> formed in serial order

43

vertebrate emryo: pharyngeal arch development

six pairs develop but only 3, 4 & 6 are retained (5 doesn't form or quickly regresses)

44

dorsal aortae:

caudal to arch 6, fuse to form adult aorta & in area where arches remain paired, extend to form internal carotid arteries

45

ventral aortae

fuse near heart:
cranial extensions form external carotid arteries & between arches 3 & 4 form common carotid arteries

46

Pharyngeal Pair 1, 2 & 5

1 & 2 degenerate and 5 either never forms or rapidly degenerates

47

Pharyngeal Arch 3

retained as connections between ventral aortae and internal carotid aa. (AKA first part of internal carotid)

48

Pharyngeal arch 4

left: forms adult aortic arch
right: forms brachiocephalic trunk

49

pharyngeal arch 6

proximal: form roots of pulmonary arteries / pulmonary trunk
distal:
right is lost & left becomes ductus arteriosus and in adult ligamentum arteriosum

50

fetal circulation from placenta to fetal tissues ("oxygenated")

placenta --> umbilical veins --> ductus venosus --> caudal vena cava --> RA --> foramen ovale --> LA --> LV --> aorta --> fetal tissues

51

Fetal circulation from fetal tissues to placenta ("deoxygenated")

venae cavae --> RA --> RV --> pulmonary trunk --> ductus arteriosus --> aorta --> umbilical arteries --> placenta

52

Foramen ovale?
Ductus arteriosus?

= communication between RA and LA
= communication between pulmonary trunk and aorta

53

4 main changes in post-natal circulation

1. closure of umbilical vessels (arteries within minutes and veins soon after)
2. closure of ductus arteriosus (72 hours b.c high oxygen concentration in blood)
3. closure of foramen ovale (pressure in right atrium higher than left - holds septum to wall and fuse - 1 wk to year)
4. complete separation of heart chambers is progressive event

54

Cardiovascular anomalies

occur in all domestic animals b.c of complex developmental processes and dramatic changes after birth
incidence higher in pedigree dogs b.c inbreeding
- humans- this is largest category of birth defects

55

cardiovascular anomalies due to : (4)

1. abnormal partitioning of cardiac chambers
2. abnormal formation of cushions (neural crest cells - AV Valves)
3. abnormal division of aortic and pulmonary channels
4. abnormal transformation of aortic arches

56

cardiovascular defects that are heritable

- often involves same anatomical site in group of related animals
- genetic testing helpful for selective breeding (especially if defect later onset)

57

degree of severity

can be proportional with defect - some defects lethal while some just limit peak performance of reproductive value

58

cardiovascular abnormalities can be single or in combination

ex. neural crest cells - heart chambers, valves, aortic channels, visceral skeleton of skull etc. - can cause microcephaly and cleft palate)
- some can be surgically corrected

59

Acyanotic anomaly

allows enough oxygenated blood to tissue for normal function

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cyanotic anomaly

not enough oxygenated blood in peripheral tissues (dx: dark bluish color of mucous membranes)

61

dilation as secondary changes with anomalies

abnormal increase in size of heart chamber(s) due to increased blood volume

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hypertrophy as secondary changes with anomalies

thickening of walls of chambers due to increased contraction force to empty chamber

63

Definition: Shunt

deviation of normal blood flow between systemic (L) and pulmonary (R)
possibilities: L-->R, R-->L, or bidirectional

64

L --> R Shunt causes:

L side pressure exceeds R side - leak of blood from systemic to pulmonary circulation (Ex. through incomplete ventricular septum)

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L --> R Shunt Symptoms:

volume overload due to increased pulmonary arterial flow and venous return --> pulmonary hypertension
Signs: exercise intolerance, dyspnea, pulmonary edema, venous distension, ventral edema, stunted growth, COPD

66

R --> L Shunt Cause:

R side pressure exceeds that on L side
--> often secondary to chronic pulmonary hypertension
- shunt reversal: will see L side chambers small and R side hypertrophied to sustain systemic BP

67

Symptoms:

cyanosis, dyspnea, exercise intolerance, occasional syncope (cerebral hypoxia)

68

Common L-->R shunt anomalies

ASD (atrial septal defect), VSD (ventricular septal defect), PDA (Patent ductus arteriosus) - more common & allow some oxygenation

