Heart Development (Mine)

Question 1

Explain extraembryonic vasculogenesis

Answer 1

Occurs day 17 in the mesoderm near yolk sac endoderm

hemangioblasts aggregate, differentiate and give rise to hematopoeitic progenitor cells and endothelial precursor cells (EPC)

form blood islands that connect to form vascular network

by end of third week, yolk sac, connecting stalk, and chorionic villi are vascularized

Question 2

What are the eventual sites of hematopoesis?

Answer 2

blood islands, yolk sac, liver, AGM, lymph organs, bone marrow

Question 3

When do embryonic hematopoietic cells appear and what do they become?

Answer 3

day 17

move to liver around day 23

generate embryonic erythrocytes, macrophages, megakaryocytes

Question 4

Definitive hematopoetic stem cells seed the liver at what day and do what?

Answer 4

day 30

undergo cell-cell interactions giving the embryonic hematopoetic cells full capacity to generate myeloid and lymphoid lineages

Question 5

Overview of the sites of hematopoiesis

Answer 5

yolk sac mesoderm: day 17, done by day 60, source of early RBCs and macrophages

liver primordia: day 23, continues until birth

AGM: dorsal aorta, day 27-40, colonizes liver

lymph organs, bone marrow (10.5wks)

Question 6

Describe the process of intraembryonic vasculogenesis which leads to angiogenesis and intussuception

Answer 6

vasculogenesis is the denovo formation of blood vessels that starts at day 18 and in the intraembryonic splanchnic mesoderm and paraxial mesoderm

angioplastic proliferation occurs via: proliferation of endothelial precursors cells, angiogenesis (budding), intussuception (splitting), and recruitment of mesoderm cells to the walls of existing vessels

Question 7

CN: Angiomas

subtypes:

capillary

cavernous

hemangioma of infancy

Answer 7

abnormal blood vessels and lymphatic growth via vasculogenesis (from abnormal levels of angiogenic factors

excessive growth of capillary network

excessive growth of venous sinus

benign tumor, mostly of endothelial cells, can be internal and compress important structures. Typically regress with age

Question 8

What is the first heart field and where is the intraembryonic coelom in relation?

Answer 8

formtion of EPC clusters that arrange in a horseshoe shape within a cardiogenic area of the intraembryonic splanchnic mesoderm

IE coelom lies dorsal to first heart field

Question 9

How does anterior/posterior body folding affect the first heart field?

Answer 9

the primary heart field and coelom get folded underneath the embryo, helping to form the foregut

the first heart field now lies ventral to the foregut and dorsal to the coelom

Question 10

How do the two primitive endocardial tubes form?

Answer 10

EPCs differentiate into endothelial cells while the first heart field is being folded under the embryo

Question 11

How is the first aortic arch formed?

Answer 11

Lateral folding brings the cardiac tubes together

now the heart is a simple tube which sits in the future pericardial cavity

as growth occurs, the tube is pulled cervically and then into the thorax

this pulls the dorsal aorta forming the first aortic arch

Question 12

What is the remnant of the dorsal mesocardium called in the adult?

Answer 12

proepicardial organ

originally, it suspends the heart tube but eventually ruptures

Question 13

What is the primordium of the epicardium?

Answer 13

proepicardial cells which migrate over the myocardial surface

Question 14

What forms the future right ventricle?

What forms the conus arteriosus?

What forms the truncus arteriosus?

Answer 14

initial outflow tract

addition of myocardium at the cranial end of the heart

distal outflow tract, forms aorta and pulmonary artery

Question 15

What is required for cardiac looping to occur?

Answer 15

lengthening of the cardiac tube at both ends, but mostly at the cranial outflow end

this results in the formation of the second heart field which forms at the ends of the rupturing dorsal mesocardium

failure results in several defects

Question 16

What are neural crest cells responsible for in the process of cardiac looping?

Answer 16

neural crest cell, PA mesoderm and PA endoderm interactions are necessary for maintaining cardiogenic mesoderm proliferation and proper myocardial cell specification within the second heart field

Question 17

CN: Ventricular Inversion

Answer 17

looping anomaly

primitive ventricle fold to the side and outflow tract ends up on the left with the outcome being a right sided, left ventricle

Question 18

CN: Heterotaxia

Answer 18

looping anomaly

any abnormal left-right development of either some or all organs, seen in immobile cilia syndrome and Kartagener syndrome

Question 19

CN: Situs Inversus

Example: Visceroatrial Heterotaxia (technically, situs ambiguous)

Answer 19

Complete reversal of some organs

heart and GI tract are asymmetrically arranged from one another, issues with inflow and outflow tract development

Question 20

What forms the coronary sinus?

What is the fate if the vitelline, umbilical and common cardinal vein?

Answer 20

the remnant of the left sinus horn

disappear

Question 21

What forms the sinoatrial orifice?

Answer 21

the sinus venosus opening into the future right atrium

Question 22

What type of growth makes the muscular interventricular septum and muscular atrial septum?

Answer 22

differential growth

requires addition of new tissue for fully closed lumen

Question 23

What is endocardial cushion tissue?

Answer 23

it is new CT used to make the membranous portion of the atrial and ventricular septa derived from mesenchymal endocardia mesenchyme

Question 24

What is the purpose of the conotruncal ridges?

