Circulatory Sytem Development II

Question 1

Interventricular septum development

Answer 1

. Muscular ridge that develops on floor btw primitive ventricles near apex of heart
. Grows sup. Toward atrioventricular endocardial cushions
. Muscular portion partitions off primitive ventricles except for small area in region close to atrioventricular valves

Question 2

Conus cordis during ventricular development

Answer 2

. Overrides outflow of both primitive ventricles

. TA immediately cranial to this

Question 3

Aorticopulmonary (spiral, truncoconal, conotruncal) septum

Answer 3

. Decides TA and conus cordis

. Spirals as it courses down though TA and conus cordis

Question 4

Truncus ateriosus (TA) divided into____

Answer 4

Ascending aorta and pulmonary a.

Question 5

What forms sup. Part of definitive left ventricle and blood flow?

Answer 5

. Left part of conus

. Sends blood into ascending aorta

Question 6

Superior part of definitive rightventrile formation and blood flow

Answer 6

. Right part of conus

. Sends blood to pulmonary a.

Question 7

Aorticopulmonary septum

Answer 7

. Completes sup. Portion of interventricular septum that’s membranous section
. Bisects 4-cusp valve present in TA dividing it into 3-cusp pulmonic and aortic valves

Question 8

Ventricular septal defect

Answer 8

. Caused by defect in interventricular septum in its sup. Aspect where it is formed by aorticopulmonary septum
. Causes blood to be shunted from L to R side of the heart causing pulmonary hypertension
. Less common defect present in thicker muscular portion of septum

Question 9

Result of persistent TA

Answer 9

. Failure of aorticopulmonary septum to develop
. TA and conus cordus not divided into aorta and pulmonary trunk
. Assoc. w/ ventricular septal defect
. Undivided conus overrides both ventricles and receives blood from both sides
. Infants die w/in first 2 years if untreated

Question 10

Transposition of great arteries

Answer 10

. Aorticopulmonary septum descends straight down instead of spiraling
. Aorta arises from the right ventricle and pulmonary trunk from left ventricle
. Must be accompanying septal defect or patent ductus arteriosus for survival so there can be mixing of oxygenated and deoxygenated blood
. Leading cause of death in infants under 1 year old w/ cyanotic heart disease

Question 11

Tatralogy of Fallot

Answer 11

. Combo of 4 cardiac defects
. Caused by unequal division of conus cordis and TA by aorticopulmonary septum
. Aorta abnormally large and pulmonary trunk is abnormally small
. Causes cyanosis of lips and fingernails
. Treated surgically in 1st year of life

Question 12

4 defects in tetralogy of fallot

Answer 12

. Pulmonary trunk stenosis
. Ventricular septal defect
. Overriding aorta (over outflow of both ventricles)
. R ventricular hypertrophy from inc. pressure from pulmonary stenosis

Question 13

Vitelline aa. Evolve into unpaired gut vessels called

Answer 13

. Celiac a.

. Sup and inf. Mesenteric aa.

Question 14

Aortae supply ____ to placenta

Answer 14

Paired umbilical aa.

Question 15

Aortic arches in great vessel development

Answer 15

. Paired aa. That arise from TA and supply each branchial arch
. Terminates in dorsal aorta on the same side

Question 16

Number of aortic arch pairs and qualities

Answer 16

6 pairs
. Develop sequentially cranial to caudal
. Many arches disappear (1st disappeared by the time the 6th forms)
. Many larger aa. Supplying head, neck and upper extremity derive from aortic arches

Question 17

Coarctation of the aorta

Answer 17

. Abnormal narrowing of aorta in area of ductus arteriosus
. Preductal or postductal
. Embryological basis

Question 18

Preductal form of coarctation

Answer 18

. More serious
. Lumen of ductus arteriosus constricts at birth
. Lower half of body receives little/no circulation damaging organs

Question 19

Postductal form of coarctation

Answer 19

. More common, less serious
. Has collateral circulation in place at birth that allows the blood to bypass blockage and provide adequate circulation to lower half of body

Question 20

Double aortic arch (aortic ring)

Answer 20

. Distal portion of right dorsal aorta fails to degenerate
. Causes double arch that encircles esophagus and trachea
. Causes problems w/ breathing or swallowing

Question 21

Retroesophageal right subclavian a.

Answer 21

. Due to persistence of distal portion of right dorsal aorta

. Causes R. Subclavian a. To arise from aortic arch and crosses post. To esophagus causing difficulty swallowing

Question 22

Prenatal circulation flow

Answer 22

. Blood leaves fetus via umbilical aa. Depleted of O2 and nutrients w/ waster products
. Placenta removes waste and replenishes nutrients via diffusion
. Blood returning to fetus in single umbilical v. Rich in nutrients and O2
. Greater part of blood goes to cranial Half via shunts
. Umbilical v. Goes through liver and to heart
. Highly oxygenated blood in IVC enters RA and mixes w/ deoxygenated blood from SVC
. Blood passes through interatrial septum into LA then enters LV
. Pumped into ascending aorta

Question 23

Ductus venosus

Answer 23

. Shunt that allows bulk of blood to bypass liver and flow directly to IVC

Question 24

Small amount of blood from developing RA goes into ____

Answer 24

Right ventricle through tricuspid valve

. Distributed by RV and pulmonary a. To developing lungs

Question 25

Blood in developing pulmonary a. Moves into ____

Answer 25

. Arch of aorta via ductus arteriosus

Question 26

Where does fetal blood flow go after moving to ascending aorta

Answer 26

. Most distributed to cranial half of embryo via carotid and subclavian aa. . Blood remaining goes to caudal half of fetus

Question 27

What occurs to ductus arteriosus postnatally

Answer 27

. Contracts from inc. O2 content of blood . Closes off opening btw arch of aorta and left pulmonary a. . Lumen replaced by fibrous CT forming ligamentum arteriosum

Question 28

What occurs to ductus venosus

Answer 28

. Collapses and becomes ligamentum venosum

Question 29

What occurs to umbilical aa. Postnatally?

Answer 29

. Contract in response to blood-borne O2 level . Lumens filled w/ fibrous CT creating obliterated umbilical aa. That lie in ant. Abdominal wall (medial umbilical ligaments) . Proximal umbilical aa. Remains patent giving off branches that supply urinary bladder (sup. Vesicular aa.)

Question 30

What occurs to umbilical vv. Postnatally?

Answer 30

. Collapses bc no blood is returning form baby to placenta . Intra-abdominal portion fills w/ fibrous CT and become round ligament of the liver (ligamentum teres hepatitis) that lies w/in falciform ligament

Question 31

Patent ductus arteriosus

Answer 31

. Ductus arteriosus fails to close . Doesn’t form ligamentum arteriosusm . 2-3x times more common in females . Most common malformation following maternal rubella infection . Indomethacin administered to cause closure before resorting to surgery

Question 32

Heart rotation during development

Answer 32

. Slight rotation to left along its longitudinal axis

Question 33

Dextrocardia

Answer 33

. Reversal of heart’s normal position

Question 34

Situs inversus

Answer 34

. Reverses normal symmetry of body . Complete: all organs reversed . Partial: reversal of 1+ organs but not everything, more likely manifest w/ difficulties