69

Common R --> L shunt anomalies

PDA, Tetralogy of Fallot, Persistent Right Aortic Arch

70

Atrial septal defect

causes: defective formation of septa, lack of closure of foramen ovale
severity proprotional to size of defect
Result: R side dilation and hypertrophy and pulmonary hypertension
Tx: surgical closure

71

Ventricular septal defect

cause: presence of opening in interventricular septum (membranous part most common)
- L--> R (or bidirectional) shunt and pulmonary hypertension
Tx: surgical correction
Most common CHD in humans and cattle (usually fatal in cats and horses)

72

Patent Ductus Arteriosus

cause: lack of closure of ductus arteriosus and severity proportional to size of patency
Dx: abnormal heart sounds
Outcome: L --> R shunt - L side hypertrophy, pulmonary hypertension - overtime can become R --> L shunt leading to heart failure
- management is ligation if no secondary changes occur yet
reported in dogs (breed disposition)

73

Tetralogy of Fallot

classical cyanotic multiple defect
Cause: unequal division of conus cordis

74

Defects assocaited with Tetralogy of Fallot

defects: pulmonary stenosis, interventricular septal defect, overriding aorta (communicates with both chambers) and RV hypertrophy - secondary

75

Symptoms of Tetralogy of Fallot

cyanosis after exercise, dyspnea, exercise intolerance, syncope (inefficient O2 to brain)
may be surgically corrected
Prognosis: poor survival due to chronic complications (stenosis of pulmonary trunk)

76

Persistent Truncus Arteriosus

cause: lack of division of conus cordis into pulmonary trunk and aortic channels and a coexisting VSD
outcome: early onset heart failure - lethal if no early correction
Tx: correction by conduit revision (RV to pulmonary A)
- humans dogs & pigs

77

Persistent Right Aortic Arch

Cause: abnormal retention of right fourth aortic arch
result: vascular ring constricting trachea and esophagus - esophageal dilation (megesophagus) and regurge of solid foods
Dx: contrast xrays
Tx: surgical removal

78

Congenital Porto-Systemic Shunt

Causes: persistence of ductus venosus (intrahepatic in labs and aussies) or extrahepatic (small dogs - yorkies)
result: blood from GI tract bypasses liver into systemic circulation

79

Porto-systemic shunt symptoms,, diagnosis, reportings and management

neurological (siezures, head pressing), GI and urinary
Dx: advanced but will notice slow to wake from anesthesia and chronic kidney infection
Rep: cats and dogs
Tx: conservative - low protein diet (reduce ammonia build up) and antiobiotics (lower bacteria)

80

Lateral body foldings:

fuse on ventral midline to create tube within a tube cylindrical embryo
- inner tube = primitive gut & outer tube = body wall (with body cavity b/w)
- temporarily communicates with yolk sac

81

Primitive gut divisions:

pharynx, foregut, midgut and hindgut

82

Primitive gut closed by what two membranes?

oropharyngeal (gone = mouth) and cloacal (gone = anus)

83

Pharnyx development

extends from oropharyngeal membrane to esophagus - not surrounded by embryonic coelem - its mesoderm not split

84

Pharyngeal arches:

aggregations of mesenchyme in area of pharynx seperated by grooves

85

pharyngeal pouches and clefts

pouches (inside) = lined by endoderm
clefts (outside) = lined by ectoderm
--> 4 paired pouches in mammals

86

Pouch 1

becomes middle ear (tympanic) cavity and auditory tube

87

guttural pouch

diverticulum of the auditory tube in horses

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Pouch 2

becomes palatine tonsil - infiltrated by lymphatic tissue

89

Pouch 3

Dorsal part = becomes external parathyroid
Ventral part = becomes thymus

90

Pouch 4

Dorsal part = becomes internal parathyroid
Ventral Part = becomes ultimobranchial body (parafollicular cells in thyroid that produce calcitonin)

91

Cervical sinus

formed by clefts of 2,3&4

92

Respiratory diverticulum

- forms as outgrowth of ventral part of foregut (just behind 4th pouch)
- tracheoesophageal septum seperates it from rest of primitive gut

93

Dog lungs have a ?

