L28: Mediastinum IV

Question 1

The atrioventricular canal is divided by the development of ____

Answer 1

two mesenchymal masseSfi

Question 2

finihs 1

Question 3

Mesenchyme that remains around the atrioventricular orifices after fusion of the ____ become
___ except for ____

Answer 3

cushions

separated from the main ventricular wall as the trabeculae form

one primary connection

Question 4

connection

Answer 4

muscular cord

Question 5

finish 2

Question 6

cardiac septa formation

Answer 6

Neural crest cells (!) form opposite spiral ridges in the truncus arteriosus and the conus cordis

Conotruncal ridges

ridges enlarge towards each other and grow distally until they fuse into a spiral septum

conotruncal septum

Question 7

cardiac septa 2

Answer 7

muscular portion of the intrventricular septum develops as a ridge that increases in prominence as the ventricles continue to expand

muscular interventricular septum does not grow to contact the endocardial cushions

interventricular foramen

Question 8

cardiac septa 3

Answer 8

as the conotruncal septum fuses, the inferior endocardial cushion proliferates to close the interventricular foramen

membranous portion of the interventricular septum

Question 9

septal defects

Answer 9

endocardial cushions are centrally placed (abnormalities can have wide ranging impacts)

ventricular septal defects (VSD) are most common cogenital malformation of the heart
- membranous (patent interventricular foramen)
-muscular (will often heal with post-natal development

Question 10

septal defects 2

Answer 10

conotruncal septal defects (often asociated with facial defects)

transposition of the great vessels

tetralogy of Fallot

Question 11

tetralogy of fallot

Answer 11

pulmonary infundibular stenosis

ventricular septal defect

overriding aorta

hypertrophy of the right ventricular wall

Question 12

cardiac septa 4

Answer 12

thin membrous crescent begins to grow between the left and right halves of the atrium toward the atrioventricular canal

septum primum

a cap remains between the inferior margin of the septum primum and the endocardial cushions
ostium primum

Question 13

ostium secundum

Answer 13

As the ostium primum is closed by
fusion with the endocardial cushions
cell death produces a second gap in
the septum primum

Question 14

septum secundum

Answer 14

A second, thicker and more muscular
septum begins to grow to the right of
the septum primum

Question 15

foramen ovale

Answer 15

when fully formed the septum secundum leaves a gap offset from the ostium secumdum

Question 16

high pressure blood from the right atrium can flow through the foramen ovale and ostium secundum to the left atrium. high pressure blood cannot flow from left to right

Answer 16

fix

Question 17

septal defects

Answer 17

atrial septal defects usually result from insufficient development of one or both septa

Excessive resorption of septum primum results
in a oval foramen that is large and fully open

Failure of the septum secondum results in the
ostium secundum remaining as a large defect
in the interatrial wall

Absence of any septa almost always
associated with other also severe heart
abnormalities

mesoderm/endoderm

Question 18

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