6 - Development of Heart Flashcards by Tyler Brown

Cardiovascular system appears in middle of

week 3; it is the first major system to function within the embryo with the heart beginning to function during week 4

How well did you know this?

Not at all

Perfectly

Cardiac crescent

(contains

primary heart field

How well did you know this?

Not at all

Perfectly

Establishing & patterning of primary heart field (

~ 3rd week)

How well did you know this?

Not at all

Perfectly

Progenitor heart cells migrate through

primitive streak

Into the splanchnic layer of lateral plate mesoderm

How well did you know this?

Not at all

Perfectly

1st sign of heart formation  a

solid, horseshoe-shaped cluster of cells

Primary heart field

How well did you know this?

Not at all

Perfectly

These cells in the primary heart field will form the

atria, left ventricle, and part of right ventricle

How well did you know this?

Not at all

Perfectly

Remainder of right ventricle and outflow tract are derived from the

secondary heart field

PHF = primary heart field
SHF = secondary heart field

How well did you know this?

Not at all

Perfectly

Once cells establish the PHF (primary heart field), they are induced by

underlying endoderm to form cardiac myoblasts & blood islands and vessels by the process of vasculogenesis

How well did you know this?

Not at all

Perfectly

Vasculogenesis

Blood vessels arise from blood islands

How well did you know this?

Not at all

Perfectly

Angiogenesis

Blood vessels sprouting from existing vessels

How well did you know this?

Not at all

Perfectly

Heart tube formation & positioning

(~18-22 days)

How well did you know this?

Not at all

Perfectly

Islands will unite & form a

horseshoe-shaped endothelial-lined tube surrounded by myoblasts within the cardiogenic region
- Endocardial tubes

How well did you know this?

Not at all

Perfectly

Other blood islands appear which will form

the pair of longitudinal dorsal aortae

How well did you know this?

Not at all

Perfectly

Lateral body folding creates

primordial heart tube.

How well did you know this?

Not at all

Perfectly

The lateral sides of the horseshoe-shaped endothelial tube fold in

ventrally and medially, approaching each other at midline to fuse, forming a single primordial heart tube.

How well did you know this?

Not at all

Perfectly

Due to rapid neural tube growth the embryo also undergoes

cranial to caudal folding (sagittal folding)

How well did you know this?

Not at all

Perfectly

Cranial – caudal folding

repositions the developing heart and pericardial cavities

How well did you know this?

Not at all

Perfectly

Prior to head folding, the heart is:

Rostral to the oropharyngeal membrane – ventral to the pericardial cavity

How well did you know this?

Not at all

Perfectly

Initially, heart tube is attached to

dorsal side of pericardial cavity via dorsal mesocardium

How well did you know this?

Not at all

Perfectly

The middle section of the dorsal mesocardium will disappear and create the

transverse pericardial sinus

How well did you know this?

Not at all

Perfectly

At this time the heart tube consists of three layers:

Endocardium
Myocardium
Epicardium (or visceral pericardium)

How well did you know this?

Not at all

Perfectly

Cardiac loop formation

(~22-28 days)

How well did you know this?

Not at all

Perfectly

The heart tube elongates, forming

dilations and constrictions. These dilations and constrictions will become the adult derivatives of the heart.

How well did you know this?

Not at all

Perfectly

TRUNCUS ARTERIOSUS

(Pulmonary trunk + aorta)

How well did you know this?

Not at all

Perfectly

CONUS CORDIS

(Outflow tract of ventricles; Caudal portion of bulbus cordis forms R. ventricle)

BULBUS CORDIS

Conus cordis and truncus arteriosus

PRIMORDIAL ATRIUM

(Right and left auricles + portions of the atria)

SINUS VENOSUS

(Coronary sinus + sinus venarum)

The tubular heart undergoes

right-handed looping ~ 23 to 28 days, forming a U –shaped loop that results in a heart with its apex pointing to the left

Primitive ventricles move

ventrally & to the right while atrial region moves dorsally & to left

Attachment of the heart tube at the sinus venosus and the truncus arteriosus is fixed by its

attachment to the pericardial sac, so growth of the tube causes it to loop anteriorly and to the right

Primitive atrium takes a

posterior/dorsal position

When heart looping is complete, blood flows

uninterrupted through the different parts, as if in the original tube.

As the heart folds, its cranial end will shift

ventrally, caudally, and to the right. Its caudal end will shift dorsally and superiorly.

Circulation through the primordial heart:

Sinus venosus  primordial atrium  atrioventricular (AV) canal  left ventricle (primordial ventricle)  interventricular (IV) foramen  right ventricle  conus cordis  truncus arteriosus  aortic sac  pharyngeal aa.  dorsal aortae

Sinus venosus development (~7-8 weeks)

Sinus venosus receives venous blood from 3 paired veins: Vitelline vv. Umbilical vv. Common cardinal vv.

Blood flow to the heart gradually shifts to the

right side due to the remodeling of vitelline, umbilical, & anterior cardinal vv. As a result, the right horn of the sinus venosus becomes larger than the left.

