Embryology of the CVS 1 Flashcards by Liam McCreadie

What are the four major stages in heart development?

Primitive heart tube
heart looping
artial and ventricular septation
outflow tract septation

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Name the labelled parts.

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Which mesoderm goes on to form the circulatory system (and other viscera)?

lateral plate splanchnic mesoderm

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Why does the primordial heart start to function at the beginning of week four, and why is CVS the first major system to develop in the growing embryo?

In a rapidly growing embryo, diffusion is not sufficient to supply required nutrients therefore embryo must utilise CVS.

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__________ ______ _______ collect in the lateral plate splanchnic mesoderm, move towards the midline and coalesce to form the two _________ ________ _______.

Angiogenic cell islands

primitive heart tubes

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Blood vessels first appear in the wall of _____ _____, ______, _______ _____ and ______.

yolk sac

allantois

connecting stalk

chorion

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Appearance of paired endothelial strands (_________ _______) appear in the cardiogenic mesoderm – 3rd week

angioblastic cords

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Angioblastic cords canalize to form _____ ________.

heart tubes

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Tubular heart joins blood vessels in other areas to form _________ _________ _______.

primordial cardiovascular system

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During cranial folding, reorientation of the heart tube positions it ________ to pericardial cavity.

dorsal

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Cephalic folding

pericardial cavity: _____ - _______

cardiac tube: _______ - ______

dorsal - ventral

ventral - dorsal

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Pericardium is derived from i______ ______ _______.

intra-embryonic coelom

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Parietal layer of serous pericardium & fibrous pericardium are formed from _______ _________.

somatic mesoderm

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Visceral layer of serous pericardium is derived from __________ ________.

splanchnic mesoderm

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Name the labelled parts.

Which part becomes the arterial system?

Which part becomes the venous system?

Arterial system = cephalic end

venous system = caudal end

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Name the labelled parts of the fused primitive heart tube.

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The venous end of the heart tube is called the what?

sinus venosus

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Each horn of the sinus venosus gets blood from which areas?

(3)

placenta

yolk sac

body of the embryo

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What are the names of the veins which drain blood into the sinus venosus?

Where do they drain blood from?

(3)

umbilical vein = placenta

vitelline vein = yolk sac

common cardinal vein = body of the embryo

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The arterial end of the heart tube is known as the what?

truncus arteriosus

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The truncus arteriosus is continuous cranially with the _______ _______.

What arises from the structure labelled above?

aortic sac

aortic arches

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How many aortic arches are there on each side?

Aortic arches terminate in the ______ _______.

dorsal aorta (R & L)

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_____________ and ________ grow faster than other regions forming a U-shaped ___________ loop.

Bulbus cordis

ventricle

bulboventricular

Name the labelled parts of the looped heart tube.

What is dextrocardia?

Heart points to the right side of the chest instead of the left side.

What happens during dextrocardia?

Heart tube loops to the left side instead of the right (so ends up to lie facing the right).

What can dextrocardia be associated with?

Situs inversus (transposition of viscera)

What does partitioning of the primordial heart involve?

One or two actively growing masses of tissues: Endocardial cushion formation Septum formation

What does the endocardial cushion do?

Seperates RA and RV from LA and LV, forming left and right AV canals.

What does the septum formation do?

Separates RA from LA and RV from LV.

What are cardiac malformations associated with defective formation of endocardial cushion and septum formation?

Atrial septal defect (ASD) Ventricular septal defect (VSD)

Name the labelled parts.

What develops during the partition of the primitive atrium?

1) Septum primum and foramen primum 2) Septum secundum and foramen secundum

What is another word for foramen?

Ostium

What is the role of the oval foramen before birth?

Allows most of the blood to pass from the right atrium to the left atrium (non-functioning lungs). Prevents the passage of blood in the opposite direction.

\_\_\_\_\_\_ _______ of adult heart is a remnant of foetal oval foramen.

Fossa ovalis

When the foramen ovales closes after birth, which structures meet?

septum primum (inferior) septum secondum (superior)

Non closure of formamen ovales results in what? What is the clinical term for this?

patent formamen ovale atrial septum defect (ASD) = 'hole in the heart'

What are the four clinically significant types of atrial septal defect (ASD)?

A) Foramen secundum defect B) Endocardial cushion defect with foramen primum defect C) Sinus venosus defect D) Common atrium

Partitioning of Primitive Ventricle What is the initial septum formed, what does this create?

muscular interventricular septum interventricular foramen

What is the name of the structure which divides the bulbis cordis and truncus arteriosus?

aorticopulmonary septum

What causes the closing of the interventricular foramen? What does this form?

The attachment of the aorticopulmonary septum with the **_muscular_** interventricular septum. They meet to form the **_membraneous_** interventricular septum.

Growth of ______ \_\_\_\_\_\_\_ also contributes to membranous portion of the interventricular septum.

endocardial cushions

What is the most common type of congenital heart disease (25% of cases)? Who is this most common in?

ventricular septal defect (VSD) males

Where do early pacemakers develop? (2)

Primitive atrium and then sinus venosus

Where is the SA node located in adults?

very proximal to the opening for the SVC, high in the RA

What does cot death or sudden infant death syndrome (SIDS) often occur due to?

Abnormalities of conducting tissue

What adult structure(s) does the truncus arteriosus develop into?

aorta and pulmonary trunk

The smooth part of the right ventricle is called the what?

conus arteriosus

The smooth part of the left ventricle is called what?

aortic vestibule

The primitive ventricle develops into which adult structures?

trabeculated parts of the L & R ventricles

The primitive atrium develops into which adult structures?

trabeculated parts of L & R atria

The sinus venosus develops into which adult structures?

smooth part of right atrium coronary sinus

The junction of the trabeculated and smooth parts of the right atrium is called the what?

crista terminalis

What are the causes of congenital heart disease? (5)

Rubella infection in pregnancy Maternal alcohol abuse Maternal drug/radiation treatment Genetics Chromosomal

Tetralogy of Fallot is associated with which four major defects?

1. Pulmonary stenosis 2. Ventricular septal defect (VSD) 3. Dextroposition of aorta (“overriding” aorta) 4. Right ventricular hypertrophy