Cardio - Embryology

Question 1

To what structure(s) does the truncus arteriosus (TA) give rise?

Answer 1

Ascending aorta and pulmonary trunk

Question 2

To what structure(s) does the bulbus cordis give rise?

Answer 2

Smooth parts (outflow tract) of left and right ventricles

Question 3

To what structure(s) does the primitive ventricle give rise?

Answer 3

Trabeculated left and right ventricles

Question 4

To what structure(s) does the primitive atrium give rise?

Answer 4

Trabeculated left and right atria

Question 5

To what structure(s) does the left horn of sinus venosus (SV) give rise?

Answer 5

Coronary sinus

Question 6

To what structure(s) does the right horn of sinus venosus (SV) give rise?

Answer 6

Smooth part of the right atrium

Question 7

To what structure(s) do the right common cardinal vein and right anterior cardinal vein give rise?

Answer 7

Superior vena cava (SVC)

Question 8

What embryonic structure(s) give(s) rise to the ascending aorta and pulmonary trunk?

Answer 8

Truncus arteriosus (TA)

Question 9

What embryonic structure(s) give(s) rise to the smooth parts (outflow tract) of left and right ventricles?

Answer 9

Bulbus cordis

Question 10

What embryonic structure(s) give(s) rise to the trabeculated left and right ventricles?

Answer 10

Primitive ventricle.

Question 11

What embryonic structure(s) give(s) rise to the trabeculated left and right atria?

Answer 11

Primitive atria

Question 12

What embryonic structure(s) give(s) rise to the coronary sinus?

Answer 12

Left horn of sinus venosus (SV)

Question 13

What embryonic structure(s) give(s) rise to the smooth part of the right atrium?

Answer 13

Right horn of sinus venosus (SV)

Question 14

What embryonic structure(s) give(s) rise to the superior vena cava?

Answer 14

Common cardinal vein and right anterior cardinal vein

Question 15

Give the development stages of truncus arteriosus.

Answer 15

Truncus arteriosus rotates; Neural crest and endocardial cell migration –> truncal and bulbar ridges that spiral and fuse to form the aorticopulmonary (AP) septum –> Ascending aorta & pulmonary trunk

Question 16

What are 3 conotruncal abnormalities associated with outflow tract formation (i.e., truncus arteriosus)?

Answer 16

(1) Transposition of great vessels (failure to spiral) (2) Tetralogy of Fallot (skewed AP septum development) (3) Persistent TA (partial AP septum development)

Question 17

Describe the steps involved in interventricular septum development.

Answer 17

(1) MUSCULAR VENTRICULAR SEPTUM forms. Opening is called INTERVENTRICULAR FORAMEN.
(2) AP SEPTUM rotates and fuses with muscular ventricular septum, closing interventricular foramen.
(3) Growth of ENDOCARDIAL CUSHIONS separates atria from ventricles & contributes to both atrial separation and membranous portion of the INTERVENTRICULAR SEPTUM

Question 18

Describe the steps involved in interarterial septum development.

Answer 18

(1) SEPTUM PRIMUM grows toward endocardial cushions, narrowing FORAMEN PRIMUM
(2) FORAMEN SECUNDUM forms in septum primum (foramen primum disappears)
(3) SEPTUM SECUNDUM develops as foramen secundum maintains right-to-left shunt (4) Septum secundum expands and covers most of the foramen secundum. The residual foramen is the FORAMEN OVALE (5) Remaining portion of septum primum forms VALVE OF FORAMEN OVALE (6) (Not shown) Septum secundum and septum primum fuse to form ATRIAL SEPTUM (7) (Not shown) Foramen ovale usually closes soon after birth because of high LA pressure

Question 19

With what pathology is interatrial septum development associated?

Answer 19

Patent foramen ovale (caused by failure of septum primum & septum secundum to fuse after birth)

Question 20

Where does fetal erythropoiesis occur and at what time intervals? What is a good mnemonic to remember this?

Answer 20

Yolk Sac (3-8 wk), Liver (6wk-birth), Spleen (10-28 wk), Bone marrow (18 wk - adult); Young Liver Synthesizes Blood

Question 21

What globin chains comprise fetal hemoglobin? What about adult hemoglobin?

Answer 21

alpha2, gamma 2; alpha2, beta2

Question 22

For blood in the umbilical vein, what is the PO2 and % O2 saturation? What kind of O2 saturation do umbilical arteries have?

Answer 22

PO2 = 30 mmHg & 80% saturated w/ O2; Low O2 saturation

Question 23

What are the important shunts in fetal circulation?

Answer 23

(1) Blood entering fetus through umbilical vein is conducted via DUCTUS VENOSUS into IVC to bypass hepatic circulation
(2) Most oxygenated blood reaching the heart via IVC is diverted through the FORAMEN OVALE and pumped out of the aorta to the head and body
(3) Deoxygenated blood entering the RA from the SVC enters the RV, is expelled into the pulmonary artery, & then passes through the patent DUCTUS ARTERIOSUS into the descending aorta (and to the umbilical arteries); due to high fetal pulmonary artery resistance (due partly to low O2 tension)

Question 24

What are the 2 major consequences of infant taking a breath at birth? Explain the factors/steps behind each of these consequences.