Answer 24

part from ECT and part from NCC

make the conus arteriosus-helps blood from LV/RV go out different vessels

makes truncus arteriosus-divides into aorta and pulmonary arteries by AP septum formation

Question 25

Describe the formation of the foramen ovalis

(initial division of the common atrium to the septated atrium)

Answer 25

The septum primum from mesenchyme and cushion tissue grows upward and then a bit of it degenerates, making the ostium secundum

septum secundum grows next to it and is much thicker and overlaps the ostium secundum. A part of the middle of it degenerates, making a hole that is overlapped by the septum primum

eventally makes the foramen ovalis which is overlapped by the septum primum making a one way valve between RA and LA

Question 26

How does the foramen ovalis close?

Answer 26

after birth, with first breath, blood pressure increases in left atrium

RV can now pump blood into lungs so the RV and RA pressure decreases

thus the pressure is always higher on the left side of the heart even during diastole, sealing shut the foramen ovalis (within about three months)

if it stays patent, it isn’t usually a big deal

Question 27

Atrial Septal Defects

Answer 27

result in initial left to right shunting because of increased blood flow returning from the lungs and decreased pulmonary resistance after the lungs expand

overtime, this leads to lung damage and pulmonary congestion

causes RV hypertrophy and congestive heart failiure

a right to left shunt begins and then cyanosis appears

Question 28

What are the three types of ASD?

Answer 28

ostium secundum (high atrial spetal defects, 90%) caused by excessive absorption of septum I or large ostium II, or inadequate development of septum II

Common Atria-no septa formed

ostium primum (low atrial septal defect)-failure of up growth of AV cushion tissue from AV septum and DMP to fill in ostium primum

Question 29

Describe fetal cardiac blood flow

Answer 29

blood entering from the IVC enters the foramen ovalis in the LA (O2) and then goes to LV and then out into fetal systemic arterial side

blood entering the RV from the RA includes less oxygenated blood from SVA and coronary sinus as well as IVC

blood leaves RV and re-enters the systemic arterial side via DA with very little passing through lungs

Question 30

What is partitioning of the outflow tract?

Answer 30

Formation of the conus arteriosus, truncus arteriosus and aortic sac

starts with a common lumen that is divided into two tubes such that the future aorta is attached to the LV and the pulmonary artery to the RV

aortic arch VI connects the RV to the lungs and aortic arch III and IV connects the LV to the rest of the body

Question 31

CN: Ventricular Septal Defects

Answer 31

one of the most common congenital heart defects

failure of proper closure by abnormal or inadequate fibrous tissues

starts with acyanosis (LtR shunt) but becomes cyanotic shortly after birth

RV hypertrophies and RtL shunt forms (cyanosis)

die of cardiac faiulure if untreated

Question 32

What does complete closure of the ventricle septum require?

Answer 32

down growth of the AV septum, proper formation of the conotruncal ridges and interventricular muscular septum formation

Question 33

CN: Persistent Truncus Arteriosus

Answer 33

Failure of contruncal ridge formation and fusion

pulmonary artery arises some distance away above the undivided truncus

causes VSD

mixing of oxygenated and unoxygenated blood

some cyanosis, pulmonary congestion, RV hypertophy, increased right ventricular pressure and worsening cyanosis

Question 34

CN: Tetralogy of Fallot

Answer 34

conotruncal ridges from off center leading to unequal division of pulmonary trunk and aorta

VSD

pulmonary infundibular stenosis

overriding aorta

RV hypertrophies-RtL shunting (cyanosis most common initial sx)

Question 35

CN: Transposition of Great Vessels

Answer 35

conotruncal ridges fail to spiral

Pulmonary A. connected to LV and aorta to RV

survive only because of existing shunts such as VSD, ASD, and patent DA

even with shunts, likely to die within 3yrs, unless treated

Question 36

CN: Pulmonary valvular atresia

Answer 36

semilunar valves are fused leading to RV hypoplasia

patent foramen ovalis forms

DA remains patent

may require heart transplant depending on severity

other sx include VSD or univentricular heart

Question 37

CN: Aortic valvular stenosis

Answer 37

leads to hypertrophy of LV and cardiac failure with pulmonary hypertension

possibly congenital, due to infection, degeneration (aging), more often in males

Question 38

CN: Bicuspid aortic valve

Answer 38

2 leaflets instead of 3 form or three form but two are fused

regurgitation and then stenosis

asymptomatic at first, later leads to LV hypertrophy

assx with development of aortic aneurysm

Question 39

CN: aortic valvular atresia

Answer 39

valves are completely fused, LV is hypoplastic

wide DA forms and leads to RV hypertrophy during fetal period

after birth, blood must enter atrium via ASD and then to systemic circulation via patent DA

likely need transplant, but some other surgeries have good outcomes

Question 40

CN: Tricuspid Atresia

Answer 40

obliteration of right AV orifice

always assocaited with patent foramen ovalis, VSD, hypoplastic RV, hypertrophic LV and patent DA

can be fixed surgerically if not too severe, otherwise needs transplant

Question 41

CN: Hypoplastic left ventricle

Answer 41

LV si developed with absent or small bicuspid and aortic valves

ascending portion of the aorta is underdeveloped and there’s a patent DA and/or patent FO

functionally a univentricular heart with RV doing all the work

surgeries help, but still high death rate at 5yrs

Question 42

CN: Persistent AV canal

Answer 42

failure of AV septum fusion

ASD and VSD due to cushion tissue from septum contributes to fibrous portion of septa

abnormal or agenesis of AV valves

s/s: pulmonary HTN, exercise intolerance, SOB, cardiac congestion, increased risk of endocarditis

linked with Down’s Syndrome