Cardiovascular Development

Question 1

Which route for BF has higher pressure?

Answer 1

Left side (systemic)

Question 2

Purpose of pulmonary route of BF

Answer 2

Oxygenation + removal of CO2

Question 3

Purpose of systemic route of BF

Answer 3

Delivery system + transport of waste

Question 4

Characteristics of fetal circulatory system

Answer 4

2 open circuits (contribution of BF to each other = parallel)

Mixing of O2 rich/poor blood

Pressure is higher on the right side

Question 5

Why is R side pressure higher in fetuses?

Answer 5

Pulmonary vasculature is closed

–> higher resistance on the R side of heart (lungs are non-functional)

Question 6

Purpose of the placenta - fetal circulation

Answer 6

Exchange site of O2, nutrients + waste

Very well vascularized & low resistance vessel –> reduces overall systemic vascular resistance in fetus

Question 7

Purpose of foramen ovale

Answer 7

Bypasses lungs

Hole that allows for BF from RA –> LA

Question 8

Purpose of ductus arteriosus

Answer 8

Connects PT and aorta

Question 9

Key changes at birth

Answer 9

Opening of pulmonary vasculature (site of gas exchange is the lungs now)

= reduces resistance on R side = more resistance on L side

Removal of placenta

Question 10

How do the fetal bypasses close?

Answer 10

Pressure differential when the baby is born (takes its first breath)

Question 11

Postnatal remanent of foramen ovale

Answer 11

Fossa ovalis

Question 12

Postnatal remanent of ductus arteriosus

Answer 12

Ligamentum arteriosum

Question 13

Postnatal remanent of ductus venosus

Answer 13

Ligamentum venosum

Question 14

Postnatal remanent of umbilical arteries

Answer 14

Medial umbilical ligaments

Question 15

Postnatal remanent of umbilical vein

Answer 15

Ligamentum teres

Question 16

What is the fossa ovalis?

Answer 16

Depression the interatrial septum

Pressure increase on L side after birth closes the flap door of the foramen ovale

Question 17

How does the ductus arteriosum close?

Answer 17

Vasoconstriction after birth (due to decrease in PGs from placenta and increase in O2 after birth)

Question 18

How does the ligament venosum form?

Answer 18

After the ductus venous collapses

Question 19

How does the ligamentum teres form?

Answer 19

After the umbilical vein collapses

Question 20

How does the aorticopulmonary septum form?

Answer 20

Bulbar ridges grow towards each other & fuse

The septum takes on a spiral shape

Question 21

What does the aorticopulmonary septum do?

Answer 21

Separates the truncus arteriosus into the aorta and PT

Spiral shape = aorta and PT twist around eachother

Question 22

How are SL valves formed?

Answer 22

Tissue outgrowth of TA divides into post. ant. right and left sections

Aorticopulmonary septum goes through the middle –> now 2 vessels with 3 cusps each

Question 23

Persistent truncus arteriosus

Answer 23

Aorticopulmonary septum fails to develop –> no division

Result is a large arterial trunk that overlies R + L ventricles = mixing of blood

Infant becomes cyanotic

Question 24

When does valve stenosis occur?

Answer 24

During truncus arteriosus development - either aortic or pulmonary valves

Unequal partitioning = aorticopulmonary septum deviation

Question 25

Treatments for valve stenosis

Answer 25

Give PGs –> dilation of SM

Balloon valvuloplasty to stretch the valve

Question 26

Patent ductus arteriosus

Answer 26

Ductus ateriosus stays open

Due to the pressure differential, this can cause volume overload in the pulmonary circuit (right side, L –> R shunting)

Question 27

Formation of interatrial septum

Answer 27

Septum primum grows down to approach endocardial cushion (leaves an opening for the foramen primum, which allows for BF from R –> L)

2 holes come together to form the foramen secundum

Septum secundum comes down + partially covers the foramen secundum, but leaves small space for the foramen ovale (which allows for R –> L flow)

Question 28

What makes up the valve foramen ovale?

Answer 28

Superior portion of the septum primum regresses (lower edge becomes the valve)

Question 29

What causes the valve of the foramen ovale to close?

Answer 29

Higher pressure on the left side causes the valve to close (happens right after birth)

Question 30

Patent foramen ovale

Answer 30

Foramen ovale fails to close –> so L to R blood shunting

Deoxygenated blood does not enter the systemic circulation –> acyanotic

Question 31

Formation of the interventricular septum

Answer 31

Starts as a growth of tissue at the bottom of the heart, grows towards the endo. cushion

Membranous portion (derived from endo. cushion) stretches out.. Plays a large role in truncus arteriosus formation

Question 32

Relationship between membranous portion and great vessels

Answer 32

Malformation of membranous portion = malformation of great vessels

Question 33

Ventricular septal defect

Answer 33

Blood shunts from L –> R

Usually occurs in the membranous portion (its thinner)

Question 34

What are the AV valves made up of?

Answer 34

Subendocardial mesenchymal tissue

Valves are sculpted by programmed cell death

Question 35

What is the tetralogy of fallot composed of?

Answer 35

1. Pulmonary valve stenosis: reduction in BF in PT
2. Overriding aorta: picks up blood from LV & RV (mixed blood entering the systemic circulation)
3. VSD: post-natal L –> R shunting = volume overload in RV = increased pulmonary pressure
4. RV hypertrophy: natural response to increased pressure

Question 36

Why does ToF occur?

Answer 36

Abnormal development of the interventricular septum