Embryology- development of heart

Question 1

formation of heart tube

Answer 1

blood vessels in lateral plate splanchnic mesoderm form two heart tubes which fuse together and join blood vessels in other areas to form primordial CVS. this bulges and starts to form arterial and venous ends to it. it invaginates pericardium

Question 2

formation of vessels alongside heart tube

Answer 2

blood vessels appear in cardiogenic field

Question 3

formation of bulboventricular loop

Answer 3

growing heart tube becomes too big so has to fold/loop which makes the bulboventricular loop. ventricle pushed left and inferiorly and atria pushed superiorly and posteriorly

Question 4

partitioning of primordial atrium and ventricle

Answer 4

primary septum grows down towards fused endocardial cushions and closes off the space (ostium primum to osmium secundum) septum secundum grows down alongside septum primum. leaves a gap (foramen ovale) between the two septums which allows one way shunt from right to left atrium

Question 5

formation of AV canals

Answer 5

fused endocardial cushions leave two gaps (canals)

Question 6

embryological basis for atrial septal defects

Answer 6

foramen ovale closes after birth, non closure results in patent foramen ovale which is.a hole in the heart

Question 7

embryological basis for ventricular septal defects

Answer 7

gaps originate between ventricles. some close themselves but some don’t. can appear in any part of septum but most common membranous

Question 8

embryological basis for transposition of great arteries

Answer 8

failure of aorticopulmonary septum to take a spiral course and defective migration of neural crest cells to heart. so coming out of wrong ventricles. usually associated with ASV and VSD

Question 9

development of cardiac valves

Answer 9

atrioventricular valves develop from ventricular wall but semilunar valves form from subendocardial valve tissue

Question 10

visceral layer comes from

Answer 10

splanchnic mesoderm

Question 11

pericardial cavity comes from

Answer 11

intraembryonic coelom

Question 12

formation of dextrocardia (abnormal)

Answer 12

the heart tube loops to left side so ventricles come to lie facing right instead of left. most frequent positional abnormality of the heart

Question 13

development of special conducting system of heart

Answer 13

SA node develops on 5th week. AV node and bundle of His develops from cells of AV canal and sinus venous

Question 14

primitive structure of aortic arches

Answer 14

aortic sac

Question 15

primitive structure of right ventricle and parts of outflow tracts

Answer 15

bulbis cordis

Question 16

primitive structure of left ventricle

Answer 16

primitive ventricle

Question 17

primitive structure of parts of left and right atria

Answer 17

primitive atrium

Question 18

primitive structure of superior vena cava

Answer 18

sinus venosus

Question 19

aortic arch derivatives

Answer 19

arise from aortic sac. during 4th and 5th weeks, 6 pairs of arches are formed from sac and these unite with dorsal aorta. 1st and 2nd disappear. 3rd forms common carotid, 4th right forms right subclavian, 4th left forms aortic arch, 5th disappears, 6th right forms right PA, 6th left forms LPA and ductus arteriosus.

Question 20

common anomalies of aortic arch derivatives

Answer 20

arise as a result of persistence of aortic arches that either normally should regress or regression of arches that normally shouldn’t eg right subclavian sometimes has abnormal region on left which may constrict oesophagus and trachea. double aortic arch (ring around trachea and oesophagus)

Question 21

patent ductus arteriosus

Answer 21

ductus arteriosus should become ligamentous arteriosum and close off but sometimes does not. can lead to blood coming back into PA.associated with maternal rubella infection in early pregnancy, cause due to failure of muscular wall to contract, respiratory distress syndrome and lack of surfactant in lungs. can lead to congestive heart failure in increasing age

Question 22

coarctation of aorta

Answer 22

aorta is narrow usually where ductus arteriosus inserts, coarctations are most common in the aortic arch. can be proximal to ductus arteriosus (pre ductal) or distal to it (postductal) unsure of cause

Question 23

thoracic duct development

Answer 23

develops from two vessels anterior to the aorta. these become the left and right embryonic thoracic ducts. left one gives rise to upper third of adult thoracic duct and lower two thirds of this are formed by the right

Question 24

development of lymphatic system

Answer 24

devekops at end of 6th week, six primary lymph sacs develop at end of embryonic period, lymphatic vessels will join lymph sacs later

Question 25

each primitive aorta has

Answer 25

ventral and dorsal part

Question 26

vitelline vessels that supply yolk sac change into

Answer 26

adult gut vessels, ivc

Question 27

umbilical vessels that supply placenta change into

Answer 27

internal iliac

Question 28

cardinal vessels that supply rest of body turn into

Answer 28

svc

Question 29

foetal circulation shunts

Answer 29

ductus venosus, foramen ovale, ductus arteriosus

Question 30

ductus venosus

Answer 30

shunt blood in left umbilical vein directly into IVC allows oxygenated blood from placenta to bypass the liver

Question 31

foramen ovale

Answer 31

shunts blood from right atrium to left atrium: allows blood to bypass the lungs

Question 32

ductus arteriosus

Answer 32

shunts blood from the right ventricle and PAs to aorta allows blood to bypass the lungs

Question 33

ductus venosus turns into

Answer 33

ligamentum venosum of liver

Question 34

foramen ovale turns into

Answer 34

fossa ovalis

Question 35

ductus arteriosus turns into

Answer 35

ligamentum arteriosum between left PA and aorta

Question 36

umbilical arteries turn into

Answer 36

medial umbilical ligaments of the anterior abdominal wall