Left sinus horn becomes:

Oblique veins of the left atrium | Coronary sinus

Right sinus horn becomes incorporated into the

right atrium to form smooth-walled part

Right sinus horn entrance is

sinuatrial orifice | Flanked by right and left venous valves

When right sinus horn is incorporated into wall (sinus venarum): Left valve & septum spurium fuse

with atrial septum

When right sinus horn is incorporated into wall (sinus venarum): Superior portion of right valve

disappears

When right sinus horn is incorporated into wall (sinus venarum): Inferior portion of right valve becomes:

Valve of IVC | Valve of coronary sinus

Partitioning of the heart

(~28 days – 7th week)

At 30 days: | Atrial partitioning

just beginning to occur

At 30 days: | Primary interventricular

foramen undivided

At 30 days: | Outflow tract

(bulbus cordis/truncus arteriosus) undivided

At 30 days: | Proximal portion of bulbus cordis becomes

trabeculated and forms the right ventricle

At 30 days: | Atrioventricular canal

undivided

Near end of week four, 4 AV endocardial cushions form on each side of the

plus one at the dorsal & the ventral walls of AV canal

Partitioning of the original single AV canal to

left and right AV canals by the AV endocardial cushions

the left and right AV canals contribute to development of the

mitral and tricuspid valves

the fusion of the superior and inferior AV endocardial cushions provide a

“landing area” for the interartial septum

Fusion of these cushions results in complete division of the

AV canal into a left and right

Around end of week 4, a crest of tissue grows from the roof of the common atrium

Septum primum

Septum primum will extend towards the

endocardial cushions in the AV canal

Opening below the septum primum & the endocardial cushions is the

ostium primum

Septum primum develops from the roof of the primordial atrium as a

thin, moon-shaped membrane

Ostium primum closes | Cell death produces perforations in

septum primum which coalesce to form ostium secundum

Ostium secundum ensures that there is

free blood flow from the right to the left primitive atrium

As holes in the septum primum coalesce to form the ostium secundum, a thicker

septum secundum develops from the roof of the primordial atrium, slightly to the right of the septum primum

Septum secundum grows inferiorly and develops an opening: the

foramen ovale (oval foramen)

Cranial portion of septum primum

degenerates

Caudal portion of septum primum forms the

valve of foramen ovale

After birth, the pressure in the left atrium

increases as the blood returns from the lungs.

Septum primum is pressed against the

septum secundum and adheres to it, permanently closing the foramen ovale and forming the fossa ovalis

Fossa ovalis is also known as the

oval fossa

End of week 4, primitive ventricles begin to

expand

Medial walls of primitive ventricles will merge together to form the

muscular interventricular septum

Interventricular foramen is located above the

muscular interventricular septum

Outgrowth of the inferior endocardial cushion closes the

interventricular foramen

Complete interventricular foramen closure forms the membranous part of the

interventricular septum

During week 5 neural crest cells migrate into

truncus arteriorsus & bulbus cordis Form truncal ridges & bulbar ridges

Ridges undergo a 180o spiraling which results in the formation of a

spiral aorticopulmonary septum when the ridges fuse.

Ridges also grow

inferiorly to contribute to membranous IV

Because of the spiraling of the aorticopulmonary septum, the pulmonary trunk twists around the

ascending aorta

Because of the spiraling of the aorticopulmonary septum, the pulmonary trunk twists around the

ascending aorta

Ventricular Septal Defect (VSD) Most common

congenital heart defect (Occurrence: 12: 10,000 or 25% of heart defects)

Ventricular Septal Defect (VSD): Failure of

IV septum to completely form

Ventricular Septal Defect (VSD): Can involve

membranous or muscular portion of the septum, but in most cases the membranous portion fails to form

Ventricular Septal Defect (VSD): Frequently 30-50% of small VSD

close spontaneously in the 1st year.

Tetralogy of Fallot Consists of:

Pulmonary artery stenosis (obstruction of right ventricle outflow, with stenosis of the pulmonary valve and infundibular stenosis) VSD Dextroposition of aorta (overriding or straddling aorta) R ventricular hypertrophy

Truncus arteriosus

Roots + proximal portions of aorta and pulmonary trunk

Conus cordis

Outflow tracts of ventricles

Proximal segment of | bulbus cordis

Right ventricle

Primordial ventricle

Left ventricle

Primordial atrium

Left and right auricles + trabeculated portions of atria

Right horn of sinus venosus

``` Sinus venarum (smooth-walled portion of right atrium) ```

Left horn of sinus venosus

Coronary sinus

Primordial pulmonary v. + its branches

Smooth-walled portion of left atrium

oropharyngeal membrane

ecto and endoderm

Truncus arteriosus

more cranial to conus cordis

Sinus venosus becomes

coronary sinus and sinus venerum

Primordial atrium becomes

R and L auricles and part of atria

Primordial ventricle becomes

L ventricle

After twisting, heart walls start to become

trabeculated

Sinus venerum

smooth walled portion of R atria

6 - Development of Heart Flashcards

(97 cards)