Answer 24

(1) Decreased resistance in pulmonary vasculature –> Decreased left atrial pressure vs. right atrial pressure = FORAMEN OVALE CLOSES (now called fossa ovalis) (2) Increase in O2 (from respiration) and Decrease in prostaglandins (from placental separation) => DUCTUS ARTERIOSUS CLOSES

Question 25

What helps close a PDA (patent ductus arteriosus)? What keeps a PDA open?

Answer 25

Indomethacin --> DA remnant (i.e., ligamentum arteriosum); Prostaglandins E1 and E2

Question 26

What is the structure derived from the umbilical vein? Within what other structure is this structure found?

Answer 26

Ligamentum teres hepatis (contained in the falciform ligament)

Question 27

What is (are) the structure(s) derived from the umbilical arteries?

Answer 27

Medial umbilical ligaments

Question 28

What is the structure derived from the ductus arteriosus?

Answer 28

Ligamentum arteriosum

Question 29

What is the structure derived from the ductus venosus?

Answer 29

Ligamentum venosum

Question 30

What is the structure derived from the foramen ovale?

Answer 30

Fossa ovalis

Question 31

What is the structure derived from the allantois?

Answer 31

Urachus-median umbilical ligament; (Note: The urachus is part of the allantoic duct between the bladder & the umbilis; Urachal cyst or sinus is a remnant)

Question 32

What is the structure derived from the notochord?

Answer 32

Nucleus pulposus of intervertebral disc

Question 33

Name the fetal structures from which the following postnatal structures are derived: (1) Ligamentum teres hepatis (2) Medial umbilical ligaments (3) Ligamentum arteriosum (4) Ligamentum venosum (5) Fossa ovalis (6) Urachus-median umbilical ligament (7) Nucleus pulposus of intervertebral disc

Answer 33

(1) Umbilican vein (2) Umbilical arteries (3) Ductus arteriosus (4) Ductus venosus (5) Foramen ovale (6) Allantois (7) Notochord

Question 34

What is the first functional organ in vertebrate embryos?

Answer 34

Heart = First functional organ in vertebrate embryos

Question 35

When does the heart begin beating spontaneously?

Answer 35

Beats spontaneously by week 4 of development

Question 36

Briefly describe the process/purpose of cardiac looping. When in gestation does it occur?

Answer 36

Primary heart tube loops to establish left-right polarity; begins in week 4 of gestation

Question 37

What is the defect in Kartagener syndrome, and how does it relate to cardiac looping?

Answer 37

Defect in left-right dynein (involved in L/R asymmetry) can lead to dextrocardia, as seen in Kartagener syndrome (primarily cilia dyskinesia)

Question 38

What is the clinical approach to most patent foramen ovale?

Answer 38

Most are left untreated

Question 39

What complication can result from patent foramen ovale? To what other congenital cardiology condition is this similar?

Answer 39

Can lead to paradoxical emboli (venous thromboemboli that enter systemic arterial circulation), similar to those resulting from an ASD

Question 40

In what structure does ventricular septal defect (VSD) most commonly occur?

Answer 40

Ventricular septal defect (VSD) - most commonly occurs in the membranous septum

Question 41

How do VSD patients appear at birth, and why?

Answer 41

Acyanotic at birth due to left-to-right shunt

Question 42

From what structure(s) are the aortic/pulmonary valves derived?

Answer 42

Aortic/Pulmonary: derived from endocardial cushions of outflow tract

Question 43

From what structure(s) are the mitral/tricuspid derived?

Answer 43

Mitral/Tricuspid: derived from fused endocardial cushions of the AV canal

Question 44

What are 4 options for valvular anomalies?

Answer 44

Valvular anomalies may be stenotic, regurgitant, atretic (e.g., tricuspid atresia), or displaced (e.g., Ebstein anomaly).

Question 45

Give an example an atretic valvular anomaly and a displaced valvular anomaly.

Answer 45

atretic (e.g., tricuspid atresia) or displaced (e.g., Ebstein anomaly)

Question 46

Compared to adult Hb, what kind of affinity does HbF have for oxygen, and why? What does this HbF affinity allow?

Answer 46

HbF has higher affinity for oxygen due to less avid binding of 2,3-BPG. This allows HbF to extract oxygen from (HbA) maternal hemoglobin across the placenta.

Question 47

Describe the shunt in fetal circulation that includes the patent ductus arteriosus. What causes this shunt?

Answer 47

Deoxygenated blood entering the RA from the SVC enters the RV, is expelled into the pulmonary artery, & then passes through the patent DUCTUS ARTERIOSUS into the descending aorta (and to the umbilical arteries); due to high fetal pulmonary artery resistance (due partly to low O2 tension)

Question 48

What does indomethacin cause in terms of cardiac embryology? What structure results?

Answer 48

Indomethacin helps close PDA (patent) --> DA remnant (i.e., ligamentum arteriosum)