Intermediate - Heart Tube Looping: Difference between revisions

Revision as of 12:34, 6 November 2009

Begin Intermediate:

Primordial Heart Tube

Heart Tube Looping

Atrial Ventricular Septation

Outflow Tract

Heart Valves

Cardiac Abnormalities

Vascular Overview

Cardiac Embryology

Begin Basic

Begin Intermediate

Begin Advanced

Looping of the heart tube allows the straight heart tube to form a more complex structure reminiscent of the adult heart. Most cardiac looping occurs during the fourth week and completes during the fifth week of development. The steps in looping can be summarised as:

The straight heart tube begins to elongate with simultaneous growth in the bulbus cordis and primitive ventricle.
This forces the heart to bend ventrally and rotate to the right, forming a C-shaped loop with convex side situated on the right.
The ventricular bend moves caudally and the distance between the outflow and inflow tracts diminishes.
The atrial and outflow poles converge and myocardial cells are added, forming the truncus arteriosus.

Hence an S-shape is formed with the first bend of the 'S' being the large ventricular bend while the bend at the junction of the atrium and sinus venosus forms the second 'S' bend.

The following animation portrays these concepts from the traditional, ventral view of the heart. You can also view this animation from a lateral left or right view.

<Flowplayer height="564" width="720" autoplay="false">Heart looping 002.flv</Flowplayer>

Throughout the morphological changes of the heart tube during looping, the locations of the divisions of the heart tube change, as described above.

Movement of the parts of the heart tube during looping

The following scanning electron micrographs illustrate the same morphological changes in the heart tube described above. The straight heart tube can be seen to form a C-shape, with the convex bulge on the right side of the embryo representing much of the expansive conotruncus and right ventricle. By day 25 it is possible to see the early formation of the S-shaped loop where the left-sided predominant bulge indicates the left ventricle and the atrium and sinus venosus have moved dorsally.

File:HeartILP draft SEMseries.jpg

Series of scanning EMs showing the rapid change in the appearance of the heart tube

Note that previously the heart was attached to the dorsal pericardial wall by the dorsal mesocardium. During heart looping, the dorsal mesocardium degenerates, forming the transverse pericardial sinus (a point of communication across the pericardial coelom).

Back to the Primordial Heart Tube		Next: Heart Septation
Go to this section in the basic level		Go to this section in the advanced level

@@ Line 8: / Line 8: @@
-Looping of the heart tube allows the straight heart tube to form a more complex structure, reminiscent of the adult heart.  Most of cardiac looping occurs during the fourth week and completes during the fifth week of development.  The steps in looping can be summarised as:
+Looping of the heart tube allows the straight heart tube to form a more complex structure reminiscent of the adult heart.  Most cardiac looping occurs during the fourth week and completes during the fifth week of development.  The steps in looping can be summarised as:
 #The straight heart tube begins to elongate with simultaneous growth in the '''bulbus cordis''' and '''primitive ventricle'''.
-#This forces the heart to bend ventrally and rotate to the right forming a C-shaped loop with convex side situated on the right.
+#This forces the heart to bend ventrally and rotate to the right, forming a C-shaped loop with convex side situated on the right.
 #The ventricular bend moves caudally and the distance between the outflow and inflow tracts diminishes.
-#The atrial and outflow poles converge and myocardial cells are added forming the '''truncus arteriosus'''.
+#The atrial and outflow poles converge and myocardial cells are added, forming the '''truncus arteriosus'''.
-Hence, an S-shape is formed with the first bend of the 'S' being the large ventricular bend, while the bend at the junction of the atrium and sinus venosus forms the second 'S' bend.
+Hence an S-shape is formed with the first bend of the 'S' being the large ventricular bend while the bend at the junction of the atrium and sinus venosus forms the second 'S' bend.
 The following animation portrays these concepts from the traditional, ventral view of the heart.  You can also view this animation from a lateral [[Intermediate_-_Heart_Tube_Looping_2|left]] or [[Intermediate_-_Heart_Tube_Looping_3|right]] view.
@@ Line 25: / Line 25: @@
 [[Image:HeartILP_draft_loopingseries.jpg|thumb|center|upright=3.5|Movement of the parts of the heart tube during looping]]
-The following scanning electron micrographs illustrate the same morphological changes in the heart tube described above.  The straight heart tube can be seen to form a C-shape, with the convex bulge on the right side of the embryo representing much of the expansive conotruncus and right ventricle.  By day 25, it is possible to see the early formation of the S-shaped loop where the left-sided predominant bulge indicates the left ventricle and the atrium and sinus venosus have moved dorsally.
+The following scanning electron micrographs illustrate the same morphological changes in the heart tube described above.  The straight heart tube can be seen to form a C-shape, with the convex bulge on the right side of the embryo representing much of the expansive conotruncus and right ventricle.  By day 25 it is possible to see the early formation of the S-shaped loop where the left-sided predominant bulge indicates the left ventricle and the atrium and sinus venosus have moved dorsally.
 [[Image:HeartILP_draft_SEMseries.jpg|thumb|center|upright=4.5|Series of scanning EMs showing the rapid change in the appearance of the heart tube]]
-Note that previously, the heart was attached to the dorsal '''pericardial wall''' by the '''dorsal mesocardium'''.  During heart looping, the dorsal mesocardium degenerates forming the '''transverse pericardial sinus''' (a point of communication across the pericardial coelom).
+Note that previously the heart was attached to the dorsal '''pericardial wall''' by the '''dorsal mesocardium'''.  During heart looping, the dorsal mesocardium degenerates, forming the '''transverse pericardial sinus''' (a point of communication across the pericardial coelom).