paired lung origin

94

initial respiratory system development

1. extends caudally into sphalnchnic mesoderm
2. bifurcates into lung buds - left forms at more perpendicular angle
3. buds enlarge and form primary bronchi
4. primary bronchi branch - forms bronchial tree

95

Bronchial tree

1. primary bronchi
2. lobar bronchi
3. segmental bronchi
4. bronchioles
4. alveoli

96

species with tracheal bronchus

pigs and ruminants

97

Embryonic stage of lung maturation

First stage:
lung bud --> primary bronchi

98

Pseudo-glandular stage of lung maturation

Second stage:
completion of bronchial tree to terminal bronchioles

99

Canalicular stage

Third Stage
terminal bronchioles divide into respiratory bronchioles

100

Terminal sac stage

Fourth stage:
stage of primitive alveoli
- respiratory bronchioles divide to form alveoli
- formation of alveoli-capillary membrane (cuboidal to squamous cells)
- production of surfactant
- at this stage: respiration is possible

101

Alveolar stage:

Fifth stage:
late fetal stage (a lot occurs after birth)
- increase in number of alveoli by separation of present ones --> lung growth and expansion (respiratory capacity increased with exercise and hypoxia)

102

species with distinct lobulation of lung parenchyma

pig, ox and goat (only cranial and middle lobes)

103

Lung maturation at birth:

functionally mature but degree of functionality dependent on species (more mature at birth more functional)
- most species in terminal sac stages

104

Surfactant

phospholipid fluid coating alveoli (produced by type II cuboidal cells) to reduce surface tension
- produced in late fetal stage to prevent collapse of alveoli in expiration

105

Breathing movements before birth

important for conditioning of respiratory muscles

106

Atelectasis

absence of air in a normally air-filled space

107

3 factors affecting lung anomalies

1. endodermal origin (low differentiating ability)
2. sequential development (insults affect different stages)
3. available space (limited expansion in thorax)

108

Pharyngeal pouch anomalies

- related to formation of cysts (enclosed space filled with fluid) & fistulas (opening between two spaces)

109

Congenital guttural pouch tympany

gaseous distension due to defective opening of guttural pouch into pharynx (increase in phillies)

110

signs of guttural pouch tympany

swelling caudal to mandible, dysphagia
tx: surgical correction

111

Tracheal Collapse

- partial occlusion of trachea due to defective cartilages
- common in mini/toy breeds of dogs (genetic)
- signs: honking, coughing, gagging, cyanosis
- Dx: difficult
- Tx: conservative: bronchodilators, chondriotin (strengthen cartilage)
surgical - prosthetic rings
- important to manage obesity

112

Tracheal stenosis

local narrowing as primary defect (or fusion of cartilages
- signs: nonspecific resp distress
brachycephalic breeds predisposed
Tx: tracheal resection
- can also be caused by trauma from tracheostomy tube

113

Tracheoesophageal Fistula

- most severe of anomalies
- abnormal partitioning of esophagus and trachea (between foregut and lung primordium
- most common form associated with esophageal atresia
- calves

114

Symptoms of Tracheoesophageal fistula

cyanosis, coughing, vomiting, inhalation pneumonia
-- usually associated with other birth defects (VACTERL 50% with cardiac anomalies)
Tx: surgical
can also be acquired from tracheostomy tubes

115

esophageal atresia

lack of opening of tubular structure - esophagus

116

Lung agenesis

RARE - failure of lung buds to develop

117

Accessory/ectopic lungs

usually off left lung - from additional lung buds

118

Pulmonary cysts

form when terminal bronchioles lose connection with main branch - poor drainage of lung secretions and chronic lung infections

119

Lung hypoplasia

small lung, poorly developed alveoli (associated with skeletal defects, diaphragmatic hernia, congenital cardiac defects, small thoracic cavity etc.)

120

Respiratory distress syndrome:

- neonatal maladjustment syndrome (barker/dummy foal syndrome)

121

Causes of dummy foals:

insufficiency of surfactant (premature birth), incomplete lung expansion (insufficient blood to newborn), dystocia --> hypoxia --> irreversible lung changes

122

Symptoms of dummy foal:

cyanosis, apnea, shallow breathing

123

treatment of dummy foal:

artificial surfactant with glucocorticoids
continuous positive airway pressure (keep alveoli open)